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EXAMPLE: If it took 23 seconds to complete one revolution of the 1/2 ft. dial (23 x 2 = 46).
This tells us that at this rate, it would take 46 seconds to consume one cu. ft. of gas. 3600 / 46 = 78.
This tells us that in one hour, the furnace would consume 78 cu. ft. of gas.
The typical value range for 1 cu. ft. of natural gas is around 1000 BTU. Check with your gas utility, if possible. In this
example, the furnace is consuming 78,000 BTUH.
NOTE: The final manifold pressure cannot vary by more than ± 0.3" w.c. for Natural and + 0.5" for LP from the specified
setting. Consult your local gas supplier if additional input rate adjustment is required.
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
R
EMPERATURE
ISE
Temperature rise must be within the range specified on the unit rating plate. An incorrect temperature rise may result in condensing
in or overheating of the heat exchanger. An airflow and temperature 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
B
S
IRCULATOR
LOWER
PEEDS
This furnace is equipped with a variable speed circulator blower.
This blower provides ease in adjusting blower speeds. The heating
blower speed is shipped set at "B", and the cooling blower speed is
set at "D". These blower speeds should be adjusted by the in-
staller to match the installation requirements so as to provide the
correct heating temperature rise and correct cooling CFM.
Use the dual 7-segment LED display adjacent to the dip switches to
obtain the approximate airflow quantity. The airflow quantity is
displayed as a number on the display, rounded to the nearest 100
CFM. The display alternates airflow delivery indication and the
operating mode indication.
Example: The airflow being delivered is 1225 CFM. The display
indicates 12. If the airflow being delivered is 1275, the display
indicates 13.
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 flows 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
Temperature Rise Measurement
T
O AVOID PERSONAL INJURY OR DEATH DUE TO ELECTRICAL SHOCK
OFF
TURN
POWER TO THE FURNACE BEFORE CHANGING SPEED TAPS
39
SUPPLY
AIR
RETURN
AIR
Figure 49
WARNING
,
.
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