Hi, I've installed a pull cord dimmer in the bathroom which controls
the 3 looped low voltage light transformers. The problem is that
although the extractor fan comes on when the lights are on, the timer
fails to turn the fan off when the lights are off. The only way to stop
the fan is to interrupt the permanent live going to it. The switched
live is coming from the dimmer pull and being a dimmer still leaks
current to the extractor even when the lights are off. I don't want to
replace the dimmer with a standard pull switch. Is there anything out
there that I can install between the dimmer and the switched live of
the extractor that will prevent any input to the extractor if the
output from the dimmer falls below a certain threshold? ie:
Undervoltage Lockout or similar?

This is now starting to really peck my head!! Any advice would be
greatly appreciated.

Thanks

wrote:
Hi, I've installed a pull cord dimmer in the bathroom which controls
the 3 looped low voltage light transformers. The problem is that
although the extractor fan comes on when the lights are on, the timer
fails to turn the fan off when the lights are off. The only way to stop
the fan is to interrupt the permanent live going to it. The switched
live is coming from the dimmer pull and being a dimmer still leaks
current to the extractor even when the lights are off. I don't want to
replace the dimmer with a standard pull switch. Is there anything out
there that I can install between the dimmer and the switched live of
the extractor that will prevent any input to the extractor if the
output from the dimmer falls below a certain threshold? ie:
Undervoltage Lockout or similar?

This is now starting to really peck my head!! Any advice would be
greatly appreciated.

Thanks


Ah. I assume these must be electronic transformers then?

Its odd, because all my dimmers (rotaries) actually DO interrupt the
live when actually switched OFF, not merely reduce it to a trickle.

However, if what you say is true, the addition of some form or resistive
load - say a low wattage mains light o the bulb sort - in parallel with
the LV stuff - should pull the voltage low enough to fool the timer.

But I suspect some mis wiring is in this equation..because I have yet to
meet a dimmer switch that applies any live to the electronics when
actually switched OFF.

The Natural Philosopher wrote:

..because I have yet to meet a dimmer switch that applies any live to
the electronics when actually switched OFF.

But this is a pull-cord dimmer. I've no idea how those work, but maybe
there's no hard-switched off state? That being the case a suitably
mounted 33 or 47 k ohm 2 watt resistor across the output (SW-L to N)
might do the trick.

--
Andy