Amana GUCA045AX30 Service Instructions Manual page 65

Gas Manifold Pressure Measurement and Adjustment
CAUTION
To prevent unreliable operation or equipment damage,
the gas manifold pressure must be as specified on the
unit rating plate. Only minor adjustments should be
made by adjusting the gas valve pressure regulator.
Only small variations in gas pressure should be made by
adjusting the gas valve pressure regulator. The manifold
pressure must be measured with the burners operating.
To measure and adjust the manifold pressure, use the fol-
lowing procedure.
WARNING
Disconnect Electrical Power and Shut Off Gas Supply:
1. After turning off gas to furnace at the manual gas shutoff
valve external to the furnace, remove burner compart-
ment door to gain access to the gas valve.
2. Connect a calibrated water manometer (or appropriate
gas pressure gauge) at the gas valve outlet pressure
tap as shown in the following figure.
Gas Valve Control
WR
ON/Off Switch
M 1
P 3
O
F
INLET
F
C 2
ON
Inlet Pressure Tap
(Side of Valve) Outlet (Manifold) Pressure Tap
Pressure Regulator Adjustment
(Under Cap Screw)
Measuring Manifold Gas Pressure
(Gas Valve Tap)
3. Turn ON the gas and electrical power supply and oper-
ate the furnace.
4. Measure gas manifold pressure with burners firing. Ad-
just manifold pressure using the table below.
Manifold Gas Pressure
Natural Gas
Propane Gas
The final manifold pressure must not vary more
than ± 0.3 " w.c. from the above specified pressures. Any
necessary major changes in gas flow rate should be made
by changing the size of the burner orifice.
5. To adjust the gas valve pressure regulator, remove the
regulator cap.
SERVICING
Manometer Hose
OUTLET
Open to
Atmosphere
(Side of Valve)
Manometer
3.5" w.c.
10.0" w.c.
6. Turn the adjustment screw clockwise to increase the
pressure, or counterclockwise to decrease the pressure.
7. Securely replace the regulator cap.
WARNING
Disconnect Electrical Power and Shut Off Gas Supply:
8. Disconnect manometer after turning off gas at manual
shutoff valve. Reinstall gas valve outlet pressure tap
plug before turning on gas to furnace.
9. Turn on gas to furnace and check for leaks. If leaks are
found, repair and then reinstall burner compartment
door.
10. Turn on electrical power and verify proper unit opera-
tion.
S-13 CHECKING FOR DELAYED IGNITION
Delayed ignition is a delay in lighting a combustible mixture
of gas and air which has accumulated in the combustion
chamber.
When the mixture does ignite, it may explode and/or rollout
causing burning in the burner venturi.
If delayed ignition should occur, the following should be
checked:
1. Improper gas pressure - adjust to proper pressure. (See
SERVICING section S-12 )
2. Improper burner positioning - burners should be in lo-
cating slots, level front to rear and left to right.
3. Carry over (lighter tube or cross lighter) obstructed -
clean.
4. Main burner orifice(s) deformed, or out of alignment to
burner - replace.
S-14 CHECKING FOR FLASH-BACK
Flash-back will also cause burning in the burner venturi,
but is caused by the burning speed being greater than the
gas-air flow velocity coming from a burner port.
Flash-back may occur at the moment of ignition, after a
burner heats up or when the burner turns off. The latter is
known as extinction pop.
Since the end results of flash-back and delayed ignition
can be the same (burning in the burner venturi) a definite
attempt should be made to determine which has occurred.
If flash-back should occur, check for the following:
1. Improper gas pressure - adjust to proper pressure. (See
SERVICING section S-12 ).
2. Check burner for proper alignment and/or replace burner
(See SERVICING section S-10 ).
3. Improper orifice size - check orifice for obstruction. (See
SERVICING section S-11 ).
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