Why Insulate the Earth Wire When it's in a Sealed Box or the Entire Length Insulated?


Postby GrumpyMike » Thu Feb 12, 2015 8:27 pm

Hi,

I understand the purpose of the earth wire, and can see the common sense in connecting a patress box to the earth, but why does it need to be insulated even when it's within a sealed box? Also, if insulating the wire is so important, then why isn't the whole length of the earth wire insulated, just like the live and neutral?

Thanks
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Postby ericmark » Fri Feb 13, 2015 5:51 am

There are two reasons.
1) Identify it as an earth wire.
2) Ensure it can't touch either of the live wires or terminals. Specially the neutral as it would not until we used RCD's automatically disconnect the supply.

I have to visit my daughters as there is an earth - neutral fault on her ring very likely due to missing earth sleeve.

514.4.2 Protective conductor
The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any, other Purpose.
Single-core cables that are Coloured green-and-yellow throughout their length shall only be used as a protective conductor and shall not be over-marked at their terminations, except as permitted by Regulation 514.4.3.
In this combination one of the colours shall cover at least 30 % and at most 70 % of the surface being coloured, while the other colour shall cover the remainder of the surface.
A bare conductor or busbar used as a protective conductor shall be identified. where necessary, by equal green-and yellow stripes, each not less than 15 mm and not more than 100 mm wide, close together, either throughout the length of the conductor or in each compartment and unit and at each accessible position. If adhesive tape is used, it shall be bi-coloured.

This regulation does not stop the over-marking of bare copper personally I feel that's a bad practice but some electricians have been know to use the bare copper wire as a line. So a bare copper wire could be a line with sleeve fallen off or an earth with sleeve fallen off so it does need that sleeve.
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