Mains powered smoke alarms

[kai]

Modern mains powered smoke alarms are normally fed with 1.0.sq.mm twin and earth from the consumer unit, and use 1.0.sq.mm three core and earth "two way switching cable" between the first alarm and any subsequent alarms - the third core is the interlink core, which sounds the other alarms, should one of them operate. Some modern alarms even have a parking terminal for the earth core (as per mine).
That's the arrangement in my current home.

 

[Taylortwocities]

Surely part p comes into this as it is rewiring a new circuit? as I say, im using battery alarms which is better than no alarm at all, but seeing as I have a 2nd floor I require linked alarms, hence this would need to be installed via a qualified part p electrician

No, power it from existing lighting cicuit . Then you could run the wiring and install the alarms. No notification needed unless one of your alarms is in a special location.

 

[Sparky1970]

Instead of hardwiring, could I use wireless battery operated smoke alarms that are interlinked via radio waves? Or do I still need mains powered to confirm to british standards?

 

[HarryDewickEisele]

You are allowed to use mains powered radio-interlinked smoke alarms. These are in accordance to BS5839 part 6 grade D, the same as mains powered cable linked smoke alarms. Ei Electronics manufactures these.

 

[Taylortwocities]

The radio base is mains powered so each base can be powered from a local power source (usually the light feed). See http://www.tlc-direct.co.uk/Technical/DataSheets/EI_Smoke/Ei168RC_Schematic.pdf for how its hooked up.

There are no

wireless battery operated smoke alarms that are interlinked via radio waves

. These would not comply with BS standards as these require mains power with battery back up.

 

[ajrobb]

I thought that mains powered smoke/fire alarms can use a regularly used lighting circuit (so far so good) and can be interlinked by radio. I'm interested as I am refurbishing a converted flat and have to put a smoke alarm in a passage and an infra-red alarm in the kitchen/living room. Isn't there a requirement to be able to isolate the alarms from the mains (lighting circuit)?

 

[HarryDewickEisele]

You are allowed to power the mains powered radio-interlinked smoke alarms from their nearest light fitting. This is actually better than creating a separate loop, as people are less likely to take the fuse out from the lighting circuit than if it is a separate loop (in case something is bleeping etc, I mean).

I can't image that you are required to have an infra-red alarm in your kitchen. Do they mean heat alarm? These can radio-interlink to the other radio-interlinked smoke alarms.

 

[Sparky1970]

So, I have two options - 1. Purchase mains smoke alarms with radio link and wire in to nearest ceiling rose.

2. Purchase battery operated smoke alarms that are interlinkable via bell wire (which i already have in place as it was used for mains 240v supply to the old smoke alarms) which is now disconnected from the mains for obvious reasons!

I do not wish to wire in mains smoke alarms from scratch as recently decorated and according to instructions they must be wired in on the same circuit which makes routing the cable awkward.

So, which is best 1,2 or neither?

 

[Taylortwocities]

Your option is option 1.

With the radio link bases the alarms can be powered from different power sources.

AFAIK there are no battery interlinkable alarms that can be connected using "bell" wire. If you were doing that you may as well run in 3C&E cable and do it properly.

Its tough that you've decorated without doing essential things like electrics beforehand..

Don't worry, you're not alone.

 

[Sparky1970]

Your option is option 1.

With the radio link bases the alarms can be powered from different power sources.

AFAIK there are no battery interlinkable alarms that can be connected using "bell" wire. If you were doing that you may as well run in 3C&E cable and do it properly.

Its tough that you've decorated without doing essential things like electrics beforehand..

Don't worry, you're not alone.

Option 1 is looking good, could not do anything with them in the time scale I had as plasterer was due and best option was to disconnect immediatly. Sometimes you dont find things as they should be!

Thats why im asking for alternatives on here

 

[flameport]

There are these:
http://www.tlc-direct.co.uk/Products/TLSD12.html
which could be used with the existing wiring, however a separate 12v power supply would be required.

 

[Taylortwocities]

There are these:
http://www.tlc-direct.co.uk/Products/TLSD12.html
which could be used with the existing wiring, however a separate 12v power supply would be required.

Those are meant to be installed as part of a fire alarm/intruder system.

Sparky 1970 would still have to run cables between each alarm, and he is trying not to have to do that.

 

[bernardgreen]

One thing has always puzzled me.

Some smoke detectors operate by detecting ionised particles in the air.

High levels of ionisation can absorb or otherwise disrupt radio communications.

I assume that wireless linked fire alarms detect the fire / smoke and alert the others long before the density of ionised particles is high enough to significantly affect the wireless linking.

They are tested and approved but I am still wary of them.

 

[HarryDewickEisele]

There are, in actual fact, radio-interlinked smoke alarms with battery power AND 10 year battery life. The Ei605CRF smoke detector and the Ei603CRF heat alarm are well suited. You would need to check with Building Inspection or whoever your approval body is to make sure they are happy. We have found that they are often prepared to accept these units, as they tick all the fire safety boxes.

These units do not use ionisation technology. But anyhow, ionisation smoke alarms do not affect radio-communication.

 

[bernardgreen]

But anyhow, ionisation smoke alarms do not affect radio-communication.

The alarms detect ionisation caused by the fire, there is evidence ( Fire brigade communications 1980's ) that short range radio comms can be affected by the ionisation in the products of combustion.

It is un-likely that a domestic fire would create enough ionisation to fully disrupt inter alarm wireless comms before the message was passed.

The other concern is battery enconomy where the receiver is not permanently powered but switches on for a short period of listening and then goes off again for several seconds. This is standard practise in most long life battery operated receivers to extend battery life. This means there is a delay from when the activated alarm starts sending the message " SMOKE" and until the other alarms are able to receive and respond to it. Hopefully the "not listening" periods are short enough to not introduce significant delay in the evacuation process. One also hopes the active alarm can continue transmitting long enough for all other alarms to receive the "SMOKE" message.