Smoke detector to trip RCD

adriandilly

No, I don't have an electrical problem with my smoke alarm. I was wondering if there is a device available that will trip your final circuits when smoke is detected.

As a considerable proportion of fires are due to electrical faults, I'm thinking it would be a good idea to have a smoke detector that created an artifical earth leakage of 30mA or 150mA causing the building's main RCD to trip, thus preventing a fire.

Yes I know you don't get smoke without fire, but most start out small and it can't be a bad thing to cut out the supply.

For older buildings not equipped, perhaps a plug in smoke circuit breaker just protecting a single high risk item?

I speak from experiencing a car electrical fire myself (while in it). Everyone was able to get out fine but the firefighters could only put it out after disconnecting the battery.

Surely it would be a good idea to protect the mains in your property too?

Is anyone aware of such a device?

Thanks

cossie23

I'm no expert on domestic devices but normally fire protection such as smoke, gas, heat and flame detectors would go back to an alarm panel. Alarm panels sometimes have a volt free contact for connecting external devices ie, smoke detected send signal to a light, buzzer, auto dialler etc.
Broadly speaking (obvioulsy this part would have to be done by qualified person), you could wire your socket supply through a relay that is connected to alarm panel so when fire detected alarm panel denergises relay thus cutting supply.

shandypants5

Its a nice idea, and I can see your reasoning, but dont you think that cutting the power would create more danger should the smoke alarm go off at night.

You would be trying to deal with the source of the smoke in total darkness, and would have no way of resetting the RCD untill the smoke cleared.

paddyrg

It's worth expanding on the idea, I think it is fundamentally potentially a good one, but with some caveats. Why not wonder down to your local fire station and have a chat with their prevention officer? They may say that the issue of the dark whilst trying to flee is a showstopper, or that most breaker boards are close to the main door for precisely this reason, I don't know - but their opinion will be worth having and may flag up some adaptations to the design for you.

shaun_from_Africa

You would be able to get around the problem of lighting by having a split bus in the consumer unit and have the lights on the part that doesn't trip off.
This will only help if it is not one of the lighting circuits that has started burning.

However, there may still be problems with things such as your telephone not working (if it is mains powered), leading to you not being able to call the emergency services.

cossie23

On industrial installations cutting the power would not be a problem as there would be emergency lighting (battery backed) or an emergency generator supplying essential services only. This is obviously taking things a bit too far for domestic use. Also just to clarify shandypants point about no way of resetting the trip, all channels would have an inhibit meaning should a spurious alarm come in the smoke detector could be inhibited from killing power.

Fifer

My gut reaction is that on balance, with the fire already started, it's better to have power to assist means of rapid escape and summoning rescue, than to cut power which is unlikely to contribute further to a fire once ignited in any case. Electricity tends to be the ingintion source, rather than the fuel.

fwor

I think you'll find that most types of electrical fire result in the RCD in the consumer unit tripping anyway.

When electrical insulation burns it leaves behind material with a high carbon content, which leaks current away to any nearby earthed conductor, which in turn causes the main RCD to trip out.

Kernel_Sanders

adriandilly wrote: »

Yes I know you don't get smoke without fire

Sure you do; that's what smoldering is, but this would have to occur quite close to the detector for your idea to be effective.

adriandilly

Kernel_Sanders wrote: »

Sure you do; that's what smoldering is, but this would have to occur quite close to the detector for your idea to be effective.

Ok, what I mean then is enough smoke to be detected in another room.


As I said, perhaps a device just for a single appliance such as an iffy secondhand fish tank, rather than the whole house would be better.

I think protecting the house while going on holiday might be a good idea although yes, the detector would have to be sensitive enough to detect smoldering and prevent extensive damage.

Smoldering seems to be the condition I was looking to remedy.

Going back to the car fire, a battery cut out could've saved my car because I was initially able to blow the flame on the dashboard out, only for it to reignite and burn the whole thing.

Have just checked my house consumer unit and actually the lights are not RCD protected. Only sockets and cooker are, so in fact, in my set up, being able to see to get out of the house would not be a problem.

Kernel_Sanders

adriandilly wrote: »

Going back to the car fire, a battery cut out could've saved my car because I was initially able to blow the flame on the dashboard out, only for it to reignite and burn the whole thing.

Could you not have isolated the battery by taking all the fuses out of the box (assuming they were accessible from inside the cabin)? I'm not claiming I would have thought of this in your situation, even if I had known enough about car electrics to realize that a battery connection could thwart an extinguisher.