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Conduit requirements and cable type

Former Community Member over 4 years ago

I’m in the process of installing seven hard wired fire alarms into our property all of which have to be interlinked.

I intend to re use a now empty steel conduit that runs from right beside our consumer unit up into the loft space. The steel conduit at its point of entry into the loft terminates there presumably the rest was removed in the past. I want to run a cable from there which will have to do an up and over brickwork in the loft.

My first question, is it acceptable in compliance with electrical regulations to simply clip the cable to the brick at the mortar joints or do I have to or even if strictly not necessary should I, put the cable in PVC conduit? This area is not trafficked.

Once I have crossed the brick work and come down to the first alarm, from there I intend to run a cable down the near center of the loft adjacent to the walkway in pvc conduit parallel to the 2 existing lighting circuit conduits located above the joists. I am not going to drill through the joists. At points along the conduit there will be junctions to allow clipped cable not in conduit to be ran parallel to the joists to the relevant alarm. The conduit is going to be a straight run, so my question is having consulted a few sources that state 1.5mm flexible cable not twin and earth must be used in conduit, does it? I understand the reason for flexible cable in conduit with a lot of turns and junctions but this is a straight run.

Thanks

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0 David Stone over 4 years ago

It is the construction Mike.

The outer sheath is almost unplasticised PVC with lots of flame retardant, then an aluminium foil, and the cores are silicone rubber insulated, with a composition that basically turns to silicon dioxide bound together under extreme heat. The foil keeps the oxygen out and the PVC to itself, and the cores are pretty inert as a result. JW didn't really heat it enough to show the worst-case state, still servicable though.

I rather like the stuff for clipped direct applications, it can be very neat, does not need trunking, the clips are small and tidy and very firm and it bends nicely around corners of woodwork or whatever. It is nearly as fireproof as pyro, although does not look too good afterwards unlike bare pyro, better than PVC coated stuff though! Insulation tests after fire exposure are excellent, even if you get the sheath bright red hot.
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0 David Stone over 4 years ago

It is the construction Mike.

The outer sheath is almost unplasticised PVC with lots of flame retardant, then an aluminium foil, and the cores are silicone rubber insulated, with a composition that basically turns to silicon dioxide bound together under extreme heat. The foil keeps the oxygen out and the PVC to itself, and the cores are pretty inert as a result. JW didn't really heat it enough to show the worst-case state, still servicable though.

I rather like the stuff for clipped direct applications, it can be very neat, does not need trunking, the clips are small and tidy and very firm and it bends nicely around corners of woodwork or whatever. It is nearly as fireproof as pyro, although does not look too good afterwards unlike bare pyro, better than PVC coated stuff though! Insulation tests after fire exposure are excellent, even if you get the sheath bright red hot.
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Conduit requirements and cable type

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