Interlinked fire alarms

[Scott]

Living in Scotland, I am bound by Nicola's instruction to fit interlinked heat/smoke detectors by the end of the month.

I am wondering about the pros and cons of wired and wireless. In ordinary circumstances, I would go for the wireless option, as the line of least resistance (excuse the pun!). However, I live in a top floor flat with easy access to the loft so (unusually) it would be perfectly feasible to go for the hard wired option.

Wireless seems to be the go-to choice. Is there any great benefit in wired? I believe the mains electricity does not recharge the batteries, so they still need to be maintained and now I hear the alarms still have to be replaced every 10 years anyway. There could be a power cut during the fire. Added to that, I am likely to move in well under 10 years so I could be leaving a legacy of a non-standard system.

I am thinking that if one battery fails, in a wired system the power supply would be distributed to all the units but in a non-wired system one unit could go silent.

Is there any technical or business case for a wired system?

[Chris Green]

How many alarms are required by the new legislation/building-rules? That's rather fundamental, you might only need one! :-)

If they're all mains with battery backup then a battery failure in one alarm won't matter unless the mains power fails as well.

I don't know if you can get linked battery only alarms, maybe they'll appear with this new legislation, otherwise what do people without mains electricity do?

If (as it is for you) a wired system is relatively easy I think I'd go for that. Apart from anything else it's significantly cheaper.

[Mark Carver]

Does 'Part P' actually  allow you to install your own hard wired electrical smoke alarms ?

[Scott]

In a flat it seem I need three - heat detector in the kitchen, smoke detector in the hall and smoke detector in the room most frequently used. If the most frequently used room is the kitchen, will I only need two :-)

You certainly can, and this is most people's approach.>

Thanks. This is what I am thinking too. It seems to me a more robust system and there is easy access to the loft.

[Scott]

On Fri, 21 Jan 2022 11:22:51 +0000, Mark Carver [e-mail] wrote: [snip]

I'm not sure 'Part P' applies in Scotland. I think there are separate regulations. However, I will be getting an electrician with practice on other flats for neatness (although I am perfectly sure I could do the wiring myself).

[charles]

I put those in our village hall about 5 years ago.

[rick]

Wired is simple, I work on principle that the more wireless devices you install the more noise you add into your environment. Also less to go wrong. They have to be changed by 'set date' typically around 10 years, sensor issue.

[Scott]

This was my thinking disparaged by others but vindicated by the experts :-)

Mad question, I know. If almost everyone uses wireless, can we be sure compatible replacement wired units will still be available in 10 years time?

[Theo]

There was an issue with the FireAngel Wi-Safe2 units a few years ago, that the battery was only lasting 3-4 years rather than 10. They have two batteries, one for the alarm and one for the (replaceable) wireless module - I think what was happening was there was a bit too much chitchat between the alarms that would drain the battery on the wireless module. They claim to have fixed that now.

On a wired alarm, the battery is only there for backup so isn't getting used at all in normal operation. While you have to replace after 10 years, that's only because the battery and sensor ages rather than because it's drained. I think the wired alarms are also wire interlinked, meaning the comms doesn't need much power either.

At replacement time, for wired alarms typically you can just swap the module, the hardwired base stays in place. Of course they could change the connector, but in that case you're just swapping one base for another, whereas you're stuck with a particular manufacturer's wireless system. (I think the wired interlink alarms are compatible across brands, but not sure)

OTOH it's just a flat, not a stately home with hundreds of alarms, so a wireless system with potentially having to replace all 3 units in the worst case might be a suitable compromise.

Theo

[Mark Carver]

Does it matter,  ? I'm sure the interconnecting cable (which is nothing more hi-tech than 1.0mm^2 Triple+Earth ?) can be repurposed for whatever is around in 2032. If any of us are still alive by then anyway !

[The Natural Philosopher]

hell. I am sure in *another* 20 years my cat 5 cable will be obsolete. But then, so will I.

[Andrew]

It's a question that works both ways. About fifteen years ago I installed wired interlinked alarms. Good manufacture, premium spec. They were on mounting plates so could be removed by unclipping the alarm and sliding off the plate.

Ten years later they needed replacement. The same model was still available so I used those. Unclip - slide off old devices, slide on new.

BUT they had slightly changed the design of the mounting plate (cost reduction?) so they all had to be rewired anyway.

[Mark Carver]

Yep. We lived in a rental house for a year (while we re-built our present home)

That had two linked smoke alarms. They were so old they had turned yellow. They both appeared to work when we moved in, (and had passed the inspections etc) so I didn't worry. However about a month into Lockdown V1.0 one started bleeping (at 3am of course). I attempted to stop it. In doing so, I discovered a label. 'Replace before Jan 2011' I looked at the second one, 'Replace before March 2013'.

Anyway, I took photos, sent them to our landlord. I offered to order new ones, and change them myself given all the Covid problems. He pragmatically agreed. The new ones came, but I too discovered the mounting plate design had changed slightly. Anyway, the whole swap out of both still took no longer than 20 mins. It helped fill in the 4 months of furlough I suppose.

[Robin]

I think one of the differences in Scotland is that you need a warrant for new main alarms in a flat where no BC notice would be needed in England. I assume that doesn't apply if you are using an electrician who belongs to an approved scheme.

[Owain Lastname]

You may be subject to Scottish Building Standards council notification for electric wiring in a flat, especially if you are piercing through a fire ceiling into a communal loft. The rules in flats are more restrictive than in houses. I don't thnk strictly speaking I can flush in a socket in a party wall.

Obviously I installed 7 hardwired Aico with a locate/hush switch in my flat and chiselled out the walls regardless of rules :)

Once you've paid for something like Aico, the cable, had a happy afternoon crawling about in the loft, etc, these wireless ones don't actually seem that expensive:

Will come in about £30 x 3 for fire and £40 for CO, so about £130 plus VAT from either range for a minimum installation.

I've got to the age I appreciate an easy job. And Aico hardwired are only going to last 10 years max anyway. If you expect a lot of false alarm triggering you might not get the 7-10 years life from the battery ones though.

Owain

[Owain Lastname]

If they aren't you'll just have to buy wireless ones then :)

Owain

[Owain Lastname]

Mine already is, if I want gigabit networking, which my PC is capable of, even if the internet isn't yet.

900 Mb FTTP is coming though (they tell us).

I'm still breating but I feel pretty obsolete too.

Owain

[The Natural Philosopher]

Apparently Moore's law has stopped for CPUs but is still applies to networking speeds...

I wonder what the limit will be there...at some level GHz switching is pretty much the electronic limit even if optical fibres can do more.

[John Rumm]

I need to replace the first set I installed here - I expect it is going to be the same problem!

Still at least the new ones still support the same master control switch.

[John Rumm]

CAT5E will run gigabit ethernet no problem.