Installer’s Information Manual
Page 27
Table 10. Factory Heating Speed and Temperature Rise.
*Gas Motor
**Input Size
(Btu/Hr) (H.P.)
Air
Temperature
Rise Range
(°F)
Heating
Operation
*Speed Tap/
Wire Color
40,000 / 1/4
50-80
LO/RED
40,000 / 1/3
30-60
LO/RED
60,000 / 1/4
45-75
ML/YEL
60,000 / 1/3
45-75
LO/RED
60,000 / 1/2
35-65
LO/RED
80,000 / 1/4
50-80
MH/BLUE
80,000 / 1/3
40-70
MH/BLUE
80,000 / 1/2
50-80
LO/RED
80,000 / 3/4
40-70
LO/RED
100,000 / 1/3
55-85
MH/BLUE
100,000 / 1/2
50-80
ML/YEL
100,000 / 3/4
40-70
ML/YEL
120,000 / 1/2
45-75
MH/BLUE
120,000 / 3/4
45-75
MH/BLUE
140,000 / 3/4
45-75
MH/BLUE
140,000 / 3/4
50-80
MH/BLUE
*These are initial Factory Settings.
**GAS INPUT and MOTOR HP can be found on furnace
rating plate.
Table 11. Cooling Speed Selection.
*Gas Motor
Input Size
Air Conditioning Tonnage
(Btu/Hr) (H.P.)
1.5
2
2.5
3
3.5
4
5
40,000
/ 1/4
MH
HI
--
--
--
--
--
40,000
/ 1/3
--
ML
MH
HI
--
--
--
60,000
/ 1/4
MH
HI
--
--
--
--
--
60,000
/ 1/3
--
ML
MH
HI
--
--
--
60,000
/ 1/2
--
--
--
ML
MH
HI
--
80,000
/ 1/4
HI
HI
--
--
--
--
--
80,000
/ 1/3
LO
ML
HI
HI
--
--
--
80,000
/ 1/2
--
--
--
ML
MH
HI
--
80,000
/ 3/4
--
--
--
--
ML
MH
HI
100,000
/ 1/3
LO
ML
HI
HI
--
--
--
100,000
/ 1/2
--
LO
MH
MH
HI
--
--
100,000
/ 3/4
--
--
--
LO
MH
MH
HI
120,000
/ 1/2
--
--
LO
ML
HI
HI
--
120,000
/ 3/4
--
--
--
LO
ML
HI
HI
140,000
/ 3/4
--
--
LO
ML
HI
HI
--
140,000
/ 3/4
--
--
--
LO
ML
HI
HI
*GAS INPUT and MOTOR HP can be found on furnace rating
plate.
This table only gives initial speed tap settings for installations
with ductwork static pressure of 0.5” W.C. figuring 400 CFM
per ton of air conditioning. Ductwork with higher than 0.5”
W.C. static pressure will cause reduced airflow and these
speed tap settings will not be correct. To determine correct
speed tap settings at ductwork static pressures above 0.5”
W.C., see Product Data Sheet.
SECTION 22. MEASURING DUCT
SYSTEM STATIC PRESSURE
System airflow can be determined from the Product Data
Sheet when duct system static pressure is known.
Improper airflow in heating mode may result in poor heating
performance and reduced heat exchanger life. Improper
airflow in cooling mode may cause poor cooling
performance or air-conditioning coil freeze-up.
High duct system static pressure is an indication of an
overly restrictive duct system. Static pressure in excess of
0.5 inches W.C. indicates a need for duct system redesign
to ensure proper volume of airflow.
You will need a 0 to 1 inch W.C. slope gauge with 0.01 inch
resolution and two pressure measurement taps.
Follow this procedure:
1. Open supply air registers and return air grilles. Make
sure the registers and grilles are free of obstruction
from rugs, carpets, drapes or furniture.
2. Set balancing dampers in supply duct system.
3. Check ductwork for obstructions or leaks.
4. Make sure filters are clean and in place.
5. Make sure that blower speed taps are set for proper
heating and cooling. Refer to Section 21, "Adjusting
Blower Speed." Heating speed should be set
according to Table 10. Cooling speed should be set to
meet cooling equipment requirements. See Table 11
for cooling airflow capacities at 0.5 inch W.C.
6. Place slope gauge near furnace, level and adjust scale
to read 0.00 inches W.C.
7. Insert one static pressure tap into supply air transition
duct between furnace and cooling coil or in the supply
air plenum for heating only systems. Connect this
pressure tap to positive pressure side of slope gauge.
See Figure 31.
8. Insert other static pressure tap in return air plenum.
Connect this pressure tap to negative pressure side of
slope gauge. See Figure 31.
Figure 31. Measuring Duct System Static Pressure.
9. Start
blower.
•
Blower heating speed can be run by jumping
terminals "R" and "G" on 24-volt terminal block
located on Control.
