36
4. Turn ON gas to and relight all other appliances turned off in
step 1. Be certain that all appliances are functioning properly
and that all pilot burners are operating.
T
EMPERATURE
R
ISE
Temperature rise must be within the range specified on the unit
rating plate. An incorrect temperature rise may result in condens-
ing in or overheating of the heat exchanger. An airflow and tem-
perature rise table is provided in the Specification Sheet applicable
to your model. Determine and adjust temperature rise as follows:
1. Operate furnace with burners firing for approximately ten
minutes. Ensure all registers are open and all duct dampers
are in their final (fully or partially open) position.
2. Place thermometers in the return and supply ducts as close
to the furnace as possible. Thermometers must not be
influenced by radiant heat by being able to “see” the heat
exchanger.
3. Subtract the return air temperature from the supply air
temperature to determine the air temperature rise. Allow
adequate time for thermometer readings to stabilize.
4. Adjust temperature rise by adjusting the circulator blower speed.
Increase blower speed to reduce temperature rise. Decrease blower speed to increase temperature rise. Refer to
Startup
Procedure and Adjustment -Circulator Blower Speeds
for speed changing details.
C
IRCULATOR
B
LOWER
S
PEEDS
This furnace is equipped with a multi-speed circulator blower. This blower provides ease in adjusting blower speeds. The Specifica-
tion Sheet applicable to your model provides an airflow table, showing the relationship between airflow (CFM) and external static
pressure (E.S.P.), for the proper selection of heating and cooling
speeds.
1. Determine the tonnage of the cooling system installed with
the furnace. If the cooling capacity is in BTU/hr divide it by
12,000 to convert capacity to tons.
Example:
Cooling Capacity of 30,000 BTU/hr.
30,000/12,000 = 2.5 Tons
2. Determine the proper air flow for the cooling system. Most
cooling systems are designed to work with air volume between 350 and 450 CFM per ton. Most manufacturers recommend an
air flow of about 400 CFM per ton.
Example:
2.5 tons X 400 CFM per ton = 1000 CFM
3.
Select the heating speed for your model from the heating speed chart in the Specification Sheet. The selected speed must
provide a temperature rise within the rise range listed with the particular model.
To adjust the circulator blower speed, proceed as follows:
1. Turn OFF power to the furnace.
2. Select the heating and cooling blower speeds that match the installation requirements from the
airflow table in the
Specification Sheet
.
3. Relocate desired motor leads to the circulator blower heat and cool speed terminals on the integrated control module.
(Terminals are identified as HEAT and COOL). If heating and cooling blower speeds are the same, a jumper wire must
be used between the heat and cool terminals.
4. Connect all unused blower motor leads to the “PARK” terminals on the integrated control module. Any leads not
connected to the “PARK” terminals must be taped.
5. Turn ON power to furnace.
6. Verify proper temperature rise as outlined in the
Temperature Rise
section of
Startup Procedure and Adjustment.
In general lower heating speeds will: reduce electrical consumption, lower operating sound levels of the blower, and increase the outlet
air temperature delivered to the home. The speeds available allow the blower performance to be optimized for the particular
homeowner’s needs.
SUPPLY
AIR
RETURN
AIR
Temperature Rise Measurement
Figure 42
T
O
AVOID
PERSONAL
INJURY
OR
DEATH
DUE
TO
ELECTRICAL
SHOCK
,
TURN
OFF
POWER
TO
THE
FURNACE
BEFORE
CHANGING
SPEED
TAPS
.
WARNING
