REVISED Comparative Analysis of a Conventional Vapor Compression System to a Variable Frequency Driven System for Air Conditioning Application

CHAPTER 1 INTRODUCTION

1.1 Overview

The normal operation of a window type AC unit runs in an on-off control system using a Thermostat. Thermostats are used to keep constant temperature inside the space. It maintains the ideal conditions. The on-off control system consumes more electricity because of motor start-up. During start-up, the motor needs more current thus consuming more power. Therefore, industry  practitioners introduced the application of variable frequency drive to vary the speed of the motor of a compressor relative to temperature changes in the environment. Varying the frequency of the motor of a compressor results to lesser energy consumption compared to the onoff control system. This drive system is currently available in multi-split AC systems and lately in window type ACs using scroll compressors. This is commonly referred to as the Variable Refrigerant Flow (VRF) Technology. This research focused on the comparative analysis of a conventional vapor compression system to a variable frequency driven vapor compression system for air conditioning application. Variable frequency drive (VFD) operation was applied to a conventional vapor compression system and compared its performance to that of normal operation at varying load profiles. The Amatrol T7082 Thermal Systems and Amatrol T7083 Environmental Application System in the HVAC Laboratory of Mapua Institute of Technology served as the vapor compression system and controlled environment respectively. The VFD driving the system was controlled by a 1

microcontroller to automatically vary the frequency of a reciprocating compressor depending on load fluctuations. 1.2 Statement of the Problem Problem

Variable Refrigerant Flow (VRF) technology exists in a multi-split and window type airconditioning system. The main advantage of a VRF system is its ability to respond to fluctuations in space load conditions. (Afify 2008)  Normal AC unit operation or the conventional vapor v apor compression system is not adaptive in load fluctuations or changes in the condition of its environment. Because of constant speed of fan motors and compressors even at high or low load requirements, it is less energy efficient compared to VRF systems with variable speed compressors or systems with Variable Frequency Drive (VFD). The power consumption of AC unit with VRF systems is dependent to space load conditions and is indeed more energy efficient. But it has high first cost compared to the conventional. The problem is the performance of these two systems that are not clearly defined at different load conditions. In order to show the energy efficiency differences of the two systems, this study made a comparative analysis of the performance of a conventional vapor compression system to a variable frequency driven vapor compression comp ression system for air conditioning application. 1.3 Objectives of the Study

The study aims to satisfy the following general and specific objectives shown below: General Objective

2

This study aims to make a comparative analysis of a conventional vapor compression system to a variable frequency driven vapor v apor compression system for air conditioning application. Specific Objectives



To construct a microcontroller that will control the operation of a purchased variable frequency drive / inverter.



To make a program for the microcontroller in such a way that it will control the VFD operation relative to load fluctuations.



To set-up the sensor, microcontroller, inverter/VFD, and the Amatrol T7082 Thermal Systems, in such a way that it may control the cooling inside the Amatrol T7082 Environmental Application System depending on varying load at a certain period.



To measure, test, and evaluate certain parameters of the vapor compression system with or without the VFD operation including the temperature in ˚C, current in Amperes, voltage, and power in Watts at 2.5 hours operation within 50% - 90% load profile.



To have a comparative analysis (conditioned space temperature, compressor power, voltage, current) of a conventional vapor compression system to a variable frequency driven vapor compression system.

1.4 Significance of the Study

In doing the comparative analysis between a conventional vapor compression system and a variable frequency driven vapor compression system, energy efficiency or power consumption may be pre-empted. This study will be able to lay down the advantages and 3

disadvantages of the two systems by comparing how they operate depending on the resulting load profiles. These advantages and disadvantages specifically pertain to energy or power. By doing the comparative analysis, the difference in performance were seen and proven by means of load profiles. Such load profiles have shown the relationship of environment temperature, flow of current, voltage, and power consumption to the varying load of the controlled environment. 1.5 Scope and Limitations

This window type air-conditioning system will be limited only to the function of cooling  because in a tropical country like the Philippines, heating function is irrelevant. This research will be limited in the integration of VRF technology or the VRV/Inverter in a conventional vapor compression system which is the Amatrol T7082 Thermal System. The Amatrol Thermal system will be the vapor compression system. The study will be limited only to sensors, inverter / VFD, and microcontroller. Air conditioned space temperature will be measured in the Amatrol T7083 Environmental Application System in the HVAC Laboratory using a digital thermocouple. Parameters such as the compressor‘s power , voltage, and current will be measured using a power meter. This study will be limited to the comparative analysis of a conventional vapor compression system and a variable frequency driven vapor compression system in air conditioning application. Load fluctuations will be focused on temperature change in the surrounding. Other factors like mass flow rate of refrigerant,  pressures, humidity of room, and wall thickness of room, indoor air-quality, heat load, and cost analysis for the systems will not be part of this study.

4

CHAPTER 2 REVIEW OF RELATED LITERATURE

2.1 Review of Related Study 2.1.1 Experimental Studies 2.1.1.1 Development of a multi-split system air conditioner for residential use (M. Masuda, K. Wakahara, and K. Matsui 1991)

Masuda et al. developed a control method for a multi-split VRF system with two indoor units. The new control method showed that, the refrigerant flow rate for the indoor unit installed in a room with higher cooling load was much more than the other indoor unit. It was obtained that the compressor frequency decreased when each room temperature reached the setting temperature, and increased in the opposite case. It was concluded that the new control method could control the refrigerant flow rate of the indoor units individually and respond to the cooling loads. 2.1.1.2 Testing methodology for VRF systems (J. Xia, E. Winandy, B. Georges, and J. Lebrun 2002)

Xia et al. applied a testing methodology to a multi-split three-pipe VRF system having five indoor units. The tests were performed in six calorimeters; the outdoor and indoor units were placed in each calorimeter. The coefficient of 5

 performance (COP) of the system was defined as the ratio of the total thermal load to the total electric consumption of the system. All the tests were performed in ‗‗cooling all‘‘ mode a nd without any latent load. It was found that the COP of

the system did not vary too much according to the part load ratio. This was explained with the use of two compressors in ‗‗tandem‘‘, which yielded good part load performance. The COP of the system was obtained within 1.9 – 2.4 for the ‗‗cooling all‘‘ mode. 2.1.1.3 Development and testing of a multi-type air conditioner without using AC inverters (Hu and Yang 2005)

Hu and Yang developed a cost effective, energy efficient, multi-split VRF system having five indoor units. A variable refrigerant volume scroll compressor was used instead of an inverter aided one. The capacity control of the compressor was  performed by an ‗‗ON/OFF‘‘ switching of the solenoid valves which changed the

 position of a static scroll to provide variable refrigerant flow. The system determined the required load of the indoor units from the difference between the room and set temperatures, and regulated the degrees of each EEV opening to control the refrigerant flow and the evaporation temperature of each indoor unit. Meantime, the outdoor unit determined the running cycle and the output time of the refrigerant in the compressor according to the requirement of the indoor units to control the ‗‗ON/OFF‘‘ cycle time of the solenoid valves, which controlled the

refrigerant volume of the compressor. It was found that the developed system could adjust the capacity within 17 – 100% with a power input of 1.3 – 4.8 kW, on 6

the other hand, the inverter system adjusted the capacity within 48 – 104% with a  power input of 2.5 – 6.1 kW. 2.1.1.4 Design and research of the commercial digital VRV multi-connected units with sub-cooled ice storage system (X.H. Hai, Z. Tao, F.H. Yun, and S. Jun 2006)

Hai et al. designed and researched a multi-split VRF system having an ice storage tank. It was mentioned that with the ice storage tank, an additional 30 8C subcooling could be achieved which increased the energy efficiency ratio (EER) about 25%. Based on the economic evaluation of the electric price in Shanghai, the payback period of the multi-split VRF system with the ice storage tank was found to be less than 3 years. 2.1.1.5 Experimental evaluation of the ventilation effect on the performance of a VRV system in cooling mode-Part I: Experimental evaluation (T.N. Aynur, Y. Hwang, and R. Radermacher 2008)

Aynur et al. investigated the effect of ventilation on the indoor temperature control, thermal comfort, outdoor unit energy consumption and the efficiency of a multi-split VRV system integrated with a heat recovery ventilation system in a field performance test under varying outdoor conditions. According to the ASHRAE summer thermal comfort zone, it was observed that ventilation did not affect the indoor temperature control instead it increased the indoor humidity ratio resulting in a less comfortable indoor environment. It was also found that even

7

though the ventilation increased the outdoor unit energy consumption due to the ventilation load (ventilation-assisted multi-split VRV system consumed 27.8% more energy than the non-ventilated one), it did not have a considerable effect on the efficiency of the multi-split VRV system. 2.1.1.6 Electric Motor Efficiency Under Variable Frequencies and Loads (C. Burt, X. Piao, F. Gaudi, B. Busch, NFN Taufik October 2006)

Burt et al. made economic trade off analyses for comparison of variable frequency drive (VFD)-controlled versus conventional single-speed motor applications for  pumps require knowledge of how the efficiencies of the pump, motor, and VFD controller changes. The annual energy cost is computed by knowing the hours of operation at various flow rates, the overall pumping plant efficiency at each flow rate, and the cost of power. The procedures for combing pump curves at various speeds with irrigation system curves to determine pump efficiencies are well understood. Some pump companies such as ITT Goulds provide software that combines user-specified system curves at various Revolutions per Minute (RPM) for user-specified pumps (Goulds, 2003). 2.1.2 Modeling Studies 2.1.2.1 Performance analysis on a multi-type inverter air conditioner (Y.C. Park, Y.C. Kim, and M.K. Min 2001)

Park et al. studied the system performance of a multi-split VRF system having two indoor units based on the compressor frequency, total cooling load, and the 8

cooling load fraction between two zones (defined as the ratio of the cooling load of the first zone to the total cooling load). It was found that the compressor power increased with a second-order of the compressor frequency with a reduction in the COP. By fixing the total cooling load of the system at 6 kW, it was obtained that the power consumption increased with an increase of the load difference between each zone with a reduction in the COP. The reason of the increase in the power consumption was due to the increase in the compressor operating frequency. It was observed that when the load ratio was changed from 50 to 100%, the compressor frequency changed only 30%, but the EEV opening changed about 92%. It was concluded that the major control parameter was the EEV opening in a multi-split VRF system rather than the compressor operating frequency when the load ratio was changed. 2.1.2.2 Testing methodology for VRF systems (J. Xia, E. Winandy, B. Georges, and J. Lebrun 2002)

Xia et al. studied the performance of a multi-split three-pipe VRF system. Instead of ‗‗ON/OFF‘‘ operation of each indoor unit, a continuous adaptation of the heat

transfer coefficient method was applied to maintain the same superheating in ‗‗ON‘‘ periods. In this control strategy, each   EEV was adjusted individually to

distribute the suitable refrigerant mass flow rate to each indoor unit in order to maintain the constant indoor room temperature. 2.1.2.3 Simulation evaluation of the ventilation effect on the performance of a VRV system in cooling mode — Part II: Simulation evaluation (T.N. Aynur, 9

Y.

Hwang,

and

R.

Radermacher

2008)

Aynur et al. investigated the effect of ventilation on the indoor temperature control, thermal comfort, outdoor unit energy consumption, the efficiency of a multi-split VRV system and energy saving options. The multi-split VRV module obtained from Y.P. Zhou, J.Y. Wu, R.Z. Wang, and S. Shiochi (2007) was used. A control strategy for the multi-split VRV system integrated with the heat recovery ventilation units, ‗‗synchronized indoor fan operation with economizer‘‘,

was proposed which promised 17 – 28% energy savings when compared with the ‗‗continuous indoor fan operation without economizer.‘‘ 2.1.2.4 Simulation comparison of VAV and VRF air conditioning systems in an existing building for the cooling season (T.N. Aynur, Y. Hwang, and R. Radermacher 2009)

Aynur et al. compared the performance of two widely used air conditioning systems, variable air volume and multi-split VRF, in an existing office building environment under the same indoor and outdoor conditions for an entire cooling season. It was found that the secondary components (indoor and ventilation units) of the multi-split VRF system promised 38.0 – 83.4% energy-saving potential depending on the system configuration, indoor and outdoor conditions, when compared to the secondary components (heaters and the supply fan) of the variable air volume system. Overall, it was found that the multi-split VRF system  promised 27.1 – 57.9% energy-saving potentials depending on the system

10

configuration, indoor and outdoor conditions, when compared to the variable air volume system. 2.1.2.5 Modeling and energy simulation of the variable refrigerant flow air conditioning system with water-cooled condenser under cooling conditions (Y. Li, J. Wu, and S. Shiochi 2009)

Li et al. developed an EnergyPlus module for a watercooled multi-split VRF system. After modeling and testing the new model, on the basis of a typical office  building in Shanghai, the monthly and seasonal cooling energy consumption and the breakdown of the total power consumption were analyzed. The simulation results showed that, during the whole cooling period under the humid subtropical climate condition, the fan-coil plus fresh air system consumed about 20% more  power than the watercooled VRF system. 2.1.2.6 Comparison of energy efficiency between variable refrigerant flow systems and ground source heat pump systems (Liu and Hong, 2009)

Liu and Hong  presented a preliminary simulation comparison of the energy efficiency between an air-source heat recovery multi-split VRF system and a ground source heat pump system. A small office building with a conditioned floor area of 360 m2 was selected, and the building required simultaneous heating and cooling year round. Two cities were selected to represent the hot and cold climates of the United States of America; Miami and Chicago. It was found that the ground source heat pump system saved 9.4% and 24.1% electricity compared 11

to the multi-split VRF system for the same office building located in Miami and Chicago, respectively. It was concluded that electricity savings go up with the increasing heating demands. 2.2 Review of Related Literature 2.2.1. Variable Refrigerant Flow (or Volume) Technology

Variable refrigerant flow (VRF) systems which were introduced in Japan more than 20 years ago have become popular in many countries, yet they are relatively unknown in the United States. The technology has gradually expanded its market  presence reaching European markets in 1987, and steadily gaining market share throughout the world. In Japan, VRF systems are used in approximately 50% of mediumsized commercial buildings (up to 70,000 ft2 [6500 m2]) and one-third of large commercial buildings (more than 70,000 ft2 [6500 m2]) (Goetzler, 2007). VRF systems are larger capacities, more complex versions of the ductless multisplit systems, with the additional capability of connecting ducted style fan coil units. They are inherently more sophisticated than multi-splits with multiple compressors, many evaporators, complex oil and refrigerant management, and control systems. They do not  provide ventilation, so a separate ventilation system is necessary (Goetzler, 2007). The term variable refrigerant flow refers to the ability of the system to control the amount of refrigerant flowing to each of the evaporators, enabling the use of many evaporators of differing capacities and configurations, individualized comfort control, simultaneous heating and cooling in different zones, and heat recovery from one zone to another. This refrigerant flow control lies at the heart of VRF systems and is the major technical challenge as well as the source of many of the system‘s advantages. Figure 1 12

(see Appendix A) illustrates a standard VRF configuration, while Figure 2 (see Appendix A) shows a heat recovery unit providing simultaneous heating and cooling (Goetzler, 2007). The main advantage of a variable refrigerant flow (VRF) system is its ability to respond to fluctuations in space load conditions. By comparison, conventional direct expansion (DX) systems offer limited or no modulation in response to changes in the space load conditions. The problem worsens when conventional DX units are oversized or during part-load operation (because the compressors cycle frequently). A simple VRF system, comprised of an outdoor condensing unit and several indoor evaporators which are interconnected by refrigerant pipes and sophisticated oil and refrigerant management controls, allows each individual thermostat to modulate its corresponding electronic expansion valve to maintain its space temperature setpoint (Afify, 2008). 2.2.2 Refrigerated Cooling or Air Conditioning

Refrigerated air conditioning is similar to commercial refrigeration because the same components are used to cool the air: (1) the evaporator, (2) the compressor, (3) the condenser, and (4) the metering device. These components are assembled in several ways to accomplish in several ways the same goal, refrigerated air to cool space (Whitman et al., 2005). 2.2.3 Package Air Conditioning

The four components are assembled into two basic types of equipment for airconditioning purposes: package equipment and split-system equipment. With package equipment all of the components are built into one cabinet. It is also called self-contained equipment. Air is duct to and from the equipment. Package equipment may be located 13

 beside the structure or on top of it. In some instances the heating equipment is built into the same cabinet (Whitman et al., 2005). 2.2.4 Variable-Speed Motors

The desire to control motors to provide a greater efficiency for the fans, pumps, and compressors has led industry to explore development of and use of variable-speed motors. Most motors do not need to operate at full speed and load except during the peak temperature of the season and can easily satisfy the heating or air-conditioning load at other times by operating at a slower speed. When the motor speed is reduced, the power to operate the motor reduces proportionately. For example, if a home or building needs only 50% of the capacity of the air-conditioning unit to satisfy the space temperature, it will be advantageous to reduce the capacity of the unit rather than stop and restart the unit. When the power consumption can be reduced in this manner, the unit becomes more efficient (Whitman et.al 2005). The frequency (cycles per second) of the power supply and the number of poles determine the speed of a conventional motor. New motors are being used to vary the frequency of the power supply depending on the type of motor. The compressor motor and the fan motors may be controlled through any number of speed combinations based on the needs (Whitman et.al 2005). The air-conditioning load on a building varies during the season and during each day. The central air-conditioning system in a house or other building will have many of the same operating characteristics. For example a house, starting at noon, the outside temperature may be 95oF and the system may be required to run at full load all the time to remove heat as fast as it is entering the house. As the house cools off in the evening, the 14

unit may start to cycle off and then back on, based on the space temperature. Remember, every time the motor stops and restarts, there is wear at the contactor contacts and a  burden is put on the motor in the form of starting up. Motor inrush current stresses the  bearings are not lubricated until the motor is turning. It will be best not to ever turn the motor off and instead just keep it running at a reduced capacity (Whitman et.al 2005). When an air conditioner shuts off, there is normally a measurable temperature rise  before it starts back up. This is very noticeable in systems that only stop and start. The humidity rises during this period. During the winter season, the typical gas or oil furnace does the same thing. It starts and runs until the thermostat is satisfied and then it shuts off. There is a measurable temperature rise before it shuts off and a measurable temperature drop before it starts back up. The actual space temperature at the thermostat location may look like the graph in Figure 3(see Appendix A). The temperature graph may look more like the one in Figure 4 (see Appendix A) when variable speed motor controls are used along with variable firing rate for a furnace. The same temperature curve profile will be true for the cooling season, a more flat profile with less temperature and humidity variations (Whitman et.al 2005). Variable-speed motors can level out the air conditioner operation by running for longer periods of time. One may notice in any building when the system thermostat is satisfied and the unit shuts off. Supposedly, one can just keep the unit running at a reduced capacity that matched the building load. If one can gently ramp the motor speed down as the load reduces and ramps it up as the load increases, the temperature and the humidity will be more constant in the summer. This can be accomplished with modern electronics and variable-speed motor drives (Whitman et.al 2005). 15

AC motor speed is directly proportional to the cycles per second, hertz. If the cycles per second are varied, the motor speed will vary. The voltage must also be varied in proportion to the cycles per second secon d for the motor to remain efficient at all speeds. Once the voltage is converted to DC and filtered, it then goes through an inverter to change it  back to AC that is controllable. Actually, Actuall y, this is still pulsating DC. The reason for all of this is to be able to change the frequency, cycles per second, and the voltage must also be reduced at the same time. As the frequency is reduced, the voltage must also be reduced at the same rate (Whitman et.al 2005). AC that is supplied from the power company is very hard to regulate for usage at the motor, so it must be altered to make the process easier and more stable. The process involves changing the incoming AC voltage to DC. This is accomplished with a device called converter or rectifier. This is much like a battery charger that converts AC to 14V DC to charge an automobile battery. This DC voltage is actually known as pulsating DC voltage. The DC voltage is then filtered using capacitors to create a more pure DC voltage (Whitman et.al 2005). 2.2.5 DC converters (Rectifiers)

There are two basic types of converters, the phase-controlled rectifier and the diode bridge rectifier. The phase-controlled rectifier receives AC from the power company and converts it to variable voltage DC. This is done by using silicon-controlled rectifiers (SRCs) and transistors that can be turned off and back on in microseconds. Figure 5 (see Appendix A) shows the wave form of AC that enters the phase-controlled rectifier which is furnished  by the power company, compan y, and the DC current that leaves the device. Notice the connection 16

for turning these diodes or transistors on and off. The DC voltage leaving this rectifier is varied within the rectifier to coincide with the motor speed. The frequency of the power will be varied to the required motor speed in the inverter which is between the converter and the motor. Remember, the voltage and the frequency must be changed for an efficient motor speed adjustment (Whitman et.al 2005). The other component in the system is a capacitor bank to smooth out the DC voltage. The rectifier turns AC into a pulsating DC voltage that looks like all of the AC voltage on one side of the sine curve. The voltage looks more like pure DC voltage when it leaves the capacitor bank, Figure 6 (see Appendix A). This type of capacitor bank is used for any rectifier to create a better DC profile (Whitman et.al 2005). The diode bridge rectifier is a little different in that the DC voltage is not regulated in the rectifier. The diodes used in this rectifier are not controllable. It is a constant pure DC voltage after it has been filtered through the capacitor bank. The diode  bridge rectifier has no connection for switching the diodes on and off (Whitman et.al 2005). 2.2.6 Inverters

Inverters produce the correct frequency to the motor for the desired speed. Conventional motor speeds are controlled by the number poles, and the frequency is a constant 60Hz. Inverters can actually control motor speeds down to about 10% of their rated speed at 60Hz and up to about 120% of their rated speed by adjusting the hertz to above the 60Hz standard (Whitman et.al 2005). There are different types of inverters. The common one is a six-step inverter, and there are two variations. One controls voltage and the other controls current. The six-step 17

inverter has six switching components, two for each phase of a three-phase motor. This inverter receives regulated voltage from the converter, such as the phase-controlled inverter, and the frequency is regulated in the inverter (Whitman et.al 2005). The voltage-controlled six-step converter has a large capacitor source at the output of the DC bus that maintains the output voltage, Figure 7 (see appendix A). Notice the controllers are transistors that can be switched on and off (Whitman et.al 2005). The current-controlled six-step inverter also has the voltage controlled at the input. It uses a large coil often called a choke in the DC output bus, Figure 8 (see Appendix A). This helps stabilize the current flow in the system (Whitman et.al 2005). A simple diagram of a variable speed motor drive is seen in Figure 9 (see Appendix A). The pulse width modulator (PWM) inverter receives a fixed DC voltage from the converter, and then pulses the voltage to the motor. At low speeds, the pulses are short; at high speeds, the pulses are longer. The PWM pulses are sine coded to where they are narrower at the part of the cycle close to the ends. This makes the pulsating signal look more like a sine wave to the motor. Figure 10 shows the signal the motor receives. This motor speed can be controlled very closely (Whitman et.al 2005). 2.2.7 Microcontroller

Today, microcontroller production counts are in the billions per year, and the controllers are integrated into many appliances that consumers have grown used to, like •

household appliances (microwave, washing machine, coffee machine, . . . )

•

telecommunication (mobile phones)

•

automotive industry (fuel injection, ABS, . . . )

•

aerospace industry 18

•

industrial automation A microcontroller already contains all components which allows it to operate

stand alone, and it has been designed in particular for monitoring and/or control tasks. In consequence, the processor includes memory, various interface controllers, one or more timers, an interrupt controller, and general purpose I/O pins which allow it to directly interface to its environment. Microcontrollers also include bit operations which allow one to change one bit within a byte without touching the other bits (Basic Stamp Editor V2.5.2 Manual). 2.2.8 BASIC Stamp 2 (BS2)

BASIC stamp modules are microcontrollers (tiny computers) that are designed for use in a wide array of applications. Many projects that require an embedded system with some level of intelligence can use a BASIC Stamp module as the controller. Each BASIC Stamp comes with a BASIC Interpreter chip, internal memory (RAM and EEPROM), a 5-volt regulator, a number of general-purpose I/O pins (TTLlevel, 0-5 volts), and a set of built-in commands for math and I/O pin operations. BASIC Stamp modules are capable of running a few thousand instructions per second and are  programmed with a simplified, but customized form of the BASIC programming language, called PBASIC (BASIC Stamp Editor V2.5.2 Manual). 2.2.9 Variable Frequency Drive

Variable frequency drive (VFD) usage has increased dramatically in HVAC applications. The VFDs are now commonly applied to air handlers, pumps, chillers, and tower fans. This device uses power electronics to vary the frequency of input power to the motor, thereby controlling motor speed (Carrier Corporation, 2005). 19

As VFD usage in HVAC applications has increased, fans, pumps, air handlers, and chillers can benefit from speed control. Variable frequency drives provide the following advantages: energy savings, low motor starting current, reduction of thermal and mechanical, stresses on motors and belts during starts, simple installation, high  power factor, and lower KVA (Carrier Corporation, 2005). 2.2.10 Delta VFD-B Series Variable Speed AC Motor Drive

This model of VFD from Delta Electronics, Inc. was used in this study. Its features include 16-bit microprocessor controlled PWM output, automatic torque boost and slip compensation, output frequency 0.1 –  400 Hz, 16-step speed control and 15-step  preset speed, PID feedback control and PG feedback control, 4 acceleration/deceleration times and 2 S-curve selections, pump control and automatic energy saving, process follower  –   10-10VDC, 4-20mA, MODBUS communication RS-485 (baud rate 38400), Coast or ramp to stop, adjustable V/F curve and automatic voltage regulation, automatic adjustment of acceleration/deceleration time, auto tuning and sensorless vector control, sleep / revival function and master / auxiliary and 1st/2nd  frequency source selectable. From the said features, the researchers used the 16-step speed control and 15-step preset speeds which were needed for this study (Parallax Inc. Delta VFD-B Series Variable Speed AC Motor Drive User Manual). 2.2.11 Amatrol T7802 Thermal Systems

The model T7082 Thermal Learning System (see Figure 11 in Appendix A) shows three types of thermal systems: air conditioning, refrigeration, and heat pumps. Students will learn industry-relevant skills including how to operate, install, analyze, and adjust these systems. 20

The T7082 is a working system with industrial components that can perform heat  pump, air conditioning, and refrigeration systems operation. These components are mounted on a bench-top workstation and supported by instrumentation, microprocessor control, student learning materials for both theoretical and laboratory, and teacher‘s guide. The T7082 uses the principle of vapor compression and offers three different types of expansion methods, enabling students to explore a wide range of thermal application and system designs. Components are arranged on a breadboard fashion on the workstation to make it easy for students to follow the system flow and understand its operation. Manual valves are provided throughout so students can create faults and change system performance. Extensive instrumentation is included. Instrumentation features - The T7082 includes many instrumentation features to observe and monitor system operation. Sight glasses are located at three points on both the evaporator and condenser coils to show how the refrigerant changes phase as it passes through each coil. Pressure and temperature gauges are placed at the inlet and outlet of the condenser and evaporator to determine heating and cooling performance. Other teaching components include moisture indicator, panel-mounted compressor ammeter, and flow meter. Variable conditions - The T7082 can replicate a variety of performance conditions with features such as heavy-duty industrial blowers attached to the condenser and evaporator coils and manual valves placed throughout the refrigeration system. The  blowers have dampers that can vary the air flow across the coils, showing the effect of varying heat transfer rates. Manual valves are used to restrict the flow of refrigerant and 21

change the amount of refrigerant in the system by allowing it to flow into or out of the accumulator. Modern temperature control - The T7082 uses a modern microprocessor-based temperature control of the air temperature at either coil. It includes a programmable keypad for both heating and cooling modes, electrical reversing valve, RTD-type remote temperature probe, and digital display. The display shows current temperature and set point. Key features includes: industrial standard components, heavy duty welded steel workstation, performance analysis under variable conditions, built-in instrumentation, 3 types of expansion control options Additional requirements are any one of the following: Amatrol workstations or equivalent: 82-610, 82-611, or 82-612 Electrical Power: 1-Phase, 115 VAC, 60 Hz, 15 Amps or 1-Phase, 230 VAC, 50 Hz, 12 Amps (Amatrol, Inc. Thermal Learning System  –  T7082). Previous analysis of the AC system using an AEV valve to operate has yielded a compressor input of 2413 BTU/hr ± 28.6 BTU/hr, compressor efficiency of 62% ± 1%, and a COP of 1.71(negligible uncertainly). This information is vital in calculating the dollar amount saving using the passive residential cooling system as compared to not using the evaporative cooling system (Schmaltz, 2009). 2.2.12 Amatrol T7083 Environmental Application System

The model T7083 Environmental Applications Learning System (see Figure 11 in Appendix A) adds to the T7082 Thermal Learning System to show heating and cooling

22

applications. Students use this set-up to learn industry-relevant skills including how to size, select, and analyze thermal systems to optimize performance. The T7083 is a working system connected to the T7082 system to provide a functional thermal application of air conditioning and heat pumps. The T7083 models the characteristics of a living structure with outside environmental effects, such as sun or humidity, and internal design characteristics such as insulation, lighting, and ceiling fans. The T7083 consists of a living structure with reversible ducting system, comfort controls, instrumentation, environmental input devices, insulation system, student learning materials for both theoretical and laboratory, and teacher‘s guide. Variable environmental conditions –   The T7083 replicates a variety of real world environmental conditions with devices that simulate effects caused by the sun, humidity, and lighting. Variable thermal design characteristics  –  The T7083 demonstrates the effects of a structure‘s design with removable insulation panels to vary insulation performance,

ceiling fan, window that can be opened, attic fan, attic exhaust, and reversible upper and lower ducts. Instrumentation features  –   The T7083 includes many instrumentation features to observe and monitor system operation. Digital thermometers are placed at key locations in the structure to show how temperature can vary inside a living space. A digital humidity sensor is also included to determine the level of comfort (Amatrol, Inc. Environmental Applications Learning System –  T7083).

23

2.2.13 Hitachi Inverter Scroll Compressor Window Type Air Conditioner

Today, there is an existing air conditioning system which uses variable frequency drive or inverter technology. This is the Hitachi Inverter Scroll Compressor Window Type AC. See Figure 12 (Appendix A) for the brochure of this equipment. 2.2.14 Thermistors

Thermistors are semiconductor devices that are used to measure temperature. The name comes from a combination of the words "resistor" and "thermal". Thermistors have an electrical resistance that is proportional to temperature. Thermistors are used in science and engineering applications. They are also useful in medicine as clinical temperature sensors or as probes during surgery. There are two types: PTC (Positive Temperature Coefficient of Resistance) and NTC (Negative Temperature Coefficient of Resistance).  NTC thermistors (see Figure 13 in Appendix A) have temperatures that vary inversely with resistance such that as the temperature increases, the resistance decreases, and vice versa. They are very often used for temperature control and indication, and for current suppression. Common materials used in their construction include oxides of materials such as nickel, manganese, copper, iron, and cobalt. Some are also made from silicon and/or germanium. They are usually packaged in an epoxy, and are the most common type of thermistors. PTC thermistors (see Figure 14 in Appendix A) are the opposite of NTCs in that they have a resistance that increase with rising temperature and decrease with falling temperature. They are used to protect circuits from overload, and can function as thermal

24

switches or as ordinary thermometers. PTCs are constructed using semiconductors combined with ceramics or polymers (Cooper, 2009). Thermistor applications are based on the resistance-temperature characteristic of a thermistor. NTC thermistors give a relatively large output (change of resistance) for a small temperature change. This output can be transmitted over a large distance. No compensation for ambient temperature is needed. The amount of change per °C is expressed by Beta value (material constant) or Alpha coefficient (resistance temperature coefficient). The larger Alpha or Beta the greater the change in resistance with temperature, and the temperature versus resistance curve is steeper. The resistance versus temperature relationship is not linear. With increasing temperature the nonlinearity decreases. The Stainhart-Hart Equation expresses the relationship between resistance and temperature: 1/T = a + b + (lnR) + c(lnR)3

where T is temperature, R is resistance and a, b, c are coefficients derived from measurements. Thermistors are calibrated at three different temperatures  —  usually at 0°, 25°, and 70°C. This gives three different values of resistance. Table 2.1 Comparison chart of thermocouples and thermistors

25

NTC thermistors  are the most sensitive of all the temperature sensing elements.

Small dimensions of wafer, bead, disc and chip thermistors result in a rapid response time. This is especially useful for control system feedback. Interchangeability

is

another

important

feature. NTC

thermistor interchangeability guarantees close tolerances (0.1 to 0.2 °C) in a certain

temperature range usually 70°C. Instruments and control systems do not have to be recalibrated when a thermistor of the same nominal value is replaced. The ceramic manufacturing process of NTC thermistors produces extremely hard and rugged sensors.  NTC thermistors are able to handle mechanical and thermal shocks better than any other temperature measuring device (Svab A., 2009). 2.2.15 Temperature Measurements

In an experiment entitled Temperature Measurement under the course MAE 300 –  Engineering Instrumentation and Measurement from the Department of Aerospace and Mechanical Engineering, California State University, instructed by Hamid R. Rahai and reported by student Kai Gemba, calibration procedures were performed by students on four types of thermometers against a Mercury-in-glass reference. The types of thermometers were a K-type thermocouple, a thermistor, a platinum resistance thermometer, and a bi-metal thermometer. The temperature range of the calibration was  between 0 C and 100 C. A transient temperature response calibration between 0 C and 100 C was subsequently performed on the K-type thermocouple, thermistor, and platinum thermometer to determine the associated time constants. The Mercury-in-glass reference thermometer data was both inaccurate and imprecise, and therefore corrected and linearized to a best of the data. The calibration data was plotted, statistically evaluated 26

and the method of least squares was applied to determine a best analytical expression for the calibration functions. Each of the four thermometers showed good correlation with a 2nd order polynomial equation. Using the calibrated data, time constants of 1.9, 2.4 and 8.8 seconds were determined for the K-type, thermistor and platinum thermometers, respectively For the calibration procedure, Professor Rahai prepared an ice-water container and all of the thermometers were submerged and allowed to reach equilibrium. A heating mechanism in the bath was initiated and raised the temperature of the bath to boiling over a period of approximately five minutes. Students recorded temperature data simultaneously for each of the 5 thermometers at 10 intervals as announced by Professor Rahai during this period. For the time-constant calibration, the K-type, platinum and thermistor thermometers were moved from an ice-water bath to a boiling water bath. Temperature readings for each of the thermometers were recorded at 5 second intervals between 0 to 40 seconds throughout the period in the boiling water (Gemba K., 2007). Table 2.2 Data Measurements (Gemba K., 2007)

27

Table 2.3 Calibrations (Gemba K., 2007)

From Table 2.1, data measurements of temperature from the experiment can be seen. While table 2.2, calibrated measurements can be seen. It can be noticed that there is small difference between measurements done using a thermistor or a K-type Thermocouple. This is significant in this study because it indicates that using either sensor can yield same or close results which are really the case. Thermistors have a sensitivity of ±0.5˚C. 2.2.16 Thermistor Sensitivity

A main advantage of thermistors for temperature measurement is their extremely high sensitivity. For example, a 2252 Ω thermistor has a sensitivity of -100 Ω/°C at room

temperature. Higher resistance thermistors can exhibit temperature coefficients of 10kΩ/°C or more. In comparison, a 100 Ω platinum RTD has a sensitivity of only 0. 4 Ω/°C. The physically small size of the thermistor bead also yields a very fast response to

temperature changes. Another advantage of the thermistor is its relatively high resistance. Thermistors are available with base resistances (at 25° C) ranging from hundreds to millions of ohms. 28

This high resistance diminishes the effect of inherent resistances in the lead wires, which can cause significant errors with low resistance devices such as RTDs. For example, while RTD measurements typically require 3-wire or 4-wire connections to reduce errors caused by lead wire resistances, 2-wire connections to thermistors are usually adequate. The major tradeoff for the high resistance and sensitivity of the thermistor is its highly nonlinear output and relatively limited operating range. Depending on the type of thermistors, upper ranges are typically limited to around 300° C (Potter D., 1996). The balance point of a Wheatstone bridge with a slide wire for ratio arms is a nearly linear function of the temperature of a thermistor in a third arm, the maximum errors of a linear calibration are made equal and proportional to the cube of the temperature range, and the off ‐ balance sensitivity is nearly constant for a considerable temperature range. For a small thermistor with a 2000 ‐ohm resistance at 25°C, the slide  position of a linear potentiometer is proportional to the thermistor temperature ±0.5°C, and the deflection of a taut suspension pointer galvanometer is 20±1 mm∕°C over the temperature range from 0°C to 50°C with a maximum thermistor temperature rise of 0.05°C in still air (Cole K.S., 1957).

29

CHAPTER 3 THEORETICAL CONSIDERATIONS

This part of the study will be discussing about certain factors that may affect the design and operation of the VFD, microcontroller, and the vapor compression system. The vapor compression system used in this study is the Amatrol T7082 Thermal System which is basically a conventional air conditioning system in a laboratory set up. Temperature measurements and different load profiles were performed in the Amatrol T7083 Environmental Application System, knowing the theories is crucial in formulating the analysis of the data gathered. Theories involved in this study need to be considered, specifically in arriving to the conclusions and recommendations. In this study, certain theories or basic principles of operations were considered.

3.1 On-Off Control Operation

An on-off controller is the simplest form of temperature control device. The output from the device is either on or off, with no middle state. An on-off controller will switch the output only when the temperature crosses the set point. For heating control, the output is on when the temperature is below the set point, and off above set point. Since the temperature crosses the set  point to change the output state, the process temperature will be cycling continually, going from  below set point to above, and back below. In cases where this cycling occurs rapidly, and to  prevent damage to contactors and valves, an on-off differential, or ―hysteresis,‖ is added to the controller operations. This differential requires that the temperature exceed set point by a certain 30

amount before the output will turn off or on again. On-off differential prevents the output from ―chattering‖ or making fast, continual switches if the cycling above and below the set  point

occurs very rapidly. On-off control is usually used where a precise control is not necessary, in systems which cannot handle having the energy turned on and off frequently, where the mass of the system is so great that temperatures change extremely slowly or for a temperature alarm. One special type of on-off control used for alarm is a limit controller. This controller uses a latching relay which must be manually reset, and is used to shut down a process when a certain temperature is reached (Omega Engineering Inc., 2003).

3.2 Variable Frequency Drive (VFD) Operation During start  –   Normal start: During a normal start the VFD will start and operate at

given frequency in open loop mode, or operate in closed loop mode according to parameter settings. During start  –   Soft start: Upon start, the VFD will softly start and accelerate to the

frequency of power grid regardless of the given frequency. When the output frequency of VFD reaches the power grid frequency (set at installation), then the output of the VFD will become zero. At the same time VFD sends a ‗transfer to power grid‘ command. This command transfers

the power supply of the motor from VFD to the power grid. During the transient transfer, there is a big inrush current. For synchronous operation (requires optional transfer reactor) the VFD and  power grid will supply the motor during the transient transfer, creating a small inrush current. During operation  –   Closed loop: In closed loop mode, the VFD will automatically

adjust the output frequency to operate at the set parameter value e.g. pressure or temperature. 31

During operation  –   Open loop: In open loop mode, the VFD will operate at the given

frequency. This frequency can be set via controller, external analog signal, or serial communications module. During operation  –   Automatic scheduling: The user can program the VFD to

automatically perform a series of tasks set by the parameters for each scheduled time. During operation  –   Operation log: Operation logs are automatically recorded. Every

operation includes a time/date-stamp. During operation  –   Motor protection: The user can modify the default settings of

overload and under load protection settings. (AuCom Electronics, 2010)

3.3 Microcontroller Operation

In general, a microcontroller's operation includes a process for initializing, or beginning, its own internal logic and/or intended software application, also known as boot method. This method for a microcontroller's application software is accomplished by the use of reset vector logic contained within the microprocessor, reset vectors in application memory space, application boot software and the application software itself. The application boot software typically determines if the application software is present and supplies the appropriate communication algorithms for reprogramming the application memory. The application software controls the functionality of the microcontroller by controlling the operations of the microprocessor. Resetting the microcontroller is done in a power-on reset operation. It can also  be prompted by an external reset signal, or by a reset signal coming from an internal circuit of the microcontroller called a watchdog circuit. Debugging the programming code in embedded microcontrollers is usually done during development using an in-circuit emulator (ICE) unit. 32

Microcontrollers allow circuit designers great flexibility in design choice. However,  programming the microcontroller to perform the desired functions can be an arduous task. Techniques for programming the user program into the non-volatile memory may be characterized by using an external programmer coupled directly to the non-volatile memory. The  programmer utilizes a control signal line to appropriately signal the non-volatile memory (as well as associated circuitry within the microcontroller) that a programming mode is being entered. By using a block of user programmable non-volatile memory, the microcontroller may  be customized to carry out any desired function within the capabilities of the device. Microcontrollers are connected via an external bus to an external memory in which a control  program and data are recorded, read out instruction code from this memory by outputting an instruction fetch request, and read or write pre-determined data by outputting a data access request (Electronics Information Online, 2007).

3.4 Power and Frequency

Electric power is the rate at which electric energy is transferred. It is measured by capacity and is commonly expressed in watts (W). While Power (by definition) is the rate of work or energy flow (which are numerically the same): P = Energy/Time. The watt is the basic unit of real power. By definition, 1 watt is equal to one joule of energy per second. In electrical terms, it can be shown that power is produced or consumed at a rate of one watt when one ampere flows through a potential difference of one volt: 1 watt = 1 volt × 1 ampere. On the other hand, frequency is the measurement of the number of times that a repeated event occurs per unit time. To calculate the frequency, one fixes a time interval, counts the number of occurrences of the event within that interval, and then divides this count by the length 33

of the time interval. In SI units, the result is measured in hertz (Hz). 1 Hz means that an event repeats once per second. Other units that have been used to measure frequency include: cycles  per second, revolutions per minute (rpm). In this study, these parameters  –   power and frequency must be related. The relationship  between these parameters can be seen in the equations P = 2πTN  –   equation 1 (where P is the  power, T is the torque, and N is the number of revolutions per minute or motor speed) and  pN=120f  –   equation 2 (where p is the number of poles, N is the motor speed, and f is the frequency of the motor). It can be seen in equation 1 that power is directly proportional to the amount of torque and the speed of the motor. In equation 2 it can be seen that the frequency is directly proportional to the number of poles of the motor and the speed of the motor. Therefore, if power is directly proportional to the speed of the motor, and if frequency is directly  proportional to the speed of the motor, then power is directly proportional to the frequency of the motor. As the motor‘s frequency increases, the power consumption or requirement also

increases, and vice versa.

34

CHAPTER 4 METHODOLOGY

The main objective of this study is to make a comparative analysis of a conventional vapor compression system and variable frequency driven vapor compression system for air conditioning application. The Amatrol T7082 Thermal Systems served as the vapor compression system used for all the testings and analyses made. The Amatrol T7083 Environmental Application System served as the air conditioned space where temperature measurements were measured and controlled. In this study, a microcontroller was constructed to control the operation of a purchased variable frequency drive depending on the temperature of the conditioned space. The microcontroller was programmed using the BASIC Stamp V2.5.2. This VFD-Microcontroller set-up was integrated to the Amatrol T7082 Thermal Systems. In order to do the analysis, different parameters such as temperature, voltage, current, and power were measured at varying loads within 2.5 hours operation. These parameters were put in a load profile.

4.1 Construction of Microcontroller

Microcontroller serves as the main processing unit for the control system of a VRF window type air conditioning unit. A thermistor was used to detect the temperature of the conditioned space. The signal, which came from the thermistor was sent to the microcontroller. 35

The microcontroller communicates the feedback from the process to the variable frequency drive. The variable frequency drive used this feedback to adjust the speed of the motor of the compressor. The materials used to construct the circuit for the microcontroller were the following: Basic Stamp II (BS2), 6pcs Single Pole Double Throw (SPDT) Relays, 2pcs Ceramic capacitor, 2pcs Mylar capacitor, 6pcs Zener diodes, 12pcs resistors, universal bread board, terminals, NTC Thermistor, and stranded wires for the connections and wirings.

Figure 4.1 Microcontroller (side view)

Figure 4.2 Microcontroller (top view)

The basic wirings and connections of the Basic Stamp II with all other parts in the bread  board were obtained from the Basic Stamp manual. In Figure 4.3, the BS2-IC is shown. The BS2-IC used surface mount components to fit in a small 24-pin DIP package.

36

Figure 4.3 Basic Stamp 2

Figure 4.4 BASIC Stamp Programming Connections

Table 4.1 BASIC Stamp 2 Pin Descriptions Pin Name 1

SOUT

Description

Serial out: connects to PC serial port RX pin (DB9 pin2 / DB25 pin 3) for  programming.

2

SIN

Serial In: connects to PC serial port TX pin (DB9 pin 3 / DB25 pin 2) for 37

 programming. 3

ATN

Attention: connects to PC serial port DTR pin (DB9 pin 4 / DB25 pin 20) for  programming.

4

VSS

System ground: (same as pin 23) connects to PC serial port GND pin (DB9 pin 5 / DB25 pin 7) for programming.

5-20

PO-P15

General-purpose I/O pins: each can sink 25 mA and source 20 mA. However, the total of all pins should not exceed 50 mA (sink) and 40 mA (source) if using the internal  – volt regulator. The total per 8-pin groups (P0  –   P7 or P8  –   P15) should not exceed 50 mA (sink) and 40 mA (source) if using an external 5-volt regulator.

21

VDD

5-volt DC input/output: if an unregulated voltage is applied to the VIN pin, then this pin will output 5 volts. If no voltage is applied to the VIN pin, then a regulated voltage between 4.5V and 5.5V should be applied to this pin.

22

RES

Reset input/output: goes low when power supply is less than approximately 4.2 volts, causing the BASIC Stamp to reset. Can be driven low to force reset. This  pin is internally pulled high and may be left disconnected if not needed. Do not drive high.

23

VSS

System ground: (same as pin 4) connects to power supply‘s ground (GND) terminal.

24

VIN

Unregulated power in: accepts 5.5 –   15 VDC (6-40 VDC on BS2-IC Rev. e, f, and g), which is then internally regulated to 5 volts. Must be left unconnected if 5 volts is applied to the VDD (+5V) pin.

38

In Figure 4.4, BASIC Stamp programming connections can be seen. This is how it is wired in the actual microcontroller circuit. It can be inferred in Table 4.1 the pin descriptions for the Basic stamp II IC which is followed by the connections in the circuitry.

4.2 Programming of the Microcontroller

BASIC Stamp V2.5.2 was used to program the microcontroller. The resistance of the thermistor was inversely proportional to the temperature. The resistance of the thermistor at a given temperature was determined by comparing it to the temperature reading from digital thermometer. A resistance of 800 ohms was approximately equal to 24 degrees Celsius based on calibration. The program was set to maintain the temperature of the conditioned space at 24 degrees Celsius. When the resistance of the thermistor was greater than 800 ohms, the microcontroller switches the system into cooling. In the program stored inside the controller, cooling means to reduce the frequency being supplied to the motor of compressor by one step. When the resistance of the thermistor was less than 800 ohms, the microcontroller switches the system into heating. Heating means to increase the frequency being supplied to the compressor by one step. The frequency being supplied by the VFD ranges from 45 Hz to 60 Hz. (See Appendix B for program).

39

4.3 Basic Wiring of Delta VFD-B Series

Figure 4.5 The VFD and the VFD to microcontroller set up The VFD used in this study can be seen in Figure 4.5 as well as the VFD to Microcontroller set-up. The microcontroller serves as the brain of the VFD. The power source of Delta VFD-B Series can be connected to any two or the three input terminals R, S, and T. The outputs lines of VFD can be connected to any two output terminals U, V, and W. The output lines were the ones connected to the outlet of the compressor. Since a single phase motor of a compressor was used, U and V output terminals were used. Refer to Figure 4.5 for the schematic diagram of the VFD.

40

Figure 4.6 Installations and Wiring

For SINK Mode, Multi-step 1-4 were normally closed (OFF). Multi-step and Digital Signal Common pins were connected into the terminals of the controller. Each terminal was connected into a relay and served as a switch. If the relays were energized and turned the switch

41

on, it would open the connection between the Multi-step and Digital Signal Common. Each Multi-step has its own terminals and relays. Refer to Figure 4.6 for wiring in SINK mode.

Figure 4.7 Wiring for SINK Mode 4.4 Programming of the Delta VFD-B

The VFD was used to vary the frequency of the compressor of the air-conditioning unit depending on the load fluctuations inside the conditioned space. In Figure 4.8, the VFD-B keypad is shown- the function of each button, indicators, and other details.

42

Figure 4.8 VFD-B Keypad

One of the features of the Delta VFD-B series was its 16-step speed control and 15-step  preset speed. This feature enabled the researchers to input 15 different step speed frequencies that will vary depending on the load on the room. Based on the manual, the Multi-Function Input Terminals (refer to Pr.04-04 to 04-09 of the manual) were used to select one of the AC motor drive Multi-step speeds. The step speed frequencies were determined by Pr.05-00 to 05-14. Speed designations for the program were the following: 1st frequency= 46 Hz; 2nd frequency= 48 Hz; 3rd frequency= 51 Hz; 4th frequency= 53 Hz; 5th frequency= 55 Hz; 6th frequency= 57 Hz; 7th frequency= 59 Hz; 8th  frequency= 60 Hz; 9th  frequency= 58 Hz; 10th  frequency= 56 Hz; 11th frequency=54 Hz; 12th  frequency=52 Hz; 13th  frequency=50 Hz; 14th  frequency= 47 Hz; 15th frequency= 45 Hz; In Table 4.2, multi-step speed frequencies up to 15th  speed and its matching program could be seen. In this study, the VFD was programmed in such a way that 15 step speed frequencies were designated to the multi-function input terminals.

43

Table 4.2 Multi-step speeds designations to program of the VFD Step speed frequencies were inputted in the keypad. Once the VFD was turned-On, in the selection mode, press PROG|DATA to set the parameters. In the parameter setting mode, press MODE to return to selection mode and press the shift cursors to move to decimal places. In setting the parameter, after pressing PROG|DATA, shift cursors up to select parameter 05, and then press PROG|DATA again to select the next parameters; from 00-14 press PROG|DATA again to input the desired Step Speed Frequency. This should be done until all parameters were given a frequency designation.

44

Figure 4.9 Multi-speed via External Terminals In Figure 4.8, the graph for the Multi-speed via External terminals could be seen. This is the behavior of varying the frequencies. This variation of speed was automated through the Microcontroller. The combination of on and off in the Multi-function input terminals (MI1-MI4) as seen in Table 4.2 was controlled by the controller through the relays.

45

Table 4.2 Multi-function input terminals as designated with the step-speed frequencies

4.5 Testing and Data Gathering

The testing of each air-conditioning unit that was installed with VFD and without VFD was 2.5 hours. The performance of the two different control system of air-conditioning units (VFD and non-VFD) was recorded every 15 minutes. Through the use of power meter, the  parameters current, voltage and power consumption were determined. Digital thermometer was used to measure the temperature of the conditioned space. For heat load, incandescent bulb with 50, 100, and 200 watts were used. These bulbs were placed inside the conditioned space and serve as a heat load. The heat load of the conditioned space was varied (full load, 90% load, 80% load, 70% load, 60% load, 50% load, and no load).

46

For a system with VFD, the thermistor of the microcontroller was placed inside the conditioned space beside the sensor of the digital thermometer. The thermistor responded to the temperature change inside the conditioned space and signal was sent to the microcontroller. The ambient temperature outside the conditioned space was maintained at 25 degrees Celsius. VFD varies the frequency of the motor of compressor. It could also vary the speed of the motor of compressor into 16-steps. For a system without VFD, sensor of the digital thermometer was placed in the middle of the conditioned space. The ambient temperature outside the conditioned space was maintained at 25 degrees Celsius.

47

CHAPTER 5 DISCUSSION AND ANALYSIS OF RESULTS

This chapter discusses the relationship of different parameters such as temperature inside the Amatrol T7803 Environmental Application System, the Amatrol T7802 Thermal System  power consumption, voltage, and current to the load fluctuations at 2.5 hours operation. In order to do the comparison, load profiles were made at no load, 90%, 80%, 70%, 60%, and 50% each for 2.5 hours of operation. With this, the behavior and relationship of every parameter to the load changes can be seen.

5.1 Testing on the Amatrol T7802 Thermal Systems and Amatrol T7083 Environmental Application System

The VFD-microcontroller set-up which was the VFD system was integrated in the Amatrol T7802 Thermal System. Parameters such as temperature, compressor power, voltage, and current were measured at different load changes inside the Amatrol T7803 Environmental Application System within 2.5 hours operation. Parameters were measured with or without the VFD system in order to make a comparative analysis. The Amatrol T7802 Thermal System was the vapor compression system used in this study. The prototype was tested in the Amatrol Thermal Systems because of practicality reasons as well as ease of use and measuring of parameters. In addition, together with the vapor compression system was a miniature room which is the Amatrol T7083 Environmental

48

Application System where temperature measurements were at changing loads and motor frequency. In Figure 5.1, the Amatrol T7802 Thermal Systems as well as the Environmental Application System could be seen. This was the vapor compression system for air-conditioning that was used in this study. In Figure 5.2, the whole set up of the testing performed could be seen which include the personal computer for programming the microcontroller, the microcontroller, inverter or variable frequency drive, and the Amatrol T7802 Thermal Systems and the Amatrol T7083 Environmental Application Systems. The temperature inside the environment was sensed  by a thermistor connected to the microcontroller. This signal was then read and sent by the microcontroller to the VFD. Depending on the temperature of the room, the frequency was varied through the VFD.

Figure 5.1 Amatrol T7802

49

Figure 5.2 Set Up for testings

In Figure 5.3, the power meter could be seen. The Amatrol Thermal System‘s outlet was plugged in the socket connected with the supply from the variable frequency drive or Inverter. The inverter‘s outlet was then plugged in the 220V main voltage supply. Through the  power meter, the power consumption, voltage, and electric current were measured with different load fluctuations in the conditioned space.

Figure 5.3 Power meter 50

Figure 5.4 Light Bulbs (50, 100, and 200 Watts) inside the environment In Figure 5.4, the air-conditioned space could be seen. Temperature was varied by increasing and decreasing the amount of heat inside the room. This was done through the three light bulbs at 50 watts, 100 watts, and 200 watts at a total of 350 watts full load. Other heat load sources such as attic heater, attic fan, and the ceiling fan were neglected. All throughout the experiments, this set-up was used to vary the temperature, thus to vary the frequency of the motor. As the load increases, the temperature also increased. As the temperature increased, the frequency of the compressor increased and as the frequency increased the more the room was being cooled and vice-versa. With this, the behavior of the vapor compression system or the Amatrol T7082 Thermal System was observed with or without the VFD. The computations were as follows: 

At No Load: Power=350 W; Energy Consumption =350Wx2.5hrs =875W-hr



At 90% load profile: Power=350Wx0.90=315 W; Energy Consumption =315W x 2.5hrs =787.50 W-hr



At 80% load profile: Power=350Wx0.80=280W; Energy Consumption =280W x 2.5 hrs =700 W-hr

51



At 70% load profile: Power=350Wx0.70=245W; Energy Consumption =245W x 2.5 hrs =612.50 W-hr



At 60% load profile: Power=350Wx0.60=210W; Energy Consumption =210W x 2.5 hrs =525 W-hr



At 50% load profile: Power=350Wx0.50=175W; Energy Consumption =175W x 2.5 hrs =437.50 W-hr

In order to have a comparative analysis especially on the energy consumption and power, load profiles were created. The energy consumption was the area covered under the graph of the load curve. Behaviors of parameters such as room temperature, compressor power, voltage, and current were observed at different load profiles for the vapor compression system with or without the VFD.

52

5.1.1 Temperature

The temperature inside the Amatrol T7803 Environmental Application System was measured using a digital thermocouple for a period of 2.5 hours. Testing was done at different total heat loads for the whole operation  –   no load, 90%, 80%, 70%, 60%, and 50% load. The temperature measurements were done every 15 minutes for 2.5 hours as the load changed. Through this, the relationship between temperature and heat load was seen through a load profile. Table 5.1 Temperature measurements inside the Amatrol Environmental Application System 90% Load Profile

No Load

80% Load Proifle

70% Load Profile

60% Load Profile

50% Load Profile

Hours

Load

w/o VFD

w/VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

0

0

22.3

24.5

0

23.9

22.9

0

25.9

24.8

0

23.8

23.4

0

26

25.4

0

25.4

25.3

0.25

0

18.6

19.6

350

24.5

22.3

350

23.6

23.7

300

23.7

21.5

300

22.4

22.9

250

21.9

21.9

0.5

0

18.4

19.8

350

24.9

22.3

350

23.2

22.7

250

23.6

22.3

300

23.2

23.4

100

20.2

19.8

0.75

0

18.8

19.9

350

25.7

22.3

350

23.3

22.7

350

24.6

21.4

250

22.4

22.9

150

20.3

19.9

1

0

19.2

19.3

350

26.1

22.3

250

22.1

21

200

23.4

21.7

200

21

23

100

19.6

19.3

1.25

0

19.5

18.1

350

25.4

22.2

250

22.1

21.4

150

23

21

150

21.3

22.9

150

20.3

20.2

1.5

0

19.6

17.7

250

24.2

22

300

22.5

21.8

250

24

21.7

250

22.2

23.4

300

21.6

21.9

1.75

0

19.6

17.5

200

24.6

21.6

150

20.9

19.8

150

23.1

20.2

100

21

21.7

150

20.3

20.4

2

0

19.1

17.3

250

25.1

21.9

150

21.1

20.2

200

23.7

20.5

200

21.9

21.9

200

20.1

20.8

2.25

0

19.3

17.1

350

25.2

22.3

300

22.7

22

250

24.5

20.9

150

22.3

21.3

250

20.9

21.7

2.5

0

19

17.2

350

25

22.6

350

24.5

22.6

350

25

22.6

200

21.8

21.3

100

19.4

19.8

53

At no load changed as seen in Figure 5.5, temperature behavior with or without the variable frequency drive was the same. There was a difference in values for the temperatures  because of the ambient air-condition. Ambient air temperature affected the temperatures inside the rooms so there was a percent difference. For Figures 5.6-5.10, the temperature inside the Amatrol T7083 Environmental Application System was measured at different load profiles  –   90%, 80%, 70%, 60%, and 50%. As the load increased, the temperature also increased, and vice-versa. As the temperature increased, the frequency of the compressor also increased, and vice-versa. Frequency of the compressor was varied from 45 –  60 Hz. With the VFD set-up, temperature tend to be controlled depending on the load inside the space. The system maintained an ideal temperature depending on the heat sensed inside the room. Without the VFD set-up, there was constant frequency for the compressor which was 60 Hz so the temperature was dependent on what was set by the thermostat which operated in an on-off control.

Figure 5.5 Temperatures at No Load

54

Figure 5.6 Temperatures vs Load at 90% Load Profile

55

Figure 5.7 Temperature vs Load at 80% Load Profile

56

Figure 5.8 Temperature vs Load at 70% Load Profile

57

Figure 5.9 Temperature vs Load at 60% Load Profile

58

Figure 5.10 Temperature vs Load at 50% Load Profile

59

5.1.2 Voltage

The voltage of the air-conditioning unit particularly the compressor‘s voltage  was measured using a power meter for a period of 2.5 hours. Testing was done at different total heat loads for the whole operation  –   No load, 90%, 80%, 70%, 60%, and 50% load. The voltage measurements were done every 15 minutes for 2.5 hours as the load is changed. Through this, the relationship between voltage and heat load was seen through a load profile.

90% Load Profile

 No Load

80% Load Proifle

70% Load Profile

60% Load Profile

50% Load Profile

Hours

Load

w/o VFD

w/VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

0

0

230.5

230

0

230.9

224.1

0

232.9

229

0

232.6

222.2

0

230.7

225.4

0

233.8

224.5

0.25

0

231.5

227.5

350

231.1

226

350

234.2

222.2

300

232

225.4

300

236.6

226.4

250

233.2

224.1

0.5

0

232.6

225.6

350

232.6

227.3

350

230.7

221.2

250

232.6

229.2

300

230.7

228.1

100

232.3

224.4

0.75

0

232.6

225.4

350

233.6

226.2

350

231.1

220.4

350

233.5

226.7

250

231.7

230.7

150

233.6

225.8

1

0

232.1

224.8

350

233.6

225.4

250

230.7

223.1

200

232.1

228.6

200

233

229.8

100

234.9

229

1.25

0

233.2

223.1

350

231.7

223.7

250

232.1

221.6

150

231.5

227.9

150

232.6

229

150

233.8

227.5

1.5

0

236.1

222.5

250

231.3

220.6

300

232.8

220.6

250

233

223.7

250

231.7

225.6

300

233.6

224.1

1.75

0

232.3

221.8

200

230.5

220.1

150

234.9

221.6

150

231.7

221.4

100

234.2

223.4

150

233.6

224.8

2

0

233.6

221.6

250

230.7

222.7

150

234.9

222.5

200

234

221

200

230.9

221.8

200

230.9

226.2

2.25

0

233

221.6

350

232.1

222.7

300

234

222

250

234

222

150

231.7

223.1

250

231.7

226.7

2.5

0

232.7

221.5

350

231.8

221.6

350

234.4

222.5

350

232.6

222.2

200

234.7

222.2

100

233.2

228.3

Table 5.2 Voltage Measurements of the Amatrol compressor for 2.5 hours operation. 60

Figures 5.11 showed the voltage behavior at no load and Figures 5.12 –   5.16 showed the voltage behavior at 90%, 80%, 70%, 60%, and 50% load profiles. Based on the figures, voltage is not dependent on the load inside the room as well as the frequency of the compressor. As frequency and temperature increased or decreased, voltage was constant. There was a percentage difference to the voltage with VFD to that of without due to friction loss and voltage drop.

Figure 5.11 Voltage vs Load at No Load

61

Figure 5.12 Voltage vs Load at 90% Load Profile

Figure 5.13 Voltage vs Load at 80% Load Profile

Figure 5.14 Voltage vs Load at 70% Load Profile

62

Figure 5.15 Voltage vs Load at 60% Load Profile

Figure 5.16 Voltage vs Load at 50% Load Profile

63

5.1.2 Current

The current of the air-conditioning unit,  particularly the compressor‘s current was measured using a power meter for a period of 2.5 hours. Testing was done at different total heat loads for the whole operation  – no load, 90%, 80%, 70%, 60%, and 50% load. The current measurements were done every 15 minutes for 2.5 hours as the load was changed. Through this, the relationship between current and heat load was seen through a load profile.

90% Load Profile

 No Load

80% Load Proifle

70% Load Profile

60% Load Profile

50% Load Profile

Hours

Load

w/o VFD

w/VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

0

0

7.3

7.42

0

7.23

7.21

0

7.34

7.39

0

7.4

7.3

0

7.44

7.41

0

7.23

7.24

0.25

0

3.88

2.91

350

3.96

3.24

350

3.96

4.54

300

3.97

4.51

300

3.93

4.51

250

3.91

3.25

0.5

0

3.89

2.95

350

3.98

3.2

350

3.92

4.47

250

3.97

3.24

300

3.93

4.65

100

3.87

3.22

0.75

0

3.91

2.95

350

4

3.96

350

3.89

4.39

350

3.98

3.32

250

3.91

3.35

150

3.88

3.2

1

0

3.92

2.92

350

4.02

3.6

250

3.91

3.29

200

3.96

3.71

200

3.88

3.84

100

3.91

3.16

1.25

0

3.93

2.93

350

4.01

3.72

250

3.89

3.29

150

3.97

3.2

150

3.91

3.35

150

3.89

3.25

1.5

0

3.97

2.9

250

3.96

3.17

300

3.9

3.25

250

3.97

3.2

250

3.91

4.69

300

3.89

3.22

1.75

0

3.93

2.88

200

3.97

2.93

150

3.92

3.24

150

3.97

3.25

100

3.92

3.35

150

3.89

3.21

2

0

3.93

2.88

250

3.97

2.97

150

3.92

3.18

200

4

3.24

200

3.91

3.28

200

3.84

3.2

2.25

0

3.93

2.42

350

3.96

3.03

300

3.93

3.22

250

4

3.21

150

3.92

3.28

250

3.85

3.24

2.5

0

3.95

2.4

350

3.96

4.56

350

3.97

3.49

350

4

3.29

200

3.92

3.26

100

3.84

3.22

Table 5.3 Current measurements of the Amatrol compressor for 2.5 hours operation 64

Figures 5.17 showed the electric current (in Amperes, A) behavior at no load and Figures 5.18 –  5.22 showed the electric current behavior at 90%, 80%, 70%, 60%, and 50% load profiles. Based on the figures, electric current was not dependent on the load inside the room as well as the frequency of the compressor. As frequency and temperature increased or decreased, electric current was constant. There was a percentage difference to the current with VFD to that of without due to friction losses and voltage drops.

Figure 5.17 Current vs Load at No Load

65

Figure 5.18 Current vs Load at 90% Load Profile

66

Figure 5.19 Current vs Load at 80% Load Profile

67

Figure 5.20 Current vs Load at 70% Load Profile

68

Figure 5.21 Current vs Load at 60% Load Profile

69

Figure 5.22 Current vs Load at 50% Load Profile

70

5.1.4 Power Consumption

The power consumption of the Amatrol‘s compressor  was measured using a power meter for a period of 2.5 hours. Testing was done at different total heat loads for the whole operation –   No load, 90%, 80%, 70%, 60%, and 50% load profile. The power measurements were done every 15 minutes for 2.5 hours as the load was changed.

90% Load Profile

 No Load

80% Load Profile

70% Load Profile

60% Load Profile

50% Load Profile

Hours

Load

w/o VFD

w/VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

Load

w/o VFD

w/ VFD

0

0

990

981

0

993

989

0

994

991

0

996

630

0

990

993

0

994

997

0.25

0

619

383

350

648

427

350

639

641

300

645

437

300

643

650

250

630

438

0.5

0

623

386

350

652

484

350

631

635

250

647

444

300

638

661

100

621

431

0.75

0

626

386

350

664

594

350

630

606

350

650

500

250

634

455

150

624

437

1

0

632

382

350

668

494

250

629

435

200

646

433

200

624

502

100

626

434

1.25

0

638

373

350

664

495

250

626

435

150

645

432

150

629

456

150

627

439

1.5

0

643

372

250

650

386

300

625

431

250

653

437

250

631

661

300

627

437

1.75

0

641

372

200

652

382

150

628

428

150

650

430

100

636

447

150

624

435

2

0

635

370

250

655

395

150

634

428

200

656

427

200

635

446

200

615

435

2.25

0

640

368

350

647

418

300

637

432

250

657

428

150

637

442

250

618

438

2.5

0

638

370

350

649

630

350

649

465

350

661

444

200

637

436

100

612

436

Table 5.4 Power consumption measurements

71

Figures 5.23 showed the power at no load and Figures 5.24  –   5.28 showed the power  behavior at 90%, 80%, 70%, 60%, and 50% load profiles. Based on the results, power was dependent on the load changed inside the room. As the load increased, the power consumption also increased, and vice-versa. For the vapor compression system without the VFD, the power consumption was constant even if the temperature increased or decreased because compressor frequency was still constant at 60 Hz standard. For the variable frequency driven vapor compression system, it could be seen in the graphs that power consumption increased as the load increased, and vice versa. It can also be noticed that power consumption with VFD is greatly smaller compared to that without because the VFD maintained the desired compressor frequency depending on the room temperature as sensed by the thermistor through the microcontroller.

Figure 5.23 Power Consumption at No Load

72

Figure 5.24 Power Consumption at 90% Load Profile

Figure 5.25 Power Consumption at 80% Load Profile

73

Figure 5.26 Power Consumption at 70% Load Profile

Figure 5.27 Power Consumption at 60% Load Profile

74

Figure 5.28 Power Consumption at 50% Load Profile

75

CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS

This chapter presents the conclusions and recommendations for the study. The conclusions are based on all the gathered data and relationships from research, experiments, and testings done in the vapor compression system with or without the VFD automated by the microcontroller. Recommendations for this study were made as seen needed.

6.1 Conclusions

The discussions and analysis of different parameters such as environment temperature,  power consumption, voltage, and electric current from the previous chapters enabled the comparative analysis of a conventional vapor compression system to a variable frequency driven vapor compression system for air-conditioning application. The Amatrol T7082 Thermal Systems served as the vapor compression system having the Amatrol T7083 Environmental Application System as the air-conditioned space. Through analyzing all the measured and calculated data especially on power and energy consumption, conclusions were made that point out the difference in performance as well as the advantages and disadvantages of the vapor compression system with and without the VFD. Based on the data that can be seen from the previous chapters, it can be concluded that: 

As the load increased the temperature also increased. As the temperature increased, the frequency of the compressor also increased, and vice-versa.

76



For the variable frequency driven vapor compression system, temperature tend to  be controlled depending on the load inside the space. The system maintained an ideal temperature depending on the heat sensed inside the room. Frequency ranges from 45 Hz to 60 Hz.



For the conventional vapor compression system, the operation without VFD showed constant frequency for the compressor which was 60 Hz so the temperature was dependent on what was set by the thermostat which operated in an on-off control.



Voltage was not dependent on the load inside the air-conditioned space as well as on the frequency of the compressor. As frequency and temperature increased or decreased, voltage was still constant.



Electric current was not dependent on the load inside the air-condtioned space as well as the frequency of the compressor. As frequency and temperature increased or decreased, electric current was still constant. There was a percentage difference to the current with VFD to that of without due to friction losses and voltage dropped.



Power consumption was dependent on the load change inside the room. As the load increased, the power consumption also increased, and vice-versa.

- For the vapor compression system without the VFD, the power consumption was constant even if the temperature increased or decreased because compressor frequency was still constant at 60 Hz standard.

- For the variable frequency driven vapor compression system, the power consumption increased as the load increased, and vice versa. It can also be noticed that power consumption with VFD was greatly smaller compared to that without. 77

Because the VFD maintained the desired compressor frequency depending on the room temperature as sensed by the thermistor through the microcontroller. 

The variable frequency driven vapor compression system (Amatrol T7082 Thermal Systems with VFD) had a lower power consumption compared to the conventional vapor compression system (Amatrol T7082 Thermal Systems without VFD).



Variable frequency driven compression system had a higher first cost but is more energy efficient compared to the conventional.

- The conventional vapor compression system worked in an on-off control wherein a certain room temperature was set by the thermostat. As the room was cooled and reached the set temperature, the compressor turned off and turned on again at another set temperature for it to turn on. The turning on and off the compressor resulted to higher peak loads during start up which led to higher energy consumption.

- The variable frequency driven vapor compression system worked in variable frequency control. In this control, the compressor‘s frequency was  varied. This drive allowed the system to match the speed of the motor-driven equipment to the  process requirement. Frequency was varied by the VFD depending on the temperature sensed by the thermistor. The thermistor sent the signal to the microcontroller which automated the VFD. Possible sources of errors and percentage differences on the experiments and testings done in this study includes: (1) the measuring devices such as the digital thermocouple and the  power meter; (2) human error; (3) equipment failure; (4) changing environment temperature; (5)

78

inefficiency of the reciprocating compressor at low frequencies; (6) open spaces in the air conditioned space and; (7) friction losses and voltage drops. 6.2 Recommendations

For the improvement of this study about the comparative analysis of a conventional vapor compression system to a variable frequency driven vapor compression system for air conditioning application, the following recommendations are made: 

Use a scroll compressor instead of a reciprocating compressor for the system. The reciprocating compressor can be run by the VFD but is not that efficient because it is not designed for variable frequency operation. This is why the compressor of the Amatrol T7082 Thermal Systems (2413 BTU/hr ± 28.6 BTU/hr or approximately 1 HP) can only work at a range of 45 Hz-60 Hz. The compressor had failure at frequencies lower than 45 Hz. Scroll compressors are greatly more expensive compared to reciprocating compressors but is efficient at variable speed operation.



Test the VFD-microcontroller set-up in an actual room and in an actual 1hp window type air conditioner (The VFD purchased is designed for up to 2 hp capacity. Dividing the capacity to a safety factor of square root of 3 yields to 1 hp capacity).



Directly connect the VFD (automated by the microcontroller) to the compressor of the vapor compression system. In this study, it is only possible to integrate the VFD to the system by plugging the plug of the Amatrol T7082 Thermal Systems to the socket connected to the supply from the VFD which is directly plugged to the 220 volts main voltage supply. This set up resulted to percent differences from voltage drops and friction losses in the wires.

79



Improve the design and construction of the microcontroller by putting additional relays to the circuit. Also, improving its temperature sensibility by putting additional thermistors (number of sensor depending on the area of the air-conditioned space) to the circuit design.



Maximize certain features of the Delta VFD-B Series Variable Speed AC Motor Drive  possible to be integrated in the variable frequency technology such as safe motor start,  passwords, 4 acceleration/deceleration times and 2 S-curve selections, automatic energy saving, adjustable V/F curve and automatic voltage regulation, automatic adjustment of acceleration/deceleration time, auto tuning and sensorless vector control, sleep / revival function and master / auxiliary.



Try other automation controls for the VFD particularly the Programmable Logic Controllers (PLC).



For the pursuit of furthering the prototype, it is suggested that a variable frequency driven vapor compression system in a window-type air-conditioner be commercialized. Because of its effective ability to lessen energy consumption, it has a potential strength to  penetrate the market.

80

APPENDIX A

Drawings / Figures

Figure 1: Typical VRF configuration in an office building.

Figure 2. Heat Recovery VRF System 81

Figure 3 page 337 This typical on-off furnace thermostat has a 3oF temperature swing during its cycle. This is enough temperature swing to be noticeable.

Figure 4 page 337 This furnace is controlled by a variable-speed fan motor and firing rate. It has only a 1oF swing. This will not be noticeable

82

.

Figure 5 page 339The rectifier moved all of the sine wave to one side of the graph.

Figure 6 page 340 Pulsating DC enters the capacitor bank and straight line DC leaves.

83

Figure 7 page 340 When the control system (computer) sends a signal to the base connection the transistor turns on and then turns it off when the signal is dropped.

Figure 8 page341 The choke coil stabilizes current flow

84

Figure 9 page339 A simple diagram of a variable-speed motor drive

Figure 10 page 341Sine coded, pulse with modulation

85

Figure 11 Amatrol T7082 Thermal System S ystem and Amatrol T7083 Environmental Application System

86

Figure 12 Brochure of Hitachi‘s newest Inverter Scroll Compressor Window Type AC 87

Figure 13 NTC Thermistors

Figure 14 PTC Thermistors

88

APPENDIX B

Microcontroller Program

' {$STAMP BS2}

x VAR Word

temp VAR Word tempdiff VAR Word time VAR Word timediff VAR Word tempdiffmem VAR Word

sense0: time = 0 HIGH 8 RCTIME 8, 1, temp DEBUG ? temp time = 0

'SPEEDS speed15:

' 45 hz

PAUSE time HIGH 0 HIGH 1 89

HIGH 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed1 IF tempdiffmem = 0 THEN speed15

speed1:

' 46 hz

PAUSE time LOW 1 LOW 2 LOW 3 HIGH 0 GOSUB sense IF tempdiffmem = 1 THEN speed14 IF tempdiffmem = 0 THEN speed15

speed14:

' 47 hz

PAUSE time LOW 0 HIGH 1 HIGH 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed2 IF tempdiffmem = 0 THEN speed1

90

speed2:

' 48 hz

PAUSE time LOW 0 LOW 2 LOW 3 HIGH 1 GOSUB sense IF tempdiffmem = 1 THEN speed13 IF tempdiffmem = 0 THEN speed14

speed13:

' 50 hz

PAUSE time LOW 1 HIGH 0 HIGH 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed3 IF tempdiffmem = 0 THEN speed2

speed3:

' 51 hz

PAUSE time LOW 2 LOW 3 HIGH 0 HIGH 1 GOSUB sense 91

IF tempdiffmem = 1 THEN speed12 IF tempdiffmem = 0 THEN speed13

speed12:

' 52 hz

PAUSE time LOW 0 LOW 1 HIGH 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed4 IF tempdiffmem = 0 THEN speed3

speed4:

' 53 hz

PAUSE time LOW 0 LOW 1 LOW 3 HIGH 2 GOSUB sense IF tempdiffmem = 1 THEN speed11 IF tempdiffmem = 0 THEN speed12

speed11:

' 54 hz

PAUSE time LOW 2 HIGH 0 92

HIGH 1 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed5 IF tempdiffmem = 0 THEN speed4

speed5:

' 55 hz

PAUSE time LOW 1 LOW 3 HIGH 0 HIGH 2 GOSUB sense IF tempdiffmem = 1 THEN speed10 IF tempdiffmem = 0 THEN speed11

speed10:

' 56 hz

PAUSE time LOW 0 LOW 2 HIGH 1 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed6 IF tempdiffmem = 0 THEN speed5

93

speed6:

' 57 hz

PAUSE time LOW 0 LOW 3 HIGH 1 HIGH 2 GOSUB sense IF tempdiffmem = 1 THEN speed9 IF tempdiffmem = 0 THEN speed10

speed9:

' 58 hz

PAUSE time LOW 1 LOW 2 HIGH 0 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed7 IF tempdiffmem = 0 THEN speed6

speed7:

' 59 hz

PAUSE time LOW 3 HIGH 0 HIGH 1 HIGH 2 GOSUB sense 94

IF tempdiffmem = 1 THEN speed8 IF tempdiffmem = 0 THEN speed9

speed8:

' 60 hz

PAUSE time LOW 0 LOW 1 LOW 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed8 IF tempdiffmem = 0 THEN speed7

sense: HIGH 8 PAUSE 1 RCTIME 8, 1, temp DEBUG ? temp IF temp => 800 THEN cooling IF temp < 800 THEN heating

cooling: tempdiff = temp - 800 tempdiffmem = 0 GOTO comptime

95

heating: tempdiff = 800 - temp tempdiffmem = 1 GOTO comptime

comptime: time = (tempdiff*10/30)*25 DEBUG ? temp DEBUG ? tempdiff DEBUG ? tempdiffmem DEBUG ? time RETURN

96

APPENDIX C Gantt chart Task

Description

1

Thesis 1 Research Title

2 3 4

Introduction Review of Related Literature and Related Studies Methodology

5

Theoretical Considerations

6

7

Oral Presentation Thesis 2 Further research and study VFD and microcontrollers and PLCs

8

Purchase the VFD and Program the frequencies And everything that is needed

9 10

11 12 11

2

3

4

5

6

7

8

9

10

Weeks

1

2

3

4

5

6

7

8

9

10

Weeks

1

2

3

4

5

6

7

8

9

10-13

Program the microcontroller Integrate the Microcontroller to the VFD/Inverter and test until program works

12

Reserve the HVAC Lab for testing using the Amatrol T7082 Thermal Systems

13

Create a set up to integrate the VFD-microcontroller system to the Amatrol Thermal Systems

16

Study the Amatrol T7082 Thermal Systems and the Environmental Application System, Create heat loads Sources (light bulbs) Data Gathering, Computation, and Evaluation for the Amatrol Thermal System with VFD and without the VFD Formulation of Conclusion, Recommendation, and Discussion of Results

17

Final Presentation / Defense

15

1

Purchase equipments to construct a Microcontroller And study about microcontrollers Design Circuit Diagram and construct the Microcontroller Integrate the thermistor to the microcontroller and calibrate the thermistor in accordance to the  program in the basic stamp 2

Thesis 3

14

Weeks

97

APPENDIX D

Budget Computation

Sponsored Amount: Php. 30,000 by Modair Manila Co. Ltd., Inc. ITEMS (per receipt) 1.) Delta Frequency Inverter VFD015B21A 2HP 220V 2.) 4pcs. Thermistor 100 ohms 3.) 10pcs. Capacitor

4.) Parts 1 5.) Solid and stranded wires 6.) Parts 2 7.) Parts 3 8.) 5pcs. 80DC-149 9.) 10pcs. Diodes 10.) 12pcs. 1N-4004 11.) Digital Thermometer 12.) Materials for Heat Loads Omni receptable E27 3‖ white 3pcs Omni 1 way switch P3 ST3 CLMB/Philflex flat cord 13.) Materials for Microcontroller 1 BASIC Stamp II PC 401 6pcs OMI-55-2061 (Relay SPDT) 6pcs WA-SH-105D (Relay DPDT) 2pcs LM7805 3pcs 0.1 microfarads capacitor 9P RS232 (F) RA 15pcs 2N3904 3m #22 stranded wire 14.) Materials for Microcontroller 1 3pcs thermistor 10k 3pcs Mylar capacitor 0.1 microF 15.) Materials for Microcontroller 1 12 pcs 1/8 12 pcs 2N3904 ICN-24

SUPPLIER GOTYCO Controls Center, Inc.

PRICE (Php) 13,450

DEECO DEECO DEECO DEECO DEECO DEECO DEECO DEECO Liongco Electronics CJR Hardware & Electrical Supplies ACE Hardware

140 180 50 266 135 254 90 15 12 1, 510 317.75

Alexan Commercial

4, 963.25

Alexan Commercial

55.50

Alexan Commercial

44.50

  

        

 

  

98

switch 16.) Plug 17.) 4pcs Bolts and Nuts x8 18.) 2pcs Plastic Light Bulb Stand 3x3 19.) Other materials 50 Watts Light Bulb 100 Watts Light Bulb 3pcs. Light bulb holder TOTAL 

Adams T.S JS Lim Prop. GKH Building Supply GKH Building Supply GKH Building Supply

35 14 64 130

  

Php. 21,726 - Php. 30,000

Cash / Investment Remaini ng Bal ance / Savin gs

Php. 8,274

99

REFERENCES

Afify, Ramez. June 2008. Designing VRF Systems. ASHRAE Journal . pp. 52-55 Amatrol, Inc. Environmental Applications Learning System –  T7083 Retrieved: September 30, 2011 from http://www.amatrol.com/product/t7083.html Amatrol, Inc. Thermal Learning System –  T7082 Retrieved: September 30, 2011 from http://www.amatrol.com/product/t7082.html AuCom Electronics Ltd., Variable Frequency Drives (MD) –  VFD: Operation Retrieved: September 30, 2011 from http://www.aucom.com/vfd-operation.html Aynur, T.N., Y. Hwang, and R. Radermacher. 2008. Experimental evaluation of the ventilation effect on the performance of a VRV system in cooling mode — Part I: Experimental evaluation, HVAC&R Research 14 (4): 615 – 630. Aynur, T.N., Y. Hwang, and R. Radermacher. 2008. Simulation evaluation of the ventilation effect on the performance of a VRV system in cooling mode — Part II: Simulation evaluation,  HVAC&R Research 14 (5): 783 – 795. Aynur, T.N., Y. Hwang, and R. Radermacher. 2009. Simulation comparison of VAV and VRF air conditioning systems in an existing building for the cooling season, Energy and Buildings 41 (11): 1143 – 1150 Aynur T.N., Y. Hwang, and R. Radermacher. 2009. Simulation comparison of VAV and VRF air conditioning systems in an existing building for the cooling season,  Energy and Buildings 41 (11) : 1143 – 1150. Aynur, Tolga N. 2010. Variable refrigerant flow systems: A review.  Energy and Buildings 42:1106 – 1112 Burt C., B. Busch, F. Gaudi, X. Piao, NFN Taufik. October 2006. Electric Motor Efficiency Under Variable Frequencies and Loads. Irrigation and Training Research Center. California Polytechnic State University. San Luis Obispo, CA 93407-0253 805-756-2379 pg.1 Carrier Corporation, October 2005. Variable Frequency Drive: Operation and Application of VFD Technology Retrieved: September 29, 2011 from http://www.docs.hvacpartners.com/idc/groups/public/documents/marketing/wp_varfreqdrive.  pdf Cole, Kenneth S. February 25, 1957. Thermistor Thermometer Bridge: Linearity and Sensitivity for a Range of Temperature. American Institute of Physics. 0034-6748. pp.2 Cooper, Crystal. 2009, June 21. HVACR: About thermistors. Retrieved: October 1, 2011 from http://www.brighthub.com/engineering/mechanical/articles/27687.aspx#imgn_0 Delta Electronics, Inc. Delta VFD-B Series Variable Speed AC Motor Drive User Manual Electronics Information Online (2006), Electronics Information –  Microcontroller Retrieved: September 30, 2011 from http://www.electronics-manufacturers.com/info/circuits-and  processors/microcontroller.html 100