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GAS METER SIZE –NATURAL GAS ONLY
Be sure that the gas meter has sufficient capacity to supply the full rated gas input of the water heater as
well as the requirements of all other gas fired equipment supplied by the meter. If the gas meter is too
small, ask the gas company to install a larger meter having adequate capacity.
GAS PRESSURE REGULATION
Minimum and maximum gas supply pressures are listed below: The minimum gas pressure specified
below is required for the full input rating specified on the water heater rating plate.
Natural Gas: Minimum: 6.0” w.c. L.P. Gas: Minimum: 10.0” w.c.
Maximum: 10.5” w.c. Maximum: 13.5” w.c.
BEFORE PLACING THE WATER HEATER IN OPERATION, CHECK FOR GAS LEAKAGE. USE SOAP
AND WATER SOLUTION OR OTHER MATERIAL ACCEPTABLE FOR THE PURPOSE OF LOCATING
GAS LEAKS.
WARNING
DO NOT use matches, candles, flame or other sources of ignition for this purpose.
Capacity Table for Natural Gas in Cubic Feet/Hour
(Table assumes 0.3 inch pressure drop, specific gravity of 0.60 for gas pressures of 0.5 psi or less)
Length of Pipe in Feet (Meters)
10 20 30 40 50 60 70 80 90 100 125 150 175 200
Pipe
Size in
Inches
(3) (6) (9) (12) (15) (18) (21) (24) (27) (30) (38) (45) (53) (61)
¾” 278 190 152 130 115 105 96 90 84 79 72 64 59 55
1” 520 350 285 245 215 195 180 170 160 150 130 120 110 100
1 ¼” 1050 730 590 500 440 400 370 350 320 305 275 250 225 210
1 ½” 1600 1100 890 760 670 610 560 530 490 460 410 380 350 320
Note: After determining the length of pipe required, select the pipe size that will supply the cubic feet per
hour of gas required for the input rating of the gas appliances on the line.
The formula for figuring the cubic feet per hour required is:
CFH =
Gas Input of Appliance on the Line (Btu/hr)
Heating Value of Gas (Btu/Cu. Ft.)
The heating value may be obtained from the local natural gas utility
Capacity Table for LP Gas in MBH of undiluted liquefied petroleum gases
(Table assumes 11 inches of water column pressure at the inlet, 0.5” press. drop)
Length of Pipe in Feet (Meters)
10 20 30 40 50 60 70 80 90 100 125 150
Pipe
Size in
Inches
(3) (6) (9) (12) (15) (18) (21) (24) (27) (30) (38) (45)
½” 275 189 152 129
¾” 567 393 315 267 237 217 196 185 173 162 146
1 “ 1071 732 590 504 448 409 378 346 322 307 275 252
1 1/4” 2205 1496 1212 1039 913 834 771 724 677 630 567 511
INITIAL OPERATION AND TESTING (INSTALLER ONLY)
1. Open the gas and water supply valves to the water heater.
2. Check for water and gas leaks. Use soap solution to check for gas leaks.
3. To check inlet supply pressure, remove the 1/8” NPT plug on the gas inlet supply fitting just below
the bottom casing and install a barb fitting for attaching a hose to a manometer. For checking the
gas manifold pressure, the plug is located just below the gas manifold connection inside the
control panel.
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