Kiln Breaker and Wire Sizing
Kilns are continuous loads. That means the circuit must be sized with a safety buffer to prevent overheating during long firings. Use the simple formula below, then match the breaker to the correct copper wire gauge.
Quick rule: Breaker size equals full load amperage times 1.25, then round up to the next standard breaker size.
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The Standard Calculation Formula
To determine the correct breaker size for any kiln, use this formula.
Breaker Size equals Full Load Amperage times 1.25
After calculating, round up to the next standard breaker size. Example: if the result is 55.2 amps, use a 60 amp breaker.
Kiln Breaker and Wire Sizing Chart
Wire sizes below are based on the circuit breaker size, not the kiln specific amperage rating.
| Breaker Size | Copper Wire Gauge AWG |
|---|---|
| 20 amps | 12 AWG |
| 30 amps | 10 AWG |
| 40 amps | 8 AWG |
| 50 amps | 6 AWG |
| 60 amps | 6 AWG |
| 70 amps | 4 AWG |
| 80 amps | 3 AWG |
| 90 amps | 2 AWG |
| 100 amps | 1 AWG |
Note: 6 AWG wire is the industry standard for both 50 amp and 60 amp kiln circuits.
Important Installation Guidelines
- Distance and voltage drop: The chart assumes a run of 50 feet or less. For every additional 50 feet of circuit length, increase the wire size by one gauge to reduce voltage drop. Voltage drop can cause slow firing, stalling at high temperatures, and shorter element life.
- Copper wire only: Manufacturers strongly recommend copper wire for kiln circuits. Aluminum is not recommended because it can expand and contract during long firings, leading to loose connections and potential fire risk.
- Dedicated circuits: A kiln must never share a circuit with other appliances, lights, or tools. It needs its own breaker and a run directly from the main panel to the kiln receptacle or disconnect.
- Hardwiring requirements: In North America, the largest commonly available plug and receptacle is typically rated for 50 amps in the NEMA 6 50 configuration. Any kiln requiring a breaker larger than 60 amps should be hardwired into the electrical supply.
