Weil-McLain 550-141-829/1201 User manual

Installer: • Make sure this is the correct manual for the boiler. Verify boiler model on
rating label.
• Leave all documentation received with boiler and burner with unit for
future reference.
User: Boiler and burner must be installed and serviced by qualified service technician.
Part No. 550-141-829/1201
SGO SERIES 3 OIL-FIRED NATURAL DRAFT STEAM BOILER
This Manual
Includes:
Installation
Start-Up
Boiler Parts

2
Hazard Definitions
The following terms are used to bring attention to the presence of hazards of various risk levels or to
important information concerning product life.
Indicates presence of hazards that will cause severe personal injury, death or substantial
property damage if ignored.
Indicates presence of hazards that can cause severe personal injury, death or substantial
property damage if ignored.
Indicates presence of hazards that will or can cause minor personal injury or property
damage if ignored.
Indicates special instructions on installation, operation, or maintenance that are
important but not related to personal injury hazards.
Symbol Definitions
The following symbols are used to indicate sequence of installation for:
Factory-assembled packaged boiler—block, jacket and controls. Sizes 3
through 6 only.
Factory-assembled block, no burner. Sizes 3 through 6 with jacket installed; steam trim controls
shipped separately. Sizes 7 through 9 with jacket and steam trim controls shipped separately.
When Calling or Writing About the Boiler
Please have boiler model number and series from boiler rating label and CP number(s) from boiler jacket,
burner and controls. On page 26 of this manual is space to list CP number(s).
Read This Page First

3
Read all instructions before installing. Failure to follow all instructions in proper order
can cause severe personal injury, death or substantial property damage.
Read This Page First . . . . . . . . . . . . . . . . . . . . . . . . .2
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Before Installing Boiler . . . . . . . . . . . . . . . . . . . . . .4-5
Install Packaged Boiler . . . . . . . . . . . . . . . . . . . . . . .6-7
Install Non-Packaged Boiler . . . . . . . . . . . . . . . . . . .7-11
Connect Breeching . . . . . . . . . . . . . . . . . . . . . . . . . .12-13
Connect Steam Piping . . . . . . . . . . . . . . . . . . . . . . .14-17
Connect Tankless Heater Piping . . . . . . . . . . . . . . .18
Connect Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-23
Connect Oil Piping . . . . . . . . . . . . . . . . . . . . . . . . . .24
Start-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Check-Out Procedure . . . . . . . . . . . . . . . . . . . . . . .26
Installation and Service Certificate . . . . . . . . . . . . .26
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Parts Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30-31
Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Back Cover
Table of Contents

Recommended Service Clearances
FIGURE 1
Installations must comply with:
• U.S.
— State and local plumbing, heating and
electrical codes.
— National codes where applicable.
• Canada
— Canadian Standards Association,
CSA B139, Installation Code for
Oil-Burning Equipment.
— CSA C22.1 Canadian Electrical Code Part One.
— Applicable local or provincial codes.
Before selecting boiler location:
• Check for nearby connections to:
— System water piping.
— Chimney. See pages 12-13. Boiler can be
top or back vented.
— Combustion and ventilation air supply. See
page 5.
— Oil supply. See page 24 for oil line routing.
— Electrical power.
• Check area around boiler. Remove any
combustible materials, gasoline and other
flammable liquids.
Failure to keep boiler area
clear and free of combustible
materials, gasoline and other flammable
liquids and vapors can result in severe
personal injury, death or substantial
property damage.
Provide clearances around boiler
(see FIGURE 1):
Jacket cap must be in place on
boiler to avoid requiring an 18"
minimum clearance from back or top of boiler to
combustible material.
•Minimum clearances from vent pipe to
combustible material:
6 inches — Type “L” doublewall vent*
18 inches — Singlewall vent*
Flue pipe clearances must take
precedence over jacket clearances.
• Recommended service clearances:
24 inches — Front and top
6 inches — Left side**, back and right side Δ
15 inches — Left side with tankless heater**
12 inches — Right side for burner door
swing radius Δ
4
Before Installing Boiler

Provide air for combustion and ventilation:
Adequate combustion and
ventilation air:
• Assures proper combustion.
• Reduces risk of severe personal injury or death
from possible flue gas leakage and carbon
monoxide emissions.
Do not install exhaust fan in boiler room.
Older buildings with single-pane windows,
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.
Follow state, provincial or local codes when sizing
adequate combustion and ventilation air openings.
In absence of codes, use the following guidelines
when boiler is in a confined room (defined by NFPA
31 as less than 7200 cubic feet per 1 GPH input of
all appliances in area. A room 8 ft. high x 33.5 ft. x
33.5 ft. is 7200 cu. ft.):
Provide two permanent openings — one within 12
inches of ceiling, one within 12 inches of floor.
Minimum height or length dimension of each
rectangular opening should be at least 3 inches.
When inside air is used — each opening must
freely connect with areas having adequate
infiltration from outside. Each opening should be at
least 140 sq. in. per 1 GPH input (1 sq. in. per 1000
Btu input) of all fuel-burning appliances plus
requirements for any equipment that can pull air
from room (including clothes dryer and fireplace).
When outside air is used — connect each
opening directly or by ducts to the outdoors or to
crawl or attic space that freely connects with
outdoors. Size per below:
• Through outside wall or vertical ducts — at least
35 sq. in. per 1 GPH input (1 sq. in. per 4000 Btu
input) of all fuel burning appliances plus
requirements for any equipment that can pull
air from room (including clothes dryer
and fireplace).
• Through horizontal ducts — at least 70 sq. in. per
1 GPH boiler input (1 sq. in. per 2000 Btu
input) of all fuel-burning appliances plus
requirements for any equipment that can pull
air from room (including clothes dryer
and fireplace).
• Where ducts are used, they should have same
cross-sectional area as free area of openings to
which they connect. Compensate for louver,
grille or screen blockage when calculating free
air openings. Refer to their manufacturer’s
instructions for details. If unknown, use:
— Wood louvers, which provide 20-25% free air.
— Metal louvers or grilles, which provide
60-75% free air.
Lock louvers in open position or interlock with
equipment to prove open before boiler operation.
Lay a foundation, if needed:
Boiler may be installed on non-carpeted
combustible flooring.
For residential garage installation, install boiler so
burner is at least 18 inches above floor to avoid
contact with gasoline fumes.
A level concrete or masonry foundation is
required when:
• Floor could possibly become flooded.
• Non-level conditions exist.
Solid concrete blocks can be used to create a pad.
5
Before Installing Boiler CONTINUED
Go to page 7
to install boiler
Go to page 6
to install boiler
BOILER FOUNDATION SIZE TABLE
MIN.
BOILER LENGTH WIDTH HEIGHT
MODEL INCHES INCHES INCHES
SGO-3 17 22 2
SGO-4 20 22 2
SGO-5 23 22 2
SGO-6 26 22 2
SGO-7 29 22 2
SGO-8 32 22 2
SGO-9 35 22 2

Place boiler:
1. Remove boiler from pallet.
Do not drop boiler or bump
jacket on floor or pallet.
Damage to boiler can result.
Smaller sized boilers may be
top heavy. Use caution when
handling to avoid minor personal injury or
property damage.
2. Boiler is shipped for back flue outlet. To
change to top flue outlet (see FIGURE 2):
a. Remove jacket cap on top of boiler.
b. Loosen two screws holding flue cap strap
to collector hood. Remove strap and flue
cap from opening. Re-tighten screws.
c. Check rope placement inside flue cap.
(Read under step #5 below).
d. Loosen two screws on back flue outlet. Set
flue cap on outlet. Install strap by engaging
slots in screws. Tighten screws. Make sure
cap is securely installed.
e. Snap jacket cap in back outlet opening.
Jacket cap must be in place
on boiler to avoid requiring
an 18" minimum clearance from back of
boiler to combustible material.
3. Check level. Shim legs, if needed.
4. Check for secure placement of insulation on
target wall, chamber floor and burner door.
5. Visually check:
a. Flue collector hood seal.
b. Burner mounting door seal.
Obtain gas-tight seal to
prevent possible flue gas
leakage and carbon monoxide emissions,
which can lead to severe personal injury
or death.
Tankless heater, if used:
1. Remove tankless heater knockout in left side of
jacket panel and, for SGO-6 only, tankless
heater control knockout.
2. Remove tankless heater cover plate and gasket.
3. Install new gasket and tankless heater over
studs around opening. Secure with 3
/8" nuts.
4. Install tankless heater operating control
where shown on page 18. If not furnished,
use operating control with maximum
10°F differential.
Perform hydrostatic pressure test:
1. Remove steam pressure gauge furnished with
boiler. Install water pressure gauge for test
only. Be sure gauge can handle test pressure.
2. Install air vent in tapping on top of boiler.
3. Remove pressure control and low water cutoff.
Plug tappings.
4. Plug supply and return tappings.
5. Drain valve is already factory-installed.
6. Fill boiler. Vent all air. Pressure test boiler at
45-55 psig.
Do not leave boiler unattended.
Cold water fill can expand and
damage cast iron, resulting in severe personal
injury, death or substantial property damage.
7. Check for maintained gauge pressure for more
than 10 minutes. Visually check for leaks if
gauge pressure drops.
8. Drain boiler. Repair leaks if found.
Using petroleum-based
compounds to repair leaks can
damage system components, resulting in
property damage.
9. Retest boiler after repairing leaks.
10. Remove pressure gauge, air vent and plugs.
Re-install steam pressure gauge, pressure control
and low water cutoff furnished with boiler.
6
Go to page 12 to connect
breeching and venting
Install Packaged Boiler

Fiberglass wool and ceramic fiber materials:
• POSSIBLE CANCER HAZARD
BY INHALATION
• CAN CAUSE RESPIRATORY,
SKIN AND EYE IRRITATION
This product contains fiberglass wool and ceramic
fiber materials. Airborne fibers from these materials
have been listed by the State of California as a
possible cause of cancer through inhalation. Apply
special care when handling ceramic fiber (chamber
lining and base insulation) materials. Ceramic fibers
can be converted to chrystobalites, a substance listed
as a probable cause of cancer.
Suppliers of fiberglass wool products recommend
the following precautions be taken when handling
these materials:
Precautionary measures:
• Avoid breathing fiberglass dust and contact
with skin and eyes.
• Use NIOSH approved dust/mist respirator.
• Wear long-sleeved, loose fitting clothing, gloves
and eye protection.
• Wash work clothes separately from other
clothing. Rinse washer thoroughly.
• Operations such as sawing, blowing, tearout
and spraying may generate airborne fiber
concentration requiring additional protection.
First aid measures:
• Eye contact — Flush eyes with water to
remove dust. If symptoms persist, seek
medical attention.
• Skin contact — Wash affected areas gently
with soap and warm water after handling.
7
Install Packaged Boiler CONTINUED
Install Non-Packaged Boiler
Change From Back Flue Outlet to Top Flue Outlet (Optional)
FIGURE 2

Place boiler:
1. Non-Packaged SGO-3 through 6 — position on site.
Smaller sized boilers may be
top heavy. Use caution when
handling to avoid minor personal injury or
property damage.
a. Boiler is shipped for back flue outlet. To
change to top flue outlet (see FIGURE 3):
1) Loosen two screws holding flue cap strap
to collector hood. Remove strap and flue
cap from opening. Re-tighten screws.
2) Check rope placement inside flue cap.
(Read under step #3 at right).
3) Loosen two screws on back flue outlet.
Set flue cap on outlet. Install strap by
engaging slots in screws. Tighten screws.
Make sure cap is securely installed.
2. Non-Packaged SGO-7, 8 & 9 — split the
assembled block for easier handling (see
FIGURE 3):
a. Open burner mounting door and using
utility knife, slit floor insulation at joint to
be separated.
b. Remove 5½" draw rod and the longest draw
rod from each side. Pull block apart. Save
draw rods, nuts, washers and sealing rings
for reassembly.
c. Move divided block to location.
d. Clean port openings with clean rag.
Do not use petroleum-based
compounds to clean
openings. Damage to system components
can result causing property damage.
e. Place rings in port openings. If ring slips
out of groove, stretch ring gently for several
seconds, then place in groove.
f. Position sections so aligning lugs fit into
sockets of next section. Make sure sealing
rope is in good condition and in position.
g. Oil threads on draw rods. Install
washer and nut on end to be tightened.
Use nut only on other end.
h. With wrench at washer/nut end, uniformly
tighten nuts starting with 5½" rod at large port,
5½" rod at small port, bottom long rod and
finally top long rod.
i. Torque on both 5½" rods and bottom long
rod should be 50-60 ft. lbs; long top rod
should be 20-25 ft. lbs. Do not
back-off nuts.
j. Metal-to-metal contact should be made
around port openings. If gap does exist, it
should be less than .020". Check with
feeler gauge.
k. If gap around port openings exceeds .020",
check for dirt on port openings, sockets or
misaligned lugs. If corrections are made
and gap still exists, contact your Weil-
McLain distributor or sales office before
continuing installation.
3. Non-Packaged SGO-7, 8 & 9 — install flue
collector hood (see FIGURE 3):
Obtain gas-tight seal to prevent
possible flue gas leakage and
carbon monoxide emissions, leading to severe
personal injury or death.
a. Thread tinnerman clip on screw so that clip
fits snugly in notch of hold-down lug. Screw
must not turn.
b. Remove paper on sealing rope. Starting at
back section near flue collar, position sealing
rope around top of block with adhesive side
to sections. Do not stretch rope. Make sure
rope ends meet. Trim excess rope.
c. Position flue collector hood on top of boiler
sections and over screws and clips as
shown in FIGURE 3.
d. Install washers and nuts. Tighten nuts
until collector hood makes contact with
tinnerman clip.
e. Back flue outlet boiler — Position flue cap
and strap over opening in flue collector
hood. Make sure rope in cap is in place
and in good condition. Tighten strap to
hood with screws provided.
Top flue outlet boiler — Position flue cap
and strap over opening in back section.
Make sure rope in cap is in place and in
good condition. Tighten strap to boiler with
screws provided in section. Install remaining
screws in holes in flue collector hood.
4. Check level. Shim legs, if needed.
8
Install Non-Packaged Boiler CONTINUED

Install Non-Packaged Boiler CONTINUED

Install burner (also refer to instructions
packed with burner):
Burners designed for use with
Weil-McLain 68 boilers must not be
used on GOLD Oil boilers. Contact individual burner
manufacturers for GOLD Oil applications.
For P-SGO and A-SGO boiler:
1. Secure universal mounting flange and gasket to
burner mounting door. Use three bolts provided.
2. Secure burner on flange with three bolts.
3. Position burner so end of air tube is level to
1½° tilt down toward chamber. Open door to
verify burner position. End of air tube should be
flush to ¼" recessed from inside wall of burner
door refractory. Check for secure placement of
insulation on target wall, chamber floor and
burner mounting door. Securely close door.
Install Packaged and Non-Packaged Boiler

Install Packaged and Non-Packaged Boiler

General chimney requirements:
• Designed for natural draft firing. Connect
boiler to vertical chimney.
Insufficient draft can cause flue
gas leakage and carbon
monoxide emissions, which will lead to severe
personal injury or death.
• Use vent material approved by local codes for
oil-fired burners. In their absence, refer to:
— NFPA 31, Installation of Oil-Burning Equipment.
— NFPA 211, Standard for Chimneys,
Fireplaces, Vents and Solid Fuel
Burning Appliances.
— In Canada, refer to CSA B139, Installation
Code for Oil-Burning Equipment.
• NFPA 211 requires chimney to be lined before
connected to boiler.
Inspect existing chimney before
installing new boiler. Failure to
do any of the following will result in severe
personal injury or death:
— Clean chimney, including removal of blockage.
— Repair or replace damaged pipe or liner.
— Repair mortar and joints.
To prevent downdrafts, extend chimney at
least 3 feet above highest point where it passes
through roof and 2 feet higher than any
portion of building within 10 feet. Increase
chimney cross-sectional area and height at
least 4% per 1,000 feet above sea level.
• Minimum clearances from vent pipe to
combustible material:
6 inches — Type “L” doublewall vent
18 inches — Singlewall vent
• Minimum chimney sizes should be used.
Oversized chimneys, outside
masonry chimneys and/or
derated inputs can result in condensation
in chimney.
Connect breeching:
Long horizontal breechings,
excessive number of tees and
elbows, or other obstructions restricting combustion
gas flow can result in possibility of condensation,
flue gas leakage and carbon monoxide emissions,
which can lead to severe personal injury or death.
1. Install 2 flue pipe brackets.
2. Connect full-sized breeching when possible.
See Minimum Chimney Size Table.
— Back outlet — see FIGURE 7.
— Top outlet — see FIGURE 8.
3. Connection must be made above bottom of
chimney to avoid blockage. Breeching must not
enter chimney far enough to cause obstruction.
Use thimble or slip joint where breeching enters
chimney to allow removal for cleaning.
4. When burner and boiler are properly installed,
draft overfire will be approximately -0.01"
to -0.02" W.C. Install barometric control in
breeching, per control manufacturer's
instructions, when excess draft needs to be
relieved or to comply with applicable codes
and regulations. Use draft gauge to adjust
proper opening.
5. An induced draft fan for the chimney may be
necessary if:
— Excessive resistance to flow of combustion
gases can be expected.
— Cross-sectional area of chimney is smaller
than minimum recommended.
— Chimney height is less than recommended.
Seal all vent joints. Interlock burner with
fan operation.
12
Connect Breeching
MINIMUM CHIMNEY SIZE TABLE
SGO-3 5" 8" x 8" 6" 15'
SGO-4 6" *
SGO-5 6"
SGO-6 7"
8" x 8" 7" 15'
SGO-7 *
SGO-8 7" 8" x 12" 7" 20'
SGO-9 * *
BOILER
MODEL
NUMBER
***
MINIMUM
BREECHING
DIAMETER
MINIMUM
I=B=R
CHIMNEY SIZE
RECT. ROUND
MINIMUM
CHIMNEY
HEIGHT
* 6¾" x 6¾" inside liner
** 6½" x 10½" inside liner
*** Flue collar on boiler is 7" diameter

Top Outlet Breeching Connection
FIGURE 8
Connect Breeching CONTINUED
Back Outlet Breeching Connection
FIGURE 7
13

General piping information:
• Hartford Loop piping arrangement and wet
return are required for steam boilers.
• Maintain 24-inch minimum from waterline to
bottom of header (minimum 507/8" from floor
or top of foundation).
• When using condensate receiver, feed pump
must be energized by boiler-mounted
pump control.
• Use swing joints in steam piping.
• If installation is to comply with ASME or
Canadian requirements, an additional pressure
limit control is needed. Install control between
existing pressure control and pressure gauge.
Control must be installed with siphon
(supplied with boiler) between control and
boiler. Set control to minimum of 5 psi above
setpoint of existing control and maximum
setting of 15 psi. Wire as shown on boiler
wiring diagram.
Install piping:
1. See Tables at right and FIGURE 9 on page 15
or FIGURE 10 on page 16.
Improperly piped systems or
undersized piping can
contribute to erratic boiler operation and
possible boiler or system damage. Piping
system must be installed as shown, using
minimum pipe sizes shown. Consult your
Weil-McLain distributor or sales office before
installing alternate piping.
2. Install relief valve vertically in “R” tapping on
back of boiler. See FIGURE 9 or 10 and also
refer to tag attached to relief valve for
manufacturer’s instructions.
Pipe relief valve discharge line
near floor close to floor drain to
eliminate potential of severe burns. Do not
pipe to any area where freezing could occur.
Do not plug, valve or place any obstruction in
discharge line.
3. Float-type low water cutoff only — install
blowdown line in bottom of cutoff. See
FIGURE 9 or 10 and also refer to low water
cutoff manufacturer’s instructions for details.
Pipe blowdown line near floor
close to floor drain to eliminate
potential of severe burns. Do not pipe to any
area where freezing could occur. Do not plug,
valve or place any obstruction in discharge line.
* Based on ASHRAE Fundamentals Handbook recommendations, allowing
½oz. pressure drop at 0 psig.
** Based on ASHRAE Fundamentals Handbook recommendations, allowing
2 oz. pressure drop per 100 feet of pipe at 3.5 psig. Maintain minimum
24" height from waterline to bottom of header.
Can be reduced to 2".
14
Connect Steam Piping
STEAM PIPING SIZE TABLE
FOR ONE AND TWO-PIPE SYSTEMS
SGO-3 2½" — 2½" 1½"
SGO-4 2½" — 2½" 1½"
SGO-5 2½" — 3" 1½"
SGO-6 2½" 2½" 3" 1½"
SGO-7 2½" 2½" 3" 1½"
SGO-8 2½" 2½" 3" 1½"
SGO-9 2½" 2½" 3" 1½"
BOILER
MODEL
NUMBER
HEADER
PIPE
SIZE
“H” * *
RISER
PIPE SIZE *
AB
EQUALIZER
PIPE SIZE
“J”
STEAM PIPING SIZE TABLE
FOR ONE-PIPE COUNTERFLOW SYSTEMS
SGO-3 2½" — 2½" 1½"
SGO-4 2½" — 2½" 1½"
SGO-5 2½" — 3" 1½"
SGO-6 2½" 2½" 4" 1½"
SGO-7 2½" 2½" 4" 1½"
SGO-8 2½" 2½" 4" 1½"
SGO-9 2½" 2½" 4" 1½"
BOILER
MODEL
NUMBER
HEADER
PIPE
SIZE
“H” * *
RISER
PIPE SIZE *
AB
EQUALIZER
PIPE SIZE
“J”

Connect Steam Piping CONTINUED

Connect Steam Piping CONTINUED

Optional reservoir piping:
Modern steam boilers are designed to steam for
less time than older, larger boilers. When replacing
an older steam boiler, the system condensate
return time may be longer than the steaming time.
This can cause the following problems:
• Boilers fitted with an automatic water feed
could overfill.
• Units fitted with only a low water cutoff would
shut down and cycle while waiting for
condensate to return.
To size and install reservoir piping, see FIGURE 11
and Bulletin AE-8403 (available through your
Weil-McLain distributor or sales office):
1. Pipe boiler as shown on pages 14 through 16.
2. Use 8" diameter reservoir pipe.
3. Locate centerline of reservoir pipe 1" below
267
/8" boiler waterline.
Connect Steam Piping CONTINUED
CONDENSATE RECEIVER CAPACITY TABLE
MINIMUM CONDENSATE RECEIVER CAPACITY – GAL.
RECOMMENDED
I=B=R GROSS CONDENSATE
OUTPUT GALLONS 15 MIN.* 30 MIN.* 45 MIN.* 60 MIN.* FEED PUMPING RATE
BOILER LBS STEAM CONDENSATE BOILER BOILER BOILER BOILER GPM
MODEL PER HOUR PER HOUR OPERATION OPERATION OPERATION OPERATION AT 15 PSI
SGO-3 114 14 4 8 12 16 0.5
SGO-4 150 18 5 11 16 22 0.6
SGO-5 180 22 6 13 19 26 0.7
SGO-6 216 26 8 16 23 31 0.9
SGO-7 246 30 9 18 27 35 1.0
SGO-8 274 33 10 20 30 39 1.1
SGO-9 303 36 11 22 33 44 1.2
* Maximum time to when condensate returns to boiler.

Hot Water Can Scald!
• Consumer Product Safety Commission and
some states recommend domestic hot water
temperature of 130°F or less.
• When installing an automatic mixing valve,
selection and installation must comply with
valve manufacturer’s recommendations
and instructions.
• Water heated to a temperature suitable for
clothes washing, dish washing and other
sanitizing needs will scald and cause injury.
• Children and elderly, infirm or physically
handicapped persons are more likely to be
injured by hot water. Never leave them
unattended in or near a bathtub, shower or
sink. Never allow small children to use a hot
water faucet or draw their own bath. If anyone
using hot water in the building fits this
description, or if state laws or local codes
require certain water temperatures at hot
water faucets, take special precautions:
— Install automatic mixing valve set
according to those standards.
— Use lowest practical temperature setting.
— Check water temperature immediately after
first heating cycle and after any adjustment.
Studies have indicated that
dangerous bacteria can form in
potable water distribution systems if certain
minimum water temperatures are not
maintained. Contact local health department
for more information.
To pipe tankless heater:
1. Size piping no smaller than tankless heater
inlet and outlet.
2. Following controls (furnished by others) must
be installed:
a. Automatic mixing valve. See FIGURE 12.
(Read at left.)
b. Flow regulating valve. Size according to
intermittent draw of tankless heater. See
Table below. Follow valve manufacturer’s
instructions to install.
3. Additional anti-scald devices may be
installed at each hot water faucet, bath and
shower outlet.
4. In hard water areas, soften cold domestic supply
water to heaters to prevent lime build-up.
* To avoid supplying steam to system during summer tankless operation,
raise water level to one inch above normal water line.
* * Gallons of water per minute heated from 40°F to 140°F with 200°F
boiler water temperature. Tested in accordance with I=W=H Testing and
Rating Standard for Indirect Tankless Water Heaters Tested with Boilers.
Connect Tankless Heater Piping
TANKLESS HEATER RATINGS TABLE
SGO-3 35-S-29 3.25 ¾"
SGO-4 35-S-29 3.50 ¾"
SGO-5 35-S-29 3.75 ¾"
SGO-6 35-S-29 4.00 ¾"
SGO-7 35-S-29 4.00 ¾"
SGO-8 35-S-29 4.00 ¾"
SGO-9 35-S-29 4.00 ¾"
BOILER
MODEL
NUMBER *
INTERMITTENT
DRAW RATINGS
(GPM) * *
HEATER
NUMBER
INLET
AND OUTLET
TAPPING SIZES

General wiring requirements:
Electric shock hazard. Can cause
severe personal injury or death if
power source, including service switch on boiler, is
not disconnected before installing or servicing.
• Installations must follow these codes:
—National Electrical Code, ANSI/NFPA 70,
latest edition and any additional national,
state or local codes.
— In Canada, CSA C22.1 Canadian Electrical
Code Part One and any local codes.
• Wiring must be N.E.C. Class 1. If original wire
as supplied with boiler must be replaced, type
105°C wire or equivalent must be used. Supply
wiring to boiler and additional control wiring
must be 14 ga. or heavier.
• Provide electrical ground at boiler as required
by codes.
Thermostat wiring:
• Install thermostat on inside wall away from
influences of drafts, hot or cold water pipes,
lighting fixtures, television, sun rays or
fireplaces.
• Follow instructions with thermostat. If it has a
heat anticipator, set heat anticipator in
thermostat to match power requirements of
equipment connected to it. Boiler wiring
diagrams give setting for standard equipment.
Junction box (furnished):
• Junction box houses electrical connections for
all boiler components.
• “P” boilers have harnesses furnished.
• “A” boilers are furnished with burner and limit
harnesses.
• All field-provided high voltage wiring must be
sheathed in flexible metal conduit.
• Connect incoming line voltage “HOT” wire to
service switch, and neutral wire to white wire.
Field-install equipment ground wire to green
wire with wire nut.
• Service switch (15 amp) is provided with boiler.
“A” boilers — install switch as shown.
• Some local codes may require an emergency
shut-off switch installed at a location away
from boiler. Follow local codes.
Burner wiring:
• Burner harness incorporates a disconnect
plug, providing a convenient way to disconnect
wiring when burner mounting door is opened.
• All “P” boilers have a power disconnect plug
installed on burner.
• On “A” boilers, mount the plug (provided in
steam trim carton) on the burner housing as
shown in FIGURE 13 or 14. For Carlin
burners, screw burner plug into threaded
conduit coupling, then mount this assembly to
the burner housing using the chase nipple.
Route wires through housing and make
connections in burner junction box as shown
in boiler wiring diagram.
19
Connect Wiring
To wire boilers, refer to the following pages:
Pages 20 to 21 Float-Type LWCO
Pages 22 to 23 Probe-Type LWCO

20
Connect Wiring CONTINUED