appliance-switched fan

Is it possible for an extractor fan (on the lighting circuit) in a hall cupboard to be switched on automatically when either a washing machine or a tumble dryer (both in the cupboard & connected to a double wall socket via 13 amp fused plugs) are started and switched off only when both are not being used? Is there an extractor fan available (4inch flue vented) which includes this type of control or any separate controlling device which could be used in this way with the fan? Could it monitor current being drawn via the double socket?
Thanks - Rob McM

In principle one could place a current transformer round the cables feeding the drier or what ever, and use this to operate a transistor assisted relay to trigger the fan. Sadly I am not aware of any commercial products made for this purpose, and unless you are of the hobby electronics bent, I could respectfully suggest its beyond the average DIYer.
Unless anyone else knows differently?

RobMcM said:

Is it possible for an extractor fan (on the lighting circuit) in a hall cupboard to be switched on automatically when either a washing machine or a tumble dryer (both in the cupboard & connected to a double wall socket via 13 amp fused plugs) are started and switched off only when both are not being used? Is there an extractor fan available (4inch flue vented) which includes this type of control or any separate controlling device which could be used in this way with the fan? Could it monitor current being drawn via the double socket?
Thanks - Rob McM

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You can get fans of 4inch dia that have a humidity sensor incorporated in them but I don’t know if when the machines started this would work??? You could use a thermostat on the dryer to trigger but not sure about the washer maybe a proximity probe

The current transformer idea is for electronics boffins only. You have to break into the supply to the double socket and put the thing round either the live or neutral wire(s), not both. I know exactly how to do this but I still wouldn't do it. Think ahead. What happens if you sell the house? How is the new owner going to maintain this bit of unorthodox wiring?

A humidity switched fan is a reasonable idea and you can get them off the shelf but, if the purpose of the fan is to remove damp air from the tumbler, why not use the one that's in the thing already? Vent the tumbler straight out through the wall.

If it's heat you're worried about why throw it away. A simple room stat can control a fan that vents the air out of the cupboard and into the hall but why bother. A louvre door consumes no power!

I agree felix -actually I was thinking one could make a custom extension lead box that detects a load, but I agree, its not a solution for someone who hasn't already got blue fingers. As it were

i know its probably a bit late! but i know someone developed a device aimed at student accomodation to stop false fire alarms when cooking or toast burning by automaticly starting extractor fan when power was used.
i dont know if it made it into production. hope this will be of some use.