Catalogue

CAB-PRC001-EN 43

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 Table 26, p. 44 through Table 29, p. 44 for motor FLAs and Table 23, p. 41 through

Table 25, p. 42 for electric heat amps.

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 240 V heat voltage for 230 V units.

Calculating MCA (units with electric heat):

MCA = 1.25 * (heat amps + sum of all motor FLAs)

Calculating MFS (units with electric heat):

MFS = (2.25 * largest motor FLA) + second motor FLA, size 10-12 units only + heat amps

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 Table 26, p. 44 through Tab le 2 9,

p. 44 for motor FLAs and Table 23, p. 41 through Table 25, p. 42 for electric heat amps.

Calculating MCA (units without electric heat):

MCA = (1.25) x largest motor FLA + second motor FLA, unit sizes 10 and 12 only

Calculating MFS (units without electric heat):

MFS or HACR

type circuit breaker = 15 amps for all units without electric heat.

HACR (heating, air-conditioning and refrigeration) type circuit breakers are required in the branch circuit wiring for all size 10 and 12

units.

CAB-PRC001-EN.book Page 43 Tuesday, May 8, 2012 10:11 AM