GAS Pressure Testing

ULTRA HIGH EFFICIENCY POWER VENT/POWER DIRECT VENT - SERVICE MANUAL

The water heater covered in this Service Manual is rated at 100,000 Btu/hr input. It is certified for elevations up to 10,100 feet (3079 meters) without adjustment. Call the technical support phone number shown on the water heater labeling before operating the water heater at higher elevations.

Service Notes - Checking Gas Pressures

Manifold and supply gas pressure can be measured at two test ports on the water heater’s gas valve. The manifold test port is closest to the blower housing and the supply test port is furthest. The valve in each test port is opened/closed with a small slotted screwdriver.

Manifold gas pressure will run at 0.00” W.C. or lower, in a negative pressure, depending on the operating state or mode the control system is currently in (see Venturi on page 14). Manifold gas pressure will be considerably lower, -6.50” to -7.50” W.C. during the pre/post purge modes when the blower is running and the gas valve is closed. When the gas valve opens (energized) gas entering the Venturi will cause a rise in manifold gas pressure. Manifold gas pressure will vary depending on vent/intake air pipe lengths. Manifold gas pressure will typically be 0.00” W.C. to +0.05” W.C. during the heating mode.

There may also be a drop in supply gas pressure noticed when the water heater’s gas valve opens. Seeing a rise in manifold pressure and a corresponding drop in supply gas pressure confirms the gas valve is opening and gas is flowing to the burner. The procedure for checking manifold and supply gas pressures is shown in the illustrations that follow.

Manifold Gas	Supply Gas
Test Port	Test Port

Turn test port needle valves counter-clockwise to open and clockwise to close. Always close test ports when finished and check for leaks

CHECKING GAS PRESSURES

1Ensure power to the water heater is turned off.

2Turn off the supply gas shut off valve.

3Open the manifold and supply gas pressure test ports on the gas valve. Turn the needle valve slotted heads 1/2 to 1 full turn counterclockwise with a small slotted screwdriver.

4Attach sensing tube from 2 digital manometers (see tool requirements page 3) to each gas pressure test port on the gas valve as shown.

CONTINUED ON NEXT PAGE

Sensing Tubes
From Manometers
Manifold Gas	Supply Gas
Test Port	Test Port

Technical Literature Department

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Servicing should only be performed by a Qualified Service Agent