New Kitchen and smoke/heat alarms.

[endecotp]

It's not impossible for wired interconnects to fail too, e.g. a screw terminal comes undone.

I wonder if any of these devices, wired or wireless, actively monitor for the integrity of the connection? Burglar alarms have extra conductors so they know if the wire has been cut. I don't think interlinked fire alarms do that.

 

[flameport]

... therefore the chances of interference should be limited.

except where your neighbours have similar alarms or other wireless safety devices using the same frequency.

I wonder if any of these devices, wired or wireless, actively monitor for the integrity of the connection?

Smoke alarms do not. Proper fire alarm systems do.

 

[SFK]

Foxhole,
This is only from one off personal experience - so all please tell me if I have anything wrong.

For my build BC specified "Mains alarm, that is interconnected, heat sensor in Kitchen, smoke sensor in other rooms". >> I think the key item here is that BC specified that I was not allowed interconnected battery powered alarms. For me they had to be Mains powered.

My electrician told me he was fitting an Aico system: http://www.aico.co.uk/I-Know-The-Product-I-Want.html
I also di not want floors lifting, so I checked with my BC and they were happy if I used the Aico Mains powered RadioLink alarm.

However my electrician highlighted the significant extra cost of each and every Aico RadioLink alarm over a Aico standard alarm, and that he would not be happy to wire each wireless smoke alram into each of the lighting wiring circuits in each room (I think because I could not isolate each smoke alarm from the mains without also isolating the lighting). So he would want to run a mains cable from fuse box to each Smoke alarm anyway.

So due to much cheaper cost, and in the end not much more mess (not many floorboards lifted as electrician did a great job pulling mains cables) I got the normal Mains interconnected alarm from Aico. These were fitted tro a dedicated fuse at fuse box.

However, I got electrician back shortly afterwards to fit a "silence" button which I now highly recommend because when smoke from (say) kitchen hits a smoke alarm, it goes off and then a few seconds later they all go off waking everyone in house. So when I know it is a false alarm (me burining toast) I hit the silence switch, so only the alarms in the smoke continue to sound and the others switch off.

SFK

 

[endecotp]

Any other thoughts about a dedicated circuit vs using the lighting circuit? The argument for using the lighting circuit is that if it fails (e.g. MCB trips) you notice quickly because the lights stop working. The idea that you can't work on the alarms without turning off the lights is an interesting point, but it's also true that you can't work on the lights without turning off the lights - so working on a ladder using a plugged-in work lamp or torch shouldn't be a big deal.

 

[ban-all-sheds]

The argument for using the lighting circuit is that if it fails (e.g. MCB trips) you notice quickly because the lights stop working.

I agree.

But AFAIK ones with battery (or supercap) backup which warn of supply failure are widely available?

The idea that you can't work on the alarms without turning off the lights is an interesting point, but it's also true that you can't work on the lights without turning off the lights - so working on a ladder using a plugged-in work lamp or torch shouldn't be a big deal.

I agree with that too.

 

[EFLImpudence]

Any other thoughts about a dedicated circuit vs using the lighting circuit? The argument for using the lighting circuit is that if it fails (e.g. MCB trips) you notice quickly because the lights stop working.

You could wire one frequently used light (hallway?) to the alarm circuit - if you wish.

The idea that you can't work on the alarms without turning off the lights is an interesting point, but it's also true that you can't work on the lights without turning off the lights

Excellent point. It's odd how these daft ideas become lore.

 

[SFK]

For my My Mains Wired Aico alarms, if I switch off the mains power to them (at their dedicated fuse) they continue working on their backup battery. But they also start flashing a red light, and then I think they start beeping (not sure if due to low battery or a timed function). So I always know if they loose mains power.

In one way, having wireless sensors connected to three different lighting wiring circuits (and so on three diffrent fuses so possible only one third of sensors will loose mains power if a fuse blows) is a better failsafe system than having my single wire/fuse to all of them.

Excuse my lack of regulation knowledge, but doesn't the electricians choice of "using dedicated fuse" or "wiring into lighting circuit fuse" just come down what your BC will approve when he sees your fuse box and if you have any spare slots?

 

[PBC_1966]

Excuse my lack of regulation knowledge, but doesn't the electricians choice of "using dedicated fuse" or "wiring into lighting circuit fuse" just come down what your BC will approve when he sees your fuse box and if you have any spare slots?

Nothing in the building regulations specifies that alarms must or must not be on a dedicated circuit.

I wonder if any of these devices, wired or wireless, actively monitor for the integrity of the connection?

Smoke alarms do not. Proper fire alarm systems do.

And the latter monitor the loop by having an end-of-line resistor at the last device on each circuit. That way the control panel can detect a break in the wiring and give a trouble signal.

 

[foxhole]

Any other thoughts about a dedicated circuit vs using the lighting circuit? The argument for using the lighting circuit is that if it fails (e.g. MCB trips) you notice quickly because the lights stop working. The idea that you can't work on the alarms without turning off the lights is an interesting point, but it's also true that you can't work on the lights without turning off the lights - so working on a ladder using a plugged-in work lamp or torch shouldn't be a big deal.

You can't notice failed lighting if you are asleep in bed? Sods law the lighting fault is the cause of your fire.

 

[mfarrow]

But AFAIK ones with battery (or supercap) backup which warn of supply failure are widely available?

Only if you like the idea of being woken up at 1am in a power cut.

 

[ban-all-sheds]

Surely that would be the same no matter what sort of circuit is used for the supply, and no matter what the reason for its loss?

 

[flameport]

The Aico smoke alarms will beep every 40 seconds if the mains fails. They do the same if the battery is low, or if the battery is low and the mains has failed.
They will operate for months on battery with no mains supply, and even when the battery is low with no mains, still give the low battery warning for at least 30 days.

Whether they are on a separate circuit or not is irrelevant. A far bigger problem is people removing them from the base for various reasons, usually in certain types of property occupied by certain types of persons.

Fire alarm systems rely on continuous monitoring, as the individual detectors and other devices do not have any batteries of their own.

 

[Taylortwocities]

Excuse my lack of regulation knowledge, but doesn't the electricians choice of "using dedicated fuse" or "wiring into lighting circuit fuse" just come down what your BC will approve when he sees your fuse box and if you have any spare slots?

I have yet to encounter a BC person who has the faintest idea (or interest) about the finer points of electrical installation. Mostly they will concentrate on what the spec says (ie n x smoke alarms + a heat alarm) and will expect to see that the alarms are in place. They don't care/have the time to be bothered about which circuit its on.

Mostly they are more interested in compliance with energy-efficient lighting (Part L, etc) and any particular "favourite" area that they spend their time thinking about.