This is probably the element shorting out as it heats up... causing an Overload on the breaker, as it's resistance lowers with heat. it could cause high current draw and blows breaker? Either that or there is some Phase Earth fault, in thermostat or similar? Or perhaps a wire moving and touching Earth as the unit heats up? Or the Breaker might be rated wrong?
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This is probably the element shorting out as it heats up... causing an Overload on the breaker, as it's resistance lowers with heat. it could cause high current draw and blows breaker? Either that or there is some Phase Earth fault, in thermostat or similar? Or perhaps a wire moving and touching Earth as the unit heats up? Or the Breaker might be rated wrong?