On Monday, September 16, 2019 at 3:29:31 AM UTC-4, micky wrote:
In alt.home.repair, on Sun, 15 Sep 2019 23:40:48 -0400, Ralph Mowery
wrote:

In article ,
says...
wanted to control an attic fan. I wanted 3 options: Off, On, and
Auto. Auto means the fan is controlled by the thermostat in the attic.
A SPDT with center off would do this, but none are available. I ended
up using one of those double switches (2 SPST single-gang). Available
in paddle and decora, and relatively cheap (I think $17).
Generally that would be accomplished using a bat-handle type switch
supplied by the fan manufacturer or the control manufacturer - but 2
switches in parallel would do the job too

Most people (wives) don't want a bat handle switch in their hall.



The attic fan where I used to live had a switch for 'on, off, timer'.
You turned it on all the time , cut it off, or there was a timer next to
the switch. It was on a flat plate about the size of most light
switches, but the switch was large and almost flat. You pushed it in
toward the wall for off or timer and it stayed in the middle for off.

In addition to the thermostatic switch, my roof fan has two switches in
one box, mounted sideways.

One switch turns it On when it would be off. This was recommended for
use after a hot shower which fills the attic with humidity, but I don't
take hot showers.

Why does taking a shower fill the attic with humidity? Bathroom fan
venting into the attic instead of outside? Something is very wrong
there.





One switch turns on Off when it would be on. I use this in late fall
and early spring to let the sun heat the house and save on fuel to heat
it. Or when it's so hot out that the fan would run all night (but
then I usually forget to turn it on the next morning.)

Normally the first switch if off and the second On. With a line on each
one whose parts are in-ine when they are set normally.

But what I should have put in is a timer, because sometimes it is so hot
out at night that the attic never cools off enough to stop the fan, and
it runs from about 11 in the morning to at least 9PM the following day.
There is no point to the fan's running if it's as hot outside as it is
in the attic. It only happens a few days a year but it annoys me. So I
may put in a timer wall switch. I think it will have to be one that
doesn't need a neutral, because I don't think I ran a neutral (from the
fan to these two switches). It would have been easier if I'd done it in
the first place. So maybe I won't do it.


The attic fan switch is set too low. And adequate natural ventilation,
eg ridge vent with soffit venting is better. I'll bet you could turn
it off from about 8PM until the next morning and not see any difference
with the temperature inside. And if you do, something else is wrong,
eg inadequate insulation.