The amperage rating of the fuse or circuit breaker needs to be 125% higher than the full load amps of the kiln. This is according to the National Electrical Code.
You then need to bump this calculated amount up to the next standard size fuse or circuit breaker.
Examples:
- A kiln has a full load amp rating of 60 amps. 60 x 1.25 = 75 amps. The next closest standard size breaker is an 80 amp breaker.
- A kiln has a full load amp rating of 48 amps. 48 x 1.25 = 60 amps. A 60 amp breaker is a standard size.
- The fuse amps are typically mentioned in the kiln electrical data located on the wiring diagram.
Always use copper wire to bring power to the kiln, NEVER use aluminum wire. Near heat, aluminum oxidizes much more quickly than copper.
Wire sizes associated with the different size breakers.
| 20 amps | 12 gauge copper |
| 30 amps | 10 gauge copper |
| 40 amps | 8 gauge copper |
| 50 amps | 6 gauge copper |
| 60 amps | 6 gauge copper |
| 70 amps | 4 gauge copper |
| 80 amps | 3 gauge copper |
| 90 amps | 2 gauge copper |
| 100 amps | 1 gauge copper |
| 125 amps | 1/0 gauge copper (pronounced "one aught") |
| 150 amps | 2/0 gauge copper (pronounced "two aught") |
| 175 amps | 4/0 gauge copper (pronounced "three aught") |
| 200 amps | 250 MCM copper wire (MCM = Thousand Circular Mils) |
| 225 amps | 350 MCM copper wire |