Did you mount it inside the stove? I am thinking about just bolting mine to the side of the stove with a pump, it stays 300 degrees and as high as 450.
if you do a search, there are numerous diagrams and discussions....I think they recommend less than 8-10' for Thermosiphon, no pump. I would leave the breaker on, if the stove can't keep up or you need to heat it up quicker. As long as the temp element is satisfied, the elements won't come on.
I actually have a timer on my tank, so it it's only on for 4 hours a day in the morning and 1 hour around 4pm. Other than that, it just sits there using no electricity. it really doesn't get too cool.