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.
CHECKING GAS PRESSURES
1 Ensure power to the water heater is turned off.
2 Turn off the supply gas shut off valve.
3 Open 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.
4 Attach sensing tube from 2 digital manometers (see tool requirements page 3) to each gas pressure test port on the gas valve as shown.
CHECKING GAS PRESSURES (CONT)
5 Open the supply gas shut off valve – restore power – start a heating cycle.
6 The rise in manifold pressure and corresponding drop in supply gas pressure confirms the water heater’s gas valve is opening and gas is flowing to the burner.
7 Record the supply and manifold gas pressures with the water heater firing.
8 Supply gas pressure should not drop below minimum given in Table 2 below.
9 Manifold gas pressure should be within the range shown in Table 2 below.
10 Look through the burner view port (page 11) burner flame should be blue.
11 Shut off power and gas supply – disconnect manometers – close test port needle valves.
12 Restore power and gas supply. Check for gas
Typical manifold and supply gas pressures during:
1 Standby Mode
2 Pre-Purge Mode
3 Heating Mode
Service Notes – Gas Pressure Adjustment
Manifold gas pressure is factory set and should not be adjusted in the field. If manifold gas pressure differs greatly from the pressures in Table 2 consider the calibration of the manometer being used – try a different manometer. Call the technical support phone number on the water heater label for further assistance if pressures are considerably different.