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4. Another 24-volt circuit is completed
INSPECTING
through the module to the main gas
valve. The valve opens. Gas passes
BURNER FLAME
through the valve to the main burner.
The gas is ignited by the glo-bar.
1. To observe burner flame, remove
5. After the main burner ignites, the
furnace front grille. Remove the two
flame detector senses the presence
screws at the lower edges of front
of flame. This opens the circuit to the
grille. Lift front grille away. Locate
glo-bar. The glo-bar shuts down.
viewing
window
on
front
of
combustion chamber. You can see
6. The circulating room air blower pulls
burner flame through this window.
return air in from the living area. This
air is heated as it flows past the
Correct Burner Flame: Blue flame with
combustion chamber. The heated air
well-defined burner ports.
is then blown out into the room.
Incorrect Burner Flame: Yellow or lazy
7. When the room temperature rises
flame without well-defined burner ports.
above the thermostat setting, the
If burner flame is incorrect, shut off
circuit to the valve opens and the
furnace and contact a qualified service
burner shuts off.
person.
8. The blower continues to run about two
to three minutes until the time delay
relay coil cools. When the coil cools,
the circuit to the motor opens. The
blower shuts off.
LIM IT SW ITCH
WARNING: Do not operate fur-
nace without a properly-working
limit switch.
The limit switch will turn off the gas to the
main burner if the furnace becomes too
Figure 19 - Burner Flame Patterns
hot. When this happens, the main burner
will go out and the blower will continue to
run for two to three minutes. This usually
NORMAL
happens when circulating air is partially or
completely blocked.
OPERATING
Occasional cycling of the limit switch is
SEQUENCE
not bad. This indicates safe operation.
Limit switch cycling will most likely occur
on warm days. If this happens too often or
1. When the room temperature drops
for a long period of time, the circulating air
below the thermostat setting, the
system should be thoroughly cleaned by
thermostat calls for heat. A 24-volt
a qualified service person.
circuit is completed through the time
delay relay coil. After three to five
If the circulating air system is cleaned and
seconds, the contacts in the relay
the limit switch continues to shut down the
close. The blowers come on.
furnace, the limit switch is defective. A
defective limit switch cannot be repaired.
2. One
motor
drives
both
the
It must be replaced. For safety reasons,
combustion air blower and the
never operate the furnace without a limit
circulating room air blower. The
switch.
combustion air blower draws air from
outside through the intake air vent.
CLEANING AND
This
air
discharges
into
the
c o m b u s t i o n
c h a m b e r .
Th e
MAINTENANCE
combustion air blower then forces the
combustion products out of the
exhaust tube(s). The combustion air
WARNING: Turn off and unplug
blower is sealed so that air does not
furnace and let cool before cleaning.
pass between it and the circulating
Turn equipment shutoff valve to OFF
room air blower.
position. Only a qualified service
person should service and repair
3. When the blower motor reaches 75%
furnace.
of normal r.p.m. (three to five
seconds), air from the blower turns on
the
microswitch.
W hen
the
WARNING: Keep furnace clear
microswitch activates, the electrical
and free from combustible mate-
circuit is completed through the limit
rials, gasoline, and other flammable
switch to the control module. The glo-
vapors and liquids.
bar begins to glow. In about 15
seconds, the glo-bar becomes hot
enough to ignite the burner.
CAUTION: You must keep control
areas, burner, and circulating air
passageways of furnace clean.
Inspect these areas of furnace before
each use. Have furnace inspected
yearly by a qualified service person.
Furnace may need more frequent
cleaning due to excessive lint from
carpeting, bedding material, pet hair,
etc.
CAUTION: Label all wiring prior to
disconnection
when
servicing
controls. Wiring errors can cause
improper and dangerous operation.
Verify
proper
operation
servicing.
CABINET
Air Passagew ays
•
Use a vacuum cleaner or pressurized
air to clean.
Exterior
•
Use a soft cloth dampened with a mild
soap and water mixture. Wipe cabinet
and front cover to remove dust.
•
Use a vacuum cleaner to remove dust
from front cover louvers.
EXHAUST AND INTAKE
VENTS
Make sure the exhaust and intake vents
are not blocked. The intake combustion
air and the exhaust gases must be
expelled to the outside. Have a qualified
service person clean dirt and loose debris
from vents annually. Do not cover the
exhaust or intake vents with screen wire,
tape, foil, etc. (See paragraph 6, page 2.)
GASKETS
Inspect all gaskets. If any gaskets show
signs of leakage or damage, replace
them. Safe operation of furnace depends
on all gaskets being tight.
FRONT GRILLE
Remove anything that may be blocking
the air to the louvers of the front.
COMBUSTION CHAMBER
AND MAIN BURNER
Check flame pattern of main burner often
(see Inspecting Burner Flame.) Have
combustion chamber and main burner
cleaned if you have run the furnace with a
high
yellow
flame.
Incomplete
combustion from lack of air causes the
yellow flame. This deposits soot inside
the combustion chamber and on the
burner. Contact a qualified service person
to clean combustion chamber and main
burner.
OUTSIDE VENT CAPS
Inspect outside vent caps for obstructions
or soot. If soot is found, do not use
furnace. Contact a qualified service
person to clean furnace.
13
TROUBLESHOOTING
NOTE: For additional help, contact:
Suburban Manufacturing Company
Customer Service Department
Post Office Box 399
Dayton, Tennessee 37321
(423) 775-2131, Ext.1
Fax: (423) 775-7015
OBSERVED PROBLEM
No heat
after
Note: All troubleshooting items are listed in order of operation.
WARNING: Turn off and unplug furnace and let cool before servicing.
Unless you need gas supply for testing, shut off equipment shutoff valve
before servicing. Only a qualified service person should service and repair
furnace.
POSSIBLE CAUSE
REM EDY
1. Thermostat off
1. Check to be sure thermostat is calling for heat.
Wire to thermostat could be off terminal.
2. Gas supply
2. Be sure equipment gas valve is in the open
position (level or parallel to gas line)
3. Electrical connections and power
3. Be sure all electrical connections are secure.
4. Motor
4. Motor must be operating at top speed before
burner will come on. If blower is not operating at
top speed, check voltage supply (minimum 100
volts A.C.). If voltage supply is okay, check for
defective motor.
5. Malfunctioning microswitch
5. Be sure the microswitch is sailing in far enough
to open the solenoid valve and to energize the
ignition control. If the switch is not sailing in,
clean any dust or dirt from the actuator pin. Other
reasons for the switch not sailing in are:
A. Insufficient blower speed - Slow motor due to
faulty motor or lint and dust accumulation on
the blower wheels or restriction of return air to
the furnace.
B. Faulty microswitch - Replace switch if circuit
to ignition control is not completed when
switch is manually engaged. Switch should
also be replaced if blower motor running at
top speed fails to engage switch within six or
seven seconds. NOTE: To service switch,
combustion chamber must be pulled out.
Follow steps 1, 2, 3, 9 and 10 on page 7 to
remove combustion chamber.
6. Gas valve
6. Within 20 seconds after motor reaches 75% of
its r.p.m. and microswitch engages, check the
following:
A. Voltage at valve - If current is present but
valve is not opening, check wire connections.
B. If wire connections okay - Replace valve
C. No voltage at valve - Check circuit completion
through microswitch and limit switch as well
as wiring and wire connections. If no defects
are found, see Ignition Failures.
14
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