[Aircooled81]

burned out? like caught on fire?
voltage drop would be my first suspect. When the voltage goes down, the current goes up, and so does the heat. If it's a coil for a load, like the strip heat, maybe when the strip heat contactor pulls in the strip heat causes a voltage drop.
throw an amp clamp on the entering power, operate the strip heat and see if you over amp. read the entering volts across all phases before, and while the strip heat is running.