I'm guessing it's some little space heater then. I would really recommend returning it immediately to get something with a digital controller that you can set built in. And do not hook it up to the same thermostat as the UTH. A thermostat isn't going to put out the watts necessary to run a space heater.
So since you didn't get one with a built in thermostat you'll have to crank it up then adjust it down by using a thermometer in the tank until it's around where it should be because it's never going to be exact.
This is my setup, door stays closed, and the temp stays at a steady 80 even though the rest of the house gets down to 64 at night/during the day and the heat lamp is never on. (the heater) You should go for something more like that for a heater than some cheap half-assed method.
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