I use the thermo cube with my oil filled electric heater in my off-road POPUP trailer.
This thermo cube turns on when the temp gets to 35 degrees and thens turns off when the temp gets to 45 degrees. I originally got this to run a 100watt light bulb inside the cabinet where my water lines at at.
It handles the 1200WATT Electric heater just fine...
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I like to use the low profile DeLonghi TRN0812T Oil filled Electric heater which has no open flames or heater cores. Also has no blower which makes it silent running... To me this is probably one of the safest heaters you can have inside a trailer. I have no problem running this unattended...
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These items are available from AMAZON...
Roy Ken