Bathroom refit, RCD?

[xr4x4]

Lo all,

Doing a bathroom refit, it already has downlights and a extractor fan.

These are currently not RCD protected.

Downlights will be replaced with new ip65 fire rated downlights, same places as old, so I'm guessing (without looking) same cables can be used.

Extractor in ceiling will be moved to above bath/shower to an inline extractor, with a LV downlight in the centre, new wiring will have to run for this.

Question is simple... Do the lights and fan need to RCD protected?

 

[sparkybird]

not if both main and supplementary equipotential bonding are in place. In some cases it's easier and more aesthetically pleasing to RCD

 

[xr4x4]

Thanks.

Will have to check the main bonding, supplementary bonding is on the bath pipes, but not the sink.

 

[sparkybird]

No problem - main bonding needs to be in place before any work is done (ie not just that in bathroom)

The supp bonds need to be to hot, cold and rad pipes, plus any metalwork such as the bath - it's often easier to RCD using rcbo or for lights an RCD FCU with 5A fuse near the fuse board unit

HTH

SB

 

[xr4x4]

No problem - main bonding needs to be in place before any work is done (ie not just that in bathroom)

The supp bonds need to be to hot, cold and rad pipes, plus any metalwork such as the bath - it's often easier to RCD using rcbo or for lights an RCD FCU with 5A fuse near the fuse board unit

HTH

SB

Ok, great.

I've seen a lot about but not to the extent you mention.

So it needs a RCD.

Can a RCD FCU for the bathroom lights be fitted outside the bathroom, or does it need to be fitted by the CU?

I'm worried that a RCBO for the lighting circuit will cause problems, shared neutrals, the stairs 2 way lighting etc.

 

[ban-all-sheds]

Can a RCD FCU for the bathroom lights be fitted outside the bathroom, or does it need to be fitted by the CU?

Should be by the CU.

There is a school of thought that suggests an RCD on a bathroom circuit should protect the whole circuit not just the part in the bathroom.

Indeed - the wording is circuits of the location, not in....


xr4x4 - the bathroom contains exposed and extraneous conductive parts. You have inadequate supplementary equipotential bonding. A L-E fault upstream of your local RCD could, until it is cleared by the circuit OPD, raise the potential of an extraneous conductive part with respect to the exposed ones to a dangerous level.

This is a Bad Thing™.

I'm worried that a RCBO for the lighting circuit will cause problems, shared neutrals, the stairs 2 way lighting etc.

Then those should be sorted anyway, not left as a block to using an RCD.

 

[ericmark]

701.411.3.3 Additional protection by RCDs
Additional protection shall be provided for all circuits of the location, by the use of one or more RCDs having the characteristics specified in Regulation 415.1.1.
NOTE: See also Regulations 314.1(iv) and 531.2.4 concerning the avoidance of unwanted tripping.

I can't see any mention of being able to wire to previous version of BS7671 in that statement.

Under 701.415.2 Supplementary equipotential bonding it does say:-

Where the location containing a bath or shower is in a building with a protective equipotential bonding system in accordance with Regulation 411.3.1.2, supplementary equipotential bonding may be omitted where all of the following conditions are met:

But as a new installation there is no real option you need RCD protection.
As to using a RCD FCU be careful to select the correct type. As long as the loop impedance is within spec then a passive type would be used. Passive means when the supply is lost it does not trip.

When the loop impedance is not good enough under fault conditions the voltage could drop to a point where the RCD would not work. In this case an active RCD is used. The idea is should the voltage drop below the point where the RCD would work it will trip anyway so fails safe. RCD's used on extension leads will be the active type. Any power cut and these will need resetting.

Who ever is doing the electrical work will need to measure the loop impedance and fill in the installation certificate which with a scheme member is sent to the scheme operator and where using the LABC direct it's sent to them to comply with the Part P laws.