40
3. Calculate the number of seconds per cubic foot (sec/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
Startup
Procedure and Adjustment - Gas Manifold Pressure Measurement
and Adjustment
section 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. Repeat steps 2 through 4 on high stage.
6. 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.
RISE =
SUPPLY
AIR
RETURN
AIR
HEAT EXCHANGER
RADIATION "LINE OF SIGHT"
T
RETURN
T
SUPPLY
T
SUPPLY
-
T
RETURN
Temperature Rise Measurement
C
IRCULATOR
B
LOWER
S
PEEDS
T
O
AVOID
PERSONAL
INJURY
OR
DEATH
DUE
TO
ELECTRICAL
SHOCK
,
TURN
OFF
POWER
TO
THE
FURNACE
BEFORE
CHANGING
SPEED
TAPS
.
WARNING
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, show-
ing the relationship between airflow (CFM) and external static pres-
sure (E.S.P.), for the proper selection of heating and cooling speeds.
The heating blower speed is shipped set at “B”, and the cooling
blower speed is set at “D”. These blower speeds should be ad-
justed by the installer 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