Strangest problem yet

Discussion in 'Electricians' Talk' started by peter palmer, Jun 14, 2016.

  1. peter palmer

    peter palmer Screwfix Select

    Got a weird problem today, fan staying on. Its actually a constant fan that is on low permanent unless you switch the light on and it goes to full power, initially I suspected the timer module so swapped this out with another fan that was working ok, its just the same.

    Next I started to fiddle about with the connections, its a 1 gang switch for the bathroom, wired loop in at the switch, basically T&E in, T&E out, T&E to the light and a 3C&E to the fan via a 3 pole fan isolator.
    (so 3 browns in common, brown and grey in L1, 3 blues and 1 black in terminal block and earths in another block all in switch)

    Now what I found out was if I disconnect the trigger wire from the 3 core out of the switch the fan works perfectly, just as if the switch was switched off - switch passing enough current to operate fan obviously - but no, if I take the brown to the light out of the switch as well and connect it to the grey trigger wire with a connector the fan starts again. WTF.

    The light fitting is a 28W 2D fitting with an electronic ballast that is obviously fed with a single T&E straight from the switch. This is where it gets really odd, with the switch in the off position the light is obviously not lit but the fan going full belt, if you remove the lamp from the fitting the fan does what its supposed to and goes back to background extraction. I then removed the fitting and put a basic lamp holder on the end of the cable.

    This is what happens, normal 60W filament lamp, switch off - light off, fan running slowly - as it should be. Switch on - lamp lights, fan runs full belt - as it should be again.

    Take the bulb out and with the switch off as soon as you put an energy saving lamp in the holder the fan starts up, I dont get it there is 0 volts on the switch wire, even if you connect the brown to the blue at the fitting the fan doesn't start, only when you put something with electronics in line.

    The fan is one I mentioned in an earlier thread, a Nuaire genie x, it does however mention something in the bumph about making sure there is no voltage present on the trigger wire so they obviously have had problems with this in the past. Very strange indeed.
     
  2. FatHands

    FatHands Well-Known Member

    Did you get to the bottom of this Pete? So if i understand correctly it works OK with a halogen lamp but not the CFL? May be worth dropping them an email: info@nuaire.co.uk
     
  3. TP&N

    TP&N Active Member

    I came across a similar problem but another make of fan it turned out there was a current sensing device on the pc board so when the lamp came on the current draw drove the fan at full speed and when turned off the fan returned to the slow speed setting all worked fine till some one changed the lamp to an LED one it didnt draw enough current to drive the fan to full speed.
     
  4. philthespark

    philthespark Active Member

    Sounds like this is an easy fix seen it before just needs something connecting across the trigger wire and neutral. Only trouble is I can't remember what it is called, lol.its a small black thing with 2 wires coming out and it absorbs the slight leakage. It's a real beggar getting old.:(
     
  5. TP&N

    TP&N Active Member

    You thinking of one of theses


    [​IMG]
     
  6. peter palmer

    peter palmer Screwfix Select

    I was thinking of using a suppressor, cap something or other they are called, but I'm not convinced it will work, basically the fan starts when a bulb effectively connects the trigger wire of the fan to the neutral of the circuit, thats the only connection being made. Yet if you connect the trigger wire directly to neutral nothing happens, neither does it come on if a normal incandescent lamp is fitted.

    I think the only answer is for a different make fan, although the other 50 fans in the building with an identical set up work ok and using a module out of a working fan makes no difference either.
     
  7. philthespark

    philthespark Active Member

    That's the thing. Lol
     
  8. stateit

    stateit Screwfix Select

    A neighbour had similar with a Worcester boiler 5 or 6 years ago. Kept randomly firing up. Paid plumber for half a dozen visits and a PCB change. I fitted a suppressor and it was fine. I couldn't find anything unusual with the rest of the wiring to cause it though...
     
  9. TP&N

    TP&N Active Member

    I've noticed of late when testing the RCD in some places the dirty mains indicator has been showing up a lot more than it use to. Makes you wonder if were going to have to fit filter caps to a lot more gear.
     
  10. retiredsparks

    retiredsparks Super Member


    where did you fit it ...and the value ?
    RS
     
  11. 14th edition

    14th edition Well-Known Member

    Capload, git mine from Edmundsons, worked a treat!
     
  12. TP&N

    TP&N Active Member

    I get mine from Maplin off the self they come in a pack of 2 for less than £3
     
  13. peter palmer

    peter palmer Screwfix Select

    Is it called a capload from maplin , I might try it.
     
  14. TP&N

    TP&N Active Member

    FatHands likes this.
  15. peter palmer

    peter palmer Screwfix Select

  16. peter palmer

    peter palmer Screwfix Select

    The Capload did the trick today.
     
  17. FatHands

    FatHands Well-Known Member

    Pleased to hear it pete, thanks for posting back too. We all to often see questions but rarely the outcome!
     
  18. peter palmer

    peter palmer Screwfix Select

    No Idea how it worked but it did, I put it across the live and neutral of the light. So even though the light is switched off touching the cap load onto the L&N terminals of the light stops the fan.
     

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