Mains Smoke and Heat Alarms

[sadlam]

Hi Guys,

I am currently having an extension built and the drawings show several smoke alarms and heat alarms.

I intend to use mains powered with battery back up.

1.  Any advice on the most suitable alarms

2.  I understand mains pored with battery back up can be wired from the lighting circuit but would you recommend having a separate circuit for this on its own breaker?

Cheers

Steve

 

[Andy™]

i use aico alarms

best wired on lighting circuit. if there is a fault with the circuit then its usually noticed quickly and fixed, on its own it may not be noticed straight away, and may be left broken...

 

[kerching]

What Andy said above....AICO.....go for thr 10year battery version

just because Life is worth it

 

[sadlam]

i use aico alarms

best wired on lighting circuit. if there is a fault with the circuit then its usually noticed quickly and fixed, on its own it may not be noticed straight away, and may be left broken...

Thanks Andy, much appreciated, makes perfect sense now.

Cheers

Steve

 

[Evans Electric]

I use Aico too and I agree with using the lighting circuit  .    Its too easy for  dedicated circuit to be switched off and forgotten. 

 

[Zeespark]

If you do have your alarms wired off of a lighting circuit, have a switched fused spur installed at the very start of the smoke alarm leg for mechanical maintenance.

Andy Guinness

 

[Andy™]

what mechanical maintenance could a smoke detector possibly need?!

if you use an aico alarm, you dont need to isolate anything to change a detector either

 

[SPECIAL LOCATION]

The ultimate reliability of the smoke/heat alarms will be down to the batteries....

e.g.

Unless you are planning on only allowing fire emergencies to occur while the mains is connected...

Never during a power cut..

With all supply wiring protected from any risk of damage during a fire...

When push comes to shove its the back up battery that is doing the work....

Any decent alarm will give intermittent bleeps / warning if the battery is getting low...

and/or if the mains is off...

so unlikely to go unnoticed.

There is not much probability that a dedicated alarm circuit should lose power as there is very little load...

No accessories been plugged / unplugged,  no light bulbs blowing...

Any more than any other circuit should just randomly lose power.

opcorn    

 

[Evans Electric]

Sorry Specs ,  I've been to quite a few jobs where unused MCBs are OFF  and one of them is the fire detectors .

One customer said he thought they were working and had never , in 5 years , looked at the consumer unit or tested the alarms ...which were not powered & with dead batteries . 

Another customer said the last bloke to mess with the consumer was a heating guy , who had been switching breakers on & off ...that had been a couple of years without alarms.    How many people test them ?  Not many .

 

[SPECIAL LOCATION]

Sorry Specs ,  I've been to quite a few jobs where unused MCBs are OFF  and one of them is the fire detectors .

One customer said he thought they were working and had never , in 5 years , looked at the consumer unit or tested the alarms ...which were not powered & with dead batteries . 

Another customer said the last bloke to mess with the consumer was a heating guy , who had been switching breakers on & off ...that had been a couple of years without alarms.    How many people test them ?  Not many .

Same argument can apply if they are taken off a lighting circuit.....

I've seen just as many jobs where lights or part of circuits are off and

I've lost count of the number of questions we get on the forum where DIY bob took down a light fitting..

no idea how to wire it back up

half the lights not working..  has been off for a few days.. can you tell me where to put all the red and black wires sort of question....

For all we know smoke alarms off this same circuit could also be dead...? :C

Whether lights or dedicated circuit if the back up batteries are not tested or verified on a regular basis

then you are living on a hope and a guess that they will work when you need them too!

Unfortunately your looking at the problem from the wrong end...

trying to get the tail to wag the dog....

No mater where you supply your alarms from if they are not checked and tested periodically 

then for all you know they might have failed anyway...

even if the light circuit is all powered up.

No different to a seized up RCD....

powers all there...

But at the critical point its unable to work due to lack of routine testing!

Same as when intruder alarm batteries are left in since the day it was installed..

come the first power cut external bells all start a howling....

(and they could well be off a lighting circuit)

A lighting circuit supply is no more fail safe than a dedicated one, if the alarm sensors themselves are not checked as per manufactures guidance.

Guinness

 

[kerching]

Did a job at a customers......smoke alarm constantly beeping

i asked if they wanted a new battery fitting in it?

No....that noise is to tell,us it is working correctly!...they had lived there for over a year with that beeping every 30 seconds

as for fitting a switch fused spur....customer gets sick of alarm going off when burning the toast so whips out the battery and switches spur off.....possibility?, or certainty!

 

[SPECIAL LOCATION]

If the customer is that way inclined then they are just as likely to remove the whole sensor....

which I have also seen...

Just a base plate stuck on the ceiling...

Again... lighting circuit or dedicated make little difference !

 

[Richard-the-Ninth]

I have to agree with the majority. Domestic smoke alarms should be supplied from the lighting circuit. No point putting in any means of isolation since a s said they will turn it off as and when, like wise dedicated MCB they will at some stage turn it off, but if its a lighting circuit with smoke alarms the lights will not stay off for long.

On the other hand a dedicated FIRE ALARM should be on its own supply.

 

[kerching]

If the customer is that way inclined then they are just as likely to remove the whole sensor....

which I have also seen...

Just a base plate stuck on the ceiling...

Again... lighting circuit or dedicated make little difference !

I See it a lot in rentals

disable the lot, put detector back on ceiling so it looks like it is working!

did an HMO when they first came in to being....full,system.commissioned it in front of Station Officer from Trumpton.

following day he range me..."tell me i am not losing it...that HMO job, we did the alarm yesterday did we not?

meet me on site

went to site

no system

they had ripped it out and sold it in the pub that night!

just saying  

 

[SLIPSHOD & SLAPDASH]

My  next door neighbour's  smokes have had the low battery beep for over a year now. I have even offered him a battery but had it declined.

 

[sadlam]

Thanks to everyone for all your help.

Cheers

Steve

 

[steptoe]

in a house I put the alarms/detectors on the upstairs lighting circuit,

feed to hallway detector, link to upstairs detector, link to first upstairs light,

that way if they turn off the smokes then NO upstairs lights work,

 

[Blue Duck]

My  next door neighbour's  smokes have had the low battery beep for over a year now. I have even offered him a battery but had it declined.

Haha, It amazes me how people put up with that..... 2 of my neighbours are tenants and they both have the beep.

At work we used to have a contact with LFB where we replaced smokes for them, but they never paid the invoice so we just stopped doing it, trouble was no one had any idea what to do with all the old detectors so they just sat in a bag in the corner of the office beeping away.

If someone in the office annoyed you there was this stuff...

:slap

 

[Andy™]

 so they just sat in a bag in the corner of the office beeping away.

i have been known to throw the odd detector in a pond / bucket of water etc when they wont shut up

 

[kerching]

Fire Angel detectors?!

my mate ended up beating it to death with a shovel and burying it in garden...like something from Terminator.

on a cold still winters night you can still hear the eerie disembodied cheep cheep from deep in the bowels of the earth .....allaegedly