Bathroom RCD Supplementary

[User]

Hello is it okay to supplementary bond from a bathroom light to pipes and leave RCD protected mains equipment (like heater, hand-dryer) on RCD protection therefore not bonding their earths

Is it safe to use both RCD protection and supplementary earth bonding on same circuit this doesn't cause any dangerous conflict does it?

Any help greatly appreciated please

 

[Spark123]

Nope, one of the requirements for omitting supplementary bonding on any of the circuit is that all circuits or the location are protected by an RCD (30mA max).
There is nothing against supplementary bonding the CPC of circuits already protected by an RCD.

 

[User]

Thanx very much Mr Spark that's cleared everything up for me now

I think I'll proceed with supplementary bonding because the bathroom lights are on the same circuit as the whole floor lighting and I wish to avoid putting the entire lighting circuit on an RCD (nuisance trips)

Thanx sir

 

[sm1thson]

I wish to avoid putting the entire lighting circuit on an RCD (nuisance trips)

Thanx sir

'nuisance trips' are very very rare, RCD's normally trip because there is a fault, if the RCD is shared with other circuits then it also become a nuisance. if your CU configuration will enable you to put and RCBO in place of the lighting circuits MCB it would be an option well worth considering. accessible bonding is often unsightly and a pain to implement.

 

[User]

Thank you very much sm1thson for your very informative reply

If what you say is true then why are lighting circuits rarely on the RCD side I always thought nuisance trips were the reason?

Aren't those RCBO thingies very expensive? Wouldn't it be cheaper to move the light circuit MCB onto the CU MCB side?

 

[Spark123]

It wasn't the norm to have the lights on an RCD unless you are talking TT systems, however the 17th edn regs now requires them for circuits where there are unprotected concealed cables less than 50mm in a wall.
There is a risk which needs to be assessed which is more from another circuit tripping the RCD, for example where an RCCB supplies multiple MCBs, a socket circuit causing the RCD to trip whilst you are holding a spinning piece of machinery wouldn't be a good design if it also plunged the room into darkness!
RCBOs are coming down in price and are certainly better than using one RCD to protect multible MCBs.

 

[User]

Thank you Mr Spark123 very informative since there's no conflict with a RCD and supplementary bonding I think since most of the supplementary bonding was done in the old bathroom already I'll just add to it for the new shower room this time (basically earth wiring all the pipes in the bathroom and shower room below to all the appliances and lights in both rooms that's a lot of earth wire!)

Thanks for all the help Mr sm1thson and Mr Spark123 appreciated

 

[Adam_151]

If what you say is true then why are lighting circuits rarely on the RCD side I always thought nuisance trips were the reason?

If there is a lot on an RCD, as in the case of a traditional split load board, then

A) If it should trip for no appreciable reason, then it becomes much more of a 'nuisense' and if lights are on it, its very much a bloody nuisense as you have to reset it in the dark!

B) It becomes more likely that it'll trip when there isn't a fault as such, some applicances leak a bit of current to earth when opperting normally, and this can add up and put the RCD near its tripping point, and then if something gets switched on or off the transiant spike can push it over the edge. Computers for example have filters in the power supplies connected to earth, so do electronic controllers on devices like microwave ovens, washing machines etc, also heating elements can get leaky as they age, so cookers, etc are another suspect.

So yeah, I wouldn't advise putting lights on the same RCD as everything else

Aren't those RCBO thingies very expensive? Wouldn't it be cheaper to move the light circuit MCB onto the CU MCB side?

Not prohibitly for 1 or 2 circuits, they cost about £30 for most makes of board, and quite often you can pick up folks leftover stock on ebay, cheapish! , just be carful of dodgy ripoffs made in chinese sweatshops...

 

[User]

Thank you very much Mr Adam_151 excellent reply I am far more interested and informed on RCBO's now thanks very much sir