LGB
Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
16
SUPPL
Y
RETURN
Note 3
Note 2
Note 1
186-14
Install piping
1. Install system supply and return piping before erecting jacket or
installing controls.
2. Do not pipe in through supply and out through return. This creates
reverse water flow that must not be used.
3. Expansion tank —
a. Closed type expansion tank - connect to 1" tapping “
F
” (refer to
Tapping tables
, pages 12 and 13). Use 1" N.P.T. piping. Any
horizontal piping must pitch upward toward tank at least 1 inch
for each 5 feet of piping. See
Figure 14
.
b. Diaphragm type expansion tank — locate between supply and inlet
to circulator. Install automatic air vent in tapping “
F
”.
4. Connect supply and return piping:
a. Size according to tables on this page.
b. Install circulator in supply piping, with the expansion tank
located on the suction side of the circulator.
c. Install system drain valve, sized per ASME Code:
Models LGB-4 – LGB-12 — use 1" drain valve.
Models LGB-13 – LGB-23 — use 1¼" drain valve.
5. When three-way valves are used for temperature modulation, install
slow-opening valves and boiler mixing pump to minimize potential
of boiler thermal shock. See
Weil-McLain Bulletin AE-8402
.
6. Multiple boilers — see
Figure 15
, page 17.
7. Piping should be sized for a 20°F rise through the boiler. See
Table 1
,
below. For higher flow rates (when specified), use pipe sizes no smaller
than those given in
Table 2
, below.
Table 1
20°F rise
through
boiler
Recommended
minimum pipe sizes
1
Models LGB-4 through LGB-12 only — alternate supply tapping for supply and return on same end.
2
Models LGB-4 through LGB-12 only — alternate return tapping for supply and return on same end.
3
Location for closed type expansion tanks only. Locate diaphragm type expansion tanks between
boiler supply connection and circulator suction connection.
Notes
Figure 14
Water boiler
piping
3a
Piping
water boilers
Improper piping systems and/or undersized piping can contribute to erratic
boiler operation and possible boiler damage. Install piping as shown below.
LGB-4 through LGB-12 only
— supply and return piping can be on same
end.
Intermittent flow at higher velocities than shown for pipe size in
Table 2
,
below, can damage boiler causing substantial property damage.
Boiler Model
Number
Pipe Size
Supply &
Return
LGB-4
2"
LGB-5
2
1
/
2
"
LGB-6 — LGB-8
3"
LGB-9 — LGB-16
4"
LGB-17 — LGB-23
5"
Water Flow Rate
GPM
Pipe Size
Supply &
Return
Up to 35
2"
36 to 50
2
1
/
2
"
51 to 77
3"
78 to 142
4"
143 to 237
5"
Table 2
For specified
flow rates
