Mains smoke alarm beep / outside security light

[JDR]

A strange situation that someone maybe able to advise on.

I have recently moved into to a house with a mains smoke alarm on the upstairs landing.

On the the back of the property is a security light (PIR type) with a lightswitch in the downstairs back room to allow manual operation.

The odd thing is that when the security light comes on, be it auto or manual the smoke alarm also emits a single beep.

Other than that the smoke alarm, security light and all other lights in the house seem to work fine. The smoke alarm does not beep when other lights are switched on, have not had any problems with the trips/fuses on the two lighting circuits.

Any ideas on what the cause of the beep is and what I should do to investigate further or to fix.

 

[Chri5]

Sounds like some 'odd wiring'.

Smoke alarms tend to beep if mains supply fails or if battery backup fails / battery needs replacing.

What type of security light is it?

Have you tried pulling the fuse that the smoke alrms are on at the CU and then checked the security light to see if it's taking power from the same circuit?

 

[breezer]

i bet its voltage drop.

when the external light comes on the voltage drops and the spoke detector picks it up