GCSS96 Installation Manual

34
indicates 1/2 cu. ft. per revolution. You will use this
number to calculate the quantity of gas in cubic ft. if
the furnace would consume if it ran steadily for one
hour (3600 seconds).
3. If the 1/2 cu. ft. dial was used, multiply your number
x 2.
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.
TEMPERATURE RISE
Temperature rise must be within the range specified on the unit
rating plate. An incorrect temperature rise may result in con-
densing 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.
GAS MANIFOLD PRESSURE MEASUREMENT AND ADJUSTMENT
Only small variations in gas pressure should be made by adjust-
ing the gas valve pressure regulator. The manifold pressure
must be measured with the burners operating. To measure and
adjust the manifold pressure, use the following procedure.
1. Turn OFF gas to furnace at the manual gas shutoff valve
external to the furnace.
2. Turn off all electrical power to the system.
3. Outlet pressure tap connections:
White-Rodgers 36J22 valve: Back outlet pressure test screw
(inlet/outlet pressure tap) out one turn (counterclockwise,
not more than one turn).
4. Attach a hose and manometer to the outlet pressure tap
(White-Rodgers valve).
5. Turn ON the gas supply.
6. Turn on power and close thermostat “R” and “W” contacts
to provide a call for heat.
7. Measure the gas manifold pressure with burners firing.
Adjust manifold pressure using the Manifold Gas Pressure
table shown on this page.
8. Remove regulator cover screw from the outlet pressure
regulator adjust tower and turn screw clockwise to increase
pressure or counterclockwise to decrease pressure. Replace
regulator cover screw.
9. Turn off all electrical power and gas supply to the system.
10. Remove the manometer hose from the hose barb fitting
or outlet pressure tap.
11. Replace outlet pressure tap: White-Rodgers 36J22 valve:
Turn outlet pressure test screw in to seal pressure port
(clockwise, 7 in-lb minimum).
12. Turn on electrical power and gas supply to the system.
13. Close thermostat contacts “R” and “W” to energize the
valve.
Using a leak detection solution or soap suds, check for leaks at
outlet or screw (White-Rodgers valve). Bubbles forming indicate
a leak. SHUT OFF GAS AND REPAIR ALL LEAKS IMMEDIATELY!
NOTE: For gas to gas conversion, consult your dealer for
appropriate conversion.
CAUTION
T O PREVENT UNRELIABLE OPERATION OR EQUIPMENT DAMAGE , THE
INLET GAS SUPPLY PRESSURE MUST BE AS SPECIFIED ON THE UNIT
RATING PLATE WITH ALL OTHER HOUSEHOLD GAS FIRED APPLIANCES
OPERATING .
GAS INPUT RATE MEASUREMENT (NATURAL GAS ONLY)
The actual gas input rate to the furnace must never be greater
than that specified on the unit rating plate. To measure natural
gas input using the gas meter, use the following procedure.
1. Turn OFF the gas supply to all other gas-burning appliances
except the furnace.
2. While the furnace is operating at high fire rate, time
and record one complete revolution of the gas meter dial,
measuring the smallest quantity, usually the dial that