Lochinvar 497 - 2067 service manual Gas manifold pressure adjustment

3 Gas connections (continued)

10.If gas supply pressure is within normal range, remove the gas manometer and replace the pressure tap fittings in the gas control as indicated by the following steps.

11.Turn power switch to the “OFF” position.

12.Turn gas valve knob to the “OFF” position.

13.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.

14.Remove the manometer and related fittings from the “inlet side of the gas valve, replace 1/8'' hex plug in the gas valve and tighten.

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

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

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

18.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.

Check burner performance by cycling the system while you observe burner response. Burners should ignite promptly. Flame pattern should be stable, see Burner Flames in the Maintenance section of this manual. Turn system off and allow burners to cool, then cycle burners again to ensure proper ignition and flame characteristics.

Figure 3-3_Measuring gas supply pressure at combination gas valve

SUPPLY INLET

PRESSURE TAP

INLET

OUTLET

GAS

VALVE

CONTROL

KNOB

Installation & Service Manual

Gas manifold pressure adjustment

NOTICE	The gas valves are referenced to the fan
	pressurized chamber by a hose connected
	from the vent of the gas valve regulator
	to the chamber pressure tap located on
	the front inside portion of the jacket.
	Reference the drawings in this section for
	component and connection points for
	pressure measurement. The referenced
	chamber pressure must be subtracted from
	the manifold pressure to obtain actual net
	manifold pressure for normal operation.

A manometer or magnahelic gauge legible in 0.1'' increments up to 10 inches w.c. is required to check and adjust the manifold pressure. The regulator cover screw on the gas valve must be in place and tight for the unit to operate properly.

1.Remove the thumbscrew that fastens the control panel access door and remove the door.

2.Turn the power switch located in the lower left corner behind the control panel access door to the “O” or “OFF” position.

3.Remove the top front jacket access panels to access the gas valve(s).

4.Locate the reference hose on the first gas valve which goes from the vent fitting on the gas valve to the barbed fitting on the deck of the unit (see FIG. 3-4).

5.Remove the flexible cap from the barbed fitting on the “tee” located in this line and hook one side of the manometer, or (-) side of a magnahelic gauge, to this “tee”. Retain this cap for future use.

6.Remove the 1/8'' hex plug from the manifold pressure tap on the gas valve (see FIG. 3-4). Retain plug for future use.

7.Install a fitting in this tap that is suitable for connection of a hose to a manometer, or (+) side of a magnahelic gauge (see FIG. 3-4).

8.Turn the power switch to the “I” or “ON” position.

9.Push the reset button(s) for the ignition control(s), if necessary.

10.Set the temperature control to call for heat (see Setting Temperature Control, page 39).

11.Once the unit is firing, the manometer/magnahelic will reflect the net manifold gas pressure. Compare this reading to the respective value in Table 3E for Natural Gas or Propane Gas.

25