Williams 2503531 Owner's Operation And Installation Manual page 9

INSTALLATION
(Continued)
Providing Gas Piping to Furnace
You must provide gas piping from gas source to furnace. The gas piping must be in a vertical
position where it connects to the furnace. This prevents interference with front cover
installation.
Consult your local gas company for proper routing of the gas lines.
Pipe size is determined by the length of pipe from the gas source to the furnace and the total
BTU load on the gas source.
Add the total BTUs required for all appliances connected to the gas source including this furnace.
Divide this number by 2500. This will give you the approximate cubic feet per hour needed.
Example:
40,000 BTU/Hr
+ 15,000 BTU/Hr for other gas appliances
55,000 BTU/Hr total
55,000 2500 = 22
Locate 22 or higher on chart below.
According to the chart below, you should use 40 feet or less of 3/8" pipe, 125 feet
or less of 1/2" pipe, etc...
MINIMUM
IRON PIPE
SIZE
10 20 30
3/8" 47 32 26
1/2" 87 61 48
3/4" 184 126 100
1" 344 232 189 162
1 1 / " 696 484 391 331
4
1 1 / " 1060 729 590 504
2
2" 2022 1392 1094 961
1
2 / " 3182 2188 1790 1524 1326 1226 1127 1060 994 928 829 749 969 649
2
3" 5635 3911 3116 2718 2387 2154 1989 1856 1724 1657 1458 1326 1226 1127
4" 11602 7956 6431 5503 4906 4508 4110 3845 3580 3381 2983 2718 2519 2320
IMPORTANT: Check gas line pressure at gas meter before connecting furnace to gas line. Gas
line pressure must be no less than 11 inches of water and no greater than 13 inches of water.
Gas pressures and input to the burners must not exceed the rated input and pressure shown on
the rating plate. For propane/LP gas, manifold pressure should be 10 inches of water. For
elevations above 2000 feet, reduce rating 4% for each 1000 feet above sea level (U.S.A. only).
CAUTION: Never connect heater directly to the propane/LP supply.
This heater requires an external regulator (not supplied). Install the
external regulator between the heater and propane/LP supply.
The installer must supply an external regulator. The external regulator will reduce incoming
gas pressure. You must reduce incoming gas pressure to between 11 and 14 inches of water.
If you do not reduce incoming gas pressure, heater regulator damage could occur. Install
external regulator with the vent pointing down. Pointing the vent down protects it from
freezing rain or sleet.
201843
LENGTH OF PIPE (FEET)
40 50 60 70 80
22 19 18 16 15
42 37 33 30 28
86 76 69 63 59
142 129 119 112 106
291 265 245 232 212 202 182 166 149 139
444 404 371 351 324 305 272 252 232 212
842 762 696 656 616 576 517 470 430 404
OWNER'S MANUAL
90 100 125 150 175 200
14 13 12 11 10
26 25 22 20 18
55 52 48 42 39
99 86 79 73
9
—
17
36
66
Continued