Changing metal for plastic??


Postby elecqs » Thu Feb 19, 2009 10:34 am

I am replacing an old metal light switch and a power point with plastic ones.
Both have an earth wire connected to the metal fascia; do I connect the earth to the metal back box when I put the new plastic fascias on? or something else?
Cheers,
Jim.
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Postby singer » Thu Feb 19, 2009 12:04 pm

The earth wires attached to the metal fascias are to earth the exposed metalwork on the metal fittings so if you are replacing with plastic are no longer required.

However in the case of the light switch the earth wire should be "parked" ie terminated into the earth terminal of the back box in the wall which is then earthing the metal box. If there isn't one then second best is to wrap it around the head of the fixing screw. This in effect is earthing nothing but stops the earth wire floating around behind the live switch.

In the case of the socket then all earth wires should be connected to the earth terminal of the socket to provide an earth to whatever is plugged into it but must also have a "tail" from the socket earth terminal to the earth terminal of the metal back box to earth this metalwork.
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Postby kbrownie » Thu Feb 19, 2009 1:08 pm

You can do it either way or put a earth link (pig tail) between backbox and face plate and connect the earth to plate or box for extra safety.
KB
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Postby sparx » Thu Feb 19, 2009 9:25 pm

Hi guys just a point,
there is no requirement to link back to back box in regs. (another bit of niceic b*ll*x) unless using metal conduit for your CPC, which is still allowed see regs 543.2.2(v1) & 543.2.5 & 543.2.7.
So if wiring in twin&E or singles with an earth conductor it is not required to install an additional pigtail lead in an already cramped back box! unless the box has both lugs moveable (unusual).
regards SPARX
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Postby singer » Fri Feb 20, 2009 9:13 am

Hi sparx

Yeah I thought someone would pick me up on that.

I always do it anyway(force of habit!!)
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Postby elecqs » Fri Feb 20, 2009 10:54 am

Thanks for your replies.
Could you please explain this comment? "unless the box has both lugs moveable (unusual)."
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Postby elecqs » Fri Feb 20, 2009 4:58 pm

Regarding the aforementioned metal light switch. It has the following wiring..
Red wire going to top hole on back of switch
Yellow and a red wire going to bottom right of switch
Blue and a black wire going to bottom left of witch

The plastic replacement switch is marked; L1 L2 COM. When I wire it up after removing the earths and attaching to the metal box(as suggested), the light stays on all of the time....
Please help!!
Jim.
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Joined: Mon Feb 02, 2009 9:42 am


Postby kbrownie » Fri Feb 20, 2009 7:12 pm

so you have a two way switch and could be a couple of ways, unless you have low resitance ohms meter, you will have to switch about the cables.
com=one of the reds
L1= a red(line/live/phase) and blue
L2=a black(neutral) and a yellow.
have a look in the other switch that operates this light to see if
L1=blue
L2=yellow
if so you may need to swap the reds around at the first switch.
Good Luck and be safe
KB
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Postby sparx » Fri Feb 20, 2009 10:50 pm

Hi, most boxes have one moveable & one fixed lug which is deemed to give adequate earth contact, but 2 moveable lugs not considered sufficient contact.
Red from 3 core to common, yellow plus red from 2 core to L1, & blue plus black to L2.
this is called 2 way conversion method.
Hi singer , not a knock, just get fed up with unneccesary OTT items , usually due to 'The Dark Side' (niceic) thinking they know better than the IET who write the regs!
Also wish people would show source data when making sweeping statements then we could all check it out & improve our collective knowledge,
NAPIT rules for me!
BW, SPARX
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Postby elecqs » Sun Feb 22, 2009 10:37 am

Thanks chaps for your help...
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