DIY Doctor

Motion Lighting and Extractor Fans but Using Motion Switch

Postby RMG » Thu Oct 10, 2019 1:24 pm

Hi I am new to this forum. Simple question for an experienced electrician.. I had lights that were already fitted basically normal pendant, normal light switch and an extractor fan via 3 pole isolator. Used 3 core from fan to isolator and isolator to fitting. The use of the building is changing so I am in the process of changing the light fitting to a motion sensor and do away with the switch. Its already decorated etc I was going to put a blank there. my problem is the fan? its a 4" expel air timed fan that I want it to run on for whatever time after the light goes out when someones left the room. Could someone kindly advise as to how it should be wired , currently the fan wont switch off . Many Thanks
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Postby Mr White » Thu Oct 10, 2019 7:07 pm

It should be wired as you would normally wire it,
The fan probably does not stop because it "thinks" the light is still on. This is due to the fact, most not all, PIR sensors switch electronically not via a relay, so they let a tiny amount of current flow when they switch off, but the fan timer detects this tiny current and assumes the light is still on.
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Postby ericmark » Fri Oct 11, 2019 9:48 am

As Mr White has said, try fitting tungsten bulb and see if it works then, if so then you may be able to use a Levante load capacitor across the supply to bulb.
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