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25 Common Problemsfor M&E Engineers
Armada Hotel , Petaling Jaya26 th May 2011
10 Common ElectricalDesign Problems Part II
Ir. Looi Hip PeuHon Sec, ACEM (2010/11)B.Eng (Hons)
(Electrical)P.Eng (5226), Jurutera Gas
[email protected]
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26 th May [email protected]
C ONTENT2
System Design Wiring Design Protection Installation
Objectives of this Workshop
1. Tariff selection
2. Generator sizing
3. Earthing system
4. PE cableselection
5. Mains cable
sizing6. Al vs Cu cables
7. RCD selection
8. Motor starting
9. Standards
10.Malaysianwiring code
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26 th May [email protected]
Aluminum & Copper Cab les6
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C u r r e nt l y t h e m a r k et f o r c o p p e r i s u n s t
a b l ea n d c o p p e r p r i c e h a s b e c o m e h i g h . T h
i s h a sa f f e c t ed t h e d e m a n d f o r c o p p e r c a b l
e s w i t hC l i e n t s a n d c o n t ra c to r s r e q u e s t i
n gd e s i g n e r s t o c h a n ge f ro m c o p p e r t o
a l u m i n u m c a b l e s .
26 th May [email protected]
W IRING D ESIGN AL & C U C ABLES4 6
What are the possible impact on design, cost and
futureoperation. Is AL cables a fire hazard?
Unfortunately professional engineers faced with suchrequest
cannot brush them off easily due to the costimplication neither can
they satisfactorily answer theirclients.
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26 th May [email protected]
6
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Proper t i e s o f Mate r i a l
26 th May [email protected]
W IRING D ESIGN AL & C U C ABLES7 6
Material Thermalexpansion, at
25 Cm-m -1 K-1
Volumetriccoefficient, ,
at 20 C(10 6 /C)
ElectricResistivity [nm] at
20 C
MeltingPoint
Aluminum 23.1 87 28.2 933 C
Copper 16.5 51 16.8 1084.6 C
Steel 17.3 51.9 ~ 100 ?? C
A L h a s h i g h e r c o e f f i c i e n t o f e x p a n s i o
n
A L h a s a h i g h e r e l e c t r i c re s i s t i v i t y. A
l c a b l e s i ze w i l lh a v e t o b e o n e s i z e l a r g e
r
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W IRING D ESIGN AL & C U C ABLES8 6
P o s s i b l e h a z a r d f o r C o p p e r C a b l e s
Galvanic reaction between AL and copper terminals.Proper AL-Cu
terminals will be required.
Al has a higher coefficient of expansion. Cable
connections may loosen in the long run.
AL wiring not properly installed is a fire hazard mainlydue to
loosening connections at terminals.
AL subject to galvanic reaction with copper and
steelterminals.
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A l l c ab le s < 70 mm s ho ul d b e c op pe r. I nd iah as
t he m o s t ex p e r i en c e i n u s i ng A l c ab l esys t e m i
n b u i l d i n g . I n I n d i a t h e r u l e o f
