small main and equipotential earths

[sijaysee]

am i right in thinking that you dont have to upgrade them if you
consider that they are not causing problems?

 

[Spark123]

Bit of an open question, you need to ensure before any additions or alterations that the earthing and bonding is adequate.

 

[sijaysee]

earthing and bondin are there. no signs of any problems.
i've read that even with pme, if the main bond is only
6mm , as long as everything is ok , then there is no
requirement to upgade it

 

[Spark123]

What do you mean by no signs of any problems? The sizes are given by BS7671, if you are carrying out an addition or alteration to that standard then your earthing and bonding needs to be to that standard.

 

[sijaysee]

bs7671 says that even though the main earth and equipotential bonding
is smaller than recommended, you can leave it if there are no signs of any problems

 

[securespark]

Can you quote a reg. number for us?

 

[Spark123]

you can leave it if there are no signs of any problems

How do you determine that it is not problematic?

 

[sijaysee]

i would have thought that if there are no signs of over heating then
there will be no problems with it.
definately saw it in one of the books.
think it was the niceic one on testing and inspection

 

[Qedelec]

Overheating? Are you sure you understand the purpose of bonding

 

[FingRinal]

Overheating can occur due to circulating currents in PME networks and was one of the reasons to increase the size to 10mm I believe.

 

[Qedelec]

yes I know that but its not the best way to determine adequacy

 

[FingRinal]

I never said it was.

I guess that means you can tell us how?

There are two situations:

1. Assessment during a PIR

2. Assessment during additions and alterations

 

[Spark123]

If you leave the bonding undersized and it is part of the protective measures of a circuit which you are working on then you need to give your reasons on the EIC as to why you deem it to be adequate. I don't think "not melted" is allowed
It is not acceptable for a new installation including a rewire or where PME (installed after 1/10/88 ) is involved.

 

[ban-all-sheds]

It does give me a wry smile to be putting in 10/16mm² main bonding and earthing cables when the link from MET to supply sheath is 2.5mm²...

 

[sijaysee]

only minor works being done
so you're saying that 6mm main earth and bonding is ok then.