HELP! Fire alarm problem, tiny fuses, much frustration!

Hello all, hoping someone here can help me out with something that is really getting under my skin.

As part of some work ive done for a regular customer, I have installed 5 new smoke detectors to his existing system (he wants mto turn a big flat into bedsits). Now, I have limited experience with big fire alarm systems and try to avoid them as all they seem to do is cause ballache, but as it was just a few additions and I had a bit of fireproof knocking about, I thought I'd do it for him.

So, everything wired up, all lights flashing the way they are meant to, I simulate a fire, the detectors pick it up, but the bells in the zone I'm working on do not sound (the other 3 zones work fine). At the panel, I now have a fault warning. I trace that to a tiny fuse (which I'll come back to), replace the fuse, check connections, everything's fine, hit the 'sound alarm' test button, fuse goes again.

Now, as the lights on my detectors are flashing as they should, and the detectors are detecting smoke, AND as the fuse only goes when the bells are set off, as far as I can see this can't be something I've done.... but the guy says it was working before, and I have no reason to doubt him.

So does ANYONE have any ideas. As I said, I try and avoid alarm work at the best of times, and am not up to speed with the ins and outs of fire alarm systems.

ALSO does anyone know what kind of fuse I need - it's tiny, about 3mm long by 1mm wide, and it's square and rated 500mA.

ALLLSO doe sanyone know how the heck to do an insulation resistance test on a fire alarm system - I'm thinking if I hit it with 500v or 250v it's going to kill it. OH and why do I need to earth a 20v system?????

SO CONFUSED, any help would be appreciated.

sounds like you have a fault on the sounder circuit that's blowing the fuse . you need to remove the sounders from circuit, also the EOL device, and then IR test +- _ and both to E. could be a short

Firstly what make of panel is being used, and is the zone and sounder circuits seperate or wired on the same zone cable

The panel seems to just be some generic thing - no manufacturer written on or in it. No manuals, nothing.

Circuit has both detectors and sounders on it... the final item in the circuit is a sounder with like a resistor across + and -


Anyone any idea on what those fuses are called, by the way?


Thanks chaps

Ok sound like a 2 wire, what make of sensor have been fitted

Ok can only guess you have 2 wire or a Sav wire systems and the sirens are wired incorrectley, fuses are usually 500mA or 1A 20mm glas quick blow, see 2 diagrams for correct wiring

Fitted these ESP Optical Smoke Detector C/W Base| MeteorElectrical.com

What make of detectors where already on the system

Thanks! Yes looks like the 2 wire one... but it looks like it's wired right. I tried putting the last bell in 'normal' polartity and that set the sounder off, without blowing the fuse... put it back to reverse and it shuts up, but still blows the fuse when alarm set off (there is at least 1 other sounder in the zone)

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I'm not sure, I think they are just generic non-branded ones

All sounders must be wired reverse polarity, does the panel look like any of these 2

Nah not like those, similar though. Got the two keys, lights for zones, faults, fire etc, small keyad with function buttons and numbers 1-4, that's about it. The most striking thing about it are these tiny square fuses inside.

ok think were getting there the old detector bases do they have a circuit board in the base or just a diode

the existing ones have a little printed circuit board, my ones have a diode

Ok its a sav wire system and your esp detectors will not work with this, You need Apollo sav bases and Apollo s65 detection, the sounders you have will be ok, This is why the fuses are blowing

Really? OK thanks very much for your help. Are you sure it is sav? The existing (circuit board) detectors have a common neutral but an 'in' and an 'out' on the positive side, is this right for sav?


Thanks again that's great