Haven't run into that problem yet, I've only been able to run it as is for a couple days. Then the weather got cold and I needed to heat the house instead. I need to get it running on 110v to continue.

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.