Smoke Alarms

[TEC2006]

Two Interlinked Smoke alarms are showing 24v between interlink connection and earth or neutral. They are sounding with no apparant cause - could this 24v on interlink wiring be causes it? The 24v is present on wiring even with smokes not connected

 

[Taylortwocities]

What is the wiring between the two alarms?

IS it 3 core and earth? Is the earth/cpc properly earthed? If not you may have voltages induced onto the interlink connection.
Have you done insulation resistance tests on the cable?

I guess the alarm stops if you remove the interlink connection?

Are the alarms the same make & model?

 

[TEC2006]

yeah 3core and earth - earth properly earthed.
IR tests >299
same make and model

 

[GaryMo]

Are you using the black conductor as the interlink? If so then it's side by side with the brown conductor IIRC which you should have as the line conductor. What you're probably seeing is capacitive coupling from the line conductor.
When I next connect 230v interlinked detectors I'll measure voltage between the line and interlink to see if I see a similar voltage.

 

[TEC2006]

Do you think replacing smokes will solve problem or will i need to sort the 24v on interlink?

 

[GaryMo]

I really couldn't comment any further as I've never measured voltage between the line and interlink but as said, will do the next time I get chance out of curiosity. 24v does seem high though.

 

[ban-all-sheds]

Measure it with an analogue moving coil meter.

 

[LoveRocket]

Measure it with an analogue moving coil meter.

Good advice.

Or if you ain't got an Avo, use your DMM but with some kind of load (like a lamp) in parallel.