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

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  • Answered

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

Posted by Moses on Jul 4, 2019 2:52 pm

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

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

Posted by ebee on Jul 7, 2019 10:53 am

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.

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

Posted by Sparkingchip on Jul 7, 2019 11:14 am

 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.



 

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

Posted by Sparkingchip on Jul 7, 2019 11:31 am

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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 

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

Posted by Chris Pearson on Jul 7, 2019 7:11 pm

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.

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

Posted by AJJewsbury on Jul 8, 2019 11:54 am

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.

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

Posted by Sparkingchip on Jul 8, 2019 9:57 pm

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https://professional-electrician.com/technical/identification-electrical-wiring/

You would not sleeve the new black conductor blue to use as the neutral and use the new blue as L3 would you?

Andy B

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

Posted by mapj1 on Jul 8, 2019 11:31 pm

hopefully you'd be very careful not to assume however that the wiring was as shown above, without checking for volts..
Not long after the change over, I  witnessed the aftermath of just such a cockup where  a large number of portable shower 'tardises' had been dropped onto a camp site, along with a 1MVA genset to power them.
The cable tail on the hired  genset was 'old colours' and perhaps the yellow core was a bit dirty looking, and may have been mistaken for a badly made  grey, or it may have been wired by someone very tired. The dis board taking the 3 phase to lots of 32A commando sockets was however very much  wired to expect the new colours.

By transposing 2nd phase and neutral,  essentially the black/blue confusion ensued.
Once the genset was started, some of the showers were between 2 phases and ran very hot but failed very quickly.. Although the mistake was quickly rectified, a number of the showers were then 'cold only' for the rest of the event. Disappointing and expensive, for the sake of a quick flick on the volts range. (all dead tests had looked OK of course.)
 
regards Mike

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

Posted by Chris Pearson on Jul 9, 2019 12:10 pm

Sparkingchip:
b70da8df00f372e8af35f67bf4546c2e-huge-aa
https://professional-electrician.com/technical/identification-electrical-wiring/

You would not sleeve the new black conductor blue to use as the neutral and use the new blue as L3 would you?

Andy B

That's daft!

I am inclined to wonder how often 3-core & earth is used for 3-phase circuits as opposed to 2-way lighting or fans.

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

Posted by Mr Neutron on Jul 9, 2019 8:10 pm

The extractor fan requires a L and N switch for isolation purposes. I have installed two recently and seen two different circuits shown in instructions. One shows a 2-pole switch prior to the single pole service switch the other after. Both demanding that a 3 Amp fuse be fitted. For the first circuit you can simply use a 2-pole switched / fuse spur. For the second a dedicated and extractor annotated 3 -pole  switch is used. This is both expensive and and not fused, so you have to provide this separately and also use 3 core and earth cable. However I think second maybe the preferred method as the industry supplies the annotated 3 pole switch, but I have not seen an annotated 2-pole switch. Another advantage of the 2-pole switched circuit is that it isolates the whole circuit and not just the branch to the extractor. The switch is however supplied to give safe isolation of the fan for maintenance / removal. 

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

Posted by AJJewsbury on Jul 10, 2019 11:45 am

However I think second maybe the preferred method as the industry supplies the annotated 3 pole switch, but I have not seen an annotated 2-pole switch.

Arguably there's little need to produce a dedicated fan-symbol marked 2-pole isolating device - as you can always employ the 3-pole version and leave one pair of terminals unused.  It's the same with simple lightswitches - if you want a 2-gang one you can only get it in 2-way versions - so you just have to leave the extra terminals unused for 1-way switching. The waste of the extra metal etc is far offset by the savings of not having multiple different products (and lower volumes of each).
 

Another advantage of the 2-pole switched circuit is that it isolates the whole circuit and not just the branch to the extractor.

But has the disadvantage of isolating the light as well as the fan - which can be a nuisance especially in bathrooms with no window.

  - Andy.

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

Posted by Denis McMahon on Jul 11, 2019 8:16 am

ebee:
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.

I was initially attracted to this thread by its reference to toilets etc., and recollections of my "oh dear!" moment. However I have followed the subsequent progression to identification colours with interest.

I don't know quite how old is meant by "old", but the idea of white for one of the phases seems to have occurred at various times.

It was around 1970, I think, that the new colours, i.e. brown for live, blue for neutral, green and yellow for earth, were introduced for flexible cords, round about the time also that sizes moved to metric. I wondered at the time why fixed wiring colours were remaining unchanged but nobody seemed able to answer that question.

I seem to recall at some stage subsequently a proposal that the three phase identification change to brown, white and grey. There seemed some sense in selecting white; it was not used for another purpose, it was bright, like yellow, and there seemed to be a historical link.

The present use of black as in identifier does seem to beg confusion with the old neutral. Much fixed wiring with the old red and black colours still exists and will continue to be there for a long time, so inevitably there will be cases of new wiring joining older with old colours.

Can anyone else remember the proposal for white, and why it "gave way" to black?
 
Denis4711

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

Posted by AJJewsbury on Jul 11, 2019 10:52 am

I wondered at the time why fixed wiring colours were remaining unchanged but nobody seemed able to answer that question.

My guess would be that the change was driven by European trade requirements - manufacturers wanted to be able to sell the same (esp single phase domestic) appliance across Europe (single  market and all that) - each country having its own flex type makes that painful for the production line and distribution. (In those days of course they didn't have to fit an appropriate plug). Fixed installations were much less of a trade issue - they didn't move about so much - and more complicated to solve as it had to address various 3-phase requirements too - so that problem got deferred.
 

Can anyone else remember the proposal for white, and why it "gave way" to black?

Probably because most of the continent already used black (or combinations of black and brown) for line (phase) - and white (well officially cream, but usually very white looking in practice) was already established as a functional earth. The continentals really weren't bothered about a third colour - they tended not to preserve phase rotation in wiring - often L1/L2/L3 were brown and two blacks or two browns and one black - that way they could reverse one pair at the motor to ensure correct rotation without anything looking wrong. It was the UK that insisted on a 3rd colour and I gather once you'd eliminated all the colours that had been used for something else in recent history across Europe (the Germans used to use red for earth for example) you were left with only pink or grey. They picked grey.

   - Andy.

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

Posted by ebee on Jul 11, 2019 9:24 pm

If memory serves (might just be folklore and mee old heed though) , some of the continent used Brown as L1, Black as L2 & also Black as L3, which meant join two Blacks could short 2 phases, then instead of being sensible and adopting the best colours (ours) they did not want to favour or disfavour any single country so they compromised on the colours we get today. A political bodge.

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

Posted by Denis McMahon on Jul 12, 2019 7:12 am

Thanks for your take on this, Andy. It accounts for quite a lot.
Denis4711

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