Bonding 😣

[bennie]

No waffling, going to get straight to the point. Main water on the exterior of the building in plastic. Changes to copper inside the building. According to regs doesn't need main bonding. Incomer to building is 120mm SWA, TNS with a 70mm earth. Current bonding to the water is 10mm but as said according to the regs it's not needed. Many water heaters & showers on the installation so when an insulation resistance test was carried out between the MET & the stop cock it was showing a dead short. As main bonding isn't required but there is still resistance between the pipework & the MET should there just be supplementary bonding & if so does that mean 6mm would be sufficient.

 

[newfutile]

I take it you measured with the bonding disconnected?
There are a few other ways a pipe can be connected though to earth ,via boiler or cylinder CPC ,or via a gas bond if there is one.
Try a low ohm test to give you a clue .
If with all parallel paths disconnected it's less the was 23 K ohms I would bond it.

 

[bennie]

I take it you measured with the bonding disconnected?
There are a few other ways a pipe can be connected though to earth ,via boiler or cylinder CPC ,or via a gas bond if there is one.
Try a low ohm test to give you a clue .
If with all parallel paths disconnected it's less the was 23 K ohms I would bond it.

Yes tested with bonding disconnected. With all parallel paths disconnected the reading is <999 so no main bond required. So as I said is only supplementary bonding required. Also if I'm testing to see if it needs to have a main bond surly I only need to do an insulation resistance tests?

 

[Pretty Mouth]

the reading is <999

Please clarify: the reading is less than 999 what?

 

[westward10]

One minute you have a dead short then you have <999?

 

[bennie]

One minute you have a dead short then you have <999?

Sorry greater than 999, that what it says on the meter. If you read what I said, with all parallel paths disconnected there is no read but with them connected it's a dead short, which is what you would expect. My only question is does it need a main bond or would supplementary suffice.

 

[bennie]

Please clarify: the reading is less than 999 what?

Sorry greater than with all parallel paths disconnected

 

[newfutile]

Unless you can't meet disconnection times why would you need supplimentary bonding ?

 

[bennie]

Sorry greater than 999, that what it says on the meter. If you read what I said, with all parallel paths disconnected there is no read but with them connected it's a dead short, which is what you would expect. My only question is does it need a main bond or would supplementary suffice.

Unless you can't meet disconnection times why would you need supplimentary bonding ?

Why wouldn't I need supplementary bonding even if disconnection times are met? So it's ok to have no main bond because the water supply is plastic and no supplementary to the copper pipe work inside even though with all accessories connected there is a path between said pipe work and the MET?

 

[newfutile]

are there more than 1 items of conductive parts that you want to prevent from different potentials ?this is what supplimentary bonding is usually for in my experience , whether it needs main equipotential bonding is another mattter,you have said it was a dead short but also stated its over 999 i guess you mean Meg Ohms?.
if its able to intoduce a potential (usually earth potential) you would need to bond it with a suitably sized cable to the met.