No earth to smoke detectors.

[Amp David]

Been at a house today doing a pert rewire and new kitchen circuits. Noticed whilst under the floor boards that the smokes have been wired in 3 core flex, using the earth as the interconnect. Is this an acceptable way of doing things? Only reason I can think is that on the back of the detectors it states they are double insulated.

 

[Mr Mark Sparks]

there is a couple of issues
there is a reg somewhere that says a green and yellow cable may not be overmarked and used as a live conductor
and the need to provide an earth in the cable and at the point

 

[Sav]

Even though its flex and the earth is insulated throughout, you MUST never use an earth for a phase/line ( not even if you sleeve it with phase/line).
Its in the regs as well (dont know what page though ).
Hope this helps,
Best regards,
Sav

 

[telectrix]

But, can you sleeve the earth cable blue as neutral? i have seen it stated in this forum that it is ok to use 3 core flex to a bathroom fan

 

[antimatter]

Don't think so because the neutral is a live conductor too!

 

[bugsy]

Flex used as fixed wiring , using the cpc as a live conductor, er hallo!

 

[Sav]

Hi Telectrix,
As animatter said, the neutral is a conductor and so you cannot use the earth for this.
also, as mentioned by Mr MarkSparks, we need to have an earth at the point.

 

[telectrix]

agreed. i always use 3 core+earth. But when will the makers of bathroom fans make them to accept this?

 

[Sintra]

Reg 514.4.2 a protective conductor shall not be oversleeved except if being used as a PEN conductor.

 

[antimatter]

The pen conductor typically occurs between the substation and the entry point into the building, and separated in the service head.

 

[sjm]

When I contacted the NIC helpline and asked whether I could use 3 core flex, with cpc oversleeved as switched live, for an extractor fan (double insulated of coarse) I was told that they could see no reason why not as cpc same conductor size, also this would not require 1 core to be cut out(which they considered was a no no).
Also quote from NIC "you could do a complete rewire using flex if you wanted too".
Reg 514.4.2 states that SINGLE CORE cables that are coloured green/yellow throughout their length shall only be used as a protective conductor and shall not be overmarked.

 

[antimatter]

sjm
Also quote from NIC "you could do a complete rewire using flex if you wanted too".



What is the chaps name that said that?

 

[sjm]

Didn't ask his name, just the question about using flex in fixed installations. If you don't agree with his answer please give reasons, reg numbers etc. I assume that NIC technical helpline is just that, a helpline, and not there to give duff information.

 

[Sintra]

Strange as it may seem flex can be used for the fixed wiring of an installation. Last year we wired a large office block completely in flex apart from the sub mains. Although this installation was overseas it was all designed, installed and tested to BS 7671.

 

[malcolmsanford]

When I contacted the NIC helpline and asked whether I could use 3 core flex, with cpc oversleeved as switched live, for an extractor fan (double insulated of coarse) I was told that they could see no reason why not as cpc same conductor size, also this would not require 1 core to be cut out(which they considered was a no no).
Also quote from NIC "you could do a complete rewire using flex if you wanted too".
Reg 514.4.2 states that SINGLE CORE cables that are coloured green/yellow throughout their length shall only be used as a protective conductor and shall not be overmarked.

In this rare instance have to agree with the NICEIC man if it's not a single core cable and not a bare conductor within a sleeved cable then you can sleeve a yellow/green and use it as a live conductor. What you can't do is use the colour yellow/green as a live conductor.

521.9.1 also prooves him right about the flexible cable. Don't you just hate it when they are right