Lighting circuit wiring advice

[raustin]

Have changed a fuse board for a consumer unit and found that there were 2 wires going into one 5amp fuse for the downstairs lights. The extra wire was for the outside light.

I have put the outside light on its own MCB now, but there is no CPC coming back from the outside light, instead it is going back to the light switch and connected to the CPC for the downstairs lights.

The way that the outside light has been connected is a bit strange, so I will try to explain it.

From the CU there is a 2 core (can't see a CPC) going to the light switch which is a 3 gang (lounge, landing and outside). They have used the brown as line going to the switch and then the blue as the switch line coming back to the CU. This blue is connected to another 2 core (again can't see a CPC) the brown going out to the light and then the blue returning to the neutral bar.

The CPC in the light has continuity back to the CPC's in the light switch. So there is a CPC somewhere.

What is the best way of putting this right. Would it have been OK leaving the two wires going into the one MCB instead of putting the outside light on its own circuit?

What about the CPC not coming back to the CU?

Re-wiring the outside light isn't an option at the moment so would it be best to disconnect it?

Any advice would be welcomed.

Thanks

Rich

 

[SirKit Breaker]

Without seeing the set up it is hard to comment, but if you can confirm 100% that there is a direct earth path back to the earth bar in the cu by whatever route through the installation(not parallel paths) then i see no problem, but if you are unsure then what about fitting a class 2 outside light. Did you do a Zs at the light?

Cheers............Howard

 

[pushrod]

Only skimmed what you wrote but sounds like you could have left it as was and noted deviation on EIC for no cpc on the outside lighting cable - that cable should have its own cpc - apologies if not read properly

 

[raustin]

Without seeing the set up it is hard to comment, but if you can confirm 100% that there is a direct earth path back to the earth bar in the cu by whatever route through the installation(not parallel paths) then i see no problem, but if you are unsure then what about fitting a class 2 outside light. Did you do a Zs at the light?

Cheers............Howard

Zs was 0.50

 

[SirKit Breaker]

Zs was 0.50

Thats low enough, i would leave it alone, and do what pushrod says.

Cheers........Howard

 

[nickblake]

Think ill have to agree with push rod and circuit breaker on this one , its one of those that you realy need to see to be able to offer any advice , i would mark it down on the EIC ,Zs reading is fine max is 7.66 on a 6amp 60898

 

[raustin]

Thats low enough, i would leave it alone, and do what pushrod says.

Cheers........Howard

OK - so leave it with the two lines going into the one MCB or on its own MCB?

 

[telectrix]

depends. if you put it on a separate mcb. from how you've described it you could have 2 live feeds into the switch. if that is the case, then keep em both on 1 mcb.

 

[raustin]

depends. if you put it on a separate mcb. from how you've described it you could have 2 live feeds into the switch. if that is the case, then keep em both on 1 mcb.

OK yeah I did wonder about the 2 live feeds to one switch. OK, so both wires into one MCB and note it and the CPC on the EIC as a departure? This will be OK as was going to use this job to show as my major install for registration?

 

[alanl]

2 feeds from one MCB is fine, so long as the expected total load will not exceed the MCB rated value.
I did a consumer unit change last year that on first inspection was 8 circuits, but when tested, it was all radial circuits.14 circuits altogether.
Daft, as 2 light fittings on one circuit, 3 on another, a single socket on one etc.
I doubled up a number of them to keep the CU size down to 10 circuits.
Alan.

 

[telectrix]

it's a big NO_NO to have 2 feeds into a switch as the next sparks to come along could isolate what he thinks to be the lighting circuit, then get a belt from the other feed when working on the switch. OK, he should prove dead, but prevention is better thasn dead.

 

[raustin]

OK thanks for all the advice. Going back to the CPC. The Zs of the outside light is 0.5. There is CPC continuity from the outside light to the switch an hence back to the CU. Is this OK or does it need noting that the CPC does not go directly back to the CU? Just it looks strange as there is one less CPC to the number of line and neutrals.

 

[pushrod]

IMO if they are on the same mcb (which you will have) and there is a Zs for the outside light (which there is) then the only thing i would note is the cable without the cpc. This will signal to any to any future spark that it is potentially unusual.

I would check that isolating the mcb also isolates all feeds into the switch.
Edit : oops as tel mentioned above!

 

[nikmet]

2 feeds from one MCB is fine, so long as the expected total load will not exceed the MCB rated value.
I did a consumer unit change last year that on first inspection was 8 circuits, but when tested, it was all radial circuits.14 circuits altogether.
Daft, as 2 light fittings on one circuit, 3 on another, a single socket on one etc.
I doubled up a number of them to keep the CU size down to 10 circuits.
Alan.

If you have a situation with for example 2 lighting circuits sharing 1 mcb, how do you fill in the columns on the test cert, as you will have 2 readings for each box?

 

[pushrod]

If you have a situation with for example 2 lighting circuits sharing 1 mcb, how do you fill in the columns on the test cert, as you will have 2 readings for each box?

It would count as just one circuit and highest values are recorded - the same as if you had a spur at CU on a radial power circuit