Brick Cracking and Hairline Cracks
Hairline cracks are common in all kilns and should not be a concern. Bricks expand and contract when heated and then cooled. The cracks will close as the kiln gets hotter. This is most prevalent in the kiln top or bottom.
Kilns fired at the higher temperatures will experience more spalling and cracking of the brick. Kilns cooled down too rapidly will effect the amount of cracking. If you are repairing a broken brick, repair cement should be used to adhere the broken piece back into place. If a brick breaks under an element and is impossible to repair, an element pin can be used under the coil to prevent drooping.
Fuse "Blows" or Breaker Trips Immediately when Kiln is Turned On
Generally speaking, if a fuse "blows" or circuit breaker trips immediately upon applying power to the kiln, or pressing the start keys, it indicates a short circuit within the kiln itself. It's also possible that the fuses or breakers protecting the circuit are not sized properly. Check the wiring for any signs of arcing (visual and smell). If there is any evidence of arcing, call a qualified electrician to fix the problem. This must be fixed before you continue firing.
Another cause of this issue, is that the electrical service to the kiln is wired incorrectly. Have a qualified electrician check the electrical service from the main service to the kiln. There have been incidences where the connections from the electrical pole outside to the main service at the house has been loose. Finally, it could be as simple as the circuit is overloaded. The easy remedy to this is just disconnect all other appliances on that circuit while operating your kiln.
Fuse "Blows" or Breaker Trips During Firing
Generally speaking, if a fuse "blows" or circuit breaker trips sometime after the beginning of the firing it indicates a problem with the electrical service itself. The causes are varied. Heat at the fuses or breakers will cause them to "blow" or trip at lower amperage levels. This heat can be caused by a weak or loose connection at the fuse or breaker or elsewhere in the service (heat travels well in copper). A fuse or breaker is not normally warm or hot. It should be very close to room temperature during normal operation.
It's possible also that the fuses or breakers are bad, weak, junk etc. Replace only with the proper size. Do not install larger fuses or breakers to solve this problem. Something out of the ordinary made the originals fail. The problem must be corrected not bullied into submission. It doesn't work that way. In this type of situation, it is suggested that a qualified electrician be asked to check for circuit problems.
Be Smart. Be Careful. Have Fun!