Instruction manual

34
ft
3
) of gas being delivered to the furnace. If the dial is
a one cubic foot dial, divide the number of seconds
recorded in step 2 by one. If the dial is a two cubic foot
dial, divide the number of seconds recorded in step 2
by two.
4. Calculate the furnace input in BTUs per hour (BTU/hr).
Input equals the sum of the installation’s gas heating
value and a conversion factor (hours to seconds)
divided by the number of seconds per cubic foot. The
measured input must not be greater than the input
indicated on the unit rating plate.
EXAMPLE:
Installation’s gas heating (HTG) value: 1,000 BTU/ft
3
(Obtained from gas supplier)
Installation’s seconds per cubic foot: 34 sec/ ft
3
Conversion Factor (hours to seconds): 3600 sec/hr
Input = (Htg. value x 3600) ÷ seconds per cubic
foot
Input = (1,000 BTU/ft
3
x 3600 sec/hr) ÷ 34 sec/ ft
3
Input = 106,000 BTU/hr
Minor changes to the input rate may be accomplished
through manifold pressure adjustments at the gas
valve. Refer to Section XIV, Startup Procedure and
Adjustment - Gas Manifold Pressure Measurement
and Adjustment for details. NOTE: The final manifold
pressure cannot vary by more than ± 0.3” w.c. from the
specified setting. Consult your local gas supplier if
additional input rate adjustment is required.
5. 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.
TEMPERATURE RISE
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 speci-
fication sheet. 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.
RISE =
T
SUPPLY -
T
RETURN
T
SUPPLY
T
RETURN
SUPPLY
AIR
RETURN
AIR
HEAT EXCHANGER
RADIATION "LINE OF SIGHT"
Temperature Rise Measurement
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 tem-
perature rise. Decrease blower speed to increase
temperature rise. Refer to Section XIV, Startup Proce-
dure and Adjustment -Circulator Blower Speeds for
speed changing details.
CIRCULATOR BLOWER SPEEDS
WARNING
To prevent death, personal injury, property
damage, or premature failure of heat
exchanger, do not adjust the limit control
(factory set).
This furnace is equipped with a multi-speed circulator
blower. This blower provides ease in adjusting blower
speeds. The Specification Sheet provides an airflow table,
showing the relationship between airflow (CFM) and exter-
nal static pressure (E.S.P.), for the proper selection of
heating and cooling speeds. The cooling blower speed is
shipped set on HIGH, and the heating blower speed is set