Where can i find a thermostat to switch line voltage for a fan, and has summer and winter settings?

Dan C.'s Avatar (by Gravatar) by Dan C. in  Climate Control 

Room 1 has a runng wood stove in the winter, and a big window A/C unit running in the summer. Room 2 has no cliamate control but is only 8' x 10', so I bought some nice grates about a foot square and cut a hole in the wall between room 1 & 2, about 6' up and furthest from the door. I ran 115vac into the hole and bought a few quiet 9" or 10" fans to try. Thats when I tried looking for a thermostat to switch the fan on and off via temp, with a summer winter switch to switch whether it is going on for heat or cool. What I found was nothing. Can you just point me in the right direction?

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Answer by homeowners

I can't really say anything about how efficient such a system will be. You're probably going to have to cut another hole in the wall so the air can return from Room 2 to Room 1. Otherwise you're going to create negative pressure in Room 1 and positive in Room 2 which will further reduce output of the small fan.

Anyhow, getting back to your actual question: if you are willing to install a 24V transformer and a 24V coil/120V load relay in some sort of an enclosure, you can just use any programmable thermostat from any hardware store and install it in Room 2. Since both heating mode and cooling mode require fan operation, the fan output of the thermostat will become energized and therefore can operate the relay every time the t-stat calls for heat in the "heating" mode or for cold in the "Cooling" mode. Most also have a "Fan on" setting if you just wanted to manually override the temperature sensing and just run the fan constantly. 

The 24V transformer would supply the line power to the t-stat. Some t-stats can operate on battery power only and may be able to energize a smaller 5V coil/120V load relay which would not normally be large enough to operate an air handler blower but in your case the fan is small enough to give it a try. The batteries will drain rather quickly though because the relay's coil drains considerable power when it's on.  So, I would recommend a 24V transformer. Could be a small one they use for door bells.

So, again, not sure about how effective the climate control will be but there's no reason you cannot use a "normal" thermostat in Room 2 if you add just two parts to it.

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