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Wiring PIR sensors, Extractor fans, LED panel lighting, overide switch. In one circuit

Former Community Member
Former Community Member
Hi,


I am currently level 2 Qualified 2365 and beginning my level 3. 

​​​​​As my interest in the field increases I always observe electrical installations, I noticed one day in a public toilet, the ceiling panels were lifted and the Extractor fan, PIR sensor, Panel lighting, and override switch we're all wired in one circuit using wago connectors. 

Now I can't help it but I really need to work out how this was wired in a wiring diagram, I have an idea as to how, but not sure.


But my question is, as normal do we calculate the whole load of this circuit and then use the correct rated mcb, and if anyone could provide me with a wiring diagram or explain how it works. I think I even noticed some resistors used. 


Thanks for your help
  • 0
    Extractor fans are normally quite small loads, and the manufacturers often specify a 3 Amp fuse to protect the wiring to them. This can pose a problem, as the permanent live and the trigger switched live for the fan if it is a timer model, both need to be 3 Amp fused. Often fans are supplied from circuits protected by 6 Amp M.C.B.s such as lighting circuits. So a 3 Amp supply needs to be available for the fan and its associated lighting circuit, say in a bathroom or shower room. A switched or unswitched fused connection unit can do this. As the lighting and fan in the public w.c. are likely to be running at the same time, the full running load will be Ib. So depending upon the size of the installation one or two lighting circuits may be installed to give reliability. If modern L.E.D. panels are installed in the ceiling they are very efficient and use less electricity than old fashioned fluorescent lights. So, to determine the total current drawn you just add up the individual loads and calculate it from there. A circuit using suitable cable and a suitable protective circuit overcurrent protective device will be used according to the total design current. R.C.D. protection will be a good ideas as you can not rely upon members of the public always being sensible, and vandalism can occur.


     I hope that the wiring  above the ceiling is  suitably enclosed in containment and not just flapping about. All single insulated wires need to be enclosed in boxes/enclosures.


    If the lights are meant to come on when somebody enters the room the P.I.R. relay will detect them. It will need a Live and Neutral supply at 240 Volts. It then has a load connected in this case  the lights. It may be set to stay on for a period of time, say 10 minutes. After 10 minutes the lights are automatically turner off.


    The fan may or may not be connected to the same  lighting circuit. The fan may have a permanent Live to it, and just be triggered by the lights coming on, and then run for longer than say 10 minutes to really exhaust the foul air thoroughly. There are several ways of wiring extractor fans. Have a look at timer extractor fans online to see the wiring diagrams for them. The popular domestic ones are 100mm (4 inch) in diameter.



    Z.
  • 0
    360 degree P.I.R. sensor. https://www.toolstation.com/3600-ceiling-pir-single-sensor/p17487?store=W9&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gclid=EAIaIQobChMI6-XWi9Cb4wIV6LztCh1oqAgaEAQYAiABEgJyofD_BwE


    Extractor fans, some basic manually operated models, others timer models.

    https://www.tlc-direct.co.uk/Type/_ExtractorFans.4inch-Timer.html


    Z.
  • 0
    You may find this technical pdf useful.

    https://www.timeguard.com/media/2400/PDRS1500_Instructs_issue1.pdf


    Z.
  • Former Community Member
    0 Former Community Member

    Zoomup:

    Extractor fans are normally quite small loads, and the manufacturers often specify a 3 Amp fuse to protect the wiring to them. This can pose a problem, as the permanent live and the trigger switched live for the fan if it is a timer model, both need to be 3 Amp fused. Often fans are supplied from circuits protected by 6 Amp M.C.B.s such as lighting circuits. So a 3 Amp supply needs to be available for the fan and its associated lighting circuit, say in a bathroom or shower room. A switched or unswitched fused connection unit can do this. As the lighting and fan in the public w.c. are likely to be running at the same time, the full running load will be Ib. So depending upon the size of the installation one or two lighting circuits may be installed to give reliability. If modern L.E.D. panels are installed in the ceiling they are very efficient and use less electricity than old fashioned fluorescent lights. So, to determine the total current drawn you just add up the individual loads and calculate it from there. A circuit using suitable cable and a suitable protective circuit overcurrent protective device will be used according to the total design current. R.C.D. protection will be a good ideas as you can not rely upon members of the public always being sensible, and vandalism can occur.


     I hope that the wiring  above the ceiling is  suitably enclosed in containment and not just flapping about. All single insulated wires need to be enclosed in boxes/enclosures.


    If the lights are meant to come on when somebody enters the room the P.I.R. relay will detect them. It will need a Live and Neutral supply at 240 Volts. It then has a load connected in this case  the lights. It may be set to stay on for a period of time, say 10 minutes. After 10 minutes the lights are automatically turner off.


    The fan may or may not be connected to the same  lighting circuit. The fan may have a permanent Live to it, and just be triggered by the lights coming on, and then run for longer than say 10 minutes to really exhaust the foul air thoroughly. There are several ways of wiring extractor fans. Have a look at timer extractor fans online to see the wiring diagrams for them. The popular domestic ones are 100mm (4 inch) in diameter.



    Z.




    Thanks Soo much for your help, 


    I've got a better understanding now. 

  • 0
    Here's a circuit wiring diagram. Try and use Fans with built in fuses (the manufacturers demand them so let them supply it !). 6A type B MCB is suitable and is likely to react faster than a cartridge fuse under short circuit.


    Legh

  • 0
    Just a word about PIR sensors.

    Some types you can wire in parallel and some you can`t.

    i.e, two or more sensors to operate one light or group of lights can sometimes be an advantage.

    Always check with a manufacturer to see if compatable otherwise you might find the output on one PIR might hold the other PIR(s) output permanently on.

    A way around this if, for some reason, you want to use a non compatable PIR is to wire the outputs each into its own relay or contactor then para up the relays switched outputs.

    The same thing applies to central heating zone valves too.
  • 0
    You'll often find PIRs operating all kinds of things in public toilets - not just lighting and fans, but frequently opening valves on the water supply - so for example urinals only flush after people have been present.

       - Andy.
  • 0
    I got a PIR operating a little waterfall . Pretty but only functons when a "person" detected and a few mins overun. Saves a shilling here and there
  • 0

    ebee:

    Just a word about PIR sensors.

    Some types you can wire in parallel and some you can`t.

    i.e, two or more sensors to operate one light or group of lights can sometimes be an advantage.

    Always check with a manufacturer to see if compatable otherwise you might find the output on one PIR might hold the other PIR(s) output permanently on.

    A way around this if, for some reason, you want to use a non compatable PIR is to wire the outputs each into its own relay or contactor then para up the relays switched outputs.

    The same thing applies to central heating zone valves too.




    I've paralled three PIR detectors together controlling five outdoor lights around the house. Depending on which one is triggered first will depend on how long the lights stay on. I've attempted to get the timing as near to each other as possible.


    Legh

  • Former Community Member
    0 Former Community Member
    Is there are a book that has unorthodox wiring diagrams? I've got the basic college one's, but there seems to be multiple ways of wiring circuits. 

    I suppose you just pick it up with experience

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