Wiring Standards & National Wiring Codes
With the adoption of the MS/IEC60364 "Wiring Installation for Building" in 2000, Malaysia, in conformity with other countries in the region are practitioners of a common wiring standard (China and Vietnam in particular are strong proponents of the IEC wiring standard). As the IEC60364 is drafted by a multi-lateral, international body, which was (and still is, though less so) Eurocentric in nature, the IEC60364 has to accommodate the multiple conditions of various (European) national standards. Due to this the IEC60364 tend , of necessity, to be performance-based in nature. By comparision the U.K. IEE 17th edition or BS7671 "Regulations for Electrical Installation", and U.S.A. NEC 2008 "National Electrical Code©" (or NFPA 70) tend to be prescriptive-based as these standards are compiled specifically for only one country.
After the publication of the MS/IEC 60364, Suruhanjaya Tenaga, convened an industry-wide work group sometime in 2003 to draft a national wiring code. This WG on national wiring, chaired by The Electrical and Electronics Association of Malaysia (Ir. Rocky Wong Hon Tang) has as their working brief:
- To draft a national wiring code suited for Malaysia and not in conflict with current laws and regulations ('Electricity Supply Regulations').
- To ensure compliance with MS/IEC60364.
- To consider particular aspect of wiring practice NOT included in the MS/IEC60364 (principally prescriptive-based rules).
- To provide a safety guide principally for residential installations catering to 'uninformed' consumers (who make up more than 80% of electricity consumers).
After 3 years of draft and public consultations and 2 more years of public gazette the following documents are now published:
- MS 1979:2007 "Electrical Installation of Buildings – Code of Practice"
- MS 1936:2006 :Electrical Installation of Building – Guide to MS IEC 60364"
The public announcement by Suruhanjaya Tenaga can be viewed in this circular dated 1st July 2008. This circular makes it mandatory that the Garis Panduan Pendawaian Elektrik (GPPE) (or "Guides to Electrical Wiring") be a basis for all wiring in residential buildings. The GPPE in turn takes as its basis MS1979, MS1936 and MS/IEC60364, a circuitious way of announcing that the 'cart' (GPPE) is the principal document which actually is powered by the 'horse' (MS1979 and MS1936).
MS 1979 – Quick Brief
As this post DO NOT propose to be a scholarly oevre on wiring installation (please PAY to attend seminars and workshops conducted by TEEAM, ACEM and IEM), I have to be of necessity brief. I will touch on the important points of the Code here.
The structure of MS1979 is a simple distillation of all the important prescriptions contained in MSIEC60364 which have direct relevance to wiring in residential buildings. Rule-based conditions are set-out in the MS1979 where only performance-based requirements are listed in the MSIEC60364. The final product is a very simple booklet containing individual "COP" (Code Of Practice) numbered COP1 to COP91.
The companion to the MS1979 is MS1936 which has a more expanded scope compared to the MS1979 as it covers all other L.V. installation under the MS60364.
A quick list of COP which are important for designers and installers are as follows:
- COP05 – All metal enclosures of electrical appliances must be connected to a protective conductor. Water, gas pipes, strucutural metal parts of the buildings and ductings of airconditioning system must also be connected to the main equipotential bonding.
- COP06 – Isolation on fault. Protection using RCD, fuse, CB etc. must comply with Ra x Ia < 50V
Ra = Resistance of earth electrode & protective conductor;
Ia = operating current of protective device (sensitivy of RCD and 5s current trip for inverse time relay).
50V is the safe contact voltage defined by IEC60749-1.
- COP07 –Earthing resistance must be less than 10Ω for operation of RCD but resistance of less than 1Ω is targetted.
- COP08 – Electrical equipment must be mounted within materials that can withstand temperatures produced (by the equipment).
- COP10 – Water heaters or forced air heaters or steam generators must be equipped with over heating devices (i.e. use o/t cut-out etc.).
- COP12 – In > IB,
- COP13 – Iz > In
- COP14 – I2 < 1.45 x Iz
In = nominal current of protective device; IB = design current; Iz = current capacity of cable ; I2 = tripping/effective operation current of protective device.
- COP16 – Requires determination of short circuit current within the installation. Effectively this requires every TNB district engineer to issue information on short circuit at the point of common coupling (PCC) at the locality of installation.
- COP19 – Surge Protection Device (SPD) is RECOMMENDED for supply from overhead lines.
- COP26 – Bending radius of 12 times diameter of cable is mandated. This effectively requires that elbows and junctions be used where cable changes direction.
In Malaysia, many wiring installation WILL FAIL THIS CRITERION.
- COP27 – Space factor for conduit shall be 40% and for trunking shall be 45%.
- COP28 – Cables installed behind walls (i.e. embedded in concrete) shall be horizontal or vertical parallel to the edges of the room and within 150mm from top and 150mm from edge of wall.
In Malaysia, many wiring installation WILL FAIL THIS CRITERION as cables are commonly installed diagonally fully and in many cases partially (picture 1).
- COP30 – Wiring within ceiling space (under roof) must be provided with mechanical protection (i.e. installed within APPROVED conduit). In addition they must be installed either parallel or perpendicular to the edges of the wall.
- COP31 – Water heater circuits shall have 2-pole switch installed at suitable location. At the vicinity of the heater a socket outlet is required (unswitched is acceptable).
- COP32 – Air Conditioner circuits shall have socket outlet (unswitched type is accepable) at vinity of unit.
- COP35 – Size of neutral conductor must be same size as phase conductor.
- COP36 – Size of neutral conductor may be reduced (reference to COP35) at the discretion of the Professional Design Engineer (i.e. only a P.Eng can decide).
- COP39 – Minimum cable size shall be 1.5mm² copper or 2.5mm² aluminum. Therefore the practice of using 1.25mm² copper cables is illegal!
Note: The use of aluminum cables WITHIN BUILDING is a FIRE HAZARD and should be carefully considered by the specifying engineer. India which has the most prevalent practice of using aluminum cables recommends that only cables above 50mm² may be aluminum.
- COP41 – Allowable voltage drop is 4%. Voltage drop for motor starting may be 10%.
- COP42 – Soldered connections to connect or terminate cables ARE NOT ALLOWED (see COP43 below).
- COP43 – Connections of 2 lengths of conductors shall be by sockets and crimping.
- COP44 – Cables for final sub circuit shall NOT BE JOINED.
- COP51 – RCD (or current type ELCB) for single phase installation shall not exceed 100mA (the previous quoted in the regulations was 30mA).
- COP52 – RCD for 3-phase installation shall not exceed 100mA. Three units of single pole type RCD instead of a 3-phase RCD may be used PROVIDED no 3-phase load(s) is/are served.
- COP53 – Hand-held equipment shall have RCD not exceeding 30mA.
- COP54 – RCD not exceeding 10mA shall be installed for special location (places of public entertainment; wet places; protection of electric water heaters).
- COP56 – Requires RCD to be regularly tested, at least twice a year.
- COP59 – It is recommended to place SPD before RCD (on the supply side), see figure 2.
- COP61 – SPD should be rated not less than 5kA.
- COP64 – The minimum earth connection from SPD to main earth terminal shall be not less than 10mm² copper and shall be as short as possible (0.5m).
- COP65 – Every circuit shall be provided with means of isolation.
- COP67 – Semiconducting devices shall not be used for isolation. Therefore a 'soft' switch must be backed up with a 'physcial' switch.
- COP70 – Earth electrodes may be round copper sheathed steel rods, copper tapes of conductors, rods or pipes or steel bars of reinforced concrete foundations of buildings. The last option (rebars in foundation) is becoming a favourite option for many designers but however must be designed, specified and installed by experienced practitioners.
- COP71 – Water or gas pipes ARE NOT allowed to be used as the sole means of earthing but equipotential bonding is permitted.
- COP72 – Requires earthing system to be checked annually
- COP73 – Earthing conductor buried in soil and without protection against corrosion shall be minimum 25mm² bare copper. This value may be reduced to 16mm² copper if protection against corrosion is present. Note: standard copper tape at 25mmx3mm complies with this requirement.
- COP74 – Connection of earth conductors buried in ground using exothermic weld is recommended. Connections to earth electrodes which require periodic inspection at earth pit/chambers may be clamp type. Note: In the author's eperience many Malaysian contractor use braze joint which is NOT ACCEPTABLE.
- COP76 – Protective conductor shall be (a) same size as line conductor if less than 16mm² (b) 16mm² if line conductor is more than 16mm² and up to 35mm² (c) half size of line conductor if more than 35mm².
- COP77 – Protective bonding conductor to main earth terminal shall not be 6mm² for copper or 16mm² for aluminum.
- COP78 – Neutral of standby system shall be separate when in operation.
- COP79 – Overcurrent for essential services (e.g. fire fighting pumpsets) may be waived. Overcurrent protective devices if provided, may provide alarm only.
- COP82 – Supervision of work on LV single phase installations shall be under direct responsibility of Wireman (single phase or 3-phase restriction). The Wireman shall certify completion under Form G.
- COP83 - Supervision of work on LV 3-phase installations shall be under direct responsibility of Wireman (3-phase restriction). The Wireman shall be required to certify completion under Form G.
- COP 84 – Testing for single phase installation shall be by Wireman (single-phase or 3-phase restriction) under Form H.
- COP 85 – Testing for 3-phase installation shall be by Wireman (3-phase restriction) under Form H.
- COP86 – Other installation at higher than low voltage shall be tested by a Electrical Services Engineer under Form H.
- COP87 – Electricity SHALL NOT BE CONNECTED until Forms G & H are submitted by the owner or building operator.
- COP88 – Insulation measurements shall be carried out on LV installation using dc voltages. Where 500Vdc is applied, the insulation resistance shall be more than 1MΩ.
- COP91 – Every completed installation shall have as-built electrical diagrams prominently displayed. Diagrams shall be endorsed by the professional design electrical engineer.
Note: All P.Eng who are submitting officer under CCC should take note of Form H and G requirements under COP 82 to 85 and electricity connection under COP87.
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