No earth to smoke detectors.

[Mr Mark Sparks]

with regards to the flex issue surely the reason we dont generally use it for whole installations is that its cost prohibitive.?

 

[nickblake]

Find this situation alot with central heating systems , and the hole in my snips shows the reason why it shouldnt be done ,yes it was isolated except for the earth well what i thought was the earth ,this is why multi core cable is made twe or flex

 

[bugsy]

quite agree with all the comments regarding the use of flex and over sleeving and as Sintra states flex is used extensivley in France and Spain for fixed installations, (and here for some modular wiring systems ) then again there's nothing to stop you using a plastic hose pipe instead of PVC conduit, all a question of professional integrity

 

[Amp David]

Thanks for all the input fellas.

Not going to touch the smokes on the job, reason is cost. The customer isn't paying for the smokes to be rewired in 3core & earth, so will be leaving alone. Just make sure I note it on the EIC

 

[rshaw125]

I personally would leave the smoke detectors as they are.

Some would say that it is save but it is an unsatisfactory state, as your smoke detectors are insulated and doesn't offer a risk of shock.

Just inform your customer and note it on your paperwork to cover yourself.

 

[accordfire]

Not ever.

Most smoke detectors have a parking terminal for the CPC. Apart from BS 7671 making clear (as has been pointed out) that the CPC can't ever be used to carry phase, even with over sleeving at terminations - if that flex is ever broken along its length, what is someone going to assume is present on the CPC? Worse, assuming disconnection from supply prior to working, that alleged CPC is then connected to the earth terminals of other circuit devices (as happens, though wrongly), and presto, a potentially "live" building - especially on non 17th installations.

IMHO, it isn't a suitable cable type for smoke detectors in any case. They are there for LIFE safety, typically, and should be treated as such.

Whilst it is still acceptable to use 624x pvc cable for some installations, BS 5839-6 has a clear distinction regarding suitable cable. Anything above a Grade D installation should be in fire resisting cable, and that's mandatory for Grades B and A. All smoke detection in dwellings should be installed to comply with BS 5839-6.

As a rule of thumb, we always use fire resisting cable on any system which has a "central control" or common power supply, and in any situation where there's likely to be a need to identify specifically cable for the fire system, distinct from a general circuit. That's most of them.

 

[antimatter]

Thanks for clearing that up Bill.

Just as I thought.