Inter-connected mains smoke alarms

[RogerS]

Noel..I would guess that the load is miniscule so go ahead and feed them all from the same circuit....but if you are running a mains cable to each unit then adopt the manufacturers recommendation and use 3 core plus earth ...that way you get your interconnection.

 

[Les Mahon]

Noel,

I stuck very similar units in my place last week. I just used 2 core 1.5 to power them and a seperate single core 1.5 as the interconnect. They test fine - thankfully I haven't had any smoke to see if they "Reaaly" work yet!

My choice of cabeling was based exclusivly on the rolls of cable I had knocking around. I took the power from the lighting circuit as IIRC the load is tiny - I haven't the figures to hand, but 2 of these units wouldn't hold a candle to putting another light on the circuit was the logic I remeber.

Les

 

[Noel]

Les, I'm doing exactly that.

Cheers

Noel

 

[Jake]

The info isn't very clear, but it seems that they may draw 80mA each at max (when sounding, presumably) - that's 19 watts by my reckoning. So four from a circuit would be 80 watts.

How many lights are on the circuit that you are tapping off from? A 6amp MCB allows 1300 watts max, with each light fitting counted as 100watts (or actual lamp wattage if greater than 100watts). So if you have 12 or less, you should be fine. IANAE, etc, - and this is UK practice.

 

[soapy]

Hi Noel, If you have a 10A circuit you should use 1.5 cable, if it's a 6A circuit you can get away with 1mm cable. Using 3c & earth will give you a much neater installation. When I've fitted these on larger jobs the client usually stipulate that they are fed from the lighting cct to stop tenants turning the fire alarms off. If you use a single core cable make sure it's insulated & sheathed unless you intend to install it in conduit.
Regards
Soapy