Gas piping — sizing gas lines
Part number 550-100-131/0120
– 18 –
®
gas
-
fired
water
boiler
— 220/299/300/399
Boiler Manual
Pipe size
inches
Equivalent length, feet
90° Elbow
Tee
¾
2.06
4.12
1
2.62
5.24
1¼
3.45
6.90
1½
4.02
8.04
2
5.17
10.30
2½
6.16
12.30
3
7.67
15.30
4
10.10
20.20
Boiler gas connection is ¾” NPT. Size gas lines
large enough to provide gas to all connected
appliances.
Natural Gas:
Pipe sizing for natural gas
1. Size gas piping from meter outlet to entrance of boiler in
accordance with Figure 20 and Figure 21.
2. Use total input of all connected appliances. Divide total input
in Btuh by 1,000 to obtain cubic feet per hour of natural gas.
a. Pipe lengths in Figure 20 are equivalent length of straight
pipe. Convert pipe fittings to equivalent lengths using
data from Figure 21.
b. Figure 20 is only for natural gas with specific gravity
0.60, with a pressure drop through the gas piping as
listed in the table.
c. For additional gas pipe sizing information, refer to ANSI
Z223.1 NFPA 54 - latest edition (or Natural Gas and
Propane Installation
CAN/CSA
B149.1 or B149.2 for
Canadian installations).
Natural gas supply pressure
1. Pressure required at gas valve inlet pressure port:
a. Maximum: 14” (356 mm) w.c. with no flow (lockup).
b. Minimum gas pressure, with gas flowing (verify dur-
ing boiler startup, while boiler is at high fire):
3½” (89 mm) w.c.
2. Install 100% lockup gas pressure regulator in supply line if
inlet pressure can exceed 14” w.c. at any time. Adjust lockup
regulator for 14” w.c. maximum.
Propane Gas:
You must follow the instructions, beginning on
page 12, to operate the boiler on propane. Failure
to comply could result in severe personal injury,
death or substantial property damage.
Pipe sizing for propane gas
1. Contact gas supplier to size pipes, tanks and 100% lockup
gas pressure regulator.
Propane supply pressure
1. Adjust propane supply regulator provided by gas supplier
between the pressures listed below:
2. Pressure required at gas valve inlet pressure port:
a. Maximum: 14” (356 mm) w.c. with no flow (lockup).
b. Minimum gas pressure, with gas flowing (verify dur-
ing boiler startup, while boiler is at high fire):
3½” (89 mm) w.c.
Gas
pipe
total
length,
feet
Capacity
Cubic feet per hour, natural gas, 0.60 specific gravity
Gas pressure 14” (356 mm) w.c. or less
Pressure drop 0.3 inches (7.6 mm) w.c.
¾”
1”
1¼”
1½”
2”
2½”
3”
4”
10
278
520
1050
1600
3050
4800
8500 17500
20
190
350
730
1100
2100
3300
5900 12000
30
152
285
590
890
1650
2700
4700
9700
40
130
245
500
760
1450
2300
4100
8300
50
115
215
440
670
1270
2000
3600
7400
75
105
175
360
545
1020
1650
3000
6200
100
96
150
305
460
870
1400
2500
5100
150
90
120
250
380
710
1130
2000
4100
Figure 20
Pipe capacity for 0.60 specific gravity natural
gas; pipe length is in equivalent feet (for non-
corrugated pipe)
Figure 21
Equivalent lengths of straight pipe for typical
gas line fittings
