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Switching off bathroom light sometimes dims living room lights

Discussion in 'Electrics UK' started by Giles Mann, 18 Oct 2020.

  1. Giles Mann

    Giles Mann

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    Every so often, when I switch off the bathroom light (which also switches off the extractor fan) the 5x dimmer spotlights in the living room dim (quite significantly) for a split second before brightening again. Seems to be the only combination of things to cause this - no other lights affected at all. Most of the time switching off the bathroom light will not affect the living room lights at all.

    Does this sound like a major potential cause for concern such as a fire risk? It's infrequent enough not to be annoying but I would rather get out an electrician if it is a potential safety hazard.
     
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  3. chivers67

    chivers67

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    Seems odd, i'd perhaps expect the Fan starting up could possibly dim the lights for millisecond. I suspect you could have a loose connection somewhere
     
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  4. bernardgreen

    bernardgreen

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    Possible cause is a voltage spike on the mains when the motor in the fan is switched OFF causing the electronics in the dimmers to become unstable for a few milliseconds.
     
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  5. Licklieder

    Licklieder

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    I recently replaced two halogen r7 bulbs with osram dimmable led variants, being controlled by a scolomore MD9014 dual mode dimmer. Since doing so these new lights have a tendency to momentarily switch off when I turn on the 5 50w halogen lights in the bathroom.

    Need to investigate further but my suspicion is that the inrush current on the halogens causes a voltage drop that the r7 led / dimmer combination is sensitive to, and the led drivers switch off. Only seems to happen when the leds are set low and the halogens are on high. The fan can sometimes cause it on switch on / off to.

    Was never an issue with the old halogen r7 / scolomore md9042 I had fitted before.
     
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  6. Giles Mann

    Giles Mann

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    Thanks. Is this something that I should get looked at in your opinion. As I said, it is quite a rare occurrence. But if it is a potential safety issue, I will definitely get an electrician to come and have a look.
     
  7. bernardgreen

    bernardgreen

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    If it is the dimmer going unstable due to a voltage spike then there is no safety hazard ( though the life of the dimmer may be reduced ).
     
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  8. Giles Mann

    Giles Mann

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    Ok good to know, thanks. I wonder if this would be easily fixable by someone who knows what they're doing. I'll monitor it and see if it gets worse
     
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