Strobe Warning light problem

[lbudden]

I have a situation where a strobe warning light was installed with an integral motion sensor/relay/time delay feature. Normally, when anyone passes this motion sensor, the strobe activates and pulses, for a short time delay (10 seconds) and then shuts off.
At times the strobe is activated, but will continue to stay lit as if stuck in the delay mode. It is wired to 1 hot of a 3 hot/1 neutral circuit with a coffee machine on one circuit and computers on the other 2 circuits.
Could not having a separate neutral for the strobe cause the light to stay on, by locking the relay closed, or has anyone ever had a problem with something like this before?
(The light has been tested on a dedicated circuit and always operates properly--only stays on too long when wired in to the multi-wire circuit)
Thanks for any help.....

 

[hbiss]

Re: Strobe Warning light problem

I can't see how that could be the case. There must be some other differences between this and the dedicated circuit, maybe noise, although I can't see that either. Poor design?

 

[flightline]

Re: Strobe Warning light problem

Just a shot in the dark, but is the output of the motion sensor relay or solid state? Additionally, does the motion sensor require a neutral? I could believe where it is solid state, and has no neutral connection, simply in series with the load, the small "charging" current, [for lack of a better term], is enough to provide a charge to the power supply of the strobe. The period of time required to charge the capacitors in the strobe's power supply would take much longer I think. Just a guess.

 

[tom baker]

Re: Strobe Warning light problem

A solid state motion sensor with out the neutral will leak a small amount of current to operate. The 2002 NEC added the requirement that if the motion sensor states "off" then it does not have any current leakage, of course the mfgs just removed the word "off".
Flightlines comment is probably what is happening. See if you can get a motion sensor with dry contact outputs...