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Topic Title: Functional Earth Identification
Topic Summary: colour of functional earth ( continuous or at terminations)
Created On: 19 June 2013 09:51 PM
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 19 June 2013 09:51 PM
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EMERY

Posts: 1
Joined: 13 March 2012

We have to install functional earths for a UPS system. These will be:
H07 installed on Cable Ladder
They will run from the UPS to a functional earth bar connected to an independent earth electrode
These are only for functional purposes and not for protection

Should they be cream the whole length of the conductor, or can they be marked at the terminations only.

BS7671 only refers to an earth conductor used as protection or combined in which case they should be green and yellow for the full length of the cable Richard Emery
 19 June 2013 10:25 PM
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broadgage

Posts: 1282
Joined: 07 August 2007

IMHO cream throughout is PREFERABLE but not a requirement.

The use of cream for functional earthing started in post office telephone days as a convention and only fairly recently became a requirement.
If you cant get cream single core cable, and it is not widely available, then in my view, white is better than green/yellow.

White is similar to cream, and has no recent history of use for phase, neutral, or protective earth.
White single core is fairly widely available.
 19 June 2013 11:58 PM
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alancapon

Posts: 5760
Joined: 27 December 2005

Cream functional earth cable started in Post Office Telephones days, and continued on with BT as being a requirement for telephone exchange installations to BS6701. If you do a search for CW1044 cable, this is the BT standard for the cream functional earth.

Regards,

Alan.
 20 June 2013 09:42 AM
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AJJewsbury

Posts: 11367
Joined: 13 August 2003

BS7671 only refers to an earth conductor used as protection or combined in which case they should be green and yellow for the full length of the cable

Not entirely. BS 7671 does state the colour code cream for functional earths (table 51), as for any colour ID reg 514.3.2 says that the identification must be at terminations, but only "preferably" throughout its length.

The requirement for green/yellow to be so coloured throughout their length is only for single-core cables - so cores of multicore cables may be some other colour oversleeved green/yellow at terminations (or indeed green/yellow oversleeved with some other colour at terminations and used for a non-protective function).

Just out of interest, how are you maintaining an equipotential zone if functional and protective earths are separate?

- Andy.
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