York Single Package Air Conditioner ZF120N24D4D2GAA1A1

Connect a manometer to the outlet pressure port on the gas valve

Remove plastic cap covering HI and LO pressure adjustment screws

Set thermostat to call for second stage heat and start furnace

Adjust second stage (100% input) pressure using the HI adjustment screw

Is the second stage manifold pressure within 3.5 IWG ± 0.3?

Verify proper compressor rotation

Check blower rotation direction

Inspect electrical connection for proper phasing

Change phasing of the Field Line Connection if necessary

Check if scroll compressor is drawing low amperage

Check if suction and discharge pressures are similar

Ensure main manual shut-off valve is closed and all power to the unit is shut off

Open the union fitting just upstream of the unit gas valve and downstream from the main manual shut-off valve in the gas supply line

Remove the screws holding each end of the manifold to the manifold supports

Disconnect wiring to the gas valves and spark igniters

Remove the manifold & gas valve assembly

Inspect and/or replace orifices

Remove the heat shield on top of the manifold supports to access burners

Reverse the procedure to replace the assemblies, ensuring burners are level and seated at the rear of the gas orifice

Check that all filters are installed ahead of the evaporator coil

Inspect filters for dirt and debris

Replace filters with the same size and type if necessary

Ensure the unit is not operated without filters properly installed

Verify panel latches are properly positioned to maintain an airtight seal

Inspect unit for possible damage during transit

Note extent of damage on carrier’s freight bill if damage is evident

Request inspection by the carrier’s agent in writing

Ensure compliance with installation instructions and applicable codes

Disconnect furnace and shut-off valve from gas supply piping system for pressure testing above 1/2 PSIG

Replace gas valve if subjected to pressure greater than 1/2 PSIG

Isolate furnace from gas supply piping system by closing manual shut-off valve for pressure testing at or below 1/2 PSIG