Service
WARNING
ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD.
Failure to follow safety warnings exactly could result in dangerous operation, serious injury, death or property damage.
Improper servicing could result in dangerous opera- tion, serious injury, death, or property damage. Before servicing, disconnect all electrical power to furnace.
When servicing controls, label all wires prior to dis- connecting. Take care to reconnect wires correctly. Verify proper operation after servicing.
At the beginning of each heating season, a qualified techni- cian should check the system as follows:
Blower
Check the blower wheel for debris and clean if necessary. The blower motors are prelubricated for extended bearing life. No further lubrication is needed.
WARNING
The blower access panel must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into living space resulting in personal inju- ry or death.
Filters
All SL280UHV filters are installed external to the unit. Fil- ters should be inspected monthly. Clean or replace the fil- ters when necessary to ensure that the furnace operates properly. Replacement filters must be rated for high veloc- ity airflow. Table 1 lists recommended filter sizes.
Flue And Chimney
1 − Check flue pipe, chimney and all connections for tight- ness and to make sure there is no blockage.
2 − Check unit for proper draft. Electrical
1 − Check all wiring for loose connections.
2 − Check for the correct voltage at the furnace (furnace operating). Correct voltage is 120VAC + 10%.
3 − Check amp−draw on the blower motor with inner blow- er panel in place.
Unit Nameplate__________Actual__________
Cleaning the Heat Exchanger and Burners
NOTE − Use papers or protective covering in front of the fur- nace during cleaning.
1 − Turn off both electrical and gas power supplies to fur- nace.
2 − Remove flue pipe and top cap (some applications top cap can remain) from the unit.
3 − Label the wires from gas valve, rollout switches, prima- ry limit switch and make−up box then disconnect them.
4 − Remove the screws that secure the combustion air in- ducer/pressure switch assembly to the collector box. Carefully remove the combustion air inducer to avoid damaging blower gasket. If gasket is damaged, it must be replaced to prevent leakage.
5 − Remove the collector box located behind the combus- tion air inducer. Be careful with the collector box gas- ket. If the gasket is damaged, it must be replaced to prevent leakage.
6 − Disconnect gas supply piping. Remove the screw se- curing the burner box cover and remove cover. Re- move the four screws securing the burner manifold as- sembly to the vestibule panel and remove the assembly from the unit.
7 − Remove screws securing burner box and remove burner box.
8 − NOX units only − Remove screw securing NOX insert. Remove NOX insert. See figure 40.
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