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SERVICING
To aid in iderntifying these controls, color-coded labels have
been affixed to the back of these controls. Refer to the Rollout
Limit Charts in furnace Technical Manual for temperature
settings and color codes.
L
INE VOLTAGE NOW PRESENT
1. Remove the burner compartment door to gain access to
the rollout switch(es) mounted to burner bracket.
The servicer should reset the ignition control by opening and
closing the thermostat circuit. Then look for the ignitor glowing
which indicates there is power to the ignition control. Mea-
sure the voltage between each side of the rollout control and
ground while the ignition control tries to power the gas valve.
2. Measure the voltage between each side of the rollout
control and ground during the ignition attempt. Refer to
the following figure.
VOLT / OHM
METER
Checking Flame Rollout Switch
a. If no voltage is measured on either side of control it
indicates ignition control or wiring to control problem.
b. If voltage is measured on one side of the control and
not the other it indicates the control is open.
c. If voltage is measured on both sides of the control the
wiring to gas valve or valve is at fault.
3. After check and/or replacement of rollout switch, reinstall
burner compartment door and verify proper unit operation.
S-303 INDUCED DRAFT BLOWER MOTOR
HIGH VOLTAGE
D
ALL
ISCONNECT
POWER BEFORE SERVICING OR
M
INSTALLING THIS UNIT.
ULTIPLE POWER SOURCES MAY
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.
WARNING
RED
RESET
BUTTON
COLOR
IDENTIFYING
TAB
WARNING
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 trial 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 in-
duced draft motor, reinstall burner compartment
door.
7. Turn on electrical power and verify proper unit oper-
ation.
S-304 CHECKING GAS VALVE (REDUNDANT)
A combination redundant operator type gas valve which
provides all manual and automatic control functions re-
quired for gas fired heating equipment is used.
The valve provides control of main burner gas flow, pres-
sure regulation, and 100 percent safety shut-off.
WARNING
D
ALL
ISCONNECT
POWER BEFORE SERVICING
Single stage gas valves should be tested on the furnace
with 24 VAC connected to the gas valve and manometers
reading supply line and manifold pressures.
S-305
CHECKING MAIN BURNERS
The main burners are used to provide complete combus-
tion 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.
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 head insert with larger diameter center hole and a
larger number of surrounding holes.
12X Ø.125
Beckett Burner
.025
±
.002
(CARRYOVER SLOT WIDTH)
16X
.125 x .030 MIN SLOT
Ø.562
49
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