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SERVICING
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.
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 in-
duced 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 induced
draft motor, reinstall burner compartment door.
7. Turn on electrical power and verify proper unit operation.
S-304 CHECKING GAS VALVE (Redundant)
A combination redundant operator type gas valve which pro-
vides 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.
D
ALL
ISCONNECT
POWER BEFORE SERVICING
Resistance of the redundant and 2nd stage coils on White-
Rodgers 36E, 36F and 36G series gas valves can't be mea-
sured at the valve terminals with an ohmmeter because of
diodes. The on/off switch may efffect the resistance mea-
surement.
1. Using an ohmmeter, test across the coils. A coil's resis-
tance increases with increasing temperature.
Nominal Coil Resistance:
Main = 95 ohms
Redundant = 98 ohms
2nd Stage = 180 ohms
2. Allow at least 20% tolerance for temperature and meter
variation. Most of the time coils will fail as open circuit.
If not as above, replace the entire valve.
118
WARNING
WARNING
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.
.023" - .027"
Beckett 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 ma-
terial, etc, refer to previous drawing.
S-306
CHECKING ORIFICES
A predetermined fixed gas orifice is used in all of these
furnaces. That is an orifice which has a fixed bore and
position as shown in the following drawing.
No resizing should be attempted until all factors are taken
into consideration such as inlet and manifold gas pres-
sure, alignment, and positioning, specific gravity and BTU
content of the gas being consumed.
The only time resizing is required is when a reduction in
firing rate is required for an increase in altitude.
Orifices should be treated with care in order to prevent dam-
age. 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.
D
ALL G
ISCONNECT
AS AND
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 physi-
cal size and angle with proper drill size opening should
be installed.
WARNING
E
P
S
LECTRICAL
OWER
UPPLY.
WARNING
E
P
S
LECTRICAL
OWER
UPPLY.
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