In an earlier contribution to this discussion,
Dave Plowman (News) wrote:

In article ,
Roger Mills wrote:
Can anyone recommend a reverse thermostat to switch *on* the
exhaust fan when the kitchen gets *too* hot. I have never seen
one but they must exist.

Pretty well any 'old fashioned' electro mechanical central heating
room thermostat.

Doesn't need to be old fashioned - or mechanical! My Honeywell CM67
programmable stat has change-over contacts and can be used for
cooling rather than heating if desired.

Yes - but rather OTT cost wise for this application?

Agreed, but I was just pointing out that you could simply have said "pretty
well any central heating room thermostat". Whereas an old fashioned
mechanical stat is adequate, it isn't the *only* type which will do the job.

It's certainly the most cost effective, though! When I fitted the RM67 to my
CH, I re-deployed the old mechanical stat inside my computer case to switch
on a mains-powered fan when it gets too hot - precisely the sort of thing
which the OP wants to do.
--
Cheers,
Roger
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