About to fit metal lights to ceiling and find there's no earth. How necessary is it? Obviously, the intructions with the fittings state that the unit must be earthed. It'll be bit of a pain to do but I'd hate to wish that I had done it. On the other hand I'd rather not if it's not really needed. Distribution board is RCCB. Tia.
It really is not earth. It is a safety ground that keeps humans from being electrocuted. However code also does permit a solution - a GFCI placed on that circuit would accomplish same. However all outlets and fixtures then require a label that reads "No equipment ground" so that future humans understand what kind of protection now exists.
I think it is interesting that NEC people and engineers believe that adding a tag that says "No equipment ground" is needed so the customer understands the instillation. That tag makes things clear as mud.
It is kind of like requiring green insulation for small wire instead of phasing tape. If someone doesn't know what the green tape is for then having green insullation somehow clears everything up.
Your suggestion is sound. The thinking behind the tag seems meanless to me.
Note that the original question was from a .co.uk address. Electrical regulations vary greatly in different parts of the world. I'm not an electrician, and I don't know what the regs here in the UK require, but I do know that electrical practice in, for example, the US is very different to it is here. It is unwise to make any assumptions about a country you are unfamiliar with.
For example, over here we do not vave the situation where one phase can be at a different potential from earth (ground) than the other two, we do not have centre tapped supplies with the centre tap at earth potential (other than the centre-tapped 110V supplies used for portable tools on building sites etc., via a transformer. We don't have a number of different Voltages, 120, 208, 240, 277, 440 etc.
On the other hand we do have single phase socket outlets fed from a ring main, which is the reason that it is essential for British 13A plugs to have internal fuses.
It's wise to take care when dealing with unfamiliar systems.
I did not realize the OP was in Britian. This changes things slightly. The principles are same. But, for example, Britian uses RCDs and not GFCIs. Also, the way some Brits talk, Britian has no electric wires without a safety ground.
The label "No Equipment Ground" is required by code in the US as part of a solution to this problem. Label's meaning is quite clear as defined by code. I suspect from other responses that UK has no equivalent label defined by code.
RCD would provide protecti> It really is not earth. It is a safety ground that keeps
I think it is interesting that NEC people and engineers believe that adding a tag that says "No equipment ground" is needed so the customer understands the instillation. That tag makes things clear as mud.
It is kind of like requiring green insulation for small wire instead of phasing tape. If someone doesn't know what the green tape is for then having green insullation somehow clears everything up.
Your suggestion is sound. The thinking behind the tag seems meanless to me.
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