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Part Number 550-141-918/0304
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Nat. Gas
3
Table 1
Gas supply pipe
capacities
1. Size natural gas piping from Table 1. Size piping to provide proper inlet pressure to gas
valve when operating at rated input.
a. Inlet gas pressure to manual main shut-off gas valve minimum 5" W.C., maximum
13" W.C.
b. If pressure to gas valve exceeds 13" W.C., install 100% lock-up gas pressure regulator
upstream of hand valve.
c. To obtain approximate cubic feet per hour, divide input (Btu/hr) by 1000.
2. Size gas piping considering:
a. Diameter and length of gas supply piping.
b. Number of fittings.
c. Maximum gas consumption (including any possible future expansion).
d. Allowable pressure drop from gas meter to boiler. For pressure drops, see ANSI
Z233.1 latest edition. Canadian installations must comply with B149.1 or B149.2
Installation Code.
3. Remove knockout disc from jacket panel side to which gas supply will be piped.
4. Follow good piping practices.
5. Pipe joint compound (pipe dope) must be resistant to corrosive action of liquefied
petroleum gases. Apply sparingly only to male threads of pipe joints.
6. Install drip leg at inlet of gas connection to boiler. Where local code/utility requires,
extend drip leg to floor.
7. Install ground joint union when required for servicing.
8. Support piping by hangers, not by boiler or its accessories.
9. Purge all air from supply piping.
10. Before operating boiler, check boiler and its gas connections for leaks.
Supply pipe sizing
Connect gas piping
to boiler
10 20 30 40 50 75 100 150
1 1/4" 1,050 730 590 500 440 360 305 250
1 1/2" 1,600 1,100 890 760 670 545 460 380
2" 3,050 2,100 1,650 1,450 1,270 1,020 870 710
2 1/2" 4,800 3,300 2,700 2,300 2,000 1,650 1,400 1,130
3" 8,500 5,900 4,700 4,100 3,600 2,900 2,500 2,000
4" 17,500 12,000 9,700 8,300 7,400 6,000 5,100 4,100
PIPE
SIZE
Pipe length, feet *
(Natural gas capacities given in MBH)
(Specific Gravity 0.60 @ Pressure Loss of 0.30" W.C.)
*Include measured length of gas supply piping and allowance in feet for number and size of fittings.
II Gas piping
Do not check for gas leaks with an open flame - use bubble test. Failure to
use bubble test or check for leaks can cause severe personal injury, death or
substantial property damage.
a. Close manual main shut-off valve during any pressure testing greater than 13" W.C.
b. Disconnect boiler and gas valve from gas supply piping during any pressure test
greater than 13" W.C.
11. In Canada — manual main shut-off valve must be identified by installer.