Have fitted a timed run-on extract fan, all fine except that when switching 'spikey' loads elsewhere in the property, the fan activates and runs for its allotted time.

Fluorescent light in the loft triggers it, and so do big power tools (mitre saw, hoover).

I presume this is something to do with spikes created as these more inductive loads switch on?

It'll be annoying if the washing machine and fridge trigger this once they arrive!

Dave.

I wonder how the fan would react to having its SL live tied to N instead of floating when the light is off? (easy enough to arrange using a 2-way switch instead of a 1-way). It should stop the SL picking up "noise".
- Andy.

Yes I've had this with a specific timer fan - I think it's this one:

http://www.tlc-direct.co.uk/Pr.../ADAUE100T.html


Happened twice - switch on any light on the circuit and the fan starts up... pants, eh?

Wiring was all OK (one was a rewire!) and once I changed the fan make all was fine

Airflow denied all knowledge and tried to blame the electrician

I wondered if it was because it was a 'low power' one????

Good idea Andy
Of course you'll need to stick a single blue from your light to your two way pullcord (presuming traditional configuration)
Or a 3 core from the pullcord to the load on your FSU if you've done it the more modern way.

Regards
Ady

-------------------------
Resistance is futile.

This can be an issue if the fan and its timer were designed for an incandescent lamp. When off, the incandescent lamps effectively place a low value resistance between the neutral terminal and the switched-live of the fan. The problem starts when you fit a CFL in place of the lamp, as its input stage is a diode bridge and a capacitor, for its inverter. This can allow the voltage on the switched live wire to rise sufficiently to start the fan.

The two ways out of this have already been mentioned - one was changing the fan to one more tolerant of having CFLs used as the lamps, the other was using a 2-way switch wired in an unconventional manner to tie the neutral to the switched live when the lamp is off.

Regards,

Alan.

Would a resistor connected across the lamp terminals not do the job as well?

A resistor should do the same job as well. A bit of experimenting may be required to determine the correct value.

Regards,

Alan.

I would start off with about 68k 1w and see if that works. An other solution would be to connect a low wattage panel lamp across the terminals.

Not just me then, - cheers guys.

It is indeed an airflow fan from TLC that Bruciebonus mentions...

Nearly all the lighting in the property is LED or CFL, - LED and t5 fluorescent in the bathroom.

It'll be very easy to try the neutral switching idea, so i'll give this a go first.

Thanks,

dave