Can a dimmer affect smoke alarm

[johnbuckley]

My relatives recently fitted a dimmer switch and have intermittently been plagued with the ceiling mounted smoke detector being activated; it only happens when the dimmer is switched on and not all of the time. Of course it may be nothing to do with the dimmer at all and I'd be grateful for any ideas please. There is also no possibility that smoke has activated the detector.
House is new build 2024 with interlinked smoke alarms connected to the upstairs lighting circuit breaker. I have had a quick look and the common wire in the dimmer was very slightly loose and I reterminated the cables so that there was no copper showing.
The dimmer is in a downstairs hallway so not on the same light circuit, and it is the same hallway smoke detector that will trigger randomly; apparently it has never happened whilst the hallway light is off and never happened prior to the dimmer being fitted.
I have turned the dimmer on/off, up/down and couldn't get the smoke alarm to activate.
I also noted that there is a very, very faint hum/buzz from the dimmer and also the lamps when it is switched on and dimmed down; lamps are the dimmable type.
I have attached a pic of the dimmer (before I reterminated the cables); can anyone tell me what the little screw is on the left? I haven't touched it and there's nothing in the installation instructions about it and I'm intrigued if anyone knows.
As a quick thought, could the proximity of the halway ceiling lamp to the smoke detector cause this issue?
Any bright ideas would be welcomed.
Thanks
John

 

[SUNRAY]

I don't imagine it is to do with the dimmer unless it is electrical interference, but my first thought would be to refit the 2 way switch for a few weeks to see if the alarm continues.

 

[johnbuckley]

Thanks for that. Yes, interference somewhere was something I'd thought about; just not sure where/why/how and if it was, if there would there be a way to suppress it! Reverting to the old switch is an idea just to see.

 

[ericmark]

As @SUNRAY and I have had EMC problems in the past, and near impossible to work out if the item receiving interference or transmitting interference is at fault.

I first had the problem with car radios in the 60s when not a standard fitment in cars, and some radios seemed to have a wide open front end. I found my mother's pacemaker did not comply with EMC directives, so was advised to remove the induction hob, three months latter they changed the pacemaker so could have used the hob.

All electronic equipment will produce a little RF and the big problem is when it does cause interference, what is faulty. If driving a filament lamp one can be reasonable sure interference is from the dimmer switch, but a radio transmitter uses aerials, diodes, capacitors, etc, and the standard LED lamp can also have the same components, with 12 volt lighting transformers there was often a warning, saying no more than 1 meter of cable to be used from the electronic transformer to the lamp.

I personally prefer smart bulbs, so everything in the lighting control is made by the same manufacturer, and the colour can also be adjusted to give ambiance, and they will connect to Wi-Fi so I can use voice commands.

So what lamps are being controlled by the dimmer, can you swap bulbs? i.e. what is the easiest bit to change to test?

We are told that the line and neutral should run next to each other, to prevent transmission, yet in most home we run two lines to the switch, this caused no problems with tungsten bulbs, but could with LED bulbs, in fact it does, and sometimes two-way wiring can have enough inductive and capacitive linking to cause bulbs to glow when switched off.

I note 60 watt minium rating, so that is not suitable for most LED lamps. Even my living room with 8 bulb chandelier does not draw 60 watt, or VA as on the switch.

 

[johnbuckley]

Thanks for that
The lamps are dimmable led's and the specs for the dimmer say 5-50w for those lamps .

 

[Murdochcat]

I would start by swapping to a standard switch to see if this helps at all

 

[ericmark]

Thanks for that
The lamps are dimmable led's and the specs for the dimmer say 5-50w for those lamps .

Yes, I have also found sites claiming for LED 5-50 watt, one even says they can be used on high voltage, sooner you than me, can't see them lasting long at 1000 volts, but since 60-400VA clearly marked on the switch, I would say designed for minium of 60 and maximum of 400 watt. Just because some website says 5-50 watt, that should not be taken as correct when so clearly marked on the switch.

 

[johnbuckley]

Thanks, I get what you're saying.
I got the info re 5-50w from the BG manufacturer info for that specific switch so I may just contact them to see if they can explain that.

 

[Colin Brenton]

Not sure if it was answered yet, but the 'adjustment' on the back of the switch is to set how bright the light will be at the minimum setting of the dimmer switch.

I found it useful to adjust it to get the best performance (as in, the least flicker!) when dimming some (allegedly dim-able...) LED bulbs.

Not sure if it has any bearing on the problem being discussed, but that's what it is for. Maybe try turning it down a bit and test, then up a bit and test?

HTH

 

[johnbuckley]

Not sure if it was answered yet, but the 'adjustment' on the back of the switch is to set how bright the light will be at the minimum setting of the dimmer switch.

I found it useful to adjust it to get the best performance (as in, the least flicker!) when dimming some (allegedly dim-able...) LED bulbs.

Not sure if it has any bearing on the problem being discussed, but that's what it is for. Maybe try turning it down a bit and test, then up a bit and test?

HTH

Thanks, that has cleared something up; always learning!