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PIR Sensor in bathroom

Discussion in 'Electrics UK' started by M1AK, 4 Apr 2017.

  1. M1AK

    M1AK

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    Hi all,

    Wanting to wire a PIR occupancy sensor in the bathroom but just had a couple of questions with regards to connections.

    At the moment the pull cord has a live and switched live w/ earth. The light fitting has live, neutral, switched live and earth. There is a Extractor fan that is tethered off this which taps into the live, switched live, and neutral.

    Am I right in thinking I just need to tether off the neutral at light fitting again, taking it to the pir sensor?

    I have the live and switched live at the pull cord already.

    Also is it wise to keep an override manual switch? If so do I simply put the override switch in between the live and switched live connection going to the PIR switch so it effectively 'intervenes' when needed?

    TIA
     
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  3. stem

    stem

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    What you describe sounds reasonable.

    What are you using the PIR sensor for? If it's for the fan, then the easiest way might be to re-route the cable containing the three wires that currently goes to the fan to the PIR (you would only need to use the live and neutral from it though) and then run a new three core cable from that to the fan. Otherwise, you will be running a single wire for the neutral from the light fitting.

    A PIR with an inbuilt timer is useful for allowing the fan to run for a preset period of time after use

    With regard to the override switch, that comes down to personal preferences, but I would avoid having a manual override that switches it 'on'. You may exit the bathroom thinking that the PIR is running the fan but someone has overridden it and so it stays on permanently.

    You might however want an 'off' override so that the fan doesn't come on should the bathroom be used during the night.
     
  4. ericmark

    ericmark

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    There are normally Instructions like these for SMSSLV360E with the PIR telling you how it should be wired. I am uncertain about the legal requirements when using a PIR? With a switch where there is a non opening window there has to be a second method of starting the extractor fan, since with a PIR even in the day time the light is controlled by the dusk to dawn function if included, if there is no dusk to dawn function then there is not need for independent switching.

    I would assume a PIR for a bathroom is likely a duel unit, with the dusk to dawn being used for supply to light. but not for supply to fan? The one I looked at is clearly not designed for bathroom use. The example I selected says not suitable for discharge lighting so I would not be keen to have it running the fan, because there may be some back-EMF from the fan.

    Looking at this web page there are so many PIR's for lighting it is really pointless talking about how to wire, until you know which one is to be used. It may be better to use two and have the fan independent of the light completely.
     
  5. DIYnot Local

    DIYnot Local

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