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If flame is established for more than 10 seconds after ignition,
the controller will clear the ignition attempt (re-try) counter. If
flame is lost after 10 seconds, it will restart the ignition se-
quence. This can occur a maximum of five times.
During burner operation, a momentary loss of power of 50
milliseconds or longer will drop out the main gas valve. When
power is restored, the gas valve will remain de-energized, and
a restart of the ignition sequence will begin immediately.
A momentary loss of gas supply, flame blowout, or a shorted
or open condition in the flame probe circuit will be sensed in
0.8 seconds. The gas valve will de-energize and the control will
restart the ignition sequence after waiting 60 seconds.
Recycles will begin and the burner will operate normally if the
gas supply returns, or the fault condition is connected prior to
the last ignition attempt. Otherwise, the control will lock out.
If the control is locked out, it may be reset by momentary power
interruption of 1/20 second or longer. Either the 24-volt thermo-
stat or line voltage may be interrupted.
MAINTENANCE
Air Filters
The filters should be checked periodically for dirt accumulation.
Dirty filters greatly restrict the flow of air and overburden the
system.
Clean the filters at least every three months. See the section
titled "Filters" for filter removal instructions. On new construc-
tion, check the filters every week for the first four weeks. Inspect
the filters every three weeks after that, especially if the system
is running constantly.
All filters supplied with the furnace are the high-velocity, clean-
able type. Clean these filters by washing in warm water. Make
sure to shake all the water out of the filter and have it reason-
ably dry before installing it in the furnace. When replacing
filters, be sure to use the same size and type as originally
supplied.
Lubrication
Blower motors in these furnaces are permanently lubricated
and do not require periodic oiling.
Burner Removal/Cleaning
The main burners should be checked periodically for dirt accu-
mulation.
If cleaning is required, follow this procedure:
1. Turn off the electrical power to the unit.
2. Remove the access door.
3. Remove the igniter.
4. Turn off the gas supply at the external manual shutoff valve
and loosen the ground union joint.
5. Remove the airshield.
6. Remove the four screws that hold the burner assembly to
the vest panel and remove the assembly.
7. Remove burners from the burner assembly.
8. Burners may be cleaned by rinsing in hot water.
9. Reassemble the burners in the reverse order, making sure
the burner shield is tightened securely in place.
Cleaning the Heat Exchanger
1. Turn off the main manual gas valve external to the furnace.
2. Turn off electrical power to the furnace.
Unitary Products Group
3. Remove the upper access door.
4. Disconnect wires from HSI sensor, rollout switch and HSI
igniter. Remove igniter carefully, as it is easily broken.
5. Remove the airshield. Remove the four screws that hold
the burner assembly to the vestibule panel and remove the
assembly. The lower portion of the heat exchanger will now
be exposed.
6. Remove inducer blower and motor at the top of the fur-
nace. Remove upper plate.
7. With upper exchanger opening exposed, remove restrictor
baffle from each cell. Upper portion of the heat exchanger
is now exposed.
8. With a stiff wire brush, brush inside cells at top and bottom.
Vacuum loose scales and dirt from each cell.
9. Clean - vacuum all burners.
10. Replace all components in reverse order. Reconnect all
wiring.
11. Restore electrical power and gas supply to the furnace.
12. Check furnace operation.
BLOWER CARE
Even with good filters properly in place, blower wheels and
motors will become dust laden after long months of operation.
The entire blower assembly should be inspected annually. If
the motor and wheel are heavily coated with dust, they can be
brushed and cleaned with a vacuum cleaner.
The procedure for removing the direct drive blower assembly
for cleaning is as follows:
1. Disconnect the electrical supply to the furnace.
2. Remove the access panels.
3. Disconnect the two wire harness plugs from the top of the
control box.
4. Remove the four screws holding the control box and
position it out of the way.
5. Remove the screws which retain blower to blower deck.
6. Remove the blower assembly with the control wiring still
attached.
7. Vacuum the motor and the blower using a soft brush
attachment. Care must be used not to disturb any balance
weights (clips) on the blower wheel vanes.
8. Before reinstalling the blower assembly, inspect the heat
exchanger which is visible in the blower opening of the
blower deck. If it requires cleaning, vacuum it with a soft
brush attachment.
9. Reinstall the blower assembly. Replace mounting screws
that hold the blower assembly to the front portion of the
blower deck. Two mounting screws used on the sides of
the blower are used for shipping purposes only, and are
not necessary after the furnace has been installed.
10. Reinstall the control box and reconnect the wiring harness
plugs.
11. Replace the access doors and restore the electrical
supply to the unit.
TROUBLESHOOTING
650.64-N4
11
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