This fall, I re-did my entire heating system to install a primary loop from my coal boiler to my old oil boiler, and while doing so I re-installed the amtrol and disconnected the DHW coil.
Since then, on occasion, I'll push water from the primary loop through the amtrol. Not all the time, but every once in a while I'll hear the high temp alarm going off down in the basement. At the moment, it's an inconvenience, but eventually I'll have to re-pipe the line so that the amtrol doesn't heat up past the set point (more for childrens safety than out of fear of damage to the unit). I suspect that I should have piped it into the primary using 1/2 inch line, instead of the 3/4 I used (primary is 1 inch).
Anyhow, I need to put the circulators for the zones on the supply to the oil boiler instead of the return to the coal boiler anyway, so it's something I'll tackle next fall.