SERVICING
37
Orifices should be treated with care in order to prevent
damage. 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 primary air, which will make it difficult to adjust
the flame properly. This same problem can occur if an orifice
spud of a different length is substituted.
WARNING
D
I
S
CONNECT
ALL
G
A
S
AND
E
LECT
R
ICAL
P
OWE
R
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
P
R
EVENT
UN
R
ELIABLE
OPE
R
ATION
O
R
E
Q
UIPMENT
DAMAGE,
THE
INLET
GA
S S
UPPLY
P
R
E
SS
U
R
E
MU
S
T
BE
A
S S
PECIFIED
ON
THE
UNIT
R
ATING
PLATE
WITH
ALL
OTHE
R
HOU
S
EHOLD
GA
S
FI
R
ED
APPLIANCE
S
OPE
R
ATING.
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 measured
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
I
S
CONNECT
ELECT
R
ICAL
POWE
R
AND
S
HUT
OFF
GA
S S
UPPLY.
1. After turning off gas to furnace at the manual gas shutoff
valve external to the furnace, remove burner compartment
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 pressure
tap or the gas piping drip leg as shown in the following
figures. Refer to
Measuring Gas Pressure: Single Stage
Valves
figure for single stage valve inlet pressure tap
connections.
NOTE:
At either location, a hose fitting must be installed prior
to making the hose connection.
NOTE:
Use apapter kit #0151K00000S to measure gas
pressure on White-Rodgers 36J22 gas valves.
10.0
Measuring Inlet Gas Pressure
(Alternate Method)
3. Turn ON the gas and electrical power supply and operate
the furnace and all other gas consuming appliances on
the same gas supply line.
4. Measure furnace gas supply pressure with burners firing.
Supply pressure must be within the range specified 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
adjustments to pressure regulator, gas piping size, etc., and/
or consult with local gas utility.
