Weil-McLain LGB-4 User manual

Part Number 550-141-186/0100
LGLG
LGLG
LGBB
BB
B
Read all instructions before installing
Installer Leave all instructions with boiler for future reference.
Any claims for damage or shortage in shipment must be filed
immediately against the transportation company by the consignee.
Owner Installation and service should be performed by qualified contractor.
Refer to
Control Supplement
for additional information
Gas–Fired Boiler
Boiler Manual
• Installation
• Start-up
• Maintenance
• Parts

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
2
When calling
or writing
about the boiler
Please have model and series from boiler rating label and CP number(s) from boiler jacket or
controls.
Do not use petroleum-based cleaning or sealing compounds in boiler
system. Severe damage to system components can result, causing
substantial property damage.
Read all instructions before installing. Failure to follow all instructions in
proper order can cause severe personal injury,death or substantial property
damage.
Read
instructions first
No petroleum-
based chemicals
Hazard
definitions The following defined terms are used throughout this manual to bring attention to the presence
of hazards of various risk levels, or to important information concerning the life of the
product.
Indicates presence of hazards that will cause severe personal injury, death
or substantial property damage.
Indicates presence of hazards that can cause severe personal injury, death
or substantial property damage.
Indicates presence of hazards that will or can cause minor personal injury
or property damage.
Indicates special instructions on installation, operation or maintenance
that are important but not related to personal injury or property damage.
Read this page first

Part Number 550-141-186/0100 3
• Installation • Start-Up • Maintenance • Parts
Pre-installation
Codes ..........................................................................................4
Air openings ...............................................................................4
Venting ........................................................................................6
Foundation..................................................................................8
Boiler assembly
Base.............................................................................................9
Sections ....................................................................................10
Hydrostatic pressure test .........................................................12
Cleanout plates.........................................................................14
Flue collector hood...................................................................15
Piping
Water boilers ............................................................................16
Steam boilers............................................................................18
Multiple steam boilers..............................................................20
Jacket ...............................................................................................21
Draft hood........................................................................................21
Install boiler controls .....................................................................22
Final adjustment
Water boilers ............................................................................24
Steam boilers............................................................................25
Placing boiler in operation ............................................................26
Check-out procedure ......................................................................27
Maintenance ....................................................................................28
Replacement parts ..........................................................................32
Dimensions ......................................................................................34
Equipment — standard and optional ...........................................35
Ratings .............................................................................................36
Gas piping............................................... (See Control Supplement)
Wiring...................................................... (See Control Supplement)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Contents

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
4
Installations must comply with all local codes, laws, regulations and ordinances, also National
Fuel Gas Code ANSI Z223.1–latest edition. When required, installations must conform to
Standard for Controls and Safety Devices for Automatically Fired Boilers, ANSI/ASME
CSD-1. Safe lighting and other performance criteria were met with the gas manifold and
control assembly provided on boiler when boiler underwent tests specified in ANSI Z21.13–
latest edition.
Canadian installations must comply with CAN/CGA B149.1 or B149.2 Installation Code.
The equipment shall be installed in accordance with those installation regulations in force in
the local area where the installation is to be made. These shall be carefully followed in all cases.
Authorities having jurisdiction shall be consulted before installations are made.
Codes
Combustion air
and ventilation
openings
Combustion air and ventilation openings must comply with Section 5.3, Air for Combustion
and Ventilation, of National Fuel Gas Code ANSI Z233.1–latest edition, or applicable local
building codes. Canadian installations must comply with CAN/CGA B149.1 or B149.2
Installation Code.
Boiler installation must assure sufficient openings in building and boiler room to provide
adequate combustion air and ventilation. Consider construction tightness of building when
deciding whether additional outside openings may be needed.
Older buildings with single-pane window, minimal weather-stripping and no vapor barrier
often provide enough natural infiltration and ventilation without dedicated openings.
New construction or remodeled buildings are most often built tighter. Windows and doors
are weather-stripped, vapor barriers are used and openings in walls are caulked. As a result,
such tight construction is unlikely to allow proper natural air infiltration and ventilation.
Figure 1
Boiler room
below grade
Air openings
Pre-installation  air openings 1a
Adequate combustion air and ventilation openings must be provided to
assure proper combustion, prevent possibility of flue gas spillage and
carbon monoxide emissions, causing severe personal injury or death.
GratingGrade
Areaway
Louver
Note Size of areaway and
grating to be equal
to or greater than
total louver area.
Boiler room floor
186-01

Part Number 550-141-186/0100 5
• Installation • Start-Up • Maintenance • Parts
Figure 2
Boiler room
partially or
completely
above grade
Combustion air
and ventilation
openings
(continued)
Air from inside building (boiler in interior room):
• Tightly constructed buildings must be provided with openings to outside for combustion
and ventilation air. These openings must be sized to handle all fuel-burning appliances,
exhaust and ventilation fans and fireplaces.
• When openings to boiler room are taken to interior spaces, provide two permanent
openings: a combustion air opening within 12 inches of floor and a ventilation opening
within 12 inches of ceiling. Each opening must provide a minimum free area of one
square inch per 1,000 Btuh input of all appliances in room plus requirements for any
exhaust fans in room. The interior space supplying combustion and ventilation air must
have adequate infiltration from outside.
Air directly from outside to boiler room:
• Tightly constructed buildings must be provided with combustion air and ventilation
openings to boiler room which are adequate to handle the boiler needs plus the needs of
all other fuel-burning appliances, fireplaces and exhaust or ventilation fans.
• Combustion and ventilation openings connecting directly or by ducting to outside, or to
attic or crawl spaces that freely connect with outside, must be sized as follows:
1. Outside wall or vertical ducting — one square inch per 4.000 Btuh input of all
appliances in room plus requirements for any exhaust fans or other appliances in
room.
2. Horizontal ducting — one square inch per 2,000 Btuh of all appliances in room plus
requirements for any exhaust fans or other appliances in room.
3. All ducting must be same size as permanent openings. Minimum area dimensions of
ducting must be no less than 9 square inches.
4. Other size ducting must comply with local codes.
Compensate for louver blockage when calculating combustion air and ventilation openings.
See Figures 1 and 2. Refer to manufacturer's instructions for sizing.
Adjustable louvers must be locked open and combustion air damper must interlock with
boiler controls to open automatically before boiler operation.
Grade
Louver Duct size equal to
total louver area
Boiler room floor
186-02

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
6
Chimney or Vent
When removing
boiler from common
venting system
Venting must be installed according to Part 7, Venting of Equipment, of National Fuel Gas
Code, ANSI Z223.1–latest edition and applicable building codes. Canadian installations must
comply with CAN/CGA B149.1 or B149.2 Installation Code.
Breeching must not be connected to any portion of mechanical draft system that can operate
under positive pressure.
At the time of removal of an existing boiler, the following steps shall be followed with each
appliance remaining connected to the common venting system placed in operation, while
the other appliances remaining connected to the common venting system are not in operation.
a. Seal any unused openings in the common venting system.
b. Visually inspect the venting system for proper size and horizontal pitch and determine
there is no blockage or restriction, leakage, corrosion and other deficiencies which could
cause an unsafe condition.
c. Insofar as is practical, close all building doors and windows and all doors between the
space in which the appliances remaining connected to the common venting system are
located and other spaces of the building. Turn on clothes dryers and any appliance not
connected to the common venting system. Turn on any exhaust fans, such as range hoods
and bathroom exhausts, so they will operate at maximum speed. Do not operate a summer
exhaust fan. Close fireplace dampers.
d. Place in operation the appliance being inspected. Follow the lighting instructions. Adjust
thermostat so appliance will operate continuously.
e. Test for spillage at the draft hood relief opening after 5 minutes of main burner operation.
Use the flame of a match or candle.
f. After it has been determined that each appliance remaining connected to the common
venting system properly vents when tested as outlined above, return doors, windows,
exhaust fans, fireplace dampers, and any other gas-burning appliance to their previous
conditions of use.
g. Any improper operation of the common venting system should be corrected so the
installation conforms to the National Fuel Gas Code, ANSI Z223.1–latest edition. When
resizing any portion of the common venting system, the common venting system should
be resized to approach the minimum size as determined using the appropriate tables in
Appendix G in the National Fuel Gas Code ANSI Z223.1–latest edition.
Canadian installations must comply to CAN/CGA B149.1 or B149.2 Installation Codes.
Flue gas spillage
1b Pre-installation  venting
See Figures 3, 4 and 5 on page 7 for typical venting configurations. Ensure that your installation
complies with the requirements given in these illustrations and with all local codes and
standards.
See the Ratings table on page 36, for minimum breeching diameter. Use heavy gauge steel
breeching (Type B vent material or single wall metal pipe). Where horizontal breeching is
used, slope upward at least ¼" per foot toward chimney or vent and support with hangers to
prevent sagging.
Long horizontal breechings, excessive numbers of elbows or tees, or other
obstructions restricting flow of combustion gases can result in possibility
of flue gas spillage and carbon monoxide emissions, causing severe
personal injury or death.
Failure to follow all instructions listed below can cause flue spillage and
carbon monoxide emissions, resulting in severe personal injury, death or
substantial property damage.

Part Number 550-141-186/0100 7
• Installation • Start-Up • Maintenance • Parts
Figure 3
Individual
stub vents
Figure 4
Combined
vents
Figure 5
Offset
vents
Notes
Minimumvent height usingfullsizeconnector.
Minimum 2 feet above any structure within 10
feet.
Vent and combined vent materials, length and
diameter must be determined using the
combined venting tables of the National Fuel
Gas Code, ANSI Z223.1–latest edition, or
otheracceptedengineering design method. Use
a connector rise as high as possible to improve
vent connector capacity.
Vent and vent connector material and design
must be determined using the individual
venting tables of the National Fuel Gas Code,
ANSI Z223.1–latest edition, or other accepted
engineering design method. Use a connector
rise as high as possible to improve vent
connector capacity.
1
2
3
4
Vent caps
Roof line
Outside
wall
3 ft
186-03
5 ft
minimum
minimum
Note 2
Note 1
2 ft
minimum
3 ft
Connector
rise (Note 3)
Minimum effective
chimney height
Combined vent
diameter (Note 3)
Combined vent
length (Note 3)
20 ft
186-04
minimum
3 ft
Connector
rise (Note 4)
Connector
lateral (Note 4)
Minimum effective
chimney height
20 ft
minimum
3 ft
minimum
Also see
note 2
186-05

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
8
Figure 6
Foundation
1c Pre-installation  foundation
186-06
46½"
Base end panel
Foundation, minimum 2" thick
W
1"
2"
Installation
clearances Suggested minimum clearances for servicing:
• 24 inches for access to controls and components front and sides.
• 6 inches from draft hood to wall, for cleaning flueways.
Required clearances in confined spaces:
• Vent pipe must be at least 6 inches from combustible material.
• Minimum 24" between jacket and combustible walls and ceiling.
For LGB-6 through LGB-23 IRI and LGB-21 through LGB-23 FM/CSD-1, the gas train is
located outside the boiler. Provide additional clearance.
Install in a space large in comparison to size of boiler.
Boiler foundation
Level concrete or brick foundation, minimum 2" thick, (Figure 6) is required if:
• There is a possibility of the floor becoming flooded.
• Non-level conditions exist.
Use foundation with airways when concrete floor is “green”.
Fire hazard. Never install boiler on combustible flooring or carpeting,
even if a concrete or aerated foundation is used. Severe personal injury,
death or substantial property damage can result.
Do not route wiring, telephone cables or piping in the floor below the
boiler. Overheating could occur, resulting in severe personal injury, death
or substantial property damage.
Select the boiler
location Consider all connections to the boiler before selecting a location.
Boiler must be installed so gas control system components are protected from dripping or
spraying water or rain during operation or service.
Flammable materials To avoid personal injury, death or property damage, keep the boiler area
clear and free from combustible materials, gasoline and other flammable
vapors and liquids.
Boiler
Model
Number
“W”
Inches Boiler Model
Number
“W”
Inches
LGB-4 21 LGB-14 71
LGB-5 26 LGB-15 76
LGB-6 31 LGB-16 81
LGB-7 36 LGB-17 86
LGB-8 41 LGB-18 91
LGB-9 46 LGB-19 96
LGB-10 51 LGB-20 101
LGB-11 56 LGB-21 106
LGB-12 61 LGB-22 111
LGB-13 66 LGB-23 116

Part Number 550-141-186/0100 9
• Installation • Start-Up • Maintenance • Parts
Figure 8
Base
assembly
Check for proper orifice size:
• Natural gas – 3.95 mm
• Propane gas – 2.40 mm
Base
assembly
Figure 7
Access
shield
(sizes D, E, F
and G
shown)
Orifices
Assembly order
Burner seating
2a
Before assembling base, relocate access shield from lower shipping holes to upper mounting holes. See Figure 7.
• Base sizes 4, 5, A, B and C — one mounting hole.
• Base sizes D, E, F and G — two mounting holes.
Boiler assembly  base
Proper orifices must be used. Failure to do so will cause severe personal injury, death or
substantial property damage.
Assemble base(s) as shown in Figure 8, in the order shown in the table below. Dual base shown.
Level and straighten burners to avoid misfiring.
Base assembly must be located in order shown in Base Arrangement Table, below, so flue
collector/draft hoods, jackets, and gas controls are installed in correct position.
Burners must be properly seated in their locating slots with openings facing up. Front of
burners must rest fully over main burner orifices. Gas orifices must inject down center of
burners. Failure to properly level and seat burners will result in severe personal injury, death
or substantial property damage.
Base Arrangement Table (Note 1)
Boiler
Model
Number
Base Size Boiler
Model
Number
Base Size
LGB-4 4 -- LGB-14 C B
LGB-5 5 -- LGB-15 C C
LGB-6 A -- LGB-16 D C
LGB-7 B -- LGB-17 D D
LGB-8 C -- LGB-18 E D
LGB-9 D -- LGB-19 E E
LGB-10 E -- LGB-20 F E
LGB-11 F -- LGB-21 F F
LGB-12 G -- LGB-22 G F
LGB-13 B B LGB-23 G G
Note 1: From boiler left side (front view). Side panels
shipped in separate carton.
186-07
Base front panel
Mounting hole
Mounting hole
Shipping hole
Base access shield
Screw
186-08
For dual
base only
Trim insulation flush with flanges
where two bases connect.

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
10
Assembly may start at either end section.
For easier assembly start with right end section.
1. Position right end section flush with right end of base. See Figure 13 on page 15.
Section assembly
Figure 9
Sealing rope and seals
2b Boiler assembly  sections
2. With caulking gun, apply 1 /8" continuous bead of sealing rope adhesive in sealing
grooves. See Figure 9.
3. Place ½" rope in groove. Around curves, grasp at 1" intervals and push together. Do
not stretch. Cut rope as each section is completed. See Figure 9.
4. Remove any grit from port opening sealing surfaces with clean rag. Note Warning below.
Clean port
sealing surfaces Remove all grit or rust from port opening sealing surfaces. Failure to do
so may cause a seal failure, resulting in severe personal injury, death or
substantial property damage.
No petroleum-
based chemicals Do not use any cleaner containing petroleum-based distillate (oil).
Elastomer seal failure will occur, causing substantial property damage.
Do not precut
rope Do not precut rope. Gas tight seal must be maintained to prevent possibility
of flue gas spillage and carbon monoxide emissions, causing personal
injury or death.
Sections are top-
heavy Sections are top heavy and will not stand individually without support.
Severe personal injury, death or substantial property damage can result.
9" Elastomer sealing ring
6" Elastomer sealing ring
Sealing
rope
186-09
5. Place sealing rings in port openings. See Figure 9.
6. Prepare intermediate section:
a. Remove grit or rust from port opening sealing surfaces. Note Warning above.
b. Position intermediate sections so alignment lugs fit into sockets of next section.
Refer to Figure 10, page 11.

Part Number 550-141-186/0100 11
• Installation • Start-Up • Maintenance • Parts
Section assembly
(continued)
Figure 10
Sealing ring installation and
port alignment
7. Discard 3 /8" diameter shipping tie rods. Do not use to draw sections together.
8. Draw sections together until metal-to-metal contact is made around machined port
opening. See Figure 10.
a. Oil threads on three draw rods. Install washer and nut on end to be tightened. Use
nut only on other end.
b. Uniformly draw sections together, starting at washer/nut end.
c. Draw rods should be torqued to a range of 100-120 ft/lbs. Do not back off draw
rods.
d. Metal-to-metal contact will be achieved around port opening. See Figure 10. If a
gap does exist, it should be no greater than .032". Check with feeler gauge.
9. Follow steps 2 through 8 for remaining intermediates and left end section.
Check sealing
rope Check sealing rope of each section before proceeding to next section. Boiler
must be sealed gas-tight to prevent possibility of flue gas spillage and
carbon monoxide emissions, causing severe personal injury or death.
End section
must be plumb End section must be plumb. After erecting 1st intermediate section, check
both sections for plumb. Failure to plumb sections may cause misaligned
piping and breeching, resulting in minor property damage.
Verify metal to
metal contact at
ports
If for any reason gap around port opening exceeds .032", check for rope
extending from rope grooves, dirt on port openings or sockets, or
misaligned lugs. If corrections are made and gap still exists, contact your
Weil-McLain distributor or sales office before continuing installation.
Failure to correct this situation could cause seal failure, resulting in severe
personal injury, death or substantial property damage.
SectionSection
Elastomer
sealing ring
Alignment
lug Socket
Metal-to-metal
contact
(see 8d above)
186-10

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
12
Hydrostatic pressure
test Pressure test before connecting gas piping and electrical supply.
1. Refer to Figures 11a and 11b for control tapping locations. Install:
a. Boiler drain (not supplied).
b. Water pressure gauge — for test only. Be sure gauge can handle test pressures. See
Step 3.
2. Plug remaining tappings.
Figure 11a
Left end section tappings
2c Boiler assembly  pressure test
3. Fill boiler. Vent all air. For more than 10 minutes, pressure-test:
a. Steam boilers between 45 - 55 psig.
b. Water boilers 1 ½ times maximum working pressure stated on castings and boiler
nameplate.
No controls
installed DO NOT pressure test with any controls installed. Damage to control can
occur.
Do not leave
boiler
unattended
Do not leave boiler unattended. Cold water fill could expand and cause
excess pressure, resulting in severe personal injury, death or substantial
property damage.
5" Return
5" Return
6" Supply
6" Supply
G1
G1
E1
E1
D1
D1
M1
M1
M2
M2
K1
K1
H1
H1
H2
H2
D2
D2
E2
E2
C1
C1
J1
J1
F1
F1
186-11a
Tapping Size
Inches
Steam Boilers Water Boilers
(note 4)
C1 11 / 4Boiler drain Boiler drain
D1 & D2 1 / 2 Gauge glass
(note 3)
--
E1 & E2 1Low water cutoff
(note 3)
Optional low water
cutoff
E1 1Pressure
operating & limit
controls and
pressure gauge
Limit control
(note 2)
F1 1 -- To expansion tank or
automatic air vent
(note 2)
G1 3 / 4-- Operating control
(note 2)
H1 & H2
(note 1)
3
/ 8Tri-cock --
J1 2Steam relief valve
& skim tapping Water relief valve & skim tapping
K1 1 / 2-- Combination pressure
& temperature gauge
(note 2)
M1 & M2 1Optional low water
cutoff
(note 3)
Optional low water
cutoff
M1 1Firing rate control
(when used)
Firing rate control
(when used) or Probe
low water cutoff
Notes:
1. Available on special request only.
2. Must be on same side as supply to system.
3. Must be on same side as steam equalizer piping.
4. Additional controls for water boilers may be placed in supply piping.

Part Number 550-141-186/0100 13
• Installation • Start-Up • Maintenance • Parts
Figure 11b
Right end section tappings
Hydrostatic pressure
test
(continued)
No petroleum-
based chemicals
G2
G2
E3
E3
D3
D3
M3
M3
H3
H3
H4
H4
K2
K2
D4
D4
E4
E4
M4
M4
C2
C2
F2
F2
J2
J2
5" Return
5" Return
6" Supply
6" Supply
186-11b
4. Check for maintained gauge pressure and leaks. Repair if found.
5. Drain boiler and remove plugs from tappings used for controls and accessories.
Do not use petroleum-based cleaning or sealing compounds in boiler
system. Severe damage to boiler will result, causing substantial property
damage.
Repair leaks
at once Leaks must be repaired at once. Failure to do so can damage boiler,resulting
in substantial property damage.
Tapping Size
Inches
Steam Boilers Water Boilers
(note 4)
C2 1
1
/ 4 Boiler drain Boiler drain
D3 & D4
1
/ 2 Gauge glass
(note 3)
--
E3 & E4 1Low water cutoff
(note 3)
Optional low water
cutoff
E3 1Pressure
operating & limit
controls and
pressure gauge
Limit control
(note 2)
F2 1 -- To expansion tank or
automatic air vent
(note 2)
G2
3
/ 4 -- Operating control
(note 2)
H3 & H4
(note 1)
3
/ 8 Tri-cock --
J2 2Steam relief valve
& skim tapping Water relief valve & skim tapping
K2
1
/ 2 -- Combination pressure
& temperature gauge
(note 2)
M3 & M4 1Optional low water
cutoff
(note 3)
Optional low water
cutoff
M3 1Firing rate control
(when used)
Firing rate control
(when used) or Probe
low water cutoff
Notes:
1. Available on special request only.
2. Must be on same side as supply to system.
3. Must be on same side as steam equalizer piping.
4. Additional controls for water boilers may be placed in supply piping.

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
14
Cleanout plates Assemble cleanout plates to section assembly as shown in Figure 12.
Figure 12
Cleanout plate assembly
Gas-tight seal
2d Boiler assembly  cleanout plates
Cleanout plates must be sealed gas-tight to prevent possibility of flue gas
spillage and carbon monoxide emissions, causing severe personal injury
or death.
186-12
Bolt & washer
Nut
Insulation
Cleanout
plate
Nut
Washer

Part Number 550-141-186/0100 15
• Installation • Start-Up • Maintenance • Parts
Flue collector hood See Figure 13 — single base shown.
Refer to the table below, for proper arrangement.
1. Assemble bolt, washer and nut to section joint.
2. Apply retort cement for gas-tight seal.
Figure 13
Flue collector hood assembly and sealing the boiler
Gas-tight seal
2e Boiler assembly  fluecollectorhood
Hood must be sealed gas-tight to prevent possibility of flue gas spillage
and carbon monoxide emissions, causing severe personal injury or death.
3. Mount hood on section assembly. Fasten with washers and nuts.
Apply retort cement between bottom of sections and top of base assembly. See Figure 13.
Sealing the
boiler Boiler must be sealed gas-tight to prevent possibility of flue gas spillage
and carbon monoxide emissions, causing severe personal injury or death.
Washer
Washer
Flue collector hood
Retort cement
Retort cement
186-13
Right end
section
Right end
of base
Carriage bolt
Carriage bolt
Nut
Nut
Boiler Model
Number Flue Collector Hood(s) (from left side of boiler)
LGB-4 4 --
LGB-5 5 --
LGB-6 A --
LGB-7 B --
LGB-8 C --
LGB-9 D --
LGB-10 E --
LGB-11 F --
LGB-12 G --
LGB-13 B B
LGB-14 C B
LGB-15 C C
LGB-16 D C
LGB-17 D D
LGB-18 E D
LGB-19 E E
LGB-20 F E
LGB-21 F F
LGB-22 G F
LGB-23 G G

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
16
SUPPLY
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
1Models LGB-4 through LGB-12 only — alternate supply tapping for supply and return on same end.
2Models LGB-4 through LGB-12 only — alternate return tapping for supply and return on same end.
3Location 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

Part Number 550-141-186/0100 17
• Installation • Start-Up • Maintenance • Parts
Primary/secondary
piping
(systems above 140°F)
Weil-McLain recommends piping
as shown in Figure 15. For single
boilers, pipe as shown for one unit.
Size secondary boiler pump GPM
for 20°F to 40°F temperature rise
through boiler. Secondary boiler
pump head will be very low.
Calculate only secondary piping
circuit resistance. Boiler resistance
will not exceed 6" w.c.
Primary pump GPM and head
calculation should not include
secondary boiler circuits. Primary
pump can operate continuously
during heating season.
Distance 12" or less.
Flow/check valve.
Hand valve.
Expansion tank(s), relief valves and
other accessories are required but
not shown.
Refrigeration system
piping The boiler must be installed so that
chilled medium is piped in parallel
with the heating boiler with
appropriate valves to prevent the
chilled medium from entering the
boiler. See Figure 16. Consult
I=B=R Installation and Piping
Guides.
If boiler is connected to heating
coils located in air handling units
where they can be exposed to
refrigerated air, gravity circulation
during cooling cycle must be
prevented with flow control valves
or other automatic means.
1
2
3
4
5
6
Figure 15
Figure 16
Diaphragm
expansion
tank (if used)
12 " maximum
Flow/check
valve
Flow/check
valve
2
1
1
4
4
5
5
55
3
186-15
Water
chiller
Expansion tank
Circulator
Check
valve
Strainer Boiler
Shut-off
valve
System
supply
System
return
Balancing
valve
186-16

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
18
Install piping
Pipe the header at least 24 inches above the boiler water line.
Weil-McLain recommends using a boiler feed system, with the pump operated by a level
controller on the boiler. Weil-McLain does not recommend using a condensate return system
on which the pump is operated by a receiver-mounted float switch. Level controls (Section
6) must be mounted on same side of boiler as the return piping and equalizer.
Install a blowdown valve in tapping C1 or C2 (see Figures 11a and 11b, pages 12 and 13),
sized per ASME Code:
Models LGB-4 through LGB-12 — use 1" blowdown valve.
Models LGB-13 through LGB-23 — use 1¼" blowdown valve.
See Figure 20, Page 20, for multiple steam boiler piping.
Figure 17
Steam boiler piping for
LGB-4 through LGB-12
(single riser)
Figure 18
Steam boiler piping for
LGB-13 through LGB-23
(riser each end)
3b Piping  steam boilers
Improper piping systems and/or undersized piping can contribute to erratic
boiler operation and possible boiler damage. The piping must be installed
as illustrated, using the recommended minimum pipe sizes.
Minimum Recommended Pipe Sizes
Boiler
Model
Number
Riser Header Equalizer
A H J
LGB-4 —
LGB-8 4" 4" 2"
LGB-9 —
LGB-11 5" 5" 2
1
/ 2 "
LGB-12 6" 6" 2
1
/ 2 "
Minimum Recommended Pipe Sizes
Boiler
Model
Number
Risers Header Equalizer
A B H J
LGB-13—
LGB-15 4" 4" 6" 4"
LGB-16—
LGB-19 5" 5" 6" 4"
LGB-20—
LGB-23 6" 6" 8" 4"
186-17
Condensate return
A
H
Steam supply
J
J
J
J
1
2
Reducing from header
to equalizer - alternate
piping methods.
DO NOT reduce the
header in the
horizontal piping.
1
OR
186-17a
Water line
Water line
Hartford loop tee
Use only close nipple
or street ell here.
Floor line
Boiler
Header
Steam
supply
24"
min
4"
33 7/16"
2
186-17b
Condensate return
A
H
Steam
supply
B
1
J
J
J
J
2
186-18

Part Number 550-141-186/0100 19
• Installation • Start-Up • Maintenance • Parts
Condensate receiver
and boiler feed pump
Figure 19
Boiler feed pump and
condensate receiver piping
Table 3
Condensate receiver capacity
(minimum)
Satisfactory operation of any steam heating system depends upon adequate
return of condensate to maintain steady water level.Avoid adding excessive
amount of raw makeup water. Where condensate return is not adequate, a
low water cutoff and pump control, condensate receiver, and condensate
boiler feed pump should be installed. Refer to Figure 19 for piping and
condensate receiver capacity table for sizing.
2"
Isolation valve
Strainer Feed pump Check valve
Receiver
Return
Vent to atmosphere
Boiler
Hartford loop
186-19
Boiler
Model
Number
Gross
Output
Steam
Condensate Minimum Condensate Receiver Capacity
(gallons)
Select minimum receiver capacity based on time
(minutes), required for condensate to return to the
receiver.
Recommended
Feed Pump
Capacity
lbs/hour gallons/hour 15 min 30 min 45 min 60 min GPM @ 15 PSI
LGB-4 324.0 39 12 23 35 47 1.3
LGB-5 421.2 51 15 30 46 61 1.7
LGB-6 526.5 63 19 38 58 77 2.1
LGB-7 631.8 76 23 46 68 91 2.5
LGB-8 737.1 88 26 52 78 104 2.9
LGB-9 842.4 101 30 60 90 120 3.3
LGB-10 947.7 114 34 68 102 136 3.8
LGB-11 1,053.0 126 38 76 114 152 4.2
LGB-12 1,158.3 139 42 84 126 168 4.6
LGB-13 1,263.6 152 46 92 138 184 5.1
LGB-14 1,368.9 164 49 98 147 196 5.5
LGB-15 1,474.2 177 53 106 159 212 5.9
LGB-16 1,579.5 190 58 116 174 232 6.3
LGB-17 1,684.8 202 61 122 183 244 6.7
LGB-18 1,790.1 215 65 130 195 260 7.1
LGB-19 1,895.4 227 68 136 204 272 7.5
LGB-20 2,000.7 240 72 144 216 288 8.0
LGB-21 2,106.0 253 76 152 228 304 8.4
LGB-22 2,211.3 265 79 158 237 316 8.8
LGB-23 2,316.6 278 83 166 249 332 9.2

LGB Gas-Fired Boiler — Boiler Manual
Part Number 550-141-186/0100
20
Figure 20
Piping
multiple
steam boilers
Notes
Each boiler has a boiler feed pump controller (not shown). Level controls (Section 6) must be mounted on same side of boiler as return.
Mount each boiler feed pump controller with body mark at the level indicated in Table 4,page 22 and Figure 23, page 23.
Locate system steam supply takeoff outboard from the boiler connecting piping, as shown, to assure liquid in line will flow to trap.
Locate combined header drain as shown. Install strainer and float and thermostatic trap in drain line as shown. Pipe trap outlet to condensate
receiver.
Size the common header piping per ASHRAE recommendations, and in no case smaller than the individual boiler headers.
Pipe the Hartford Loop tee 4" below boiler waterline.
Boiler controls and trim (valves, low water cutoffs, pump controllers, burners, etc.) are omitted in order to emphasize steam and return piping.
Provide a separate feed pump for each boiler.Alternatively, provide a separate automatic valve with end switch and a single feed pump.When
valves are used, activate the valve with the boiler pump controller. Activate the feed pump with the valve end switch.
Manual steam valve or slow opening automatic steam valve, sized to boiler output capacity.
Boiler steam header for single boiler, see page 18.
Install a float and thermostatic trap and strainer off the equalizer of each boiler from 2 to 4 inches above the water line. Connect the trap outlet to
the condensate receiver. The trap will prevent an idle boiler from flooding due to condensed steam from the system.
3c Piping  multiple steam boilers
1
2
3
4
5
6
7
8
9
10
11
186-20
Hartford
loop
detail
6
6
8
8
11
11 10
10
To feed pump
To feed pump
5
3
9
9
4
Water line
Water line
Hartford loop tee
Use only close nipple
or street ell here.
Floor line
Boiler
Header
Steam
supply
24"
min
4"
33 7/16"
2 to 4"
To
trap