Domestic PIR Problem

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Spaced

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Hi everyone

I have had a callout to replace a malfunctioning stand alone PIR unit.
The unit when acivated would just flick the lamp on and off regardless of the time control setting position.
The customer had advised me that the unit has been functioning correctly for 2 years.
Unfortunately the maunfacturers of this original unit have discontinued production with no like for like replacement.
The unit is switching a 100W tungsten lamp and a 16W 2D fitting.
I have now tried 3 replacement units, 2 BEG and 1 Robus and am still experiencing problems.
The BEG units would both function correctly with the minimum time setting which ran at about 6 seconds, however
as soon as this was increased the units function correctly twice and then stay on permanently.

The 3rd unit fitted was a Robus. This functioned perfectly coming on for the set 2 minutes approximatey 6 times but
has now ceased to operate.

The technical team at BEG thought that the problem may be due to the mixed nature of the loads ie one inductive and one resistive
and suggested fitting a capacitor across the 2D unit. The NIC advised that this may not be a suitable solution due to the control
gear in the 2D.

Any ideas or suggestions as to the cause or how to rectify this issue would be greatly appreciated.

Thanks
 

telectrix

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suspect the 2d fitting being inductive. as i=p/u says, replace with tungsten fitting.
 

stef

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Can you use a relay which switches the load instead of switching the load directly via the PIR?
 

telectrix

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relays are inductive so would need a capacitor across the coil. 0.1uF is what i have used before on relays. alternatively, buy a PIR that will accept inductive loads.
 
OP
S

Spaced

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Thanet - Kent
Thanks for your advice, the PIR states that it can switch 1200W tungsten or 300W flourescent - would replacing the tunsten lamp with a compact flourescent (would this be an inductive load?) perhaps resolve the issue? I know they take a while to warm up but I suspect the customer would rather do this to keep the cost down if feasible.

Thanks again
 

Richard Burns

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Fluorescents tend to be inductive because of the switch gear. you may find changing both lamps to inductive could solve the problem since the spec of the PIR should be able to cope with this (16W+28W= 44W < 300W) and it may only be the two different types that is causing the problem.
However it may also be that there is a minor fault in the lighting circuit / lamps after the PIR that is pulling more current than expected and overloading the PIR, might be worth clamping the outgoing line from the PIR (or bypass the PIR) and see what current is being taken, just in case. It might be just a case of replacing the 2D lamp!

You can also get LED 2D replacement lamps that would be less inductive than a fluorescent and replacement LED R7s lamps.
However they are more expensive than the originals so may not be suitable.
 
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