I did a bit of figuring and ohms law tells me that the fuse alone became an approximately 1200 watt "heater" every time the strips were energized. 69.9 ohms in series with 277 volts and about 12 amps to the heater strips yields a lotta watts. It could be more or less since the fuse reading probably was different when it was hot than when it was cold. The initial inrush current would have given the fuse an awful jolt of current before the impedances went up when things were cooking.
Hope my thinking is right.
