Appendix e: electrical data, Electric preheat and post heat calculation, Electric preheaters and post heaters – Mammoth 800 to 5500 CFM: Dedicated Outdoor Air System with Enthalpy Wheels (VHC) User Manual
Page 24: Important, Caution, Warning
MAMM-VHC-IOM-1A (JANUARY 2013)
24
Appendix E: Electrical Data
Electric Preheat and Post Heat Calculation
FLA = W / (1.73 x voltage)
Electric Preheaters and Post Heaters
Electric preheaters 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
Electric single point preheaters and post heaters have the
following limitations:
• 208 VAC – 24 kW maximum
• 230 VAC – 27 kW maximum
• 460 VAC – 67 kW maximium
• 575 VAC – 84 kW maximum
IMPORTANT
Electric preheaters 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, tem-
perature 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 control
panel and one to the electric heater fed from a field sup-
plied single disconnect.
!
Table E1: 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
0.5
4.5
4.0
1.8
2.2
1.1
0.9
0.75
5.4
6.0
2.7
2.7
1.4
1.1
1.0
6.8
7.0
3.4
3.4
1.7
1.4
1.5
10.2
10.2
5.0
5.0
2.5
2.0
2.0
14.0
14.0
6.4
6.0
3.0
2.4
3.0
17.8
17.0
10.6
10.6
4.8
3.4
5.0
22.0
22.0
15.3
12.8
6.4
5.1
7.5
32.0
32.0
25.0
19.2
9.6
7.8
10.0
29.3
26.8
13.4
10.3
Wheel Drive Motor and Controls
2.4
2.2
2.4
2.2
1.1
0.9
The blower motor FLA values show in in the above table are for one motor only.
Table E2: Electric Preheater 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