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 19.
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
Combination Gas Valves
These units fire in up to 2 stages of burner input. Each stage of burner operation has a combination gas valve or series of gas valves 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 stage 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 19.
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 does not exceed the maximum safe leakage rate allowed by agency requirements. Combination gas valve/regulators equipped with integral vent limiters are
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
4.Remove the 1/8" hex plug, located on “inlet” side of the gas valve. You may also use a tapping on the
5.Turn on gas supply at the manual gas cock, turn on L.P. gas at 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 16 for minimum and maximum gas supply pressures.
TABLE - H
Multiple Unit Installations Gas Supply Pipe Sizing
Nominal Iron |
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Pipe Size, |
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(Inches) | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 125 | 150 | 175 | 200 |
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3/4" | 369 | 256 | 205 | 174 | 155 | 141 | 128 | 121 | 113 | 106 | 95 | 86 | 79 | 74 |
1" | 697 | 477 | 384 | 328 | 292 | 267 | 246 | 226 | 210 | 200 | 179 | 164 | 149 | 138 |
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1 1/4" | 1,400 | 974 | 789 | 677 | 595 | 543 | 502 | 472 | 441 | 410 | 369 | 333 | 308 | 287 |
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1 1/2" | 2,150 | 1,500 | 1,210 | 1,020 | 923 | 830 | 769 | 707 | 666 | 636 | 564 | 513 | 472 | 441 |
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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 |
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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 | |
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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 |
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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 |
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Maximum capacity of pipe in thousands of BTU’s per hour for gas pressures of 14 Inches Water Column (0.5 PSIG) or less and a total system pressure drop of 0.5 Inch Water Column (Based on NAT GAS, 1025 BTU’s per Cubic Foot of Gas and 0.60 Specific Gravity).
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