supplementary bonding query

[jimbosweed]

Hi, i am new to this forum so please excuse me if i havent posted in the right section etc. I am a plumber for my sins, and have always been a bit confused about the laws and regulations on supplementary bonding. Especially nowadays when a lot of plastic pipe and fittings are used. I wanted someone to advise me when sup bonding is required and when not. At the moment i have been advised that sup bonding not required if circuits in hazardous areas are RCD protected? Do you need to sup bond short lengths of visible copper pipe which is connected to plastic pipe? I know that there is lots of different scenarios, but just wanted more of a clear and updated answer. I am grateful of any response. Thanks

 

[telectrix]

it's a little complex to explain in layman's terms. basically, supplementary bonding is not required as long as all extraneous conductive parts are bonded, disconnection times are met, and in the case of a bathroom, RCD protection is fitted, to determine whethe or not a metal pipe or the like is or is not extraneous requires an test from the part in question to the main earthing terminal of the installation. this is done with a "megger" and if the reading is above 22k ohms, then that part is not required to be bonded. bonding a pipe which is not extraneous may give rise to an increased risk of shock.

 

[jimbosweed]

Thanks for your reply. So basically all exposed pipework in a bathroom would need to be tested with a meggar to see if it is extraneous, and therefore needs bonding?

 

[telectrix]

not necessarily. if you have copper pipe in a bathroom that comes from plastic, then there's no way that it can be connected to earth, so you don't bond it. if , say its all copper, and that copper comes from the rising main, it's already bonded by means of the fact that the cold water intake is bonded by the main bonding.

 

[jimbosweed]

Thanks again, that seems clear now. so if all pipework is copper, then why do you need to sup bond if the rising main is bonded by the main bonding. Sorry if thats a stupid question!

 

[Strima]

Where the various copper pipes run in and out of boilers, tanks, valves etc you may not get continuity through the system hence the bonding so the current has some where to flow rather than through you when in contact.

 

[jimbosweed]

Makes sense now thanks guys

 

[Guest55]

One thing to remember is that all circuits in the bathroom need to be rcd protected in order to leave out supp bonding.
So if say , electric shower and towel heater have rcd , but lights dont , then supplementary bonding is still required.

 

[Guest55]

I am a plumber.........

Didnt think you'd get away without a mention did you lol.
I'd have thought all the rocket scientists on your plumbers forum would have answered that for you. ;-)

 

[telectrix]

nah, they're all too busy bonding all the boiler pipes.