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SERVICING
S-302 CHECKING FLAME ROLLOUT CONTROL
A temperature activated manual reset control is mounted to
the manifold assembly as shown in the following illustration.
FLAME
ROLLOUT
SWITCHES
Flame Rollout Switch Location
(90% Upflow Furnace Shown)
The control is designed to open should a flame roll out oc-
cur. An over firing condition or flame impingement on the
heat shield may also cause the control to open. If the rollout
control opens, the air circulation blower will run continuously.
L
INE VOLTAGE NOW PRESENT
WARNING
1. Remove the burner compartment door to gain access to
the rollout switch(es) mounted to burner bracket.
2. Reset the manual roll out switch
3. Remove wires from roll out switch
4. Using an ohmmeter, check for continuity across the
switch.
5. If the switch will not close after manually resetting, it
must be replaced.
6. Measure the voltage between each side of the rollout
control and ground during the ignition attempt. If a roll
out switch has tripped, it is important to find out why.
Possible causes could be flame impingement, orifice plate
out of position, burners with excessive cross-over slot
dimension, over-firing, improper orifices, improper gas
pressure, air leaking from around the heat exchanger
into the burner compartment, air leaking through the heat
exchanger itself.
7. After check and/or replacement of rollout switch, rein-
stall burner compartment door and verify proper unit op-
eration.
S-303 INDUCED DRAFT BLOWER Motor
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY
BE PRESENT.
F
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 ther-
mostat 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 induced
draft motor, reinstall burner compartment door.
7.
Turn on electrical power and verify proper unit opera-
tion.
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.
Two stage gas valves always require 24 volts between com-
mon 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
S-305 CHECKING MAIN BURNERS
B
URNERS
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.
