Lennox HVAC Unit KGB120S4-3

Turn off electrical power to unit at disconnect switch(es)

Label all wires prior to disconnection when servicing controls

Inspect condenser coil for dirt and debris

Clean condenser coil with detergent or commercial coil cleaner

Flush coils with water following cleaning

Replace all screws and gaskets removed prior to cleaning

Turn off electrical power to unit at disconnect switch(es)

Label all wires prior to disconnection when servicing controls

Disconnect pressure switch air tubing from combustion air inducer port

Remove screws securing combustion air inducer to flue box and retain them

Remove screws from bracket supporting vent connector and retain them

Connect test gauge to the inlet pressure tap on unit gas valve GV1

Test supply gas pressure with unit firing at maximum rate (both stages energized)

Enter the gas supply pressure reading

Is the gas supply pressure within the normal range for natural gas units (4.7”W.C. to 10.5”W.C.)?

Is the gas supply pressure within the normal range for L.P. gas units (10.8”W.C. to 13.5”W.C.)?

Check each unit separately while operating at maximum rate, starting with the one closest to the supply gas main

Test multiple units with and without the other units operating

Does the supply pressure fall within the specified range when testing multiple units?

Connect test gauge to the outlet pressure tap on the gas valve

Start the unit (call for second-stage heat) and allow five minutes for the unit to reach steady state

Observe the flame while waiting for the unit to stabilize

Is the flame stable without flashback and not lifting from the burner heads?

Does the natural gas burn basically blue with some clear streaks?

Does the L.P. gas burn mostly blue with some clear yellow streaks?

Compare the recorded manifold pressure to the values given in table 4

If manifold pressure is incorrect and no other source of improper manifold pressure can be found, the valve must be replaced

Turn off electrical power to unit at disconnect switch(es)

Label all wires prior to disconnection when servicing controls

Remove combustion air inducer assembly as described in section D

Remove flue box cover and clean with a wire brush

Replace combustion air inducer gasket