Most 3rd party firmware has power scaling features that will adjust the power usage based on temperature so as more heat gets built up in the system the miner powers down slowly. I've not gotten to the point where it's at the minimum power usage and it still over heats. I have the critical chip temp set pretty low at 78c too, so if there is a thermal runaway, it should shut down before anything gets cooked.
Discussion
Thanks for the answers, definitely on my todo list. I have the spare breaker space, thinking about leaving the water heater on but setting it very low so you would have more hot water even if the miner didn't keep up.
I already use that idea for my home heat. Baseload from miner and the final few degrees from my central system. That way I get normal levels of comfort and control without a lot of engineering on my part.