Double feed?

[Garymcdee]

Hi, I was installing two downlights today in a bathroom and noticed a feed coming from smoke alarm to lighting circuit! Problem is the smoke alarms have there own circuit? Is there a reason someone might do this or has it been done by mistake??
Thankyou

 

[pc1966]

It is quite common to feed smoke alarms from the lighting circuit.

They are fixed low-current devices and the advantage is if the circuit trips folk the to get it fixed so they are not in the dark, whereas a dedicated smoke alarm circuit is not always checked for operations.

 

[littlespark]

I think this is lights fed FROM the smoke alarm circuit.

Not a huge problem. Possibly the only supplky they could find at the time.

Ive seen it myself where the smoke detectors were fed from lights, then the attic light was fed from the landing smoke. (because all the feeds were at switches)

 

[Garymcdee]

It is quite common to feed smoke alarms from the lighting circuit.

They are fixed low-current devices and the advantage is if the circuit trips folk the to get it fixed so they are not in the dark, whereas a dedicated smoke alarm circuit is not always checked for operations.

I understand that but the smoke alarms are on there own breaker and the last smoke alarm feeds into lighting so if I’m right when lighting breaker is off it could still be live because of smoke alarm feed??

 

[pc1966]

OK I had not clocked the fact they are linking two circuits. That is a definite no-no!

If that is the case it is clearly a mistake.
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Have you checked if they are linking circuits? It might be the smoke alarm MCB feeds all other but not that one for some reason (difficulty in wiring, lazy, etc, etc)

 

[Garymcdee]

OK I had not clocked the fact they are linking two circuits. That is a definite no-no!

If that is the case it is clearly a mistake.
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Have you checked if they are linking circuits? It might be the smoke alarm MCB feeds all other but not that one for some reason (difficulty in wiring, lazy, etc, etc)

It’s looks like they have just crossed over with cable from lighting junction box and gone into the smoke alarm which is already fed??

 

[westward10]

I understand that but the smoke alarms are on there own breaker and the last smoke alarm feeds into lighting so if I’m right when lighting breaker is off it could still be live because of smoke alarm feed??

Did you not test it to verify/carry out safe isolation.

 

[James]

quick simple test, turn off circ. breaker to lights but leave on smoke circ. breaker.
check if light still works.

if so, light is fed from smokes breaker.

then turn on lights circ. breaker and turn off smokes breaker.

if light still works then you have a join between circuits that is definitely not right.

if light goes off then light is fed from smoke circuit. not necessarily a problem but not perfect.

 

[Garymcdee]

Did you not test it to verify/carry out safe isolation.

Unable to access property 10 minutes after finding problem, will test tomorrow
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Thanks all

 

[telectrix]

Unable to access property 10 minutes after finding problem, will test tomorrow
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Thanks all

report back to us nosy sods what you find.

 

[Garymcdee]

report back to us nosy sods what you find.

Will do ?

 

[Garymcdee]

Yep!! Some nutters put a cable in connecting smoke alarm to light point linking the two circuits!!!!!!! (Smokes on its own dedicated circuit)

 

[Zerax]

report back to us nosy sods what you find.

Ideally with pictures... we love a good picture ! (not all blurry with the fun bits half cropped out)