Advice on regulation 521.5.1

[spadge47]

Hi all,

A couple of guys at work are getting return visits to properties because they have been taking the earthing conductor into the new AMD3 metal boards through a separate hole than the tails. Apparently it is against these regs. Now I have read it and I am seeing it from both sides but I need your help.

We have been using the wylex boards with the wylex tail glands, and they have the 2 holes in it ( for line and neutral), however when explaining that if you have to take the earth through the same hole then surely these glands would have 3 holes ? The reply was to 'drill a 3rd hole then'. :thinking:

So please could I have some clarification on this. Do you have to bring the earthing conductor through the same hole as the line and neutral tails for metal boards??

Please could you give me your answers and reasoning please

 

[telectrix]

only the L and N need to be through the same hole to avoid the possibility of eddy currents in the steel casing.

 

[spadge47]

they are quoting 521.5.1 on the technical reports. what could they possibly be misinterpreting to take the earth through?

 

[davesparks]

Who are the 'they' who are quoting this?
Whoever they are they obviously don't understand some pretty basic concepts in the science of electricity.

 

[spadge47]

they = the electrical quality control managers of the company i work for.

I had never heard of having to bring all cables through the same hole until colleagues had technical reports back.

It seems they are taking the first paragraph of the reg 521.5.1,

'the conductors of an a.c circuit installed in a ferromagnetic enclosure shall be arranged so that all line conductors and the neutral conductor,if any, and the appropriate protective conductor are contained within the same enclosure'.

as 'enter the enclosure through the same entry'.

 

[davesparks]

they = the electrical quality control managers of the company i work for.

I had never heard of having to bring all cables through the same hole until colleagues had technical reports back.

They clearly haven't got a clue, what would they say if you just bolted the earthing conductor to the side of the cu with a lug?

What do you mean you've never heard of bringing all conductors through the same hole? Are you a trainee?

 

[netblindpaul]

only the L and N need to be through the same hole to avoid the possibility of eddy currents in the steel casing.

Wrong.

 

[netblindpaul]

they are quoting 521.5.1 on the technical reports. what could they possibly be misinterpreting to take the earth through?

Correct.

 

[netblindpaul]

Who are the 'they' who are quoting this?
Whoever they are they obviously don't understand some pretty basic concepts in the science of electricity.

Wrong.

 

[netblindpaul]

they = the electrical quality control managers of the company i work for.

I had never heard of having to bring all cables through the same hole until colleagues had technical reports back.

It seems they are taking the first paragraph of the reg 521.5.1,

'the conductors of an a.c circuit installed in a ferromagnetic enclosure shall be arranged so that all line conductors and the neutral conductor,if any, and the appropriate protective conductor are contained within the same enclosure'.

as 'enter the enclosure through the same entry'.

Right.

 

[spadge47]

sorry - what I mean is that I had never heard of having to bring the earthing conductor through the same hole until the management threw that one out there. ( I know the L-N need to.)

 

[netblindpaul]

Read and understand 521.5.1.

 

[HappyHippyDad]

they = the electrical quality control managers of the company i work for.

I had never heard of having to bring all cables through the same hole until colleagues had technical reports back.

I expect this is something that is going to become far more talked about over the next year when we have to start fitting metal consumer units (I suppose I should say non-combustible, but it's looking like the manufacturers of the boards are going with steel to comply).

Could you explain why you are 'seeing it from both sides' Spadge? The regulation makes it very clear that all conductors (including CPC) should be brought through the same hole. Some manufacturers are making grommets that specifically take x2 25mm tails and 16mm earthing conductor which look quite good to use.

Have to admit Eddy currents are not something that I fully understand and it would be good to know more. Is this a likely occurance on a single phase domestic supply?

 

[netblindpaul]

spadge, you are almost right, or at least your employer is correct.

 

[Deleted member 26818]

Did they not introduce a new Regulation in the 17th allowing a separate earth to be run along side an SWA cable?
Obviously the earth would have to enter the enclosure separately to the other conductors.