Lochinvar 497 - 2067 service manual Combination gas valves, D, Venting of combination gas valves

Installation & Service Manual

3 Gas connections

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 25.

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 (FIG. 3-3). 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 22 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.

TABLE 3D

GAS PIPING SIZE CHART

Nominal					Length of Pipe in Straight Feet										Maximum
Iron Pipe															Capacity of Pipe
Size															in Thousands of
Inches	10	20	30	40	50	60	70	80	90	100	125	150	175	200	Btu/hr per hour
3/4	369	256	205	174	155	141	128	121	113	106	95	86	79	74	for gas pressures
															of 14 Inches
1	697	477	384	328	292	267	246	256	210	200	179	164	149	138	Water Column
															(0.5 PSIG) or less
1 1/4	1,400	974	789	677	595	543	502	472	441	410	369	333	308	287
															and a pressure
1 1/2	2,150	1,500	1,210	1,020	923	830	769	707	666	636	564	513	472	441	drop of 0.5 Inch
															Water Column
2	4,100	2,820	2,260	1,950	1,720	1,560	1,440	1,330	1,250	1,180	1,100	974	871	820
															(Based on NAT
2 1/2	6,460	4,460	3,610	3,100	2,720	2,460	2,310	2,100	2,000	1,900	1,700	1,540	1,400	1,300
															GAS, 1025 Btu/hr
3	11,200	7,900	6,400	5,400	4,870	4,410	4,000	3,800	3,540	3,300	3,000	2,720	2,500	2,340	per Cubic Foot
															of Gas and 0.60
4	23,500	16,100	13,100	11,100	10,000	9,000	8,300	7,690	7,380	6,870	6,150	5,640	5,130	4,720
															Specific Gravity)

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