Goodman Mfg VC8 instruction manual Measuring Inlet Gas Pressure Alt. Method

START-UP PROCEDURE AND ADJUSTMENT

Gas Line

Gas

Shutoff

Valve

Gas Line

To Furnace

Open To

Atmosphere

Drip Leg Cap

With Fitting

Manometer Hose

Manometer

Measuring Inlet Gas Pressure (Alt. Method)

GAS MANIFOLD PRESSURE MEASUREMENT AND ADJUSTMENT

CAUTION

TO PREVENT UNRELIABLE OPERATION OR EQUIPMENT DAMAGE, THE GAS MANIFOLD PRESSURE MUST BE AS SPECIFIED ON THE UNIT RATING PLATE. ONLY MINOR ADJUSTMENTS SHOULD BE MADE BY ADJUSTING THE GAS VALVE PRESSURE REGULATOR.

Only small variations in gas pressure should be made by ad- justing the gas valve pressure regulator. The manifold pressure must be measured with the burners operating. To measure and adjust the manifold pressure, use the following procedure.

1.Turn OFF gas to furnace at the manual gas shutoff valve external to the furnace.

2.Turn off all electrical power to the system.

3.Outlet pressure tap connections:

a.Honeywell VR9205 valve: Remove the outlet pressure boss plug. Install an 1/8" NPT hose barb fitting into the outlet pressure tap.

b.White-Rodgers 36G54 valve: Back outlet pressure test screw (inlet/outlet pressure boss) out one turn (counterclockwise, not more than one turn).

4.Attach a hose and manometer to the outlet pressure barb fitting (Honeywell valve) or outlet pressure boss (White-Rodgers valve).

5.Turn ON the gas supply.

6.Turn on power and close thermostat “R” and “W1” contacts to provide a call for low stage heat.

7.Measure the gas manifold pressure with burners firing. Adjust manifold pressure using the Manifold Gas Pressure table shown below.

8.Remove regulator cover screw from the low (LO) outlet pressure regulator adjust tower and turn screw clockwise to increase pressure or counterclockwise to decrease pressure. Replace regulator cover screw.

9.Close thermostat “R” and “W2” contacts to provide a call for high stage heat.

10.Remove regulator cover screw from the high (HI) outlet pressure regulator adjust tower and turn screw clockwise to increase pressure or counterclockwise to decrease pressure. Replace regulator cover screw.

11.Turn off all electrical power and gas supply to the system.

12.Remove the manometer hose from the hose barb fitting or outlet pressure boss.

13.Replace outlet pressure tap:

a.Honeywell VR9205 valve: Remove the 1/8" NPT hose barb fitting from the outlet pressure tap. Replace the outlet pressure boss plug and seal with a high quality thread sealer.

b.White-Rodgers 36G54 valve: Turn outlet pressure test screw in to seal pressure port (clockwise, 7 in-lb minimum).

14.Turn on electrical power and gas supply to the system.

15.Close thermostat contacts “R” and “W1/W2” to energize the valve.

Using a leak detection solution or soap suds, check for leaks at outlet pressure boss plug (Honeywell valve) or screw (White- Rodgers valve). Bubbles forming indicate a leak. SHUT OFF GAS AND REPAIR ALL LEAKS IMMEDIATELY!

NOTE: For gas to gas conversion, consult your dealer for appropriate conversion.

	Manifold Gas Pressure
	Gas	Range		Nom inal
Natural	Low Stage	1.6 - 2.2"	w .c.	1.9" w .c.
	High Stage	3.2 - 3.8"	w .c.	3.5" w .c.
Propane	Low Stage	5.7 - 6.3"	w .c.	6.0" w .c.
	High Stage	9.7 - 10.3" w .c.		10.0" w .c.

GAS INPUT RATE MEASUREMENT (NATURAL GAS ONLY)

The gas input rate to the furnace must never be greater than that specified on the unit rating plate. To measure natural gas input using the gas meter, use the following procedure.

1.Turn OFF the gas supply to all other gas-burning appliances except the furnace.

2.While the furnace is operating, time and record one complete revolution of the smallest gas meter dial.

3.Calculate the number of seconds per cubic foot (sec/ft3) of gas being delivered to the furnace. If the dial is a one cubic foot dial, divide the number of seconds recorded in step 2 by one. If the dial is a two cubic foot dial, divide the number of seconds recorded in step 2 by two.

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