Checking Hot Surface Ignitor; Checking For Flashback; Checking Pressure Switch - Goodman Amana AMH8 Service Instructions Manual

SERVICING
e. Remove the 1/8" NPT hose barb fitting from the
outlet pressure tap. Replace the outlet pressure
boss plug and seal with a high quality thread
sealer.
HIGH VOLTAGE
D ALL
ISCONNECT ELECTRICAL POWER AND SHUT OFF GAS SUPPLY
BEFORE SERVICING OR INSTALLING.
5. Turn on gas to furnace and check for leaks. If leaks
are found, repair and then reinstall burner compart-
ment door.
6. Turn on electrical power and verify proper unit op-
eration. Make sure furnace operates at the proper
manifold pressure at both high and low stage out-
puts.
Manifold Gas Pressure
Gas Rate
High Stage 3.2 to 3.8" w.c. 3.5" w.c.
Natural Gas
Low Stage 1.6 to 2.2" w.c. 1.9" w.c.
HIGH VOLTAGE
D ALL
ISCONNECT ELECTRICAL POWER AND SHUT OFF GAS
SUPPLY BEFORE SERVICING OR INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY BE PRESENT.
DO SO MAY CAUSE PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
HIGH VOLTAGE
D ALL
ISCONNECT ELECTRICAL POWER AND SHUT OFF GAS SUPPLY
BEFORE SERVICING OR INSTALLING.
Manifold Gas Pressure
Gas Rate
High Stage 9.7 to 10.3" w.c. 10.0" w.c.
Propane Gas
Low Stage
S-308 CHECKING HOT SURFACE IGNITOR
120V Silicon Nitride Igniter - Amana® and Goodman®
Brand H model furnaces use a 120V silicon nitride ig-
niter for ignition. The normal
approximately 2156°F - 2678°F.
the igniter ohm reading should be from 37-68 ohms.
60
WARNING
Range Nominal
WARNING
F
AILURE TO
WARNING
Range Nominal
5.7 to 6.3" w.c. 6.0" w.c.
operating temperature is
At room temperature
Place unit in heating cycle, measure current draw of
ignitor during preheat cycle. The steady state current
at 120V is 0.37 to 0.68 amps. After checking and/or
replacing of hot surface ignitor, reinstall burner com-
partment door and verify proper unit operation.
S-309 CHECKING FOR FLASHBACK
Flashback will also cause burning in the burner ven-
turi, but is caused by the burning speed being greater
than the gas-air flow velocity coming from a burner
port.
Flashback may occur at the moment of ignition, after a
burner heats up or when the burner turns off. The lat-
ter is known as extinction pop.
Since the end results of flashback and delayed ignition
can be the same (burning in the burner venturi) a defi-
nite attempt should be made to determine which has
occurred.
If flashback should occur, check for the following:
1. Improper gas pressure - adjust to proper pressure
(See S-307 CHECKING GAS PRESSURE)..
2. Check burner for proper alignment and/or replace
burner.
3. Improper orifice size - check orifice for obstruction.
S-310 CHECKING PRESSURE SWITCH
The pressure switch a safety device to prevent the com-
bustion cycle from occurring with inadequate venting
caused by a restricted or blocked vent pipe on the 80%
and 90% furnaces.
1. Remove burner compartment door to gain access to
pressure switch(es).
2. Remove wires from the pressure switch(es) electri-
cal terminals.
3. Using a VOM check from common terminal to NC
(Normally Closed) - should read open.
If switch reads as above proceed to Step 4, otherwise
replace control.
4. Remove the pressure control hose from the control
and interconnect with an inclined manometer as
shown in the following figures.