Balanced vs. Unbalanced 3-Phase Kilns
A balanced 3-phase kiln divides its total element amperage equally among all three legs. In contrast, an unbalanced design may put the full load on only two legs, leaving the third inactive—these skews the numbers you see on spec sheets.
Load Distribution Across Phases
- Balanced example: 48 A total ÷ 3 legs = 16 A per leg.
- Unbalanced example: 40 A total ÷ 2 legs = 20 A per active leg; third leg carries zero.
Calculating True Kiln Amperage
To convert single-leg amps to the three-phase value that electricians use, multiply by √3 (1.732). A 16 A per-leg load becomes 27.7 A, while a 20 A per-leg load becomes 34.6 A. Always design circuits for this higher number. Hot Kilns
Using the √3 (1.732) Multiplier
Per-Leg Amps × 1.732 = Required Breaker Amps
Why Spec-Sheet Amps Look “Odd”
Manufacturers list the highest leg current because that dictates conductor and breaker size. When only two legs carry the load, the “nameplate” amperage will seem higher than a fully balanced kiln of similar wattage. Hot Kilns
Device Amperage Equals Highest Leg
Even if one leg shows zero, you must size for the leg with the highest current—it determines the heat rise in conductors and breaker trip points.
Choosing the Right Breaker
Select a three-pole breaker rated for at least 125 % of the calculated phase amperage and use conductors sized per NEC tables or local code. Balanced kilns can often use smaller wire than unbalanced models of the same wattage.
Wiring and Breaker Sizing Rules
- Confirm supply voltage (208 V or 240 V).
- Compute per-leg amps and multiply by 1.732.
- Choose copper conductors one gauge larger if runs exceed 50 ft.
- Install a breaker and disconnect rated for the calculated amperage plus 25 %.
By understanding phase balance and the √3 factor, you can interpret “odd” amp listings correctly and ensure every 3-phase kiln is wired for safe, efficient operation.
