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Hi, everyone

I'm moving some light fittings. The current fittings are wired so there is only a switched live to each fitting. The permanent live is fed to a junction box along with the switch and the switched lives go from there to the fittings.

The existing wiring is a real mess - literally just laying on top of the plasterboard under the insulation. When I re-do the wiring I will clip it to the joists, but - 2 questions.

1) Do I have to use fireproof clips or are the plastic ones I've been using for years still ok

2) The whole place is wired like this, including the socket wiring. Mostly done in the 80's although there have certainly been some changes over the years. Is/was this legal, or should all the cables be clipped?

Thanks
 
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TJ Anderson

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If you are referring to cabling causing premature collapse in fire then no. T&E over a plasterboard ceiling is not going to cause it to collapse prematurely.
 

TJ Anderson

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Covering cables completely in thermal insulation over 500mm of its length reduces the current carrying capacity rating by 50%. Even so, very unlikely that your lighting load exceeds 50% even if it's 1mm.
 
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  • #4
Hi - thanks for the reply. Cables are 1.5 mm and only supplying about 200w worth of flourescent lights.

I was more worried about whether the cables had to be clipped as opposed to just laying there like electric spaghetti, and if do, what to use. For the cables to fall down, the ceiling would have to be completely destroyed anyway, and they're over the joists.
 

TJ Anderson

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Ok, so about 1A. No worries there then. If it makes you feel better, Just use plastic flat twin and earth clips if you want to tidy them up bit.
 
Are cables not rated for the protective device rather than expected load? If you cover them in insulation technically you could require larger cables?
 
  • Thread Starter Thread Starter
  • #8
Protective device WAS a 6 amp MCB, now a 6 amp RCBO. Might possibly have a ceiling fan on the circuit one day but I would never connect a socket on a lighting circuit.

In my case, if I wanted a socket in the loft (for power tools or whatever) it would be just as easy to connect it to the socket ring, since ALL the wiring is in the loft space anyway.
 
I'm just pointing out how the regulations are and how that affects both your safety and the safety of future occupants of the property.
What brand is the rcbo?
 
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  • #10
It's a Schneider RCBO. The CU is an old square D QO board that I can still get new (although ecoensive) parts for.

Every circuit I touch is being upgraded to RCBO from the original MCB's. When I moved in, the only RCD's in the place were on the electric shower and one of 4 socket RFC's.
 
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  • #11
Why would I want a 3a RCBO? Don't think I've ever seen one. Am I missing something fundamental here? It's a standard lighting circuit with a 6a protective device feeding cables rated at about 7.5 a even if de-rated to 50% because of the insulation.

It's always been a 6 a circuit.
 
Hi, everyone

I'm moving some light fittings. The current fittings are wired so there is only a switched live to each fitting. The permanent live is fed to a junction box along with the switch and the switched lives go from there to the fittings.

The existing wiring is a real mess - literally just laying on top of the plasterboard under the insulation. When I re-do the wiring I will clip it to the joists, but - 2 questions.

1) Do I have to use fireproof clips or are the plastic ones I've been using for years still ok

2) The whole place is wired like this, including the socket wiring. Mostly done in the 80's although there have certainly been some changes over the years. Is/was this legal, or should all the cables be clipped?

Thanks
Hello Philip,the Niceic carried out tests for insulation values and found cables laying on plasterboard beneath insulation were least likely to be affected by thermal insulation problems,clipping to joists on the side or laying on top of the insulation would increase the thermal effects,this may sound strange but they are the experts.
 
You may be right I did not bother doing any calculations but neither did anyone mention it. people were mentioning load instead of the rating of protective device. If you want to derate a properly install cable by 50% and you aren't going to calculate it then derating the protective device would ensure safety.
 
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Wilko

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Good Morning Folks - looking Appendix 4 and Table 4A2 for installation method, I'm picking that it's "most like" method 101. This refers me to Table 4D5 which for 1.5mm cable gives 13A at 30C ambient. So all is well with 6A OLPD :) .
 

telectrix

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Good Morning Folks - looking Appendix 4 and Table 4A2 for installation method, I'm picking that it's "most like" method 101. This refers me to Table 4D5 which for 1.5mm cable gives 13A at 30C ambient. So all is well with 6A OLPD :) .
Swot ! :eek::eek::eek:.
 
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