The Old Smoke Alarm Circuit Debate

[pewter]

having a little read of 560.7  circuits of safety services  .....

and i have had countless debates on what circuit should the smoke alarms be on.

Personally i have gone from, on there own circuit, to on lighting as discussed with my fare alarm friend, but now seem to be going back to on there own circuit.

I think after reading

560.7.4 Overcurrent protective devices shall be selected and erected so as to avoid an overcurrent in one circuit impairing the correct operation of safety circuits and services.

which to my simple mind tells me to put my smoke alarms on there own MCB/RCBO. 

I can not find reference to bunch on a lighting circuit so you would know if the circuit tripped, and the batteries ran out argument ....

An old debate, but i one i enjoy

 

[Zeespark]

Try manufacturers literature, I think AICO say on the lighting circuit with a Switched Fused Spur as one method, the other being on its own ciruit method. I have read someone, that if you are using a multy RCD board, then the MCB controlling the smokes cant share an RCD bank that has 13A sockets on it, I could be wrong though.

Andy Guinness

 

[Technician]

Now, smoke and heat alarms can no longer be powered from lighting circuits,

despite being a common practice endorsed in both national Building Regulations

and BS 5839-6:2004, the current Code of Practice for domestic fire alarm systems.

I pulled the above from a website which has an observation on the impact of the regs as from 2008.

The website is linked to Kidde Fyrnetics.

 

[Hefferl]

From the Aico website:

"Q: Do I need a mains feed to each RadioLINK base?

Yes, each base needs a permanent mains feed. This can be taken from the lighting circuit nearest to that base – as long as it's a permanent feed"

 

[Evans Electric]

I think the trade has constantly confused the issue with this and applied their experience of commercial systems to domestic.

Commercial systems vary between a dedicated supply from a dist. bd.   to a switchfuse with removable handle , painted bright red and a notice with 3 mtr high letters stating Fire Alarm and connected ( and I've seen this)   to the live side of the building main switch.

I am of the " Connect to the well used light circuit " brigade for the the following reason  :- 

Adding circuits to a board  for an extension , the guy at the house says theres a couple of spare ways , they're switched off , one of them was the feed to the smoke alarms , unmarked, the other was indeed a spare.

Thing was they'd lived there for 3 years ,  that breaker was off when they moved in and he decided it was a spare , so they'd never had any protection .

 

[Evans Electric]

Know what you mean there Canoey ,  theres the usual cost issue when quoting to consider though .

 

[binky]

smoke detectors bleep when power is off (or at least AICO units do) so pretty much same thing as paddlers suggestion for domestic.

 

[Steve3948]

On refurbs its local lighting feed and radio bases for me, new installs we run a circuit from DB.

 

[Hefferl]

Also worth bearing in mind that Aico at least, specify that their alarms should not be fitted to circuits which have dimmers connected.

Now there might not be dimmers present at the time you install the alarm, but somebody might add them after and undermine the smoke alarms.

 

[Steve3948]

Also worth bearing in mind that Aico at least, specify that their alarms should not be fitted to circuits which have dimmers connected.

Now there might not be dimmers present at the time you install the alarm, but somebody might add them after and undermine the smoke alarms.

I think it say's something like  should not be connected to a dimmer circuit, so on the supply side would not be the dimming side.

 

[Evans Electric]

Dimmer would have to be in the feed to cause a problem there Hefferl :coat

 

[Hefferl]

Well perhaps I'm wrong but that's not how I read it - that's a bit like saying dont supply the alarm via a standard switch (fairly obvious!)

I thought they were talking about 'noise' etc

and this is from their website:

New Installation – What do I need to check?

• Choose the right alarms for the job. Have a look at the Alarm Selector below to check which ones to fit
• Decide where to fit them. Are there any obstructions or sloped ceilings? Check the siting requirements
• Taking the supply from the lighting circuit? Is there a permanent mains feed at the pendant?
• Will the circuit take the additional load?
• Anything that can cause noise or spikes (e.g. dimmer)?

 

[batty]

They also say don't wire them into circuits with fluorescent lights in circuit. Well as CFL lamps are fluorescent that rules them out and what if somebody changes a fitting for a flourescent in the future. As said I will always install smokes on there own circuit.

 

[NozSpark]

Batty... if someone changes a fitting in the future then thats their lookout

As for what I'd do... well I'd probably do it differently on different days