Proving Earth Bonding

sparkyparky · May 2, 2013

Hi guys was just after some opinions really, hope you can help please bear with me I'm from a commercial/industrial background and have recently gone self employed so getting more into domestic.
I understand that we're supposed to check main bonding is in place before any work is carried out (which 90%of the time is when I quote) but to what extent?
Gas is generally pretty simple but a surprising amount of people have no idea where their water comes in which turns a simple looking at a job into emptying kitchen cupboards looking for a stop cock.
Even if they know where it is and it's accessible the most I feel you can realistically do for small/medium jobs is a visual check but what does this prove? I've come across jobs a few times where cables have been chopped by kitchen fitters or just poked through the wall at both ends.
Do you think it would be acceptable to put in a quotation that it's assumed earth bonding is in place but if it can't be confirmed through testing then will require upgrading?
This to me makes more sense but don't think I could really complete a cert showing it missing if the customer refuses when work has started and wouldn't want to be liable for doing it at my expense.
Any thoughts would be greatly appreciated!

telectrix · May 2, 2013

test with a wander lead before quoting. don't take long.

Badged01 · May 2, 2013

You cant do any domestic work to meet 17th edn regs unless there is bonding in place, full stop.

Regardless of whether you cant physically "eye-ball" the connection to any of the services you still need to confirm continuity of bonding with a wander lead -- as Tel states.

Once you have a continuity reading between say the water stop cock handle and the cable end at the consumer unit then you have confirmed bonding. You just now need to make a comment on whatever cert you are using that explains this -- "continuity of bonding confirmed but physical connection not verified as customer unwilling to allow distruptive/intrusive work to verify physical connection".

In the ideal world you would open up the cupboard, housing, tiling or wall to confirm the physical connection, correct earth warning label etc ... but unfortunately lots of customers dont want their property damaged so cover your butt by annotating what you have done on the cert.

Silly Sausage · May 2, 2013

A sub 0.1ohm reading off the pipe where the clamp is, to the disconnected other end, would be good enough for me.
Without a visual of the entire run.

chopper76 · May 2, 2013

You can put any stipulations in your own quotations, it's an written statement of what will/is going to happen for the amount should they accept, I regularly state that any unknows will need to be sorted and floorboards will need to be removed but will be reinstated, etc etc

Octopus · May 2, 2013

Badged01 said:
You cant do any domestic work to meet 17th edn regs unless there is bonding in place, full stop.

Tell that to Bob the Builder, kevin the Kitchen fitter, Bob the bathroom fitter and Harry the handyman!

skydog23 · May 2, 2013

Forgive me if I'm wrong,
but 0.05 ohms springs to mind for the limit ?
Think it came from the resistance of 25m of 10mm2 copper cable which works out at 1.83mohms/M x 25 divided by 1000, gives 0.0457ohms. ?

Badged01 · May 2, 2013

Very true Murdoch, Ive often wondered how they sign off their certificates for the work ........ ooops, what certificates!!

Richard Burns · May 2, 2013

skydog23 said:
Forgive me if I'm wrong,
but 0.05 ohms springs to mind for the limit ?
Think it came from the resistance of 25m of 10mm2 copper cable which works out at 1.83mohms/M x 25 divided by 1000, gives 0.0457ohms. ?

0.05 ohms is given as a recommended level at which you can assume, in a periodic inspection, that main and supplementary bonding is adequate, however this is not a limit as such just a recommendation for periodic inspections.

No reason not to use this value as a guide but not as a requirement.