Mains supply to alarms

[JohnW2]

Hi folks,

Recent discussions about 'fire' alarms have reminded me of a decision I'll have to make soon in relation to a house I am refurbishing.

I will be installing a few (probably Aico) interconnected (hard-wired) mains-powered (and re-chargeable battery backed-up) smoke/heat/CO alarms. Although the presence of backup batteries makes this much less important, as often discussed I am personally no fan of supplying such things from a 'dedicated' circuit, much preferring to power them from the ground floor lighting circuit (whose failure would be rapidly noticed).

The question is whether I should include any sort of 'isolation' facility in the feed to the alarms. Such would obviously be convenient if it were ever necessary to 'work on' the wiring of the alarms (without having to disable the lighting) but that would probably be a 'once-in-a-blue-moon' activity.

Were it not for the backup batteries, a concern might be that any 'means of of isolation' might result in the alarms being 'switched off' (and perhaps then never re-instated, in the event of some annoying malfunction of the alarm system. However, at least for a while, the batteries would continue powering the alarms even if the mains supply were switched off - which could be a problem (annoyance) with some sorts of malfunction (maybe very improbable?).

There are things I can't remember about Aico alarms,, so maybe someone can remind me (I'm not at home at the moment, and therefore can't experiment with my own system)? Do they 'make a noise' if they loose mains power, even if they are still being powered by the back-up battery? .. and this which I can't easily test ... does anyone know whether they make a noise in the event that the (rechargeable) battery gets 'low' (I imagine they do)?

The compromise I'm currently contemplating is to feed the alarms (from ground floor lighting circuit) through an unswitched FCU and/or a key-operated switch (with the key available adjacent to the switch) - in both cases to more-or-less eliminate the risk of it being accidentally switched off, but not preventing deliberate switching off. What do you think?

There is another issue, but which I don't think I can do much about. All the alarms will be ceiling-mounted and some, probably most, of the rooms will be over 3m high - so the alarms may well not be accessible using an average domestic step ladder, even for 'able' people. I presume that the alarms could be temporarily silenced/'hushed' by use of a broomstick or similar, but that wouldn't last long if the alarms were continuing to alarm/malfunction. I don't think there is any way of remotely (and 'permanently') 'killing' a whole (hard-wired') Aico system, is there?

Any thoughts/suggestions would be much appreciated.

Kind Regards, John

 

[pete01]

 

[AndyPRK]

My (old) ones only beep on battery low.

I wouldn’t bother with an isolator. Just work on them in daylight!

Mine are on the same circuit as burglar alarm, so would be noticed within hours of a failure

 

[JohnW2]

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What is that and what does (can/could) it do with a system of interlinked Aico alarms?

 

[JohnW2]

My (old) ones only beep on battery low.

With re-chargeable ones, unless the battery does not live up to its expected life expectancy, that would presumably only happen after a pretty long period without mains power? Anyway, from what you say, it sounds as if, at least with yours,it won't beep with mains failure, provided the battery remains OK?

I wouldn’t bother with an isolator. Just work on them in daylight!

That would certainly be my personal inclination, but (for whatever reason) I've read quite a lot of contrary opinions about that.

Mine are on the same circuit as burglar alarm, so would be noticed within hours of a failure

Why is that - because the burglar alarm 'chimes up' in the event of mains failure?

 

[pete01]

What is that and what does (can/could) it do with a system of interlinked Aico alarms?

I've never used one myself but here's the info.

Ei1529RC Hard Wired Alarm Control Switch | Aico

Install as part of the system to get more control over your alarms. Mains powered. Hard wired interconnection.

www.aico.co.uk

 

[AndyPRK]

Yes, they don’t beep when mains off.
They have a green power light on them.

The burglar alarm battery would go flat,
And the outside sounder would then go off.

Some alarms won’t set with power off (configurable )

 

[JohnW2]

I've never used one myself but here's the info.

Ei1529RC Hard Wired Alarm Control Switch | Aico

Install as part of the system to get more control over your alarms. Mains powered. Hard wired interconnection.

www.aico.co.uk

Very many thanks. That's just what I need to address the 'high ceilings' issue but I've never found that - only a 'wireless' equivalent. I'll see where i can get one.

However, that still leaves me having to decide about switching/isolation (if any) for the mains supply. Do you have any view or thoughts about that?

Kind Regards, John

 

[flameport]

However, that still leaves me having to decide about switching/isolation

Aico devices have the isolator built in - achieved by removing the alarm from the backing plate.
Separate isolator not required and not desirable either.

That's just what I need to address the 'high ceilings' issue but I've never found that - only a 'wireless' equivalent. I'll see where i can get one.

The wired version has less functionality compared to the wireless option.
Whether that is a problems depends on what functionality you require - but if going for the wireless remote control, you also need the alarms with a wireless interlink, NOT hardwired.

 

[pete01]

Very many thanks. That's just what I need to address the 'high ceilings' issue but I've never found that - only a 'wireless' equivalent. I'll see where i can get one.

However, that still leaves me having to decide about switching/isolation (if any) for the mains supply. Do you have any view or thoughts about that?

Kind Regards, John

Do you mean local isolation? I've never seen that before, suppose you could put an FCU by the consumer unit but I cant see the point.

 

[Harry Bloomfield]

Although the presence of backup batteries makes this much less important, as often discussed I am personally no fan of supplying such things from a 'dedicated' circuit, much preferring to power them from the ground floor lighting circuit (whose failure would be rapidly noticed).

Mine are mains powered, battery backed. If the mains fails, then the bleep, as a warning.

 

[JohnW2]

Aico devices have the isolator built in - achieved by removing the alarm from the backing plate.. Separate isolator not required and not desirable either.

We know that - but, as I wrote, that sort of 'isolation' is of no help IF ...

....... it were ever necessary to 'work on' the wiring of the alarms (without having to disable the lighting)

... but I also said that such was probably a once-in-a-blue moon activity (so probably doesn't warrant consecration).

The wired version has less functionality compared to the wireless option. Whether that is a problems depends on what functionality you require - but if going for the wireless remote control, you also need the alarms with a wireless interlink, NOT hardwired.

Thanks. As I said, I had only been aware of the wireless version. However, my only real concerns were about problems of testing and 'silencing' due to the high ceilings, so the hard-wired version will be fine for me.

 

[JohnW2]

Do you mean local isolation? I've never seen that before, suppose you could put an FCU by the consumer unit but I cant see the point.

Yes, that's what I was talking about, and I'm a little surprised that you've never seen it, because a lot of people seem to advocate it. However, as I've implied, I'm not at all sure that there's any point (not to mention that it would require a bit more cable )

 

[JohnW2]

Mine are mains powered, battery backed. If the mains fails, then the bleep, as a warning.

That's what I suspected. However, but what brand are you talking about, since I suppose that it may vary. Do I taking it that the beeping continues (intermittently or continuously) until the mains supply is restored?

 

[Murdochcat]

Never put an isolator on a smoke alarm circuit and make sure it’s on a lighting circuit