power for smoke and heat detectors

[matt.leung]

do smoke alarms and heat detectors need to be wired into an RCBO? as this is what i have been told, as i wish to take it from the lighting circuit.

The smoke alarm and heat detector will be mains operated with battery backup, this is for a domestic re-wire.

 

[Zeespark]

Off a locally sourced lighting circuit should be fine. I would never put smokes on RCBO, MCB yes.

AndyGuinness

 

[matt.leung]

cos there is a leaflet in B&Q saying that they need to be installed on a RCBO circuit...

 

[Zeespark]

So long as you install the cable in mini trunking/metallic conduit if poss you dont need an RCBO bud. The miliampage of the RCBO is the issue when it comes to smoke/intruder alarm/fridge circuits bud.

AndyGuinness

 

[kme]

They do need to be on an RCD protected cct (though don`t believe everything you see/read in B&Q!) ; as Zee has said, take `em from the lighting cct if that has RCD cover - if not, change the MCB to an RCBo.

The issue with putting them on a standalone RCBo is that it could trip, and no-one notice. If its a lighting cct, someone would realise that the lights weren`t working.

NB this info is only good for domestic (grade D) alarm installs. If you get into 5839-1, you have to do things differently.

KME

 

[Zeespark]

Thanks alot for that KME, you got to explain better what I was trying to say.

AndyGuinness

 

[initforthemoney]

Why do they need to be on an RCD protected circuit?

 

[tom1]

Why do they need to be on an RCD protected circuit?

its the burid cable that needs rcd, unless >50 deep or earthed armor

 

[kme]

Why do they need to be on an RCD protected circuit?

Why DON`T they??

refer BS5839-6. (para as quoted last time we discussed smoke alarm power supplies).

 

[Andy™]

cos there is a leaflet in B&Q saying that they need to be installed on a RCBO circuit...

so B&Q now thinks there are the NIC who think the are british standards?

 

[Evans Electric]

Why do they need to be on an RCD protected circuit?

Because of the bloody stupid change in the regs with the 17 th Ed. Cables buried 10 feet in the wall and covered by steel armoured plate 1" thick are OK .

This sudden obsession with drilling holes in cables has compromised people's safety in a fire condition . As said in other posts , if an RCD or MCB trips no one will notice that the Alarms are not powered.

If it was up to me they would be on a HRC fuse ,sealed like the main cut-out.

 

[batty]

Not sure if this relevant about putting them on a local lighting circuit but was called out to a property last week. Builders electrician had fitted two screwfix mains smokes three years before. They had been playing up beeping in the night. I changed batteries but called out again still doing it. Went around this evening lady said she wanted them taking out altogether so talked her into having two EI141 smokes now hoping they are going to be ok. Not sure what problem could be but she has low energy lamp in pendant feeding smokes. I always put seperate circuit in for smokes not happy running them of lighting circuit. if you read instructions smokes should not be put on circuit containing fluorescent lights and dimmers and there is a lot of other things you need to be aware of in instructions. I am happy to have them on a seperate circuit as the only time they would trip is if you have a short on cable but that is unlikely.

 

[kme]

Seperate cct - fine. Seperate residual current device, though - for grade D - not recommended

 

[bluetobits]

The issue with putting them on a standalone RCBo is that it could trip, and no-one notice. If its a lighting cct, someone would realise that the lights weren`t working.KME

What if it was the middle of the night, asleep with all lights out anyway, and there was a fire?

 

[Lee321]

What if it was the middle of the night, asleep with all lights out anyway, and there was a fire?

headbang

 

[Andy™]

What if it was the middle of the night, asleep with all lights out anyway, and there was a fire?

thats why they have battery backup

 

[kme]

Which happens to be the spec. of a grade D system.

Otherwise, you could also use the reasoning that there might be a power failure, which would cause the smokes to become inoperative, during the period they`re most likely to be required - candles & oil lamps front & centre.....??