Safety over Requirements

[STI]

I have an L shaped bathroom. A single light in the bathroom does not cast enough light round the L. Wife wants a second light put in. No other elecrtics are in the bathroom. The bathroom lights are on the same circuit as the rest of the upstairs lights circuits. The lights are on a 6 amp MCB which is not protected by an RCD.

If i add the extra light, just run the cable to it from the existing light, does this mean that i have extended the circuit and therefore because they are in a bathroom,the lights now have to be protected by the RCD. And the work notified etc,

If the answer is yes could it not be argued that this makes the existing installation less safe than it was before, as if a bulb blows there is a good chance the RCD would trip and all the upstairs lights would be off.

To run a seperate circuit to the bathroom lights seems an excessive and relatively expensive option.

 

[RF Lighting]

If i add the extra light, just run the cable to it from the existing light, does this mean that i have extended the circuit and therefore because they are in a bathroom,the lights now have to be protected by the RCD. And the work notified etc,

Yes

If the answer is yes could it not be argued that this makes the existing installation less safe than it was before, as if a bulb blows there is a good chance the RCD would trip and all the upstairs lights would be off.

No. A failing lamp can not create an earth fault, so it can not cause an RCD to operate. The only thing it may operate is an MCB which you already have.

To run a seperate circuit to the bathroom lights seems an excessive and relatively expensive option.

You don't have to.

You can either have an RCBO installed at the CU, or even an RCD FCU local to the bathroom.

 

[electronicsuk]

If i add the extra light, just run the cable to it from the existing light, does this mean that i have extended the circuit and therefore because they are in a bathroom,the lights now have to be protected by the RCD. And the work notified etc,

As all circuits entering the bathroom must now be RCD protected, I would say yes, any additions you make must have such protection. As the work is in a special location, it should be notified regardless of whether or not you work on the consumer unit.

With regard to nuisance tripping, the best way to avoid this may be to feed the bathroom lighting from an RCD Fused Connection Unit.

EDIT: Well, seems that I was beaten to it!

 

[ban-all-sheds]

If i add the extra light, just run the cable to it from the existing light, does this mean that i have extended the circuit and therefore because they are in a bathroom,the lights now have to be protected by the RCD. And the work notified etc,

Notified, yes.

RCD protected, not IMO, but I'm in a minority with that one.

My argument is that the RCD requirement applies to bathroom circuits - it is a separate requirement to that for sockets, and a separate requirement to that for concealed cables in walls & partitions.

My argument is that as you have not created a circuit in the bathroom, just modified it, then you are not bound by the regulations which apply at the circuit level. The work for which you are responsible is not a circuit, so the circuit regulations do not apply to the work you do.

if a bulb blows there is a good chance the RCD would trip and all the upstairs lights would be off.

Actually there isn't - bulbs blowing take out MCBs because of the surge - they don't generate an imbalance between L & N.

To run a seperate circuit to the bathroom lights seems an excessive and relatively expensive option.

Put an emergency light in?

 

[Paul_C]

Personally, whatever the official interpretation of the Wiring Regs. may be, I think it's completely over the top to start saying that RCD protection needs to be added just to run a few feet of cable in the roof to add another light in the bathroom. This whole RCD business really needs to be put into better perspective.

However, whatever one's interpretation of the rule, remember that this regulation comes only from BS7671, which is not mandatory, so you are in no way obliged to follow every last detail of it.

Notifiable? According to the rules (which in this case are mandatory by law), then yes. Although I'm pretty sure that most people would rather do something with £100 to £200 other than throw it away on a £15 job.

 

[ban-all-sheds]

Buying an installation tester on eBay would be an apposite use.