Chilled Water Installations, Dubai, UAE 23.05.2016

IMI Hydronic Engineering Technical report Office 2107, Jafza View 19, PO Box 262611, Jafza, Dubai, U.A.E Tel +971 (0) 4 8864500 Fax +971 (0) 4 8864500 www.imi-hydronic.com

CONTROL PHILOSOPHY FOR CHILLED WATER INSTALLATIONS

23rd of May 2016

DISTRICT COOLING CONNECTION (ETS ROOM): Most of the current District Cooling Systems are variable flow, thus subject to differential pressure variations which occur at partial load conditions. In this report we refer to DC systems with Independent Building Connection, where each load (building) is connected with the set of Plate Heat Exchangers (PHEX). While manual balancing, as a typical solution shown on Fig. 1, is essential and effective in order to achieve PHEX design flow rate, it is important to note that the same cannot be obtained at partial loads. The static balancing valves (DRV) do not compensate for any stabilization of ’differential pressures’ occurring at partial and varying load conditions.

2 Fig. 1. Typical PHEX arrangement That’s why DC system is subject to overflow and underflow scenarios during most part of the year. This leads to supply & return water temperature fluctuation and poor indoor conditions of the building resulting on low system delta T, hence increase in energy cost apart from many other limitations. Recommendations: We recommend use of Pressure Independent Balancing & Control Valves (PIBCV) with adjustable Kvs and EQM characteristic (TA-FUS1ON-P model) on the primary side of each Plate Heat Exchanger instead of typically proposed control valve and DRV, as shown on Fig. 2. Each valve shall be equipped with modulating actuator. PIBCV selection shall be based on design flow rate, available differential pressure. Actuator selection shall be based on required closing force of the PIBCV, power supply voltage, control and feedback signals provided by BMS supplier. Once selected and installed, the Kvs value of PIBCV should be adjusted to required value in order to regulate design flow rate and maintain it at valve’s fully open position and design load conditions. Differential Pressure Controller of PIBCV maintains a constant differential pressure across the control part of the valve, thus provides good valves authority at any load conditions. We recommend equipping of the hot (secondary) side of each PHEX with Balancing valve (VODRV) for proportional balancing of the plate heat exchangers and on/off Motorized Butterfly Valve (MBTV) to connect/disconnect each PHEX.

2

Fig. 2. PHEX arrangement with PIBCV If the flow rates for each Plate Heat Exchanger are higher than 50 l/s, we recommend 2 or 3 numbers of Pressure Independent Balancing & Control Valves to be installed in parallel for each PHEX, as shown on Fig. 3.

3

Fig. 3. PHEX arrangement with set of PIBCVs Primary side of PHEX to be controlled by set of connected in parallel 2-way Pressure Independent Balancing & Control Valves. PIBCV valve shall be equipped with modulating actuator in order to provide enough closing force at maximal available differential pressure. Both PIBCVs will be controlled simultaneously to work as a pair in order to avoid distortion of the total EQM characteristic. The final number of valves in parallel shall be evaluated as a division of the total flow rate for PHEX by 50-55 l/s (as a maximum recommended flow rate for the PIBCV). The use of few PIBCVs in parallel gives: • • • •

3

much accurate modulating control especially at the partial load conditions, better rangeability of the set of the valves compared to only one device, control redundancy (backup), easy service & maintenance without system shut down.

Operation sequence: The BMS shall take over the operations of the secondary pumps and Pressure Independent Balancing & Control Valves in Auto mode. Temperature sensors shall be located in the supply and return water lines of the Primary and Secondary sides of each PHEX. The temperatures shall be continuously monitored and controlled by PLC/DDC controller. The Pressure Independent Balancing & Control Valve should be set to maintain the differential temperature in the primary circuit. When demand chilled water flow in the secondary circuit is less than supply flow rate from the primary side and the temperature difference will decrease the set limit, BMS shall send a signal to the actuators in order to close the Pressure Independent Balancing & Control Valves in sequence until primary delta T reaches the set value. When the demand chilled water flow in the secondary circuit is more than supply flow rate from the primary side and the temperature difference will increase the set limit, BMS shall send a signal to the actuators in order to open the Pressure Independent Balancing & Control Valves in sequence until primary delta T reaches the set value. The set point of the secondary pumping station to be controlled by the signal from differential pressure sensor (DPS) installed on the index circuit/branch (to be submitted with Hydronic Calculation). Temperature difference between T3 and T4 equal to 9oC has to be considered in the control sequence of the secondary pumping station and maintained by BMS. Balancing valves should be equipped with test points in order to provide flow, differential pressure, 4 on site. They can be proportionally balanced during temperature and power (cooling load) measurement commissioning using TA Hydronics Methodology (TA Diagnostics, TA Wireless) with TA-SCOPE balancing instrument. TERTIARY PUMPING STATIONS: In order to avoid interactivity between Secondary and Tertiary pumping stations, we recommend modification of the direct connection to the auto adapting variable flow decoupling circuit (as shown on Fig. 4).

Fig. 4. Connection details for the Tertiary pumping station The Differential Pressure Control Valve (DPCV) keeps constant and very low flow (1% of design flow rate for the load) through the bypass. Secondary flow rate is automatically adapted to the tertiary flow variations. Both secondary and tertiary flow rates are variable. This circuit was designed for supply water temperature preserving (secondary supply water temperature will remain unchanged). 4

Auto adapting variable flow decoupling circuit is entirely self-acting. It has to be equipped with robust Differential Pressure Control Valve for accurate control and long lifetime. We recommend pilot operated DPCV model TA-PILOT-R. Differential pressure stabilized through the bypass (ΔPAB) can be deducted from needed pump head in the tertiary side. This circuit provides optimization of the Tertiary pumping station since available differential pressure from the Secondary pumping station is directly transferred to the Tertiary side. Available differential pressure for connection of each Tertiary station can be calculated during the Hydronic calculation with the help of HySelect software. Balancing valve (VODRV) in the bypass should be sized for qB that is 1% of the design tertiary flow rate qT. SMALL TERMINAL UNITS: Each Fan Coil Unit to be controlled by 2 port Pressure Independent Balancing & Control Valve (model TBV-CMP or KTCM512) as shown on Fig. 5 with the following features: • stroke of 4 mm, • EQM characteristic, • modulating actuator in order to satisfy required indoor climate conditions at any system load variations, • direct flow measurement based on Kv-methodology.

5

Fig. 5. Connection details for group of FCUs. Design flow rates will be adjusted on every valve based on presetting given in the PIBCV selection and actual flow rate is measured with TA-SCOPE balancing instrument in order to provide design flow rate for each FCU at full load conditions and avoid over/under flows in the consumption/dissipation chilled water side. MEDIUM AND LARGE TERMINAL UNITS: Air Handling Units (and also secondary plate heat exchangers or other medium terminal units) to be controlled by 2 port Pressure Independent Balancing & Control Valves (model TA-FUS1ON-P) with adjustable Kvs and EQM characteristic (as shown on Fig. 6). PIBCV will be equipped with MC55/MC100 Modulating actuator in order to provide accurate flow control and enough closing force at maximal available differential pressure.

5

Fig. 6. Connection details for AHU. Design flow rates will be adjusted on every PIBCV based on presetting given in the PIBCV selection and actual flow rate is measured with TA-SCOPE balancing instrument in order to provide design flow rate for each AHU at full load conditions and avoid over/under flows in the consumption/dissipation chilled water side. Pressure Independent Balancing & Control Valves from IMI Hydronic Engineering are combining and not compromising functions of control valve, balancing valve and differential pressure controller in one body. The Kvs value of PIBCV will be adjusted to required value in order to regulate design flow rate and maintain it at valve’s fully open position and design load conditions. Differential Pressure Controller of PIBCV maintains a constant differential pressure across the control part of the valve, thus provides good valves authority at any load conditions, even in circumstances where the inlet pressure is very unstable. 6 FUTURE CONNECTIONS: If CHW system commissioning and balancing require flow rate and differential pressure limitation for future connections and also verification that installed pumping stations can deliver required flow rate to every part of the entire installation, we recommend the following arrangement for stub out connections. Future extensions can be equipped with balancing valve (VODRV) installed on the supply line and differential pressure control valve (DPCV) installed on the return (as indicated on Fig. 7).

Fig. 7. Connection details for future loads VODRV has to be sized as per design flow rate for future extension and ΔP = 3kPa with presetting close to full opening. DPCV has to be sized as per design flow rate and ΔPmin = 5kPa, DPCV spring range has to be selected with respect to expected circuit (future load) pressure drop. Commissioning of the Shall & Core will be done in two steps: 1) VODRV has to be adjusted to presetting which, at design flow has the pressure drop equal to sum of retail unit (load) pressure drop and pressure drop across balancing valve at fully open position and design flow (at least 3 kPa). Isolation valve (IV) has to be fully 6

open. DPCV has to be adjusted to design flow using balancing valve as a flow measuring device. 2) When the retail tenant will be connected balancing valve (VODRV) has to be adjusted to hand wheel setting which, at design flow provides pressure drop equal to 3kPa. Isolation valve should be closed. Retail unit flow rate will be maintained dynamically regardless of other circuit activity or pump speed changes. When future loads get connected to existing buildings, installed PIBCVs and DPCVs will see the variation in differential pressure and will dynamically move to adjust to the new situation. Hence the balancing of the branches will not be affected and thereby do not require any re-adjustment. PRESSURIZATION EQUIPMENT: Each individual CHW Zone should be equipped with the pressurization unit containing expansion vessel(s), buffer vessel, pumps, break tank and all controls, interlocks and ancillary equipment necessary to maintain the system static pressure in accordance with the operating conditions (as shown on Fig. 8). The pressurization unit shall be connected to the suction side of the pumping station if it is possible, however other locations are also acceptable, but requires detailed selection for correct static pressure maintenance. Each unit shall be provided with sufficient number and capacity of expansion vessels. These shall handle the full expansion volume of the system from normal cold fill or ambient conditions to normal working temperature and minimal water reserve. We recommend the use of expansion and buffer vessels with butyl rubber bladder. 7

Fig. 8. Pressurization unit and Vacuum Degasser The actual system water contents and the capacity of the expansion vessels, buffer vessel and break tank shall be calculated by the contractor to achieve and accept the total system contraction/expansion volume of water. Instead of indicated on the drawings air separators, we recommend the use of pressure-step Vacuum degasser as a standalone device or integrated part of the pressurization unit in order to remove air from a closed water system. The vacuum degasser shall be selected based on the system volume. Where a single degassing unit cannot deal with the system volume separate multiple degassers shall be installed in parallel. The feed line to the deaerator shall be provided with dirt separator.

7

The pressure step degasser works on the basis of exposing part of the system water to a vacuum which forces all dissolved gases from the water. These gases then will be expelled via an automatic air vent. Once the water sample has been deaerated it will be fed back in to the main system. This cycle will be repeated every 30 seconds to gradually remove all air from the system. IMI Hydronic Engineering has a wide range of pump based pressurization units with combined function of water make-up and vacuum degassing called Transfero TV Connect and Transfero TI (fig. 9.)

Fig. 9. Pump based pressurization units Transfero TV Connect and Transfero TI Transfero is a precision pressure maintenance device recommended in high rise installations where high 8 performance, compact design and precision within ± 0.2 bar are required. In the medium performance range they can also be used as combination devices with integrated degassing and water make-up. The pressure is measured on the water side with the pressure transducer PIS and compared to the calculated target value of the BrainCube control. If the pressure falls below this target value, the pump (P1) switches on, and if the pressure exceeds the target value, the spill valve (V1) opens. In systems with 2 pumps and 2 spill valves, switching occurs alternately depending on the load, but with the same level of precision. The water level is measured by the measuring foot LIS, analyzed in the BrainCube and displayed graphically. If it is signaled that the water level has dropped below the minimum, then the pumps are locked. If the temperature in the system increases, then the pressure also rises. The spill valve opens when the target value is exceeded, and system water flows into the airproof butyl bag of the primary vessel. The air between vessel wall and the bag is displaced to the atmosphere through an open vent. If the temperature in the system falls, the pressure also decreases. When the pressure drops below the target value, the pump switches on and pumps the expanded water back into the system. So that the smallest volume changes do not immediately run the pump or spill valve, a small pressure buffer vessel is integrated into the Transfero range. Transfero consists of a TecBox, a primary vessel and optional secondary vessel(s), supplemented by a pressure buffer vessel from the Statico range. The TecBox includes hydraulics and the BrainCube which controls and monitors all processes of precision pressure maintenance, fillsafe water make-up and oxystop degassing. The hydraulics of the Transfero are housed in a steel case and installed on the basement plate. All the hydraulic connections to the primary vessel needed for assembly are included in the delivery scope.

8

The necessary vessel volume can be shared between a primary vessel and optional additional secondary vessel(s). The primary vessel is equipped with a measuring foot for content measurement. The content is indicated on the graphical display of the BrainCube. The primary vessel is connected to the TecBox on the water side. Air sides of both primary and secondary vessels are open to atmosphere. Water is accommodated in airproof butyl bag with extraordinary diffusion tightness that has been proven in countless practical applications and laboratory tests. The vessel can be filled up to 90% of its total volume. If it is signaled that the water content has reached the maximum, then the spill valves are locked. Both primary and secondary vessels are available from 200 up to 5000 l and have maximal operating pressure equal to 2 bar. They are used as open water storage vessels in principle and hydraulically protected against exceeding of pressure higher the maximal limit. In addition to BrainCube protection there is pressure safety valve which protects the vessels in case of failure or leakage of spill valve(s). That is why Transfero stations can be used in HVAC applications with different operating pressures up to 25 bar. Benefits: •

Precision pressure maintenance with tight pressure tolerances ± 0.2 bar.

•

Compact design. Almost the entire vessel volume is available for water acceptance.

•

Speed control permits elastic starting and stopping of pumps, smooth pump operation and system protection against abrupt pressure variations.

•

The pump switching frequency is minimized due to buffer vessel.

•

9 Smaller Vessel size compared to conventional solution.

•

Simple integration of water make-up and degassing.

•

Almost unlimited performance.

•

The BrainCube guarantees fully automatic self-optimizing operation and control of system parameters, shows on graphical display all relevant parameters as well as the digital and analogue display of pressure and water content, sends feedback to BMS via RS 485 interface or 2 volt-free outputs in case of any alarm, stores alarm messages.

ENGINEERING SUPPORT CENTER: Engineering Support Centre (ESC) is a part of IMI Hydronic Engineering. ESC is a centralized technical team to support with complex, intensive and precise HVAC engineering to enhance IMI HE value to our customer and stakeholders. IMI Hydronic Engineering, as leading global provider and expert in hydronic distribution systems and room temperature control, has experience in more than 100,000 projects worldwide, delivering significant energy savings, extending the longevity of the system and ultimately increasing the building value to our customers. ESC covers everything within: • Product selection; • Detailed Hydronic calculation; • HVAC design & redesign; • System re-engineering; • Reducing installation, maintenance and life cycle costs; • Optimization of the energy consumption in the HVAC installation.

9

The expertise of the Engineering Support Center was used in many projects where IMI Hydronic Engineering provided efficient solutions and our products were successfully installed and commissioned. In 2014 – 2015 we have extended our support through ESC to the following projects in the Middle East Region: • City Walk Phase 1, Dubai, UAE • City Walk - The Avenue Phase 2, Dubai, UAE • Nikki Beach Resort, Dubai, UAE • Four Season Hotel, Abu Dhabi, UAE • Musheirab, Doha, Qatar • Al Bandary, Doha, Qatar • IMG Theme Park, Dubai, UAE • Sulaiman Al Habib Hospital, Dubai, UAE • Sheikh Khalifa Medical City, Abu Dhabi, UAE • Kingdom Tower, Jeddah, KSA • Government Agencies Compound, Riyadh, KSA • Dubai Mall Fashion Avenue, Dubai, UAE • Manazir Al Khor, Dubai, UAE • King Fahd Medical City, Riyadh, KSA • King Abdul Aziz International Airport, Jeddah, KSA • Al Suwaidi Hospital, Riyadh, KSA • World Trade Center Residences, Dubai, UAE • Madinat Jumeirah Phase 4, Dubai, UAE • Lusail Marina, Doha, Qatar • Sky Views, Dubai, UAE 10

10

PROPOSED PRODUCTS: TA-MODULATOR (shown in Fig. 10) is Pressure Independent Balancing and Control Valve for Fan Coil Units combining the key hydronic functions of control and balancing in one valve with differential pressure controller. EQM characteristic of TA-MODULATOR allows compensation of non-linear coil characteristic and provides stable and accurate temperature control. The Measuring points enable accurate measurement of flow, differential pressure, temperature, cooling power and available differential pressure.

11

Fig. 10 TA-MODULATOR with TA-SLIDER actuator KTCM 512 (shown on Fig. 11) is a high differential pressure model of Pressure Independent Balancing and Control valve for Fan Coil Units combining the key hydronic functions of control and balancing in one valve with differential pressure controller. KTCM 512 valve has EQM characteristic, measuring points for flow measurement based on Kv-methodology. Maximal differential pressure for the KTCM 512 is 800 kPa (8 bar).

Fig. 11. KTCM 512

11

TA-FUS1ON-P (shown in Fig. 12) is innovative Pressure Independent Balancing and Control Valve for chilled water applications combining the key hydronic functions of control, balancing and differential pressure control in one valve. Adjustable Kvs and inherent independent EQM characteristics allow correct valve sizing and optimum system controllability. The Measuring points enable accurate measurement of flow, differential pressure, temperature, cooling power and available differential pressure. This will simplify system commissioning and also offer key diagnostic feature for trouble shooting. TA-FUS1ON-P valve is equipped with pressure balanced cone that gives possibility to use actuators with smaller closing force. Maximal differential pressure for the TA-FUSION-P is 800 kPa (8 bar).

12 Fig. 12. TA-FUS1ON-P with MC55 and MC100 actuators KTCM 512 and TA-FUSION-P valves have special inline design, robust construction and durable materials (AMETAL, Ductile Iron and Stainless Steel) in order to assure: • High system performance. • Stable and precise control at any load conditions and differential pressure variations. • Accurate flow measurement, easy system commissioning and troubleshooting. • Compact installation. • Low noise generation. Differential pressure control valves from IMI Hydronic Engineering are compact controllers with adjustable set-point for cooling applications. Those DPCVs are particularly effective in situations requiring high differential pressure up to 8 bar and even 16 bar with low noise generation. Differential pressure controllers are required to protect control valves and system branches from large differential pressure variations experienced at varying load on the system. This will give better authority and controllability of control valves which provide a stable and accurate room temperature control throughout the system, whatever the control mode and Dp sensor location were selected. DPCVs help to reduce the risk of noise and cavitation in control valves and other equipment, decrease required actuation close-off force for the control valves that depends on: differential pressure applied on the plug; tension of the return spring if available; frictions in O-rings, seals, etc.

12

Fig. 13. TA-PILOT-R and DA 516 Balancing valves from IMI Hydronic Engineering deliver accurate hydronic performance in cooling & heating applications. All balancing valves are equipped with measuring points that provides accurate measurement of flow, differential pressure, temperature, cooling power and available differential pressure and simplifies the balancing procedure with TA-SCOPE balancing instrument and IMI Hydronic Engineering Methodology (TA Diagnostics, TA Wireless), increases its accuracy and enables troubleshooting and delivers desired differential pressure ensuring accurate balancing. 13

Fig. 14. STAD & STAF

TA-SCOPE is a tough, effective, accurate and easy-to-use balancing instrument for measuring and logging of differential pressure, flow, temperature and power in hydronic systems. TA-SCOPE delivers quicker, more cost-efficient balancing with new TA-Diagnostics and TA-Wireless methods and enables rapid troubleshooting. TA-SCOPE links effortlessly to the HySelect PC software gaining the maximum benefit from recorded data and enabling professional report writing and automatic software upgrades.

13

Fig. 15. TA-SCOPE

14 IMI Hydronic Engineering as a reputable and high We trust this information is of use when evaluating quality supply partner. Should further information or clarifications be required, please do not hesitate to contact the undersigned. Your Faithfully, Roman Yerema Regional Technical Manager - Middle East

14