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Why does domestic LED bulb permanenetly glow?


StephenFord
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I have replaced every bulb in my house to LED equivalents, apart from one. It's a downstairs toilet, so when the light is switched on, it also activates an extractor fan. When I put in an LED bulb, it works fine, except that when I turn the light switch off, the LED bulb permanently glows. Is there a cure for this, or simply a side effect of the light switch also activating the extractor fan?

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It's normally one of two things, either low quality LED lamp or a wiring issue such as poor grounding. 

An LED will glow with a minimal amount of power going to it. You should try another lamp or you could look at getting a neon indocator on the neutral wire before the LED lamp and hope that soaks up the power. The indicator will illuminate but the LED won't. 

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This can happen with cheap bulbs that don’t have circuitry to overcome the issue. 
 

LEDs require very little power and can light with induced current just from parallel running power cables. The circuit powering your fan is probably causing a small amount of induced current going to the LED. 
 

You could try a different manufacturers bulb otherwise you could get the electrics checked to make sure it’s wired correctly. 

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I had a bedroom LED that would occasionally flicker when turned off, replaced it. Job done.

They churn them out by the million and an occasional bad one slips by. as said there maybe a bad earth as it also runs a fan

 

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17 minutes ago, Jonro2009 said:

It's normally one of two things, either low quality LED lamp or a wiring issue such as poor grounding. 

 

Have tried 3 different brands, a cheapie, Phillips and EverReady - all same result. If it is a 'wiring' issue, I'll just leave it, the cost of an electrician would far outweigh any potential saving of using an LED bulb...

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1 hour ago, StephenFord said:

Have tried 3 different brands, a cheapie, Phillips and EverReady - all same result. If it is a 'wiring' issue, I'll just leave it, the cost of an electrician would far outweigh any potential saving of using an LED bulb

Hi Stephen, just seen your post.

You won't fix the problem. It's caused by the very low power required by the LED lamp being able to draw just enough power back through the timer circuit of the extractor fan. New designs of extractor fans are starting to be fitted with 'opto' isolators on the control wire to prevent back feeding to LED lamps.

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18 minutes ago, unofix said:

Hi Stephen, just seen your post.

You won't fix the problem. It's caused by the very low power required by the LED lamp being able to draw just enough power back through the timer circuit of the extractor fan. New designs of extractor fans are starting to be fitted with 'opto' isolators on the control wire to prevent back feeding to LED lamps.

That makes much sense!! Both my upstairs bathrooms are fully fitted with LEDs with no issues, but the fans have been broken for years!

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4 hours ago, Jonro2009 said:

 low quality LED lamp 

 

4 hours ago, alexp999 said:

cheap bulbs 

I'm guessing @Jonro2009 has sparkie experience, calling it a lamp, whilst @alexp999 like most of us, calls it a bulb! 😀

 

A sparkie once informed me, grumpily, that bulbs grow in the garden and lamps light up. 

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1 hour ago, Turvey said:

A sparkie once informed me, grumpily, that bulbs grow in the garden and lamps light up. 

very true !!!

I knew an electrical maintenance dept. that used to keep a box of daffodil bulbs ready for when some came in and asked for a 'bulb'  

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3 hours ago, Turvey said:

 

I'm guessing @Jonro2009 has sparkie experience, calling it a lamp, whilst @alexp999 like most of us, calls it a bulb! 😀

 

A sparkie once informed me, grumpily, that bulbs grow in the garden and lamps light up. 

No professional experience, but I've been to places like the one @unofix describes. You quickly learn the correct terminology 🤣

6 hours ago, StephenFord said:

That makes much sense!! Both my upstairs bathrooms are fully fitted with LEDs with no issues, but the fans have been broken for years!

I wonder if you turn the fan off at the isolator switch, usually outside the room above the door, would that make any difference? It's worth a try. 

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11 hours ago, Jonro2009 said:

I wonder if you turn the fan off at the isolator switch, usually outside the room above the door, would that make any difference? It's worth a try. 

Afraid I don't have 'isolator' switches, they weren't part of build code when house built 30 years ago...

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45 minutes ago, StephenFord said:

Afraid I don't have 'isolator' switches, they weren't part of build code when house built 30 years ago...

Is the fan separately fused?  Can just pop the fuse out if so.

That's how my property was built about 25 years ago.  Just had to have a switched & fused plate fitted to meet current regs (which only affect rental properties. :rolleyes: ). So that's a finger pushed rocker switch 2 foot above a handwash basin in a bathroom.  Struggling to work out how that's safer than a fuse alone!  Tried to find my old on site guide from 2008 but I'm guessing that's probably out of date now. :laugh:

 

 

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2 minutes ago, TomsFocus said:

Is the fan separately fused?  Can just pop the fuse out if so.

 

Honestly buddy, there is no way to isolate the fan apart from a dismantle of it. When this house was built the 'troubles' were in full swing, not much attention was being paid to the safety of new builds 🤣

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2 minutes ago, TomsFocus said:

Tried to find my old on site guide from 2008 but I'm guessing that's probably out of date now.

Yes that has been superseded at least 4 probably 5 times now. You can not install any type of 230V electrical equipment (including switches and fuses) in what is now termed 'Zone Zero' which would definitely include any area immediately around a washbasin.

 

BS 7671 - 18th Edition, The IET Wiring Regulations

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8 minutes ago, TomsFocus said:

So that's a finger pushed rocker switch 2 foot above a handwash basin in a bathroom.  Struggling to work out how that's safer than a fuse alone! 

It is because both Poles now need to be isolated, not just the Live. Sorry for stealing your thunder @unofix😄

Edit, posted before I saw your answer @unofix 

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10 minutes ago, StephenFord said:

Honestly buddy, there is no way to isolate the fan apart from a dismantle of it. When this house was built the 'troubles' were in full swing, not much attention was being paid to the safety of new builds 🤣

It's not just safety tbf...will be annoying if the fan motor pops and takes out your whole lighting ring one night! :laugh: 

6 minutes ago, Tizer said:

It is because both Poles now need to be isolated, not just the Live.

Ah, that makes sense, thanks!

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Thank you @Tizer 🤣

A bathroom fan isolator switch is a 3 pole device. It switches the 'constant live' - 'neutral' - 'switched live (from light)'

Before 1992 it was only recommended that an isolator be fitted to a bathroom fan for service purposes. The problem was that a domestic 3 pole isolator was not readily available. Some electricians used a standard two pole switched fused spur and put both the constant live and the switched live through the 2 pole isolator and left the neutral unswitched. This of course was not ideal and could in certain situations lead to potential safety issues. Once it became a mandatory requirement for a 3 pole isolator to be fitted then the manufactures of domestic switch gear quickly produced a suitable product.

 

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14 minutes ago, unofix said:

Yes that has been superseded at least 4 probably 5 times now. You can not install any type of 230V electrical equipment (including switches and fuses) in what is now termed 'Zone Zero' which would definitely include any area immediately around a washbasin.

 

BS 7671 - 18th Edition, The IET Wiring Regulations

Zone 0 would be in the bath or shower tray, above the 600mm above the sink is ok

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3 minutes ago, unofix said:

A bathroom fan isolator switch is a 3 pole device. It switches the 'constant live' - 'neutral' - 'switched live (from light)'

Yes thanks for the reminder, my brain is not up to speed at this time on a Sunday morning😄

It was always my understanding too that the main purpose of the Isolator was so that anyone doing maintenance or cleaning did not have to pull the fuse/breaker.

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27 minutes ago, TomsFocus said:

It's not just safety tbf...will be annoying if the fan motor pops and takes out your whole lighting ring one night! :laugh: 

 

Thankfully, both upstairs fans died quietly with no side effects LOL

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46 minutes ago, unofix said:

Thank you @Tizer 🤣

A bathroom fan isolator switch is a 3 pole device. It switches the 'constant live' - 'neutral' - 'switched live (from light)'

Before 1992 it was only recommended that an isolator be fitted to a bathroom fan for service purposes. The problem was that a domestic 3 pole isolator was not readily available. Some electricians used a standard two pole switched fused spur and put both the constant live and the switched live through the 2 pole isolator and left the neutral unswitched. This of course was not ideal and could in certain situations lead to potential safety issues. Once it became a mandatory requirement for a 3 pole isolator to be fitted then the manufactures of domestic switch gear quickly produced a suitable product.

Now, that is interesting!  My property was built around the turn of the Millennium.  Just had a standard fuse plate, no switch.  Wish I'd seen how that was wired now. 🤔

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29 minutes ago, TomsFocus said:

Now, that is interesting!  My property was built around the turn of the Millennium.  Just had a standard fuse plate, no switch.  Wish I'd seen how that was wired now. 🤔

If the fan has an overrun then that is quite frightening if someone who does not know what he is doing ever tries to change it.

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There’s no regulation in BS7671 saying there has to be a fan isolator switch fitted, the MCB which can be locked off is good enough. There is a regulation that says manufacturers instructions should be followed, so if they say they want one fitted you should take that into account, some fan makers want it on a 3 amp supply, some don’t, there aren’t many fused fan isolators available.

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