Electric Shower - Supplementary Bonding

[stl]

I have an electric shower connected to an MCB on the CU via a two core and earth cable with a separate double pole isolator switch outside the bathroom. The case of the shower is plastic and is connected via a 15mm plastic water pipe.

Does this shower unit (earth connection) need separate supplementary bonding to other metal objects in the room which are already connected to each other? - mainly metal incoming water pipes and radiator as bath and other pipes are plastic?

Also, if required, what is the best way to install this bonding as connecting an earth cable up to the shower unit would be difficult due to the bath panneling? - can it be connected to the double pole earth wire?

thanks

 

[Adam_151]

You should bond the cpcs of all circuits entering the bathroom together with all other services which could introduce a potential, this should be close to the bathroom, but doesn't need to be in it, in a nearby airing cupboard is fine.

Perfectly ok to connect to the shower circuit via the isolator as long as as you can get it in (some are a bit tight and full of wiring!)

Typically, things you'd bond together are the shower circuit cpc, the lighting circuit cpc, the hot and cold pipes and the heating pipes, there is no point in bonding daft things that can't introduce a potential, for example toothbrush holders or door handles

 

[ColJack]

I've never really understood that.. if the cpc's are all in the same terminal rail at the board, aren't they already at the same potential?

also, if my mothers CU is in the cupboard under the stairs directly below the bathroom ( about 3 meters length of cable from breaker to shower ), do i still need to bond the cpc's together?

 

[Adam_151]

I've never really understood that.. if the cpc's are all in the same terminal rail at the board, aren't they already at the same potential?

Voltage dropped on a long cpc during a fault situation?

also, if my mothers CU is in the cupboard under the stairs directly below the bathroom ( about 3 meters length of cable from breaker to shower ), do i still need to bond the cpc's together?

That'd be a judgement call, 3m is probably close enough to be said to be in close proximity to the bathroom, as long as the lighting and any other circuits are connected with a similarly short piece of cabling and doesn't go to other fittings first, etc, I suppose you could say the boning of the CPCs has been done (but still need to do pipes)

 

[stl]

Thanks - most useful.

I understand therefore that the CPC's need to be bonded to the metal pipes etc. in the bathroom and this can be done via the switches instead of at the light fitting / shower unit itself.

Also, I have a plastic bath on a metal frame - does the metal frame need to be bonded?.

There is already some bonding in place which connects mains water pipes (in addition to main earth) with the metal pipes which lead to the sink (from plastic pipes under the floorboards) and the metal radiator also fed by plastic CH pipes. Bath pipes are all plastic. This existing bonding is connected to an earth stake under the kitchen floor as there is no incoming earth supply.

So is it o.k to connect up the CPC via the isolators to the existing supplementary bonding and leave it also connected to the earth rod, so in effect it is connected to earth in two places?.

Also as the radiator and basin are connected by plastic pipes (the latter with say 2m of coppper pipes leading to taps) is it correct that these are already connected to the supplementary bonding or is this not really required but ok to have. The radiator is connected via short lengths of copper pipe then plastic pipe under the floorboards

Thanks