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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
    Andy, at what point in the existing wiring would you stop stripping the old black and red cabling? As the black neutral is part of the existing wiring. The most you can do is to sleave the black with blue.


    Legh
  • 0
    There is no need you strip out old black neutrals,  but you should not be installing new black neutrals. 


    Andy Betteridge
  • 0

    AJJewsbury:

    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.




    As a practical point rather than a regulatory one - and particularly for "windowless" toilet areas - don't rely on just one PIR; make sure the "cubicles" are covered or give a very generous time delay. Otherwise a person using a cubicle may suddenly find themselves plunged into total darkness.


    Yes it has happened to me.

  • 0
    You will still need to wave your arms or something else about to trigger the lights again.


    PIR sensors in toilets with fluorescent lighting is not a good idea as they need to be turned on for a minimum period of fifteen minutes to avoid damage to the lighting control gear, flicking the fluorescent lights on an off within a short period will destroy the lights within a few weeks.


    Which also means fluorescent lights are not particularly suitable for use in domestic bathrooms and toilets when there will be frequent short visits.


    Andy Betteridge
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    Sparkingchip:




    Chris Pearson:

    Or black, the old N, over-sleeved blue; and grey for switched line, over-sleeved brown. Same applies for 2-way lighting.




    No, that's not good practice,  it may comply with the regulations, but is not considered correct as it is continuing the idea that black identifies the neutral. 



    Not at all - the neutral conductor is identified by the blue marking.


    514 and Appendix 7 stipulate that line conductors must be marked brown. There is no reference to the use of 3-core cable for L, SwL, and N. In the absence of any regulation or even published convention, there is a free choice as to which of black and grey are used for SwL and N. The only obligation is to ensure that the same marking is applied at both ends of the same conductor!

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    I`d never use Black in a 3 core for N and that stems partly from the phase rotation jobby I mentioned.


    Mind you I am out of kilter with a lot of folk with my 3 core for two way switching configuation. I know I`ve mentioned it before but Both Browns say L1 = perm L., Black sleeved Brown and Blue sleeved BrBrown into L2 and Finally Grey sleeved Brown as C. Of course I was brung up with Reds for L and Black for N, and R/Y/B for 3 phase, well I know some might think I`m old enough for white as 2nd phase but no I am not quite that old.
  • 0
    I had a moment this week, I wired a Aico carbon monoxide alarm and forgot the wiring terminal configuration is different to the smoke and heat alarms with the neutral in the centre.


    The alarm sounded immediately upon powering it up and required the neutral to be moved to its correct location to silence it.


    A daft moment, but that’s life.




  • 0
    e59a7547546c0f04285368b821cb58e9-huge-e06dd234-4d39-4af7-b21f-feeee910b23b.jpg



    Note that hat there is not any need to over sleeve the black with brown, doing so only confirms that it is what it is.


    Indeed when wiring time controlled fans and the like with brown, black and grey only the grey needs over sleeving with blue, over sleeving the the black with brown is unnecessary, but it has become an accepted working practice to aid conductor identification.


    Andy Betteridge
  • 0

    Sparkingchip:

    Indeed when wiring time controlled fans and the like with brown, black and grey only the grey needs over sleeving with blue, over sleeving the the black with brown is unnecessary, but it has become an accepted working practice to aid conductor identification.




    BS 7671 is less than clear on the matter - what's new? ?


    514.4.4 "Other conductors shall be identified by colour in accordance with Table 51." Table 51: Line of a single-phase circuit - brown. Appendix 7 para 5: Power circuit line conductors should be coloured as in Table 51. Other line conductors may be brown, black, red, etc.


    If you think that switched line is an "other line conductor" by all means leave the sleeving off. However, if you feel that Table 51 applies, the conductor must be marked brown. The latter option is, IMHO, the safer one.

  • 0

    If you think that switched line is an "other line conductor" by all means leave the sleeving off. However, if you feel that Table 51 applies, the conductor must be marked brown.



    But if you consider the wire to be a signal or 'control' wire - (trigger to a fan or communications line between smoke alarms perhaps being better examples than a switch wire supplying a light) the table 51 permits Brown, Black, Red, Orange Yellow, Violet, Grey, White, Pink or Turquoise. (Arguably green should be listed too - since the recent revision to 514.4.5)


      - Andy.

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