Equipotential bonding in bathrroms

[John Rumm]

Conventional practice would dictate that the CPCs of any circuits introducing power into a bathroom would be included in the rooms equipotential bonding.

However I have to admit to not being able to think of any logical justification wrt to a lighting circuit where light is supplied by 12V downlights (i.e. no earth to the metalwork)) fed from a SMPS/transformer concealed within the ceiling void, and with a plastic cased pull switch in zone 3. Hence there is no way for someone to ever make contact with anything connected to the lighting circuit CPC. Can anyone think of a reason to include the CPC in the bonding in this situation?

[David Hansen]

On Fri, 23 Feb 2007 01:37:04 +0000 someone who may be John Rumm wrote this:-

The reason someone gave a few days ago. Provision for future changes.

[Andy Wade]

This could be a moot point but I think that no supplementary bonding would be needed if the switch were to be outside the zones.

Clearly the switch could be replaced, in principle at least, with one having earthed exposed-conductive-parts - so bonding is needed if it's in the zones [601-04-01].

The lights, however, are not class 1 or class 2 equipment but rely on protection by SELV (provided the transformer/SMPS meets the requirements for an SELV source). On the output side of the transformer there is no CPC to be bonded and on the input side the CPC terminates outside the zones so doesn't require bonding.

Of course if the circuit also feeds other equipment inside the zones, such as a shaver point or mirror heater etc., then bonding will be needed anyway.