33
For PSC systems, the ½ hp motor is equipped with 4 speeds. The unit is set for mid-fire temp rise @
65ºF. See table for proper blower motor set up:
OH6FA072D48
ALTERATIONS REQ’D FOR A/C @ DESIGN EXTERNAL STATIC PRESSURE
COOLING UNIT
HTG Speed by Input
Low Mid High
Fire Fire Fire
Recommended CLG Speed
24,000 Low ML MH Low
30,000 Low ML MH Med Low
36,000 Low ML MH Med High
42,000 Low ML MH Med High
48,000 Low ML MH High
Figure 19A: Heating speed by input
Furnace Airflow (CFM) vs. External Static pressure (in. WC.)
Speed Tap\ Static
Pressure
0.1 0.2 0.3 0.4 0.5 0.6 0.7
Low 930 915 912 910 822 774 730
ML 1155 1152 1130 1126 1085 1042 920
MH 1442 1432 1418 1382 1334 1293 1230
High 1802 1762 1705 1635 1569 1493 1428
Furnace Motor Current Draw (Amps) vs. External Static pressure (in. WC.)
Low 3.3 3.1 3.0 2.9 2.6 2.5 2.4
ML 4.2 4.0 3.9 3.7 3.6 3.3 3.0
MH 5.4 5.2 5.0 4.7 4.4 4.2 4.0
High 6.6 6.4 6.0 5.7 5.5 5.2 5.0
High Fire Temperature Rise vs. External Static pressure (in. WC.)
Speed Tap\ Static
Pressure
0.1 0.2 0.3 0.4 0.5 0.6 0.7
Low 90 91 91 92 101 108 114
ML 72 72 74 74 77 80 91
MH 58 58 59 60 62 64 68
High 46 47 49 51 53 56 58
Mid Fire Temperature Rise vs. External Static pressure (in. WC.)
Speed Tap\ Static
Pressure
0.1 0.2 0.3 0.4 0.5 0.6 0.7
Low 72 73 73 73 81 86 91
ML 58 58 59 59 61 64 72
MH 46 47 47 48 50 52 54
High 37 38 39 41 42 45 47
Low Fire Temperature Rise vs. External Static pressure (in. WC.)
Speed Tap\ Static
Pressure
0.1 0.2 0.3 0.4 0.5 0.6 0.7
Low 60 61 61 61 68 72 76
ML 48 48 49 49 51 53 60
MH 39 39 39 40 42 43 45
High 31 32 33 34 35 37 39