Mains smoke alarms

I have two mains smoke alarms installed in my house.
They have both recently started going off for no
reason.
The only way I seem to be able to reset them is to
flick the CU off the back on again.
Where would these be wired into? Would they be wired
in the lighting ring main or from the sockets?

If they are Mains operated,they should have small green LED's to indicate a healthy supply and a red LED which flashes at intervels to indicate a battery check.

Flick off each individual circuit breaker at the board,when the correct breaker is open,the LED will go out.
Any idea why they would be going off?

Could be any number of reasons,usual one is they are located in the wrong place ie. close to a scource of smoke or steam,may require further investigation

I have an extractor fan in the bathroom that as
recently stopped working. i.e. no power st ceiling
switch. Could this have something to do with it?

mmm,not sure there,further inspection needed.

If you feel unsure,get a spark in

SF

 

I have two mains smoke alarms installed in my house.
They have both recently started going off for no
reason.
The only way I seem to be able to reset them is to
flick the CU off the back on again.
Where would these be wired into? Would they be wired
in the lighting ring main or from the sockets?
Any idea why they would be going off?
I have an extractor fan in the bathroom that as
recently stopped working. i.e. no power st ceiling
switch. Could this have something to do with it?

If the alarms are installed as per the regs they should be supplied from thier own dedicated circuit and the circuit should have a warning label at the CU. Some people wire them from the local lights, test that you have a 230volt supply at the fittings and if back-up batteries are fitted then make sure they are servicable, if in doult ask a sparky to have a look, also depending what type of smoke detector you've got dust with set them off.

 

Have you cleared the problem? Was it just the batteries? Trust you realise that the batteries are completely concealed on these mains-powered alarms, such that you have to completely disconnect the mains connection to access the battery compartment.

 

I believe building regs require smoke alarms to be fed off a regularly used cct. eg lighting.
A dedicated fuse/mcb could trip and be out of action for long oeriods without the consumer knowing.

 

[/quote]I have two mains smoke alarms installed in my house. They have both recently started going off for no reason.
The only way I seem to be able to reset them is to flick the CU off the back on again.[/quote]

sounds like you got a faulty smaoke alarm unit/head . If it was just a flat battery you would probably be hearing a small chirp every 30secs-1min

without further testing or tracing you will not find out , but they most probably will be wired back to the dis board on their own circuit or failing that , wired to a local lighting ceiling rose with possibly a spur nearby

yes , faulty head

i doubt very much this has anything to do with it . The fan prob is no doubt a failure on the 12v side of the transformer ( usually in the loft and you may find a tripole pole isolator switch for it nearby so it can be safely isolated and worked on or swapped out.

hope that helps

 

i think your talkin about emergency lighting there

 

ok , i just checked , appologies


The new British Standard 5834: Part 6 recommends that mains-powered smoke alarms in domestic buildings without a standby supply should be connected to an independent circuit at the distribution board. Smoke alarms with a standby supply can be connected to a lighting circuit, providing the standby supply (battery back-up) has a minimum duration of 72 hours and a low power warning signal to warn when the standby supply is exhausted.

 

I'm about half the way through my rewire. I'm putting in 2 mains powered some alarms with BB on their own 6amp MCB (no RCD protected.

Will that be ok - as you said earlier if the mains goes for a long period of time it will start churping as the batt. runs low

 

@johnyb , yes mate that will be fine . I take it one upstairs and one down ?
also the type of smaoke alarm downstairs would be an optical type , whilst the smoke alarm upstairs would be an ionization type ( they will look different because of the different types , even if they are from the same manufacturer ).

simply ...... optical type work by the alarm being sounded once the optical eye inside is blocked with smoke and the ionization type work by having some radioactive isotope inside wich reacts with certain particles in the smoke

i would say , in general , that the ionization ones are less prone to false alarms and are more acurate (sensitive even) and tend to be installed upstairs and depending on layout and length of landing even 2 or three.

hope that helps

 

no doubt they will be class II equipment ( double insulated ) , make sure you dont cut off the cpc . Connect it together in a connector block , 6amp one will do

 

I have the same problem. I have mains ionization type. I got this as I thought it wouldn't go off so often as the optical battery one we have. It's been fine for 5 months and then went off at about 3am for about a minute. It then went off about 4 weeks later during the day both for no apparent reason. It's been fine since. I was wondering if dust or a very small spider could get in it and set it off

 

have the same problem. cause - leaving the bathroom door open and steam crossing the alarm.

 

you should use three and earth between alarms so you can link them

 

@Gopher , solution : keep the door shut and install an extract fan in the bathroom that is upto the job.
The correct size, type and number of fan unit(s) required for any area is determined by three factors: the room size, its use and location.
First, work out the volume of the room by multiplying length x width x height. This volume is then multiplied by the required number of air changes per hour (ACH) to provide the total number of air movements required per hour. Select the number of fans necessary to achieve the desired volume.
Bathrooms:
an extract rate of no less than 54m3/h 15 l/sec. For calculation purposes its recommended an air change rate of 6 per hour

 

Intermittent alarming can be caused by ....

loose connections can intermittently disconnect power to the smoke alarm. The effect is the same as a power failure. When power is restored, the units may alarm briefly.

Cover or sensor chamber is covered by dust or dirt.
Alarms may look clean, but dust can accumulate inside the cover, even in newly built homes. Gently vacuum smoke alarms regularly using the soft brush attachment.


Smoke alarm may need to be relocated...

Install smoke alarms at least 20 feet from appliances like furnaces and ovens, which produce combustion particles. Alarms should be at least 10 feet from high humidity areas like showers and laundry rooms, and at least 3 feet from heat/AC vents whenever possible.

 

have the same problem. cause - leaving the bathroom door open and steam crossing the alarm.

That happened to me once. I was staying in a hotel where the bathroom could also be used as a sauna. "I'll give that a go", I thought, so I read the instructions, set the controls, and as instructed left the bathroom door closed for 15 minutes for the steam to build up before going in there. After the 15 minutes was up, I opened the door, and a vast cloud of steam surged out and enveloped the smoke detector in the room, setting off the fire alarm. It was very loud.

So there was I, b*llock naked, having just set off the fire alarm in a hotel...

I immediately phoned reception to explain, hoping that they could cancel it, stop evacuation, tell the fire brigade not to come.

It was with mixed emotions that I heard the person on reception say "what fire alarm?"