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LGB-6 to LGB-23
Series 2 – Control Supplement
Part Number 550-141-916/0304
1. 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 outlet to boiler. For pressure drops, see
ANSI-Z223.1 – latest edition. Canadian installations must comply with B149.1 or
B149.2 Installation Code.
2. Size natural gas piping from Table 3, below. 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 7" W.C. standard (5" on special order) – maximum 13" W.C.
b. If pressure to gas valve exceeds 13" W.C., install positive dead-end lockup gas pressure
regulator upstream of hand valve.
c. To obtain approximate cubic feet per hour, divide input (BTU/HR) by 1000.
3. Remove gas supply knockout disc from jacket panel.
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 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.
Table 3
Natural gas supply pipe sizing
10 20 30 40 50 75 100 150
1 ¼" 1,050 730 590 500 440 360 305 250
1 ½" 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 ½" 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 length, in feet (Natural Gas capacities, listed in MBH)
Pipe
Size
*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 – BUBBLE TEST. Failure to
use bubble test or test for leaks can cause severe personal injury, death or
substantial property damage.
a. Close manual main shut-off valve during any pressure testing at less than 13" W.C.
b. Disconnect boiler and gas controls from gas supply piping during any pressure test
greater than 13" W.C.
11. Set gas pressure switch as follows or to local inspector’s requirements (LGB-21 through
LGB-23 only):
a. High – 14" W.C.
12. Canada only - manual main shut-off valve must be identified by installer.