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P/N 42-9470 11/07 Copyright 2007 Mestek, Inc.
Cast iron condensing boiler
Cast iron condensing boiler
— Installation and operation manual
Gas piping
(continued)
Table 3
Gas fl ow capacity for black iron pipe
Iron
pipe
size
(inches)
Pipe length, equivalent feet
(length plus allowance for fi ttings)
10
20
30
40
50
60
80
100
150
Natural gas pipe fl ow capacity
(cubic feet per hour)
(notes
1, 2, 3
)
¾
278
190
152
130
115
105
90
79
64
1
520
350
285
245
215
195
170
150
120
1 ¼
1050
730
590
500
440
400
350
305
250
1 ½
1600
1100
890
760
670
610
530
460
380
Propane gas pipe fl ow capacity
(cubic feet per hour)
(notes
2, 3
)
¾
172
118
94
81
71
65
56
49
40
1
320
220
175
150
135
120
105
95
75
1 ¼
650
455
365
310
275
250
220
190
155
Notes, Table 3
1
2
3
Natural gas fl ow capacity is based on 0.60 specifi c gravity. Refer to the National Fuel Gas Code, ANSI
Z223.1/NFPA 54, for other pressure drops and other specifi c gravity gases.
Th e fl ow rates above allow for a pressure drop of:
Natural gas — 0.30 inches water column, with gas pressure 14 inches water column or less.
Propane — 0.30 inches water column, with gas pressure 14 inches water column or less.
To determine required fl ow rate in cubic feet per hour for all appliances connected to the gas line:
Natural gas — Divide total Btuh by the gas Btu per cubic foot rating (typically 1,000 Btu/ft
3
nominal).
Propane — Divide total Btuh by 2,500.
Table 4
Equivalent feet of pipe for common gas line components
Iron
pipe
size
(inches)
Equivalent feet of pipe for each fi tting
90° Elbow
Tee
(note
1
)
Gate valve
(note
2
)
Gas cock
(note
2
)
1”
2.6
5.2
0.6
1.5
1 1/4”
3.5
6.9
0.8
1.9
1 1/2”
4.0
8.0
0.9
2.3
2”
5.2
10.3
1.2
3.0
Notes, Table 4
1
2
Allows for fl ow through the branch of the tee.
Assumes valve is full open.
Gas piping joints
Always use a pipe sealant that is suitable for use
with LP gas. Failure to comply could result in
an explosion, causing possible severe personal
injury, death or substantial property damage.
Only use pipe dope listed for use with propane gas. Even natural
gas may contain some amount of propane.
Use pipe dope sparingly. Excessive pipe dope can block pipe
fl ow or foul gas train components.
Gas pipe sizing
Required supply pressure at boiler
Minimum gas supply pressure (natural gas or propane), both for
fl owing and static conditions:
4 inches (102 mm) water column.
Maximum gas supply pressure (natural gas or propane), both
for fl owing and static conditions:
14 inches (356 mm) water column.
Sizing guidelines
Th
e sizing recommendations of Table 3 are taken from the National
Fuel Gas Code, ANSI Z223.1/NFPA 54. Propane values are based
on adjustment from propane specifi c gravity and pressure.
Table 3 allows for a pressure drop from the main supply regulator
to the boiler of 0.3 inches (7.6 mm) water column for natural
gas or propane.
For conditions not shown in Table 3, other pressure drops, or
natural gas with other than 0.6 specifi c gravity, refer to the ap-
propriate code guidelines for sizing.
Equivalent length
Do not neglect the pressure drop due to pipe fi tt ings.
Equivalent length is the sum of the actual length of piping plus
the total equivalent lengths of all fi tt ings in the line from the
main regulator to the boiler connection. See Table 4 for equiva-
lent lengths of common fi tt ings and components.
Multiple appliances
If more than one appliance is supplied by the same supply pipe, the
piping must be sized based on the maximum possible demand.
Undersized gas supply piping can cause the
gas line pressure to become negative during
operation of the
200i
boiler. Th is can cause pilot
outages and operation failures of other appliances
connected to the line, including gas ranges, water
heaters, etc. Failure to properly size the gas lines
can result in potential for severe personal injury,
death or substantial property damage.
Test all gas piping for leaks
All gas piping, components and connections must be leak tested
before putt ing the boiler in operation. Isolate the boiler from the gas
supply piping if testing with pressure greater than 14 inches (12.7 mm)
pressure. Failure to do so could result in severe personal injury, death or
substantial property damage.
Check all gas piping components and joints for
leaks. Use either a soap suds mixture, a gas leak
detector or other suitable means.
Aft er testing the system gas piping, remove the
gas valve cover plate on the left side of the boiler
(see illustration at right). Inspect and leak test
around the interior gas line and gas valve. Replace
the cover aft er completing the gas connection
inspection and testing.
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