Catalogue

36 UV-PRC004-EN
Performance Data
Minimum Circuit Ampacity (MCA) and Maximum Fuse Size (MFS) Calculations
for Unit Ventilators with Electric Heat (Single Phase) Heater Amps =
(Heater kW x 1000)/Heater Voltage
Note: Use 120 V heater voltage for 115 V units. Use 240 V heater voltage for 230V 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 Unit Ventilators with electric heat.
Refer to Figure 26, p. 35 for motor FLAs.
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 (increase to 150 amps)
Unit Ventilator electric heat MBh = (Heater kW) (3.413)
Note: Incoming power to the unit ventilator is 3-phase, 4-wire for a 480 Volt system (3-hot, 1-neutral). This does not include
an equipment ground.
Electrical
UV-PRC004-EN.book Page 36 Monday, February 4, 2013 11:01 AM