CODE OF PRACTICE FOR
Energy Efficiency of Electrical Installations
 
 
Foreword

The Code of Practice for Energy Efficiency of Electrical Installations aims to set out the minimum requirements on energy efficiency of electrical installations in buildings. It forms a part of a set of comprehensive Building Energy Codes that addresses energy efficiency requirements on building services installations. Designers are encouraged to adopt a proactive approach to exceed the minimum requirements of this code.
 

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CONTENTS
Paragraph
1.
SCOPE
2.
DEFINITIONS
3. 
GENERAL APPROACH
4.
ENERGY EFFICIENCY REQUIREMENTS FOR POWER DISTRIBUTION IN BUILDINGS
4.1 High Voltage Distribution
4.2 Minimum Transformer Efficiency
4.3 Locations of Distribution Transformers and Main Switchboard 
4.4 Main Circuits
4.5 Feeder Circuits
4.6 Sub-main Circuits
4.7 Final Circuits
5.
REQUIREMENTS FOR EFFICIENT UTILISATION OF POWER
5.1 Lamps and Lurninaires 
5.2 Air Conditioning Installations 
5.3 Vertical Transportation 
5.4 Motors and Drives 
5.5 Power Factor Improvement 
5.6 Other Good Practice 
6.
ENERGY EFFICIENCY REQUIREMENTS FOR POWER QUALITY
6.1 Maximum Total Harmonic Distortion (THD) of Current on LV Circuits 
6.2 Balancing of Single-phase Loads 
7.
REQUIREMENTS FOR METERING AND MONITORING FACILITIES
7.1 Main Circuits
7.2 Sub-main and Feeder Circuits
8.
SUBMISSION OF INFORMATION
SCHEDULE OF FORMS:
FORM EL-l:     Electrical Installations Summary
FORM EL-2:    Electrical Power Distribution Worksheet 
FORM EL-3:    Electrical Power Utilisation Worksheet
FORM EL-4:    Electrical Power Quality Worksheet 
FORM EL-5:    Electrical Metering & Monitoring Worksheet
APPENDICES:
Appendix A: Explanatory Notes and Sample Calculations 
Appendix B: Case Study 

 
1. SCOPE
1.1 The Code shall apply to all fixed electrical installations, other than those used as emergency systems, for all buildings except those specified in Clause 1.2, 1.3 and 1.4 below.
1.2  The following types of buildings are not covered in the Code:
(a) buildings with a total installed capacity of 100A or less, single or three-phase at nominal low voltage; and
(b) buildings used solely for public utility services such as power stations, electrical sub-stations, water supply pump houses, etc.¡@
1.3 Buildings designed for special industrial process may be exempted partly or wholly from the Code subject to approval of the Authority.
1.4 Equipment owned by the public utility companies (e.g. HV/LV switchgear, transformers, cables, extract fans, etc.) and installed in consumers' substations will not be covered by the Code.
1.5  In case where the compliance of this Code is in conflict with the safety requirements of the relevant Ordinance, Supply Rules, or Regulations, the requirements of this Code shall be superseded. This Code shall not be used to circumvent any safety, health or environmental requirements.

 

 
2.  DEFINITIONS

The expressions, which appear in this Code, are defined as follows:-
  'Appliance' means an item of current using equipment other than a luminaire or an independent motor or motorised drive.
'Appliance, fixed' means an appliance, which is fastened to a support or otherwise secured at a specific location in normal use.
  'Appliance, portable' means an appliance which is or can easily be moved from one place to another when in normal use and while connected to the supply.
  'Building' means any building as defined in Building Ordinance Cap. 123.
  'Circuit, feeder' means a circuit connected directly from the main LV switchboard to the major current-using equipment.
  'Circuit, final' means a circuit connected from a local distribution board to a current-using equipment, or to a socket-outlet or socket-outlets or other outlet points for the connection of such equipment.
  'Circuit, main' means a circuit connected from a distribution transformer to the main LV switchboard downstream of it.
  'Circuit, sub-main' means a circuit connected from the main LV switchboard or a rising mains to a local distribution board.
  'Communal Installation' means an installation provided by the building owner as part of the services to the tenants or to comply with a particular statutory requirement.
  'Distribution Transformer' means an electromagnetic device used to step down electric voltage from high voltage distribution levels (e.g. 11KV) to the low voltage levels (e.g. 380V), rated from 200kVA, for power distribution in buildings.
  'Effective Current-carrying Capacity' means the maximum current-carrying capacity of a cable that can be carried in specified conditions without the conductors exceeding the permissible limit of steady state temperature for the type of insulation concerned.
  'Emergency System' means any statutory required system, which is installed for the purpose of fire services as defined in Code of Practice for the Minimum Fire Services Installations and Equipment published by the Fire Services Department.
  'Equipment' means any item for such purposes as generation, conversion, transmission, distribution, measurement or utilisation of electrical energy, such as luminaires, machines, transformers, apparatus, meters, protective devices, wiring materials, accessories and appliances.
  'Harmonic' means a component frequency of a harmonic motion (as of an electromagnetic wave) that is an integral multiple of the fundamental frequency. For the power distribution system in Hong Kong, the fundamental frequency is 50 Hz.
  'Installation' means the wiring installation together with any equipment connected or intended to be connected
  'Load Factor' means the ratio of the average load of a building in kW, consumed during a designated period, to the peak or maximum load in kW occurring in that same period.
  'Maximum Demand' means the maximum power demand registered bv a consumer in a stated period of time such as a month. The value is the average load over a designated interval of 30 minutes in kVA.
  'Meter' means a measuring instrument and connected equipment designed to measure, register or indicate the value of voltage, current, power factor, electrical consumption or demand with respect of time, etc.
  'Non-linear Load' means any type of equipment that draws a nonsinusoidal current waveform when supplied by a sinusoidal voltage source.
  'Power Factor, Displacement' of a circuit means the ratio of the active power of the fundamental wave. in watts, to the apparent power of the fundamental wave, in volt-amperes. Its value in the absence of harmonics coincides with the cosine of the phase angle between voltage and current.
  'Power Factor, Total' of a circuit means the ratio of total active power of the fundamental wave, in watts, to the total apparent power that contains the fundamental and all harmonic components, in volt-amperes.
  'Rated Circuit Current (at Rated Load Condition)' means the magnitude of the maximum current (r.m.s. value for a.c.) to be carried by the circuit at its rated load condition in normal service.
  'Total Harmonic Distortion (THD)' in the presence of several harmonies, is a ratio of the root-mean-square (r.m.s.) value of the harmonics to the r.m.s. value of the fundamental expressed in percentage. In equation form. the definition of  %THD for current is:
 
Where : 
I1= r.m.s. value of fundamental current
Ih= r.m.s. value of current of the hth harmonic order
  'Variable Speed Drive (VSD)' means a motor accessory that enables the driven equipment to be operated over a range of speeds. Electronic types VSD include, but not limit to, current source inverter, cycloconverter, load-commutated inverter, pulse-width modulated, and voltage-source inverter.
  'Voltage, nominal' means voltage by which an installation (or part of an installation) is designated. The following ranges of nominal voltage (r.m.s. values for a.c.) are defined:
 
 
- Extra Low  normally not exceeding 50V a.c. or l20V d.c., whether between conductors or to earth.
- Low normally exceeding Extra Low voltage but not exceeding l000V a.c. or 1500V d.c. between conductors, or 600V a.c. or 900V d.c. between conductors and earth.
- High exceeding Low voltage.

 

 
3.  GENERAL APPROACH
3.1 This Code sets out the minimum requirements for achieving energy efficient design of electrical installations in buildings without sacrificing the power quality, safety, health, comfort or productivity of occupants or the building function.
3.2  As the Code sets out only the minimum standards, designers are encouraged to design energy efficient electrical installations and select high efficiency equipment with energy efficiency standards above those stipulated in this Code.
3.3 The requirements for energy efficient design of electrical installations in buildings are classified in the Code into the following four categories;
(a) Minimising losses in the power distribution system.

(b) Reduction of losses and energy wastage in the utilisation of electrical power.

(c) Reduction of losses due to the associated power quality problems.

(d) Appropriate metering and energy monitoring facilities.

 

 
 
4.  ENERGY EFFICIENCY REQUIREMENTS FOR POWER DISTRIBUTION IN BUILDINGS
4.1
High Voltage Distribution
High voltage distribution systems should be employed for high-rise buildings to suit the load centres at various locations. A high-rise building is defined as a building having more than 50 storeys or over 175m in height above ground level. 
 
4.2
Minimum Transformer Efficiency
The privately owned distribution transformers should be selected to optimise the combination of no-load, part-load and full-load losses without compromising operational and reliability requirements of the electrical system. The transformer should be tested in accordance with relevant IEC standards and should have a minimum efficiency shown in Table 4.1 at the test conditions of full load, free of harmonics and at unity power factor. 
Table 4.1: Minimum Transformer Efficiency Transformer Capacity Minimum Efficiency


Transformer Capacity
Minimum Efficiency
<1000kVA
98%
>100kVA
99%
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4.3
Locations of Distribution Transformers and Main LV Switchboards
The locations of distribution transformers and main LV switchboards should preferably be sited at their load centres.
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4.4
Main Circuits
The copper loss of every main circuit connecting the distribution transformer and the main incoming circuit breaker of a LV switchboard should be minimised by means of either:
(a) locating the transformer room and the main switchroom immediately adjacent to, above or below each other, or
(b) restricting its copper loss to not exceeding 0.5% of the total active power transmitted along the circuit conductors at rated circuit current.
The effective current-carrying capacity of neutral conductors should have ratings not less than those for the corresponding phase conductors.
 
4.5
Feeder Circuits
The maximum copper loss in every feeder circuit should not exceed 2.5% of the total active power transmitted along the circuit conductors at rated circuit current. This requirement does not apply to circuits used for compensation of reactive and distortion power.
 
4.6
Sub-main Circuits
The maximum copper loss in every sub-main circuit including the rising mains, should not exceed 1.5% of the total active power transmitted along the circuit conductors at rated circuit current.
 
4.7 
Final Circuits
The maximum copper loss for every single-phase or three-phase final circuit over 32A should not exceed 1% of the total active power transmitted along the circuit conductors at rated circuit current.
Note: Table 4.2A & 4.2B are given in the following pages to provide guidance for preliminary selection of appropriate cable size for main, feeder, sub-main and final circuits based on the maximum allowable resistance value for a certain percentage copper loss.

TABLE 4.2A
Multicore armoured and Non-armoured Cabled (Copper Conductor) Conductor Resistance at 50Hz Single-phase or Three-phase a.c.
(Based on BS7671:1992 The Regulations for Electrical Installations, Table 4D2B, 4D4B, 4E2B & 4E4B)
 
Conductor cross-sectional are
(mm2)
Conductor resistance for PVC and XLPE cable in millionhm per meter
(mW/m)
PVC cable at max. conductor operating temperature of 70oC
XLPE cable at max. conductor operating temperature of 90oC
1.5
14.5
15.5
2.5
9
9.5
4
5.5
6
6
3.65
3.95
10
2.2
2.35
16
1.4
1.45
25
0.875
0.925
35
0.625
0.675
50
0.465
0.495
70
0.315
0.335
95
0.235
0.25
120
0.19
0.2
150
0.15
0.16
185
0.125
0.13
240
0.095
0.1
300
0.0775
0.08
400
0.0575
0.065


TABLE 4.2B
Single-core PVC/XLPE Non-armoured Cables, with or without sheath (Copper Conductor)
Conductor Resistance at 50Hz Single-phase or Three-phase a.c.
(Based on BS7671-1992, Table 4D1B & 4E1B)
 
 

Conductor cross-sectional area
(mm2)
Conductor resistance for PVC and XLPE cable in milliohm per meter 
(mW/m)
PVC cable at max. conductor operating temperature of 70oC
XLPE cable at max. conductor operating temperature of 90oC
Enclosed in conduit/trunking
Clipped direct or on tray, touching
Enclosed in conduit/trunking
Clipped direct or on tray, touching
1.5
14.5
14.5
15.5
15.5
2.5
9
9
9.5
9.5
4
5.5
5.5
6
6
6
3.65
3.65
3.95
3.95
10
2.2
2.2
2.35
2.35
16
1.4
1.4
1.45
1.45
25
0.9
0.875
0.925
0.925
35
0.65
0.625
0.675
0.675
50
0.475
0.465
0.5
0.495
70
0.325
0.315
0.35
0.34
95
0.245
0.235
0.255
0.245
120
0.195
0.185
0.205
0.195
150
0.155
0.15
0.165
0.16
185
0.125
0.12
0.135
0.13
240
0.0975
0.0925
0.105
0.1
300
0.08
0.075
0.0875
0.08
400
0.065
0.06
0.07
0.065
500
0.055
0.049
0.06
0.0525
630
0.047
0.0405
0.05
0.043
800
-
0.034
-
0.036
1000
-
0.0295
-
0.0315

 

 
 
5. REQUIREMENTS FOR EFFICIENT UTILISATION OF POWER
5.1 Lamps and Luminaires

All lamps and luminaires forming pan of an electrical installation in a building should comply with the latest edition of the Code of Practice for Energy Efficiency of Lighting Installations.
5.2  Air Conditioning Installations

All air conditioning units and plants drawing electrical power from the power distribution system should comply with the latest edition of the Code of Practice for Energy Efficiency of Air Conditioning Installations. Any motor control centre (MCC) or motor for air conditioning installations, having an output power of 5kW or greater, with or without variable speed drives, should also be equipped, if necessary, with appropriate power factor correction or harmonic filtering devices to improve the power factor to a minimum of 0.85 and restrict the total harmonic distortion (THD) of current to the value as shown in Table 6.1.
5.3  Vertical Transportation

All electrically driven equipment and motors forming pan of a vertical transportation system should comply with the latest edition of the Code of Practice for Energy Efficiency of Lifts and Escalators Installations.
 
5.4  Motors and Drives
5.4.1 Motor Efficiency

Except for motors which are components of package equipment, any polyphase induction motor having an output power of 5kW or greater that is expected to operate more than 1.000 hours per year should use "high-efficient" motors tested to relevant international standards such as IEEE 112-1991 or IEC 34-2. The nominal full-load motor efficiency shall be no less than those shown in Table 5.1 below.

Table 5.1: Minimum Acceptable Nominal Full-Load Motor Efficiency for Single-Speed Polyphase Motors


Motor Rated Output (P)
Minimum Rated Efficiency (%)
5kW<P<7.5kW
84.0
7.5kW<P<15kW
85.5
15kW<P<37kW
88.5
37kW<P<75kW
90.0
75kW<P<90kW
91.5
P>90kW
92.0
5.4.2  Motor Sizing

Every motor having an output power of 5kW or greater should be sized by not more than 125% of the anticipated system load unless the load characteristic requires specially high starting torque or frequent starting. If a standard rated motor is not available within the desired size range, the next larger standard size may be used.
5.4.3  Variable Speed Drives (VSDs)

A variable speed drive (VSD) should be employed for motor in a variable flow application. Any motor control centre (MCC) with VSDs should also be equipped. if necessary, with appropriate power factor correction or harmonic reduction devices to improve the power factor to a minimum of 0.85 and restrict the THD current to the value as shown in Table 6.1.
5.4.4  Power Transfer Devices

Power transfer devices used for motors having an output power of 5kW or greater, and to change continually the rotational speed, torque, and direction. should be avoided. Directly connected motors running at the appropriate speed via variable speed drives should be used as far as is practicable. If the use of belts is unavoidable, synchronous belts -which have teeth that fit into grooves on a driven sprocket, preventing slip losses - should be employed to provide a higher efficiency over friction belts.
 
5.5 Power Factor Improvement

The total power factor for any circuit should not be less than 0.85. Design calculations are required to demonstrate adequate provision of power factor correction equipment to achieve the minimum circuit power factor of 0.85. If the quantity and nature of inductive loads and/or non-linear loads to be installed in the building cannot be assessed initially. appropriate power factor correction devices shall be provided at a later date after occupation.
5.6  Other Good Practice
5.6.1  Office Equipment

Office consumers should be encouraged to select and purchase office machinery/equipment. e.g. personal computers. monitors, printers, photocopiers, facsimile machines, etc., complete with "power management" or "energy saving" feature which power down unnecessary components within the equipment while maintaining essential function or memory while the equipment are idle or after a user-specified periods of inactivity.
5.6.2  Electrical Appliances

Consumers should be encouraged to select and purchase energy efficient electrical appliances such as refrigerators, room coolers, washing machines, etc. which are registered under the Energy Efficiency Labelling Scheme (EELS) with good energy efficiency grade 3 or better.
5.6.3 Demand Side Management (DSM)

The Demand Side Management (DSM) programmes developed by the utility companies have tried to change consumers' electricity usage behaviour to achieve a more efficient use of electric energy and a more desirable building load factor, which is beneficial to both consumers and the utility companies. Designers are encouraged to incorporate into their design all latest DSM programmes available in order to reduce the building maximum demand and the electrical energy consumption. DSM Energy Efficiency Programmes include utilities special ice-storage air-conditioning tariff and time-of-use tariff rebates offered to participants to purchase energy efficient electrical appliances/installations (e.g. refrigerators, air-conditioners, compact fluorescent lamps. electronic ballasts, HVAC systems) etc.

 

 
 
6. ENERGY EFFICIENCY REQUIREMENTS FOR POWER QUALITY
6.1 Maximum Total Harmonic Distortion (THD) of Current on LV Circuits

The total harmonic distortion (THD) of current for any circuit should not exceed the appropriate figures in Table 6.1. According to the quantity and nature of the known non-linear equipment to be installed in the building, design calculations are required to demonstrate sufficient provision of appropriate harmonic reduction devices to restrict harmonic currents of the non-linear loads at the harmonic sources. such that the maximum TAD of circuit currents, at rated load conditions. shall be limited to those figures as shown in Table 6.1 below.

Table 6.1: Maximum THD of current in percentage of fundamental

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Circuit Current at Rated Load Condition 'I' at 380V/220V
Maximum Total Harmonic Distorting (THD) of Current
I<40A
20.0%
40A<I<400A
15.0%
400A<I<800A
12.0%
800A<I<2000A
8.0%
I>2000A
5.0%

In case of motor circuits using VSDs, group compensation at the sub-main panel or MICC is allowed. provided that the maximum allowable fifth harmonic current distortion at the VSD input terminals during operation within the variable speed range is less than 35%.

If the quantity and nature of non-linear equipment to be installed in the building cannot be assessed initially, appropriate harmonic reduction devices shall be provided at a later date after occupation.
6.2 Balancing of Single-phase Loads

All single-phase loads. especially those with non-linear characteristics. in an electrical installation with a three-phase supply should be evenly and reasonably distributed among the phases. Such provisions are required to be demonstrated in the design for all three-phase 4-wire circuits exceeding 100A with single-phase loads.

The maximum unbalanced single-phase loads distribution. in term of percentage current unbalance shall not exceed 10%. The percentage current unbalance can be determined by the following expression:

Iu= (Id X100}/Ia
Where 
Iu= percentage current unbalance
1d= maximum current deviation from the average current 
Ia= average current among three phases

 

 
 
7. REQUIREMENTS FOR METERING AND MONITORING FACILITIES
7.1  Main Circuits

All main incoming circuits exceeding 400A (3-phase 380V) current rating should be incorporated with metering devices. or provisions for the ready connection of such devices, for measuring voltages (all phase-to-phase and phase-to-neutral), currents (all lines and neutral currents) and power factor and for recording total energy consumption (kWh) and maximum demand (kVA).
7.2 Sub-main and Feeder Circuits

All sub-main distribution and individual feeder circuits exceeding 200A (3-phase 380V) current rating should be complete with metering devices, or provisions for the ready connection of such devices. to measure currents (3 phases and neutral) and record energy consumption in kWh for energy monitoring and audit purposes. This requirement does not apply to circuits used for compensation of reactive and distortion power.

 

 
 
 
8. SUBMISSION OF INFORMATION
  Relevant information. drawings and calculations for the buildings should be submitted on the following standard forms set out in the schedule of this Code:

(a) FORM EL-1: Electrical Installations Summary

(b) FORM EL-2 Electrical Power Distribution Worksheet

(c) FORM EL-3 Electrical Power Utilisation Worksheet

(d) FORM EL-4 Electrical Power Quality Worksheet

(e) FORM EL-5 Electrical Metering & Monitoring Worksheet

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SCHEDULE OF FORMS FORM EL-1: Electrical Installations Summary 
page 1, 2

FORM EL-2; Electrical Power Distribution Worksheet 
page 1, 2, 3

FORM EL-3: Electrical Power Utilisation Worksheet 
page 1, 2

FORM EL-4: Electrical Power Quality Worksheet 
page 1, 2

FORM EL-5: Electrical Metering & Monitoring Worksheet 
page 1

 
 
APPENDICES Appendix A: Explanatory Notes and Sample Calculations
 
A1     Cable Sizing (Conventional Method) 
page 1
A2     Power Factor and Losses due to Harmonic Distortion in Circuits with Non-linear Loads
page 1, 2
A3     Copper Loss Calculation
page 3, 4, 5
A4     Sample Calculations for Cable Sizing
page 6, 7, 8, 9
A5     Power Loss Calculations for Main Circuits
page 10
  Appendix B: Case Study for a Typical Commercial Building in Hong Kong 
page 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11

 
  This code was developed by the Task Force on Electrical Energy Code that was established under the Energy Efficiency & Conservation Sub-committee of the Energy Advisory Committee. The Task Force members include: -
 
 
Convenor Mr. Ronald S. Chin (Electrical & Mechanical Services Department)
Members Mr. K.Y. Chung (The Hong Kong Electric Co. Ltd.)
Mr. Y.F. Kwok (The Hong Kong Polytechnic University)
Mr. W.K. Lam (The Hong Kong E&M Contractors
Association Ltd.)
Mr. Thomas K.S. Lam (The Hong Kong Institution of Engineers)
Mr. Bernard V. Lim  (The Hong Kong Institute of Architects)
Mr. Y.F. So (Hong Kong Electrical Contractors' Association Ltd.)
Mr. Winston Tse (China Light & Power Co. Ltd.)
Mr. Martin Wu (Electrical & Mechanical Services Department)
Secretary & Member (prior to Jan. 1997) Mr. C.K.Lee
(Electrical & Mechanical Services Department)
(from Jan. 1997) Mr. K.K. Lam
(Electrical & Mechanical Services Department)

 

 
 
 
 
 
 

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