smoke detector earth/interconnect

[asc]

Noticed a smoke detector circuit today where the bare earth wire was taped with insulating tape on the exposed parts outside the sheath, and was being used as the interconnect.
I know the lack of an earth is not a big deal in this type of circuit (class II)but is the interconnect live with supply voltage during the alarm phase or is it just a signal voltage below 50V?

 

[Qedelec]

Not what I would call good practice.
Someone coming along later could mistake it for an earth and fail to check.
Personally I would terminate it in a connector block and sleeve it as earth then ran a separate for the interconnect.

 

[Adam_151]

Change it for 3C + E, use the brown for live, sleeve the grey blue and use as neutral, use the black unsleeved as interconnect, sleeve earth as earth and maintain continutity of it using a connecter block as QED says

 

[asc]

I agree it's bad practice but what I am trying to find out is if the interconnect is just a signal wire (below 50v) or is it live with 240v during an alarm condition?

 

[plugwash]

you'd have to ask the manufacures but its going to have to be relative to one of live or neutral since the alarms have no earth connection which means it counts as a live conductor from an installation design pov

 

[shortcircuit]

Was the smoke detector a stand-alone mains type detector or part of a system(ie panel, detector cirtcuit in pvc, sounder circuit in MI) when the voltage would have been 24v dc. System type alarms can have the detector circuit in pvc.

Still no excuse for bare earth as it should have been sleeved and carried through

 

[kendor]

I agree it's bad practice but what I am trying to find out is if the interconnect is just a signal wire (below 50v) or is it live with 240v during an alarm condition?

are you able to meter it during a test?

 

[asc]

I have phoned the manufacturer and it is a 9v signal wire, so not right but no danger, thanks for the input guys

 

[baldelectrician]

You could use twin and earth to supply both of them and radio link base,

http://www.aico.co.uk/smoke_radio.htm

costly but better practise

base £25 - £35 each + detectors < £15

 

[Softus]

I agree it's bad practice but what I am trying to find out is if the interconnect is just a signal wire (below 50v) or is it live with 240v during an alarm condition?

The manufacturer will know the answer.