Haier GE NF80LS Service Manual page 24

3. Clock gas meter to ensure that the unit is operating
at the specified firing rate. Check the supply pressure
and the manifold pressure. On two-stage gas furnaces
check the manifold pressure on high fire and low fire.
If manifold pressure adjustment is necessary, consult
the Service Literature for unit specific information on
adjusting gas pressure. Not all gas valves are adjustable.
Verify correct temperature rise.
Cleaning the Heat Exchanger and Burners
NOTE: Use papers or protective covering in front of the
furnace during cleaning.
1. Turn off both electrical and gas power supplies to
furnace.
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, primary
limit switch and make-up box then disconnect them.
4. Remove the screws that secure the combustion air
inducer/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 combustion
air inducer. Be careful with the collector box gasket. If
the gasket is damaged, it must be replaced to prevent
leakage.
6. Disconnect gas supply piping. Remove the four screws
securing the burner manifold assembly to the vestibule
panel and remove the assembly from the unit.
7. NOX units only - Remove screw securing NOX insert.
Remove NOX insert. See Figure 20.
8. Remove screws from both sides, top and bottom of
vestibule panel.
9. Remove heat exchanger. It may be necessary to spread
cabinet side to allow more room. If so, remove five
screws from the left side or right side of cabinet. See
Figure 21.
10. Backwash using steam. Begin from the burner opening
on each clam. Steam must not exceed 275°F.
11. To clean burners, run a vacuum cleaner with a soft brush
attachment over the face of burners. Visually inspect
inside the burners and crossovers for any blockage
caused by foreign matter. Remove any blockage. Figure
22 shows burner detail.
12. To clean the combustion air inducer visually inspect
and using a wire brush clean where necessary. Use
compressed air to clean off debris and any rust.
13. Reinstall heat exchanger in vestibule. (Replace the five
screws in the cabinet from step 10 if removed).
14. NOx units only - Replace NOx inserts.
15. Reinstall collector box and combustion air assembly.
Reinstall all screws to the collector box and combustion
air inducer. Failure to replace all screws may cause
leaks. Inspect gaskets for any damage and replace if
necessary.
16. Reinstall burner box and manifold assembly.
17. Reconnect all wires.
18. Reconnect top cap and vent pipe to combustion air
inducer outlet.
19. Reconnect gas supply piping.
20. Turn on power and gas supply to unit.
21. Set thermostat and check for proper operation.
22. Check all piping connections, factory and field, for gas
leaks. Use a leak detecting solution or other preferred
means.
Some soaps used for leak detection are corrosive to
certain metals. Carefully rinse piping thoroughly after
leak test has been completed. Do not use matches,
candles, flame or other sources of ignition to check for
gas leaks.
23. Repair any leaks and repeat step 22 until no leaks are
detected.
24. Replace access panel.
NOx Insert
Figure 20. NOx Inserts
Page 24
CAUTION
31-5000737 Rev. 0