Dimmable Pull switches / problem.

gcx51 · 25 May 2009

Hi all, wonder if anyone can help.

I have 3 downlighters and an inline fan in my bathroom. Since fitting a dimmable pull-switch the inline fan runs on and does not turn off.

At the pull switch with the lights turned off I have measured a voltage of 27v. Thinking the switch was faulty I exchanged it, however this did not cure the problem.

I have been told that it may be possible to add an electronic component to the switch feed in the fan. A resistor? Any help would be much appreciated!

Rob

flameport · 25 May 2009

Dimmers and fans are not compatible.

Either get a normal switch
or get a separate switch for the fan
or change the fan for one with an occupancy sensor.

gcx51 · 25 May 2009

The fan is an inline type and is timer controlled and only requires a "voltage present" to activate the fan, the permanite supply is not dimmed.
I’m looking for a solution as when I’ve used inline fans but with a normal dimmer switch on the wall I dont get this problem

Steve · 26 May 2009

gcx51 said:
The fan is an inline type and is timer controlled and only requires a "voltage present" to activate the fan, the permanite supply is not dimmed.

Yes, but the dimmer, when off, outputs 27 volts as you measured! Which is not enough to light the lights, but will trigger the fan. The dimmer is an electronic device and requires energy to run. Not being connected to neutral means it is connected in series with the load, therefore some current will ALWAYS flow.

I’m looking for a solution as when I’ve used inline fans but with a normal dimmer switch on the wall I dont get this problem

¿que?

ColJack · 26 May 2009

normal dimmers are resistive, and quite often have an integrated switch that actually breaks the circuit..

Steve · 26 May 2009

ColJack said:
normal dimmers are resistive, and quite often have an integrated switch that actually breaks the circuit..

I know rotary and push dimmers have a mechanical switch, but ...

I'm thinking varilight dimmers with touch sensitive and IR, they have to draw a little power constantly for these to work - like a TV on standby. I'd think a pullswitch dimmer would be similar, and not have a mechanical switch - how could it, when all the pulling does is vary the lights up and down - theres no user-operable mechanical switch, unless its automatic.

ColJack · 26 May 2009

i was answering your last "que?" and the quote above it that you posted..

the reason he doesn't get this problem with "normal dimmers" is that which I posted above.

Steve · 26 May 2009

ColJack said:
i was answering your last "que?" and the quote above it that you posted..

the reason he doesn't get this problem with "normal dimmers" is that which I posted above.

apologies mate, I misunderstood.

gcx51 · 27 May 2009

I have been told that by reducing the current using a resitor this should solve the problem. Question is how many milli amps would the sensing circuit be? Which resistor would be needed. 1 ohm, 2 ohm, 3 etc? cheers

ColJack · 27 May 2009

( gcx51 ignore the following, we're discussing it amongst ourselves.. )

what do we think steve? 2M resistor in parallel with the fan?

RF Lighting · 27 May 2009

Use a relay in parallell with the lights to switch the fan

ColJack · 27 May 2009

I was sure I already said that higher up.. 110v relay..

must be one of many dissapearing posts i've noticed in the past few days..

RF Lighting · 27 May 2009

Wouldn't the relay go bang when the lights were fully on if it was a 110V coil?

ColJack · 27 May 2009

good point.. was trying to think of a way to get the fan on when the lights are dimmed..
230V relay might start to chatter when you get down to the lower voltages..
but as said, the 110V one won't appreciate being run at 240V..

argh...

ok final solition, wire the fan in permanently and get one with a PIR and Humidistat built in.. it'll turn itself on when it needs to..

gcx51 · 28 May 2009

it's an inline fan with a 35w mr16 lamp in the middle, there must be someone out there who knows their electronics stuff?
thanks for everyones help so far, need to keep this setup !

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Dimmable Pull switches / problem.

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