Earth Bonding on a Submain

[walsall]

Morning all,

I’ve had a ‘discussion’ with my local NIC rep about a particular scenario that I’d like others advice on please.
Property is TNS. There are two boards, one which does the house and a single switch fuse (BS1361) which feeds a 4mm SWA to garage/workshop. There are main protective bonds to the gas & water as expected from the MET. The 4mm terminated in a box with loads of flex out to lighting & power points in the garage (v. bad)

Customer requested that I rewire the garage with something more suitable and safe. I provided a 2way board with RCBO’s so that his lighting didn’t fail while using power tools and used plastic trunking. There is an incoming water pipe (plastic) which feeds the sink in the garage which then turns in to copper. I ran a 4mm G/Y from the board to the pipe (in the plastic trunking) to bond the copper pipe. NIC bloke said that should be 10mm as it’s a main protective bonding conductor. I said that if it was it should be run continuously from MET to that pipe but realistically that’s not really practical. As the pipe is plastic anyway there is no realistic prospect of there being different earth potential either like there could be if the garage water main was lead and the main install PME for instance. I chose 4mm as it matched the size of the line conductors.

Any thoughts on what’s correct?

 

[Deleted member 9648]

If the incoming pipe is plastic it is unlikely to be extraneous,a test will confirm.Why did you consider it required bonding?
If it does require main bonding...(unlikely)...and it is TNS then the minimum size will be 6.0mm,not 10.0mm.

 

[Pete999]

Agree with wirepuller

 

[Simlec]

Why are you bonding a plastic pipe.

 

[7029 dave]

Ditto post 2, but I would go for 10mm IMO

 

[SPARTYKUS]

Wirepullers got to the nub. Test it. If greater than the prescribed limit then no bond required.

And agree with WP on tuther bit too

 

[Simlec]

Don't forget to also test your plastic soil pipe from your toilets and drains, as they also enter your building from outside..

 

[SPARTYKUS]

Well thats just silly!

:thinking:

 

[Simlec]

Well thats just silly!

:thinking:

And so is testing to see if plastic is a good conductor !

 

[telectrix]

all depends on the conductivity of sh!te.

 

[Simlec]

all depends on the conductivity of sh!te.

Lol

just remember we don't test what's in the pipe!

 

[Silly Sausage]

Lol

just remember we don't test what's in the pipe!

I do...if it's connected to a beer engine!

 

[SPARTYKUS]

Well, I think the suggestion was to test on the copper bit....but I think you knew that.

who's to say what else is going on there, I for one can't see it.

what WP has said is what you're supposed to do.

Maybe theres a branch of ....copper pipe later on that, well, maybe goes into the ground and makes the value betwixt MET and potential (or not) extraneous part, well, less than 22 thousand ohms.

just a thought. Can't see it. By the book is to test it whether the bit you refer to is plastic or not.

hope that makes sense.

more beer please.

 

[Simlec]

Well, I think the suggestion was to test on the copper bit....but I think you knew that.

who's to say what else is going on there, I for one can't see it.

what WP has said is what you're supposed to do.

Maybe theres a branch of ....copper pipe later on that, well, maybe goes into the ground and makes the value betwixt MET and potential (or not) extraneous part, well, less than 22 thousand ohms.

just a thought. Can't see it. By the book is to test it whether the bit you refer to is plastic or not.

hope that makes sense.

more beer please.

So to test the plastic pipe you would disconnect your copper part and then test to MET, which would then give you a reading of ?? Remember it's plastic!

 

[SPARTYKUS]

So to test the plastic pipe you would disconnect your copper part and then test to MET, which would then give you a reading of ?? Remember it's plastic!

im a bit lost now.

I meant the copper bit.