Lochinvar 999 - 750 Combination Gas Valves, Checking Gas Supply Pressure, INSTALLATION Continued

Hydronic Heating Boilers and Domestic Water Heaters

INSTALLATION Continued

Water heater models do not have downstream test valves, but the rest of the gas train is represented by Figure 29.

Combination Gas Valves

These units fire in multiple stages of burner input. Each stage of burner operation has a combination gas valve(s) to cycle the gas supply on and off and regulate gas to the burners. Each combination valve consists of a gas regulator and two valve seats to meet the requirements for redundant gas valves. The valve has a gas control knob that must remain in the open position at all times when the unit is in service. The gas control valve has pressure taps located on the inlet and discharge sides of the valve. Manifold pressure is adjusted using the regulator located on the valve. A manifold gas pressure tap for each burner stick is located on the discharge side of the valve.

The manifold pressure is preset at the factory and adjustment is not usually required. If you must adjust regulator pressure, follow the instructions under Gas Manifold Pressure Adjustment, page 31.

Venting of Combination Gas Valves

The combination gas valve/regulator used on all units is equipped with an integral vent limiting orifice per ANSI Z21.78. The vent limiter ensures that the volume of gas emitted from the valve in the event of a failed gas diaphragm does not exceed the maximum safe leakage rate allowed by agency requirements. Combination gas valve/regulators equipped with integral vent limiters are not required to have vent or relief lines piped to the outdoors. The termination of the vent limited opening on the combination gas valve/regulator complies with the safety code requirements of CSD-1, CF-190(a) as shipped from the appliance manufacturer without the installation of additional vent lines.

Checking Gas Supply Pressure

Use the following procedure to check gas supply pressure.

1.Turn the main power switch to the “OFF” position.

2.Turn gas valve knobs to the “OFF” position.

3.Shut off gas supply at the field-installed manual gas cock in the gas piping to the unit. If fuel supply is L.P. gas, shut off gas supply at the tank.

4.Remove the 1/8" hex plug, located on the “inlet” side of the gas valve. You may also use a tapping on the field-

installed main manual gas cock or gas piping. Install a fitting in the inlet pressure tapping suitable to connect to a manometer or magnehelic gauge. Range of scale should be 14" w.c. or greater to check inlet pressure.

5.Turn on gas supply at the manual gas cock, turn on L.P. gas at the tank if required.

6.Turn the power switch to the “ON” position.

7.Turn the gas valve knobs to the “ON” position. Set the electronic temperature control or thermostat to call for heat.

8.Observe the gas supply pressure as all burners are firing. Ensure that inlet pressure is within the specified range. See Connecting To Gas Supply, page 28 for minimum and maximum gas supply pressures.

9.If gas pressure is out of range, contact gas utility, gas supplier, qualified installer or service agency to determine necessary steps to provide proper gas pressure to the control.

10.If gas supply pressure is within normal range, turn the power switch to the “OFF” position.

11.Turn gas valve knobs to the “OFF” position.

12.Shut off gas supply at the manual gas cock in the gas piping to the unit. If fuel supply is L.P. gas, shut off gas supply at the tank.

13.Remove the manometer and related fitting from the “inlet” side of the gas valve, replace 1/8" hex plug in gas valve and tighten.

14.Turn on gas supply at the manual valve, turn on L.P. gas at the tank if required.

15.Turn the power switch to the “ON” position.

16.Turn the gas valve knob to the “ON” position.

17.Set the electronic temperature control or thermostat to call for heat.

WARNING: After completing any testing on the gas system, leak test all gas connections. Apply a soap/water solution to all gas connections while main burners are operating. Bubbles forming indicate a leak. Repair all leaks at once. Do not operate this unit with a leak in the gas train, valves or related piping.

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