Installation and Maintenance Manual

Installation—Electrical
UNT-SVX07D-EN 51
Minimum Circuit Ampacity (MCA) and
Maximum Fuse Size (MFS) Calculations for
Fan-Coils with Single Phase Electric Heat
Heater amps = (heater kW x 1000)/heater voltage
Note: Use 120 V heater voltage for 115 V units. Use 240 V
heater voltage for 230 V units.
MCA = 1.25 x (heater amps + all motor FLAs)
MFS or HACR type circuit breaker = (2.25 x largest motor
FLA) + second motor FLA + heater amps (if applicable)
HACR (heating, air-conditioning and refrigeration) type
circuit breakers are required in the branch circuit wiring for
all fan-coils with electric heat.
Select a standard fuse size or HACR type circuit breaker
equal to the MCA. Use the next larger standard size if the
MCA does not equal a standard size.
Standard fuse sizes are: 15, 20, 25, 30, 35, 40, 45, 50, 60
amps
Fan-coil electric heat MBh = (heater kW) (3.413)
Table 10. Electric heat kW, low vertical fan-coil
Unit Size Unit Voltage kW kW kW kW
3.0 115 1.0 1.5 2.0
4.0 115 1.0 1.5 2.0 2.5
6.0 115 1.0 1.5 2.0 2.5
Note: Low vertical units are only available with electric heat in combination
with the two-row cooling coil.
Table 11. Force-Flo single-stage, max kW electric heat
Unit
Size Voltage # Wires Heater kW
Heater
amps/ph
02 208/60/1 2 2.25 10.9
240/60/1 2 3.0 12.5
277/60/1 2 3.0 10.9
208/60/3 3 2.25 6.3
240/60/3 3 3.0 7.3
480/60/3 4 3.0 3.7
03 208/60/1 2 4.5 21.7
240/60/1 2 6.0 25.0
277/60/1 2 6.0 21.7
208/60/3 3 4.5 12.6
240/60/3 3 6.0 14.5
480/60/3 4 6.0 7.3
04 208/60/1 2 5.7 27.5
240/60/1 2 7.5 31.3
277/60/1 2 7.5 27.1
208/60/3 3 5.7 15.9
240/60/3 3 7.5 18.1
480/60/3 4 7.5 9.1
06 208/60/1 2 7.9 38.0
240/60/1 2 10.5 43.8
277/60/1 2 10.5 38.0
208/60/3 3 7.9 21.9
240/60/3 3 10.5 25.3
480/60/3 4 10.5 12.7
Note: All data based on individual units. Electric heat will operate only with
fan at high speed.
UNT-SVX07_-EN.book Page 51 Friday, April 27, 2012 9:40 AM