BS Load Calc[1]

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Tables of contents 1. Legislation, statutory regulation in Hong Kong & relevant

standard for electrical services

All of building services system is designed in accordance to legislation, statutory regulation in Hong Kong , relevant standards and guidance listed in the followings. Services Electrical

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BS 7671 – Requirements for Electrical Installation. Guide Books of Chartered Institute of Building Services Engineers. General Specification for Electrical Installation in Government Buildings, Hong Kong and General Requirement for Electrical Contract/Sub-contract/Quotation let by Building Development Department, Hong Kong, 1984 edition. (E.G.S) Code of Practice for the Electricity (Wiring) Regulations issued by EMSD 1997 edition. Supply Rules of Hong Kong Electric Co., Ltd.

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Code of Practice for Energy Efficiency of Electrical Installations (Draft)

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Chartered Institute of Building Services Engineers (CIBSE) Technical Memoranda TM12 Chartered Institute of Building Services Engineers (CIBSE) Technical Memorandum No.5 Chartered Institute of Building Services Engineers (CIBSE) Code for Interior Lighting BS5266, Part 1, Code of Practice for Emergency Lighting.

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Code of Practice for Energy Efficiency of Lighting Installations (Draft)

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Code of Practice for minimum Fire Service Installations and Equipment and relevant circular letters issued by the Fire Service Department (COP/Fire)

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Regulation of Environmental Protection Department.

Lightning Protection

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BS6651, Code of Practice for Protection of Structures against lightning.

Lift and escalator

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Code of Practice on the Design and Construction of Lifts and Escalators, EMSD 1993. (COP/Lift) General Specification for Lift and Escalator Installation, in Government

Lighting

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Emergency Generator

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Buildings, Hong Kong, 1984 edition.

Closed circuit television System (CCTV)

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Building Regulation, CAP 123

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General Technical Specification for Monochrome closed circuit television systems, Specification No .ESG 14 Issue No. 2 – Electronics Division, EMSD.

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General requirements for electronics contracts, Specification No. ESG01, Issue No. 6 – Electronics Division, EMSD

Security System

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Communal aerial broadcsat distribution system (CABD)

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General Technical Specification for Communal aerial broadcast distribution systems and aerial distribution systems, Specification No. ESG 17 Issue No. 3-Electronics Division, EMSD

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General requirements for electronics contracts, Specification No. ESG01, Issue No. 6 – Electronics Division, EMSD.

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General specification for Air Conditioning, Refrigeration, Ventilation and Central Monitoring and Control System Installation in Government Building, Hong Kong, 1988 Edition (A/C,\. G.S.)

Building Management System (BMS)

BS 4737 Intruder alarm systems.

2. Electrical load estimation 1. For flats According to ‘Code of practice for electricity (wiring) regulation), the electrical load demand for each flat is calculated as the following table: Purpose of switchgear Air-conditioning for living room (for summer) Air-conditioning for bedroom (for summer) Air-conditioning for bedroom (for summer) Heater for living room (for winter) Lighting for living room & terrace Lighting for bedrooms, bathroom Lighting for kitchen & entrance Lighting for staircase & lav Exhaust fan for kitchen Washing machine Socket outlet for living room Socket outlet for bedrooms Socket outlet for kitchen, entrance & staircase

Rating of Estimated switchgear design current 20A 12A

Diversified Diversified factor current demand 100% 12A

20A

8A

40%

3.2A

20A

8A

40%

3.2A

15A

13A

100%

13A

10A 10A 10A 10A 10A 15A 30A 30A 30A

8A 4A 4A 3A 4A 7A -

66% 66% 66% 66% 100% 100% 100% 30% 30%

5.28A 2.64A 2.64A 1.98A 4A 7A 30A 9A 9A

Overall

89.14A (for summer) 81.24A (for winter)

The main switch for each flat shall be 100A single phase or 30A three phase. However, according to HEC’s supply rule, 30A three phase is recommanded as the main switch rather than 100A single phase because meter for 100A single phase is not available. The electrical load for all flat = 89.14A/3 per flat x 220V x 64 flats = 418.4kVA 2. For shops and kindergarten In reference to ‘COMMERCIAL CODE OF PRACTICE 215 LOAD ASSESSMENT PROCEDURE (REVISION 2)’ issued by China Light & Power Company Ltd., the electrical load is estimated as below: Usage

Location

U.F.A.*1

ADMD*2

(m2) 3

Shops* Shops*3 Shops*3 Kindergarten Total

G/F 1/F 2/F 3/F

254 270 320 212 1056

Estimated Load

(kVA/m2) 0.23 0.23 0.23 0.05*4

(kVA) 58.42 62.1 73.6 10.6 204.72

*1 means Usable Floor Area (U.F.A) *2 means After Diversified Maximum Demand (ADMD) based on COP 215 by CLP *3 Shops is assumed as light metal retail stores. *4 ADMD is included central A/C. 3. For landlord Supply Usage

Qty

Estimated Load Estimated Load (kVA)

AC System Escalators

43.6TR 6 Nos

1.85 kVA/TR @30kVA

80 180

P&D System General Lighting & Power

1 Lot 1000m2 including 20W/m2*5 Mech/F External Lighting, Atrium Lighting 180m2 40W/m2*5 & Facade Lighting Total

60 23.5 7.2 350.7

*5 Data is based on Maximum Allowable Lighting Power Density extracted from Code of Practice for Energy Efficiency of Lighting Installation. 4. For essential Supply Usage

Qty

Estimated Load

Estimated Load (kVA)

Firemen’s Lift FH/HR System Sprinkler System Sump pump Essential Lighting & Power Security & BMS System Total

2 Nos 1 Lot 1 Lot 1 Lot 1 Lot 1 Lot

@40kVA

80 40 20 15 10 10 175

Overall electrical load = (418.4 + 204.72 + 350.7 + 175)kVA = 1138.82kVA However, two factors shall be considered as below: Electrical load Mixed development diversity factor (MDDF) Future extension Total electrical load

1138.82kVA 1.14 15% 1493.0kVA

Total usable floor area = 7600m2 Total demand density = 0.196kVA/m2 So, 1 No of 1500kVA HEC’s transformer is required for the proposed residential building. 3. Generator loading

An emergency generator set is required to handle the following essential loads in case of power failure & fire conditions. If the equipment is started simultaneously, the starting current will be larger. So, in the building, the equipment of essential load is started in sequence and control by BMS to reduce the starting current so as to select a smaller generator. The essential load estimated in (1) = 175kVA Taking a safety factor of 10% for overload and a factor of 30% for future expansion, The total essential load = 175kVA x 1.1 x 1.3 = 250kVA So, a 300kVA generator set is selected. The generator should be operated normally within 15 seconds in case and the capacity of fuel tank should be capable to operate the generator for 6 hours. Based on some manufacturer’s catalogue, the capacity of fuel tank is about 400L. 4. Lightning hazards

Based on BS 6651:1992, Part 2, the overall lightning is calculated as the following to determine whether or not lightning protection is needed. Probability of being struck, P = Ac x Ng x Ka x Kb x Kc x Kd x Ke x 10-6 ,where Collection area, Ac = Area of roof + Area of perimeter of building + Area of four rounded corners formed by quarter circles of building height = LW + 2LH + 2WH + πH2 = 46x12 + 2x46x73 + 2x16x73 + πx732 = 26.3 x 103 m2 No. of flash per km2 per year, Ng = 1.1 Factor for use of structure, K = 1.2 Factor for type of construction, Kb = 0.4

Factor for contents (or consequential effects), Kc = 0.3 Factor for degree of isolation, Kd = 0.4 Factor for type of terrain, Ke = 0.3 So, P = 26.3 x 103 x 1.1 x 1.2 x 0.4 x 0.3 x 0.4 x 0.3 x 10-6 = 5.0 x 10-3 The probability of risk (5.0x10-3) is greater than the critical risk (10-5) so that lightning protection is necessary. And, the actual design of the installation is illustrated by drawing no. EE-EP-RF 5. Earthing system In accordance with BS 7671, the earthing loop impedance shall not be greater than 0.5 Ω Due to the site constraint, the plate electrode and tape electrode cannot be used as the earthing conductor. The most suitable and economic way is to use the rod electrode. The following calculation is to determine the no. of rod electrode and the size. Resistance of rod electrode, where L = length of rod, d = diameter of rod, ρ = soil resistivity Code 12C of COP electricity (wiring) regulation stated that the diameter of rod electrode should not be less than 12.5mm. The standard size of rod electrode in the market is 12.5mm & 15mm. After site visit, the soil in the Wan Chai is marshland. The soil resistivity is around 4 Ω-m. Consider a rod electrode of 4.5m length and 15mm diameter, the resistance = = 0.9596 Ω so that 2 rod electrodes in parallel is required to maintain 0.5 Ω earth loop impedance. And, the spacing between the earth pits shall be more than 9m (2x4.5m) to avoid the return loop. 6. Cable sizing In this design report, the cable sizing procedure is referring to Code of Practice for Energy Efficiency of Electrical Installation (Draft). •

To determine the design current Ib, nominal rating of protective device In

•

To calculate the min. tabulated value of current It(min) as the below formula: , Ca = Correction factor for ambient temperature (Assume the ambient temp = 35 0C) Cg = Corection factor for grouping Ci = Correction factor for thermal insulation

Note that all correction factor is referring to Appendix 4 of IEE Wiring Regulation (16th Edition) • • •

To select a suitable size It of conductor which satisfy It To find effective current-carrying capacity Iz (Iz = It x Ca x Cg x Ci) and ensure that To calculate the voltage drop along the conductor and determine whether or not cable size selected is acceptable. For sub-main circuit, the max. voltage drop is 1.5% and for final circuit, the max. voltage drop is 2.5%. V.D. = r x p.f. x k x Ib x L , where r = Voltage drop per ampere per metre at the conductor operating temperature p.f. = Power factor (assume 0.85) k = correction factor of operating temperature , where tl = operating temperature tp = max. permitted conductor operating temp , ta = expected ambient temp. (assume 35 0C)

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To calculate the percentage copper loss with respect to the total active active power transmitted.

The following table (EE-Table 1) shows the cable size.

7. Vertical transportation

1. Lift Performance In accordance to the CIBSE Guide D, the lift performance is calculated as the following table: Number of floor Capacity of lift car Number of passenger Floor height Highest reversal floor Probable number of stop Total lift travel Contract speed Acceleration /deceleration Upward running time Downward running time Door opening/closing time for centre door Door operating time Passenger transfer time Round trip time (RTT) No. of lift cars Waiting interval Handling capacity in 5 minutes Total occupants Peak arrival rate

9 9 passengers 7.2 passengers 6m 7.34 5.146 54m 2.5m/s 1m/s2 47.33 seconds 26.6 seconds 2.5 seconds 30.73 seconds 10.8 seconds 115.46 seconds 2 57.73 74.83 6 persons/flat x 64flats = 384 19.49%

The lift performance is also simulated by computer software HEVACOMP (Results please refer to ) From the CIBSE Guide D, the recommended arrival rate and waiting interval are 57% and 40-90s for flats. For the proposed building, the performance is satisfactory.

2. Escalator performance

According to CIBSE Guide D,

the escalator handling capacity, Cp = 60 v k s , where v = horizontal speed (m/s) k = average occupant density (people/step) s = number of step (steps/m) Due to architectural constraint, the physical data of escalator: inclination of escalator = 300 height of escalalator = 4m length of escalator = 6.9m no. of step = 6900mm/400m = 17.25 width of step = 800mm k = 1.5 h = height of step = 4000/17.25 = 231mm s = 1000mm/231mm = 4.33 the speed = 0.5m/s (max. for 300) the handling capacity = 60 x 0.5 x 1.5 x 4.33 = 194.85 person/min From the CIBSE Guide D, the handling capacity for kindergarten is 92 person/min. For the proposed building, the performance is satisfactory.

8. Lighting system 1. Shopping arcade corridor for G/F-2/F Physical data of corridor, width = 2m, height = 4m Data of luminaire: Manufacture = BEGA Model no. = 6743 Type = Wall mounted discharge lamp with asymmetrical reflector

Lamp = 250W metal halide lamp (MBI-E) Lumen output = 17000lm Mounting height of luminaire = 3.5m The angle of illuminating area = 300-00 The following calculation is based on technical data of BEGA 6743 the spacing between luminaires = 4m (obtained from cone diagram) the average illuminance = 265 lx (obtained from cone diagram) the luminous intensity (angle = 300) = 360 cd/klm x 17 lm = 6120 cd the horizontal illuminance at the opposite side of corridor = 6120cd/(22+3.52)x0.8 = 302 lx the luminous intensity (angle = 00) = 300 cd/klm x 17 lm = 5100 cd the horizontal illuminance below the light fitting = 5100cd/(3.5)2x0.8 = 333 lx (Assume the light loss factor = 0.8 & neglect the reflectance of walls due to open corridor) 2. Canopy Physical data of corridor, width = 3m, height = 4m Data of luminaire: Manufacture = BEGA Model no. = 6180 Type = Recessed ceiling downlight c/w aluminium refelctor Lamp = 80W metal halide lamp (MBF) Lumen output = 4000lm Mounting height of luminaire = 4m The angle of illuminating area = -200-200 The following calculation is based on technical data of BEGA 6743 the spacing between luminaires = 4m (obtained from cone diagram)

the average illuminance = 80 lx (obtained from cone diagram) the luminous intensity (angle = 300) = 360 cd/klm x 4 lm = 1440 cd the horizontal illuminance at the side of canopy = 1440cd/(1.52+42)x0.8 = 63 lx the luminous intensity (angle = 00) = 600 cd/klm x 4 lm = 2400 cd the horizontal illuminance below the lighting fitting = 2400cd/(4)2x0.8 = 120 lx (Assume the light loss factor = 0.8 & neglect the reflectance of walls due to open corridor) 3. Open atrium/corridor for L1-L5 Data of luminaire: Manufacture = THORN Model no. = DLC 250/400 Type = Narrow bam medium bay lighting Lamp = 250W/400W high pressure sodium lamp (SON-E) Lumen output = 25500/45000 lm Power input = 260W/410W per luminaire The illuminance level is simulated by OPTILUME INTERIOR V3.03 by THORN LIGHTING LTD. And the results is summarised as below tables Floor L1

Mounting height above floor level 12m

Displacement from Nos. of corridor luminaire 3.5m 5

Type of luminaire

L2

12m

2.5m

5

2450W

L3

12m

2m

5

2450W

L4

6m

2m

5

2450W

L5

6m

1m

5

2450W

4. Shops Physical data of typical shop: 9m(L) x 6m(W) x 4m(H) Data of luminaire: Manufacture = SIEMENS Model no. = CR370SA-cent04-S70T

Direct illuminance Power 2450W

Type = Sealed-frame luminaire with dished triumph lens Lamp = 70W high pressure sodium lamp (SON-T) Lumen output = 5900lm Mounting height of luminaire = 3.3m By using lumen method, According to CIBSE Lighting Guide LG1(The Industrial Environment), the standard illuminance is 500lx. Assume UF = 0.5 & LLF = 0.7 nos. required So, the decision is made to use N=15 luminaires. (3 columns of 5 pcs each). The spacing between each luminaires = 1800mm The power input = 15x87W = 1305W Lighting power density = 24W/m2 The results is also simulated by manufacturer software SILICHT V4.1. Appendix Appendix - P.