SERVICING
51
Orifices should be treated with care in order to prevent dam-
age. They should be removed and installed with a box-end
wrench in order to prevent distortion. In no instance should
an orifice be peened over and redrilled. This will change the
angle or deflection of the vacuum effect or entraining of pri-
mary air, which will make it difficult to adjust the flame prop-
erly.
WARNING
D
ISCONNECT
ALL
G
AS AND
E
LECTRICAL
P
OWER
S
UPPLY.
1. Check orifice visually for distortion and/or burrs.
2. Check orifice size with orifice sizing drills.
3. If resizing is required, a new orifice of the same physical
size and angle with proper drill size opening should be
installed.
A
GAS
STREAM B
The length of Dimension "A" determines the angle of Gas
Stream "B".
DENT OR
BURR
GAS
STREAM B
A dent or burr will cause a severe deflection of the gas
stream.
S-307 CHECKING GAS PRESSURE
Gas Supply Pressure Measurement
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.
CAUTION
Gas inlet and manifold pressures should be checked and
adjusted in accordance to the type of fuel being consumed.
The line pressure supplied to the gas valve must be within
the range specified below. The supply pressure can be mea-
sured at the gas valve inlet pressure tap or at a hose fitting
installed in the gas piping drip leg. The supply pressure
must be measured with the burners operating. To measure
the gas supply pressure, use the following procedure.
WARNING
D
ISCONNECT ELECTRICAL POWER AND SHUT OFF GAS SUPPLY.
1. After turning off gas to furnace at the manual gas shut-
off valve external to the furnace, remove burner com-
partment door to gain access to the gas valve.
2. Connect a calibrated water manometer (or appropriate
gas pressure gauge) at either the gas valve inlet pres-
sure tap or the gas piping drip leg as shown in the fol-
lowing figures.
NOTE:
At either location, a hose fitting must be installed
prior to making the hose connection.
NOTE:
Use adapter kit #0151K00000S to measure gas
pressure on White-Rodgers 36G22 gas valves.
GAS LINE
GAS SHUTOFF VALVE
GA S LINE
TO FURNACE
DRIP LEG CA P
WITH FITTING
MANOMETER HOS E
MANOMETER
OPEN TO
ATMO SPHE RE
Measuring Inlet Gas Pressure
(Alternate Method)
3. Turn ON the gas and electrical power supply and oper-
ate the furnace and all other gas consuming appliances
on the same gas supply line.
4. Measure furnace gas supply pressure with burners fir-
ing. Supply pressure must be within the range speci-
fied in the following table.
Natural Gas
Minimum: 4.5" w.c.
Maximum: 10.0" w.c.
Propane Gas
Minimum: 11.0" w.c.
Maximum: 13.0" w.c.
INLET GAS SUPPLY PRESSURE
If supply pressure differs from above, make necessary ad-
justments to pressure regulator, gas piping size, etc., and/
or consult with local gas utility.
