Is bonding required?

[DaftPunk]

Been to look at a job today. It's a new build detached garage.

We are installing a swa to feed the garage CU. The existing house installation is a brown wylex standard so we will Henley the tails to supply a switch fuse for the garage supply.

There is no bonding in the house. Do we need to install it as we are not touching the house installation?

 

[JohnW2]

We are installing a swa to feed the garage CU. The existing house installation is a brown wylex standard so we will Henley the tails to supply a switch fuse for the garage supply. ... There is no bonding in the house. Do we need to install it as we are not touching the house installation?

What exactly do you mean by "need" - are you just talking about 'rules' as they apply to someone who is 'only installing a garage supply'? If the house has any extraneous-conductive parts which are not bonded, they clearly 'need' to be bonded. Do I take it that you have informed the householder of this need - and, if so, are you saying that they do not want the bonding to be installed?

Kind Regards, John

 

[EFLImpudence]

Is there anything in the garage that requires bonding?

 

[mikeyd]

Please sir, can I answer? Disclaimer: I have no idea with the information given.

It depends how you are going to supply the garage. Are you intending to earth rod it, or export the earth from the house? Have you any understanding why or how you should or should not 'bond' a detached building?

 

[EFLImpudence]

To be fair, mikeyd I think DP is asking if the work should be done when there is no bonding in the house becuase all the guides state work must not be done in the house until bonding is brought up to date.

 

[JohnW2]

To be fair, mikeyd I think DP is asking if the work should be done when there is no bonding in the house becuase all the guides state work must not be done in the house until bonding is brought up to date.

Indeed - as was probably apparent from my response, that is how I interpreted the question. However, as I implied, I would have thought that the reasonable and responsible approach in such a situation would at least include bringing the issue to the householder's attention and suggesting that the house's bonding should be addressed before any other electrical work was undertaken - regardless of whether or not anything in the garage needs bonding.

Kind Regards, John

 

[DaftPunk]

We have brought the lack of bonding to the house owners attention. They have said they are planning to have an extension built in the next year and have the house rewired as part of the works as the existing wiring is all 50+ years old.

We are exporting the TN-S earth to the garage, and there is nothing extraneous in there. It's a block built garage with no services other than the electricity.

We had a discussion and couldn't decide wether we must install bonding in the house to leave our new garage installation fully compliant with BS7671.

 

[EFLImpudence]

I don't think there is actually anything in 7671 stating that you should walk away if the customer refuses to have it fitted, unlike NIC and ESC, and as it is not really related to your work I would say it is up to you as long as you have advised the customer.

Would it entail much additional work?

 

[JohnW2]

We have brought the lack of bonding to the house owners attention. They have said they are planning to have an extension built in the next year and have the house rewired as part of the works as the existing wiring is all 50+ years old.

Fair enough - but, as EFLI has asked, would it be a big/difficult job (i.e. are there problems of access to a decent route for the bonding cables(s) )? If not, you presumably could point out that if you installed the bonding now (maybe leaving a bit of spare cable at the MET end, 'just in case'), it would not need to be re-done when the house was rewired and, in any event, was only a fairly 'small job'.

We are exporting the TN-S earth to the garage, and there is nothing extraneous in there. It's a block built garage with no services other than the electricity. We had a discussion and couldn't decide wether we must install bonding in the house to leave our new garage installation fully compliant with BS7671.

I can't speak for what organisations such as scheme operators and insurers might say (and, as EFLI has said, I don't think BS7671 imposes any such requirement). However, in electrical terms, whether or not there is main bonding in the house surely has absolutely no relevance to the garage - and therefore poses no safety issue in relation to the garage installation. If the garage itself had extraneous-c-ps, they would obviously need main bonding - but, even if that were the case, the garage installation would be 'safe' (bonding-wise) if those parts in the garage were bonded, even if extraneous-c-ps in the (separate) house were not. After all, main bonding is nothing to do with making the installation's earth any 'safer' - it is to prevent the presence of extraneous-c-ps within the same building presenting a potential risk.

Hence, whilst, as I said, I can't speak for the organisations who may 'have a view', I can see no electrically rational reason why they should feel that you should not install a supply to the garage because house bonding is not in place.

As I see it, bonding (in the house) is really no different from any other safety issue in the house which doesn't affect the garage. If, for example, you knew that the house was full of unearthed metal accessories, you would hopefully bring that safety issue (within the house) to the attention of the owner, but you presumably wouldn't regard it as a reason for not doing work on a supply to a detached garage, would you?

Kind Regards, John