Checking Gas Valve; Checking Orifices; Checking Main Burners; Induced Draft Blower Motor - Goodman GMEC96 Series Service And Troubleshooting

SERVICING

INDUCED DRAFT BLOWER MOTOR

HIGH VOLTAGE
D ALL
ISCONNECT POWER BEFORE SERVICING OR
M
ULTIPLE POWER SOURCES MAY
INSTALLING THIS UNIT.
F
BE PRESENT. AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove burner compartment door to gain access to
the induced draft blower motor.
2. Disconnect the motor wire leads from its connection
point at the induced draft motor.
3. Using a ohmmeter, test for continuity between each of
the motor leads.
4. Touch one probe of the ohmmeter to the motor frame
(ground) and the other probe in turn to each lead.
If the windings do not test continuous or a reading is
obtained to ground, replace the motor.
5. If the windings have a continuity reading, reconnect
wires. Turn power on to the furnace and turn the
thermostat on in the heating mode. Check voltage for
115V at the induced draft motor terminals during the tri-
al for ignition. If you have 115V and the motor does not
run, replace the induced draft motor.
6. After completing check and/or replacement of induced
draft motor, reinstall burner compartment door.
7. Turn on electrical power and verify proper unit opera-
tion.
CHECKING GAS VALVE (Redundant)
A combination redundant operator type gas valve which
provides all manual and automatic control functions required
for gas fired heating equipment is used.
The valve provides control of main burner gas flow, pressure
regulation, and 100 percent safety shut-off.
Two stage gas valves always require 24 volts between
common and low fire (main coil) to open. Also, the furnace
front cover pressure switch is wired in series with the low
(main) solenoid of the gas valve. In the event of a non
functioning gas valve, always check the front cover pressure
switch. Also see section S-307 on Checking Gas Pressure
and section S-310 on Checking Pressure Switches

CHECKING MAIN BURNERS

Burners
Burners have been redesigned for 34.5" chassis furnaces.
Overall length and width dimensions remain the same as 40"
model burners. The burners used 34.5" models have burner
52
WARNING
head insert with larger diameter center hole and a larger
number of surrounding holes.
The main burners are used to provide complete combustion
of various fuels in a limited space, and transfer this heat of
the burning process to the heat exchanger.
Proper ignition, combustion, and extinction are primarily due
to burner design, orifice sizing, gas pressure, primary and
secondary air, vent and proper seating of burners.
34.5" Burner
D ALL G
ISCONNECT AS AND
In checking main burners, look for signs of rust, oversized and
undersized carry over ports restricted with foreign material,
etc, burner cross-over slots should not be altered in size.

CHECKING ORIFICES

*MEC96/*CEC96 model furnaces have factory installed #45
natural gas orifices (except *mec/*CEC96030 which has #50).
The only time resizing is required is when a reduction in firing
rate is required for an increase in altitude or a furnace is being
converted for use with LP gas.
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
E P S
LECTRICAL OWER UPPLY.