Thermostat switch (close when below freezing)

[Jester]

I have been searching without much luck for a simple thermostat type switch that closes when below freezing.

Something like this https://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK

but smaller and preferable less than 1$. Prefer if it can switch a small load perhaps 5-10W @12Vdc, however I can use a FET if the device can't handle switching a load.

 

[BradtheRad]

There are heated water pans to put outdoors for birds/ squirrels. They might contain a thermostat that works in freezing temps. You might find a spare in a shop that caters to backyard animals.

Seems there ought to be a similar thermostat to heat small ponds during a frost. A garden/ landscaping supply might be worth a look.

There might be a suitable thermostat in heaters for greenhouses, pump houses, barns, etc. Places where you don't need to turn on heaters until the interior temp drops to freezing.

 

[jiripolivka]

There are heated water pans to put outdoors for birds/ squirrels. They might contain a thermostat that works in freezing temps. You might find a spare in a shop that caters to backyard animals.

Seems there ought to be a similar thermostat to heat small ponds during a frost. A garden/ landscaping supply might be worth a look.

There might be a suitable thermostat in heaters for greenhouses, pump houses, barns, etc. Places where you don't need to turn on heaters until the interior temp drops to freezing.

Any bimetal contact thermostat can be adjusted to switch at any point from -20 to +120 deg.C.
Try a discarded thermostat from an iron, use flat nose pliers to bend the contacts so the switching happens at 0 deg.C. I tried it and it worked.

 

[Jester]

I need a part that can be purchased on a ongoing basis, and it has to be small.

Best solution so far is a MCP9504 driving a FET, small and < $1

 

[FvM]

Best solution so far is a MCP9504 driving a FET, small and < $1

Realistically, you'll hardly find a mechanical thermostat with similar accuracy and size.