Thermostat to turn on fan when it's hot ???

I just put a fan in the gable of my barn so my indoor farm animals are not overheating on hot days. Rather than buying a commercial barn fan, which is costly and most are too big for my small barn anyhow. I bought a used fan that is intended to be used as an exhaust fan. I already had a vent up there, so I just mounted the fan over tbe vent inside the barn.
However, I dont want this fan running all the time. Only when the temperature gets about a specific temperature up there at the roof line. I am assuming it should turn on around 85 degrees. and off at 70 deg.
I have been looking for a way to install a thermostat, but as simply as possible. To install a standard heating - cooling thermostat like the types used in a house for furnace and AC, would require a transformer and quite a bit of wiring. Not that it's out of the question, but I am thinking there must be an easier way, where the thing is simply installed in the 120vac line, right next to the fan. I know they make devices like this for portable and baseboard electric heaters. But those will be just the opposite of what I want to do. (it would switch on at the low temp and on at the high - That's backward). But something similar to that is what I am hoping to find.
Does anyone have any suggestions? I do have an old air conditioner with a dead compressor. Could something be salvaged from that? I'm always looking to save a buck if I can salvage something from junk.
Anyone?
Thanks
Mark
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Try these: http://www.littlegreenhouse.com/accessory/controls.shtml
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I believe the 110V thermostats have either normally closed or open contacts, so you can choose heating or cooling mode. Just keep in mind the T-stat should be mounted close to the roof. What I would do is also put it in series with a switch down at ground level so you can shut off the fan whenever you don't want it on.
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I think they are commonly called "attic thermostats". They are available in line voltage. Try Graingers.
Or you could get a line voltage cooling thermostat. Same deal.
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Another source is the local home center, eg HD, etc. Then should have replacement ones for attic fans. I'd make sure that fan is properly fire rated for where you're using it too, ie that it has a thermal cut off.
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This is Turtle.
most thermostats on window units have a range of 64F to 90F and would do fine for turning you fan on when you needed it to. so rob the thermostat out of the old window unit and use it to control it.
TURTLE
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snipped-for-privacy@UNLISTED.com wrote in

For my torpedo shaped kerosene heater, I purchased the optional thermostat for about $35 at Home Depot. Has male prongs and female receptacle slots both in one plug. Insert thermostat plug into current outlet. Insert fan plug into thermostat plug, dial in temp from about 40 to 90.
If this link works, here's a picture: http://www.tools - plus.com/masha1210.html
Uses 110v current. No transformer needed.
In the winter, take it off the vent fan and use it on your torpedo heater.
(I'm a poor man. I look for multiple functions for everything I buy.)
//rus//
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Forget that. I'm such an idiot. T-stat for a heater works backwards regarding your needs.
Heater t-stat will turn off your fan when it gets hot ... that's no good.
Sorry.
//rus//
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snipped-for-privacy@UNLISTED.com wrote:

First, attic fans with a thermostat cost only about $30 at the cheapest but $50 is more normal. Second, the standard way is to put a thermostat near the fan and it is set for around 95 which starts the fan earlier than having the thermostat near the floor, i.e., it may get up to 90-95 degrees at the top of the building while it is still only 70 near the floor.
Third, if you really want a thermostat near the height of the animals you may want to get a thermostat for a hot water tank. These normally are set in the 110 to 160 degree range but I've messed around with them and found they could be set reliably well below 80 degrees. If you look around you should be able to find one for free. So find someone with a bad hot water tank and ask to remove one or both thermostats since bad thermostats are seldom the cause of replacing the tank. Or, just buy one (about $10) And, the thermostats are intended to operate on 240 volts, so there is no problem operating them on 120 volts. Just put the thermostat in the hot line, and put some kind of metal or wood housing around the thermostat for safety since they are rather open.
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