27
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.
Gas
Range
Nominal
Natural 2.8 - 3.2" w.c. 3.0" w.c.
Manifold Gas Pressure
TABLE 8
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
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.
This tells us that in one hour, the furnace would consume 78
cu. ft. of gas. (3600 / 46 = 78)
The typical value range for 1 cu. ft. of natural gas is around
1025 BTU. Check with your gas utility, if possible. In this
example, the furnace is consuming 80,000 BTUH.
NOTE:
The final manifold pressure cannot vary
by more than ± 0.2” w.c. for Natural gas 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 (if applicable) 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 air
-
flow and temperature rise table is provided on page 34 and 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.
SUPPLY
AIR
RETURN
AIR
Temperature Rise Measurement
Figure 36
Circulator Blower Speeds
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. Table
9 on page 34 and the Specification 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.
