Installer’s Information Manual
Page 29
Figure 32. Main Blower Speed Selection.
3. Connect two unused motor leads to terminals marked
"UNUSED MOTOR LEADS" on Fan Timer. See Figure
32.
WARNING
: Failure to properly terminate unused
motor leads could cause electrical shock.
Table 9. Factory Heating Speed and Temperature Rise.
GAS*
INPUT
(Btu/hr)
MOTOR
SIZE
(HP)
AIR
TEMPERATURE
RISE RANGE
(°F)
HEATING
OPERATION
**SPEED TAP /
WIRE COLOR
54,000
1/3
30-60
MH / BLUE
72,000
1/2
30-60
ML / YEL
72,000
3/4
25-55
ML / YEL
90,000
1/2
45-75
MH / BLUE
90,000
3/4
35-65
MH / BLUE
108,000
3/4
35-65
ML / YEL
126,000
3/4
40-70
MH / BLUE
* Gas Input and Motor HP can be found on rating plate.
** These are factory settings.
Table 10. Cooling Speed Selection.
GAS*
MOTOR
AIR CONDITIONING TONNAGE
INPUT
SIZE
AT 0.5 INCHES WC -- 400 CFM PER TON
(Btu/hr)
(HP)
1.5
2
2.5
3
3.5
4
5
54,000
1/3
LO
ML
MH
HI
--
--
72,000
1/2
LO
LO
ML
HI
--
--
72,000
3/4
LO
ML
MH
HI
--
90,000
1/2
LO
LO
ML
HI
--
--
90,000
3/4
LO
ML
MH
HI
--
108,000
3/4
--
--
LO
ML
HI
126,000
3/4
--
--
LO
ML
HI
* Gas Input and Motor HP can be found on rating plate.
This table gives speed tap settings for installations with duct
static pressure of 0.5” W.C. Duct work with a static pressure
less than 0.5” W.C. will have increased airflow. To determine
correct speed tap settings at ductwork static pressures other
than 0.5” W.C., see specification sheet.
SECTION 19. MEASURING DUCT
SYSTEM STATIC PRESSURE
You will need a 0 to 1 inch W.C. slope gauge with 0.01-inch
resolution and two pressure measurement taps to measure
duct system static pressure.
System airflow can be determined from Specification 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.
Follow this procedure:
1. Open supply air registers and retu rn air grilles. Make
sure registers and grilles are free of obstruction from
rugs, carpets, drapes or fu rniture.
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 18, "Adjusting
Blower Speed." Heating speed should be set
according to Table 9. Cooling speed should be set to
meet cooling equipment requirements . See Table 10
for cooling airflow capacities at 0.5 inch W.C.
6. Place slope gauge near fu rnace, level and adjust scale
to read 0.00 inches W.C.
7. Insert one static pressure tap into supply-air duct
between furnace and cooling coil or in supply air
plenum fo r heating only systems. Connect this
pressure tap to positive pressure side of slope gauge.
8. Insert other static pressure tap in retu rn air plenum.
Connect this pressure tap to negative pressure side of
slope gauge.
9. Start blower.
??
Blower heating speed can be run by jumping
terminals "R" and "G" on 24-volt terminal block
located on Fan Timer.
??
Blower cooling speed can be run by jumping
terminals "R" and "Y" on 24-volt terminal block
located on Fan Timer.
NOTE: On cooling speed, there is a short on-delay before
blower starts and a 60-second off-delay before blower
stops.
10. Read duct system static pressure from slope gauge.
NOTE: If air filter location is upstream of retu rn-air pressure
tap, static pressure must be adjusted to exclude filter
pressure drop. Do this by subtracting 0.08 inches W.C.
from the measured static pressure.
Duct System
= Measured - 0.08 inches W.C.
Static Pressure
Pressure
