John Wood Commercial - AJWSC User Manual
Page 8
Note: If using a flexible gas connector, make sure its rating
tag matches or exceeds the input of the water heater.
Tables 1, 2, and 3 provide a sizing reference for commonly
used gas pipe materials. Consult the “Natural Gas and
Propane Installation Code” or “National Fuel Gas Code”
for the recommended gas pipe size of other materials.
Follow the instructions below and reference Figure 3 for gas
piping installation.
Note: When installing gas piping, apply sealing compounds
approved for use with natural and propane gas.
1. Install a readily accessible manual shut-off valve in the
gas supply line as recommended by the local utility. The
owner/operator must be shown the location of this valve
and be given instructions on how to use it to shut off the
gas to the heater.
2. Install a drip leg (if not already incorporated as part of
the water heater) as shown. The drip leg must be no
less than 76mm (3 in.) long for the accumulation of dirt,
foreign material, and water droplets.
3. Install a ground joint union between the gas valve and
the manual shut-off valve. This is to allow easy removal
of the gas valve.
4. Turn the gas supply on and check for leaks. Use a chlo-
ride-free soap and water solution (bubbles forming indi-
cate a leak) or other approved method.
Gas Pressure
Important: The gas supply pressure must not exceed the
maximum supply pressure as stated on the water heater’s
data plate. Minimum supply pressure should also be main-
tained per the data plate.
L.P. Gas Capacity
Size, (in)
10
20
30
40
50
60
70
80
90
100
125
150
1/2
275
189
152
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
3/4
576
393
315
267
237
217
196
185
173
162
146
132
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
Maximum capacity of gas pipe in thousands of BTU per hour of undiluted liquified petroleum gasses (at 11 inches
water column pressure). Based on a Pressure Drop of 0.5 Inch Water Column.
Nominal Iron Pipe
Length of pipe, Feet
Example: Input BTU requirements of the water heater, 199,000 BTUH
Total pipe length, 80 feet - 1" IPS required.
L.P. Gas Capacity
Size, (in)
10
20
30
40
50
60
80
100
125
5/8
206
141
n/a
n/a
n/a
n/a
n/a
n/a
n/a
3/4
348
239
192
164
146
132
n/a
n/a
n/a
7/8
536
368
296
253
224
203
174
154
137
Maximum capacity of gas pipe in thousands of BTU per hour of undiluted liquified petroleum gasses (at 11 inches
water column pressure). Based on a Pressure Drop of 0.5 Inch Water Column.
Copper Tubing OD
Example: Input BTU requirements of the water heater, 199,000 BTUH
Total pipe length, 50 feet = 7/8" IPS required.
Length of pipe, Feet
Natural Gas Pipe Capacity (Cu. ft./hr)
Size, in.
10
20
30
40
50
60
70
80
90
100
125
150
175
200
1/2
132
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
3/4
278
190
152
130
115
105
96
n/a
n/a
n/a
n/a
n/a
n/a
n/a
1
520
350
285
245
215
195
180
170
160
150
130
120
110
100
1-1/4 1050
730
590
500
440
400
370
350
320
305
275
250
225
210
1-1/2 1600 1100
890
760
670
610
560
530
490
460
410
380
350
320
Cu. Ft. Per Hr. Required =
Gas Input of Water Heater (BTU/HR)
Heating Value of Gas (BTU/FT
3
)
The gas input of the water heater is marked on the water heater data plate. The heating value of the gas (BTU/ft
3
) may
be determined by consulting the local natural gas utility.
Capacity of gas pipe of different diameters and lengths in cu. ft. per hr. with pressure drop of 0.3 in. and specific
gravity of 0.60 (natural gas).
Nominal Iron Pipe
Length of Pipe, Feet
After the length of pipe has been determined, select the pipe size which will provide the maximum cubic feet per hour
required for the gas input rating of the water heater. By formula:
Table 1
Table 2
Table 3
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