Did a brew the other day, all was going well when suddenly lights out in the Guten on ramp up to boil at about 85C, no warning, just complete lights out, no power to controller or pump.....WTF !...... so back up plan enacted, grabbed my newly acquired hang over the side bucket immersion heater, and plumbed in a spare 240v pump to circulate from the digiboil to the Guten, as I essentially run 2 kettles for bigger volumes, and got things back on track, not ideal, but saved the day, well worth the investment as a back up tool, and handy anyway.
After investigation, it turns out there is a sneaky little inline thermal fuse rated at 227 degrees Celsius 10 amp on the main power wire hiding under some white heat shielding wrap from the thermal cut-out button to the main power switch, that also supplies the pump switch power, and this had failed cutting all the power coming in.
Now I carefully inspected every thing in this compartment, and could not see any evidence of excessively high temps, so my conclusion is it just failed, not sure why they have it as the thermal cut-out disc in the same area is rated at about 150C would probably be adequate.
I have replaced this wire with a decent thick gauge wire (Brown wire) and no thermal fuse and all is good again, but bringing this incident to everyone's attention so as to preempt a future WTF ! moment half way through a brew. I had a plan C as well, gas burner with an old keg kettle that I use as a sparge tank with the bucket heater and a cheap thermostat arrangement, like the Inkbird, but cheaper.
I always like a back up plan or two, and this strategy paid off to get me through the day, something to think about!