How can I protect an existing power supply?

Circuit Breakers

  1. Circuit breakers that have tripped and have been reset continually will be more apt to trip at a lower amperage than they are rated for. They get worn out.
  2. A breaker in a small kiln room will trip sooner because of the higher ambient temperature.
  3. An inductive amp meter will indicate whether the kiln is pulling more amperage than the breaker allows.
  4. Remember to size it for 125% of the total amp load.

Wire Size Too Small

  1. Using a wire size that is too small for the amperage draw will cause the wire and conduit to heat up and the voltage to the kiln will drop.
  2. Voltage will be lost in the form of heat.  The breaker can trip from the local heat.
  3. Without a properly sized breaker, the connection points can start to corrode and this may cause an electrical fire.


  1. Any visible corrosion in an electrical circuit- especially on a plug and receptacle connection - will result in heat generated at that point.
  2. Heat leads to corrosion, which leads to more heat and eventually the melting of the component or connection point.
  3. This could start a fire if the breaker fails to trip.

Dedicated Circuit

  1. The kiln should be on its own circuit. If anything else is on the circuit the voltage will drop when the other device is turned on.
  2. The circuit breaker must be rated for more than the combined amperage of all the devices if the kiln must share a circuit.

Melting power cord

  1. Look for the power cord melting if it is close to the kiln.
  2. Look at the receptacle that it plugs into for signs of overheating; these include bulging, discolored, and swollen.
  3. Look for flattened insulation (like a small slice from the side of the cord). This is where the cord came up against the side of the hot kiln but for whatever reason, did not stay there long. If the cord is only very slightly melted it may be OK to use if the situation that caused the melting is rectified.
  4. If the cord appears to be getting worse or gets hot when the kiln is firing, replace it. If the insulation on the cord has deteriorated it is possible that the power wires could short out and cause a fire.