Mains CO2 and fire alarms - link?

[David.WE.Roberts]

Anyone know if the fire alarms and CO2 alarm should be linked or on separate circuits?

Google is not being my friend at the moment.

Cheers

Dave R

[Tim Watts]

On Thursday 25 July 2013 14:01 David.WE.Roberts wrote in uk.d-i-y:

I was going to link mine on one circuit. I cannot see any reason to do it any other way -

1) CO alarm will set off all alarms = good

2) The supply should be high integrity (reliable) or one where it's failure is quickly apparant (often a ground floor lighting circuit covering the main hallway) - having identified and used on of these, you'd want all your alarms on it.

My 2p's worth :)

[dom]

My home has Aico ionisation/optical/heat/CO alarms - all linked, and designed to be.

[dennis]

Is this for a brewery? I would think CO2 alarms are quite specialist and you probably need to consult an expert.

[Stephen H]

It all depends on the choice of make and model.

For example I have 12 Dicon mains with battery backup smoke and heat detectors. These are interlinked. Dicon do not do any CO detectors. I can have up to 12 interlinked according to the instructions.

I also have 4 CO detectors made by Kidde Fyrnetics. These are mains with battery backup. These are also interlinked but on a separate daisy chain to the smoke & heat ones.

Howeer, Kidde Fyrnetics do smoke and heat detectors that will interlink with their CO detectors but are more expensive than the Dicon ones. From memory I think you can have up to 16 interlinked and different sounds are made to allow you to tell the difference between a CO leak and a heat/smoke event.

As I already have an intruder alarm with some spare 24 hour zones and an on-board dialler, ethernet module and a GSM module, Both Dicon and Kidde Fyrnetics do relay bases so I used one on each daisy chain, to create two additional 24 hour zones, one for heat & smoke, i.e. fire and one for CO leaks.

The bonus is that the alarm panel can then dial out, send me emails to my mobile and also send text messages.

The intruder alarm, smoke/heat detector chain, CO detector chain all take their power from a single 6A RCBO. Nothing else is connected to that RCBO so ensuring high integrity.

If this RCBO tripped or if there was a power cut, the intruder alarm will email, text and phone me to notify me of the fact.

Hope that helps you,

Stephen.

[ARW]

They are a lot more expensive that CO alarms.

It looks like David made a small error in his post.

[Dave Liquorice]

CO2?

CO is rather different. A good CO alarm isn't really a go/no-go device like a smoke or heat detector either. They have intermediate warnings by different coloured lights or short beeps before going into a full "get the hell out now" alarm.

Continuos low levels of CO aren't good for you. It's these low levels that can creep up on you and take you quietly off into a longer sleep than you intended. With the higher levels you are more likely to notice something "odd" and take action (if you know the symptoms).

[David.WE.Roberts]

Ah!

When the sparkie said "Do you want CO2 did he mean CO too?"

That will do until I find a better excuse :-)

Cheers

Dave R

[ARW]

I like that :-) :-)

[Rick Hughes]

I wrote a sect for UK SElfbuild faq some while back on what detectors had to be used where and wiring requirements .. not refreshed it recently but at the time written the requirement was the following sections:

5.2. Mains Powered Alarms Mains powered alarms are potentially more reliable and therefore required for all new builds. They should also be installed in all dwellings where occupants are liable to ignore need to change batteries However they have limitations ? they do not work in the event of fire, and they do not work if the circuit has tripped at consumer unit. This non-working could easily go unnoticed. Circuits may also be deliberately disabled if there are nuisance alarms triggers.

...

1. Grades of Alarms There are 6 grades of protection systems specified by BS5839: Part 6, these are designated protection grade A ? F The last 3 of these being relevant for Selfbuilders ?

9.1. D ? systems with one or more mains powered smoke alarms each with an integral stand-by supply. 9.2. E ? systems are mains powered smoke alarms, but with no stand-by supply 9.3. F ? systems comprising of one of more battery powered alarms.

9.4. A Grade D or E system should protect 2 storey domestic homes

1. Power Supply The alarms must be connected to mains power.

10.1. Grade D systems should be connected to an independent dedicated alarm power circuit, with no other equipment connected other than a dedicated monitoring device. Or alternatively a separate, electrically protected, regularly used lighting circuit.

10.2. Grade E systems can only be connected to an independent dedicated separately fused alarm power circuit, with no other equipment connected other than a dedicated monitoring device.

1. Cabling The electrical installation must conform to BS 7671. (16th Edition regs )

11.1. What does this mean in practise? The first alarm is supplied power by a T&E cable (1.0 mm2 6242Y) and then a 3core & E cable is used to interconnect between them (1.0mm2 6243Y) Any interlinked alarms MUST all be on same power circuit. The earth wire must NOT be used as the interlink wire. The circuit should NOT be fed at the consumer unit via an RCCD protected circuit.

---------------------------

In practice this means put it on a non rccd protected cct along with a frequently used item - landing light ? so it would be noticed if tripped.

[ARW]

[Bob Eager]

Yup. In fact I have a non-maintained emergency light on the stairs, on the same circuit. The presence rather than the absence of a light is just as good, if not better.

And it helps to stop accidents in a power cut.

[Dave Liquorice]

Do you mean maintained? As that is the type that is on all the time. Non-maintained only come on when the power goes. You would have the charge tell tale, which in the case of the non-maintained light over our stairs is bright enough to move about by... The mains smoke/heat detectors also have a tell tale.

[Dave Liquorice]

Bit hard these days were having a non RCD protected circuit means it has to be mechanically protected or buried at least 50 mm from any surfce etc B-)

[Bob Eager]

No, I mean non-maintained. I want it to come on when the power goes. I'm interested in lack of power, not power!

Since it's on the same circuit, it makes a good tell-tale.