Electrical Data
Minimum Circuit Ampacity
(MCA) and Maximum Fuse
Size (MFS) Calculations
Units with Electric Heat
HACR (heating, air conditioning, and refrigeration) type circuit breakers are required in the branch circuit wiring for all units with electric heat. To compute MCA and MFS, see Tables
Calculating electric heat amps: Single stage, three phase = heat kW * 1000/1.732/volts
Two stage, three phase =
total heat kW * 1000/1.732/volts
Note: Use 240V heat voltage for 230V units.
Calculating MCA:
MCA = 1.25 * (heat amps + sum of all motor FLAs)
Calculating MFS:
MFS = (2.25 * largest motor FLA) + second motor FLA, size
Use the closest larger fuse or HACR circuit breaker above the MCA. Standard fuse sizes are: 15, 20, 25, 30, 35, 40, 45, 50, 60 amps.
Electric heat MBH = heater kW * 3.413
Units Without Electric Heat
To compute MCA and MFS, see Tables
Calculating MCA:
MCA = (1.25) x largest motor FLA + second motor FLA, unit sizes
Calculating MFS:
MFS or HACR1 type circuit breaker = 15 amps for all units without electric heat.
1HACR (heating,
Table
Unit Size | Decimal | Fraction | ||
02 |
| .03 |
| 1/30 |
|
| .07 |
| 1/15 |
03 |
| .04 |
| 1/25 |
|
| .05 |
| 1/20 |
|
| .08 |
| 1/12 |
04 |
| .05 |
| 1/20 |
|
| .06 |
| 1/16 |
|
| .10 |
| 1/10 |
|
| .13 |
| 1/8 |
06 |
| .07 |
| 1/15 |
|
| .12 |
| 1/8 |
|
| .16 |
| 1/6 |
|
| .24 |
| 1/4 |
08 |
| .12 |
| 1/8 |
|
| .13 |
| 1/8 |
|
| .24 |
| 1/4 |
10 | .05 | .07 | 1/20 | 1/15 |
| .06 | .12 | 1/16 | 1/8 |
| .10 | .16 | 1/10 | 1/6 |
| .13 | .24 | 1/8 | 1/4 |
12 | .05 | .12 | 1/20 | 1/8 |
| .06 | .13 | 1/16 | 1/8 |
| .10 | .24 | 1/10 | 1/4 |
| .13 | .24 | 1/8 | 1/4 |
Note:
Values for fractional HPs (kWs) are approximate values and not necessarily the actual HP (kW).
30 |
