York Rooftop Unit DJ300N32S4BBC2A

Close main manual shut-off valve and shut off all electric power to the unit

Remove the screws holding either end of the manifold to the burner supports

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

Remove the gas piping closure panel

Disconnect wiring to the gas valves and spark ignitors

Remove the manifold-burner gas valve assembly by lifting up and pulling back

Ensure burners are accessible for service

Reverse the procedure to replace the assemblies

Remove pilot adjustment cover screw

Adjust the clearance for air to the desired level

Replace cover screw after adjustment to prevent possible gas leakage

Observe through complete cycle to ensure all controls function properly

Ensure the pilot flame envelopes the end of the flame sensor

Ensure the furnace is turned off before starting the adjustment

Gather necessary tools for adjustment

Remove the cap on the regulator located next to the push-on electrical terminals

Select the adjustment needed for gas pressure

Measure the current manifold gas pressure

Is the manifold gas pressure within the correct range of 3.65 IWG ±0.3?

Measure the return air temperature (6 feet from the furnace)

Measure the heated air temperature (6 feet from the furnace)

Calculate Temperature Rise and CFM

Calculate the temperature rise (difference between heated air and return air)

Calculate the CFM using the formula: CFM = (Btuh Input x 0.8) / (108 x deg F Temp Rise)

Is the temperature rise within the acceptable range?

Adjust the blower CFM to correct the temperature rise

Turn off all other gas appliances connected to the gas meter

Measure the time needed for one revolution of the hand on the smallest dial on the meter with the furnace turned on

Enter the size of the test dial increment (1/2 or 1 cubic foot)

Enter the number of seconds for each revolution

Calculate the cubic feet of gas consumed per hour using Table 26

Is the actual input within 5% of the furnace rating?