FURNACE CLEANING SECTION
NOTE: The cleaning operations listed below must be performed only by a qualified service agency.
Burner Removal/Cleaning
The main burners should be checked periodically for dirt accumulation. If cleaning is required, follow this procedure:
1.Turn off the electrical power to the unit.
2.Turn off the gas supply at the external manual shut-off valve and loosen the ground union joint.
3.Remove the upper access panel and remove the burner box cover.
4.Disconnect wires from flame sensor, rollout switch and HSI igniter. Remove igniter carefully, as it is easily broken.
5.Remove the screws that hold the burner box assembly to the vest panel and remove the assembly.
6.Remove burners from the burner assembly.
7.Burners may be cleaned by rinsing in hot water.
8.Reassemble the burners in the reverse order.
Cleaning the Heat Exchanger
Lower Heat Exchanger Access
1.Turn off the electrical power to the unit and turn off gas supply at the shutoff valve.
2.Remove the blower and burner compartment access doors. Dis- connect the gas supply piping at the union to permit removal of the entire burner and gas control assembly from the vestibule panel. Use the wrench boss on the gas valve when removing or installing this piping. See Figure 4.
3.Unplug the igniter from the wire harness. Disconnect sensor and rollout switch wires located on top of the air shield. Identify and note the location of all leads for ease of reinstallation. Also discon- nect the wires at the side rollout switches (upflow only) and the gas valve wires.
4.Remove the screws holding the burner assembly to the vestibule panel and remove this assembly. Handle the assembly carefully since it contains the igniter, which is fragile and easily broken. The lower portion of the heat exchanger will now be exposed. To clean the burner assembly, use a vacuum cleaner, or remove the burn- ers as outlined in burner cleaning, and clean in hot water.
Upper Heat Exchanger Access
1.Perform steps 1-4 above.
2.Disconnect vent piping from the vent motor assembly at the top panel on the furnace (upflow only). On downflow models, the vent pipe is secured to the vent motor outlet with a screw. Remove this screw before proceeding.
3.Unplug the vent motor wires and ground wire. Remove the pres- sure switch tubing at the top on the vent motor housing.
NOTE: It is recommended that replacement gaskets be available before removing vent motor.
1.Remove six mounting screws that hold the vent motor to the restrictor plate. The surface is gasketed and the gasket can be reused if it is carefully removed. It is necessary to remove this assembly to gain access to the restrictor plate mounting holes. The assembly may be vacuumed if cleaning is necessary. If any vent assembly parts are damaged, replace with an entire new assembly (except for gaskets).
2.Remove the perimeter screws attaching the restrictor plate assem- bly to the vestibule panel. The surface is also gasketed. The assembly, including the flue baffle plate (rear) may be vacuumed or cleaned with hot water if necessary.
3.The upper portion of the heat exchanger is now accessible. With a long flexible wire brush, clean inside each tube at both the top and bottom. The brush must pass around the rear heat exchanger tubes. Vacuum loose scale and dirt from each tube.
4.Clean - Replace all components in reverse order. Re-gasket all surfaces which required a gasket. Reconnect all wiring. Reattach vent pipe and gas supply lines before restoring service to furnace. Restore electrical power, check gas supply piping for leaks, and then verify furnace operation.
Label all wires prior to disconnection when servicing controls. Wiring errors can cause improper and danger- ous operation. Verify proper operation after servicing.
SEQUENCE OF OPERATION
The following describes the sequence of operation of the furnace. Refer to Figure 1 for component location.
Continuous Blower
Cooling/heating thermostats have a fan switch that has an ON and AUTO position. In the ON position the thermostat circuit is completed between terminals R and G. The motor will operate on the speed tap wire that is connected to the cooling terminal on the control board.
Intermittent Blower
Cooling/heating thermostats have a fan switch that has an ON and AUTO position. In the AUTO position the thermostat circuit is completed between terminals R and G when there is a call for cooling and termi- nals R and W when there is a call for heating. The integrated control will energize the delay ON timer relay, which is a non-adjustable fan on delay timer. The delay on timer relay will energize the indoor fan motor relay after the delay ON time has expired. The indoor fan motor will be turned off after the delay OFF time on the integrated control has expired. The delay OFF time is adjustable by changing the jumper pin setting on the integrated control. Refer to Figure 10 for the location of the fan off adjustment jumper. The fan off setting is fixed at 60 seconds for SEER enhancement.
Heating Cycle
When the thermostat switch is set on HEAT and the fan is set on AUTO, and there is a call for heat, a circuit is completed between terminals R and W of the thermostat. When the proper amount of combustion air is being provided, the pressure switch will close, the ignition control pro- vides a 17-second warm-up period, the gas valve then opens, the gas starts to flow, ignition occurs and the flame sensor begins its sensing function. The blower motor will energize 30 seconds after the gas valve opens, if a flame is detected. Normal furnace operation will continue until the thermostat circuit between R and W is opened, which causes the ignition system and gas valve to de-energize and the burner flames to be extinguished. The vent motor will operate for 15 seconds and the blower motor will operate for the amount of time set by the fan-off delay jumper located on the control board. See Figure 10. The heating cycle is complete, and ready for the start of the next heating cycle.
