Appendix F: Electrical Data
Electric Pre-heat and Post-heat Calculation
FLA = W / (1.73 x voltage)
Electric Pre-heaters and Post-heaters
Electric pre-heaters and post-heaters are available in:
• Single-point or two-point power connection
• Two-stage, four-stage* or SCR control
• 1 kW increments for all three-phase voltages.
Electric Heater Performance Calculations
Temperature rise (°F) = kW x 3,160
cfm
kW = cfm x Temperature rise (°F)
3,160
Single-point power supply electric pre-heaters and post-
heaters have the following limitations after which two-point
power connection is required:
• 208 VAC – 24 kW maximum
• 230 VAC – 27 kW maximum
• 460 VAC – 67 kW maximum
• 575 VAC – 84 kW maximum
IMPORTANT
Electric pre-heaters and post-heaters range from 1 to 120
kW (see below for heater limitations) and actual FLA values
of individual heaters will vary based upon the size, temper-
ature rise and voltage. Consult the factory for actual FLA
values. All electric heaters require three-phase voltage.
IMPORTANT
Four-stage electric post-heaters are only available with
kW ratings higher than 10 kW.
CAUTION
All electrical installations and wiring require correct wire gauge
sizing and protection according to local building codes.
WARNING
All units equipped with two-point electric post-heaters
require two-point power connections, one to the con-
trol panel and one to the electric heater circuit breaker
mounted inside the unit control panel.
Table F1: Full Load Amperage (FLA)
HP
Voltage
208/1/60
230/1/60
208/3/60
230/3/60
460/3/60
575/3/60
Blower Motor
0.50
4.50
4.00
1.80
2.20
1.10
0.90
0.75
5.40
6.00
2.70
2.70
1.40
1.10
1.00
6.80
7.00
3.40
3.40
1.70
1.40
1.50
10.20
10.20
5.00
5.00
2.50
2.00
2.00
14.00
14.00
6.40
6.00
3.00
2.40
3.00
17.80
17.00
10.60
10.60
4.80
3.40
5.00
22.00
22.00
15.30
12.80
6.40
5.10
7.50
32.00
32.00
25.00
19.20
9.60
7.80
10.00
29.30
26.80
13.40
10.30
Wheel Drive Motor and Controls
2.40
2.20
2.40
2.20
1.10
0.90
Indirect Gas Heat
3.60
3.30
3.60
3.30
1.60
1.30
The blower motor FLA values shown in the above table are for one motor only. The power feed to all indirect gas heaters is via step-down
transformer.
The above FLA values are for the transformer and are not the actual FLA values of the heater.
Table F2: Electric Pre-heater and Post-heater Limitations
VAC
VHC-36 up to 50
kW
VHC-42 up to 70
kW
VHC-50 up to
120 kW
208
24
24
24
50
70
120
230
27
27
27
50
70
120
460
50
70
67
50
70
120
575
50
70
84
50
70
120
Shaded areas – single-point post-heater limitations
White areas – two-point post-heater limitations
VCES-VHC-IOM-1F – VHC-36, -42 & -50
38
