Weil-McLain UltraOil User manual

Part number 550-141-986/1005
• Installation
• Startup
This manual must only be used by a qualified heating installer/service technician. Before installing,read all instructions,
including this manual, the burner manual and any related supplements. Perform steps in the order given. Failure to
comply could result in severe personal injury, death or substantial property damage.
Oil-Fired Water Boiler
• Maintenance
• Parts
Boiler Manual

Part number 550-141-986/1005
water boiler — Boiler Manual
2
The waTer boiler – how iT works . . .
1. Weil-McLain logo plate (standard) or
Remote Display Module (optional)
The Remote Display Module (RDM) is used when the optional
AFM (item 28) is installed. The display shows boiler and system
status and is used to adjust operating parameters.
2. ON/OFF switch
3. Control Pod cover fastener
4. Pressure/Temperature gauge
Displays boiler water pressure and outlet water temperature.
5. Jacket top rear panel
6. Control Pod cover
The Control Pod cover is hinged to allow easy access
to the aquastat, boiler wiring and optional Advanced Features
Module (AFM).
7. Jacket side panels
jacket side panels are interchangeable.
8. Jacket rear panel, with insulation
9. Terminal strip
Electrical connections, both line and low voltage, connect to the
terminal strip.
10. Front section
11. Intermediate sections
12. Back section
13. EnviraCOM®wire harness
Low voltage wire harness from L7248 aquastat to the Honeywell
burner primary control’s EnviraCOM® connector — a commu-
nications port designed to optionally allow you to add greater
system capability at the time of installation. Examples include
test instruments and dial-in access and, in the future, efficiency
optimization, zoning, and sequencers. Look for products with
the Honeywell EnviraCOM® name indicating products that are
compatible with your new boiler.
14. Burner wire harness
Line voltage wiring to burner, terminated in a Molex connector in
the jacket crosstie (item 19). An additional harness connects from
the crosstie connector to the burner.
15. Burner door hinge bracket
The hinge bracket can be installed on either side to allow for right
or left-hand swing.
16. Swing-away burner door
The burner door is hinged to provide easy access to the
boiler heat exchanger for inspection and cleaning.
17. Rotating observation port
The observation port is designed to prevent soot from
depositing on the sight glass. During normal operation the sight
glass is located at the 12:00 position. To view the burner flame,
loosen the center mounting bolt and rotate so the sight glass is
in the 6:00 position.
18. Overfire pressure tapping
1/8” npt, with plug.
19. Jacket crosstie
20. Sensor wells
Boiler aquastat sensor and P/T gauge capillary and temperature
sensor are installed in the top of the rear section.
21. Outlet tapping
The boiler outlet water tapping is located in the top of the rear
section.
22. Return tapping
The boiler return tapping is located in the bottom of the rear
section.
23. Insulation blanket
24. Boiler drain valve
25. Flue connection
boilers can be chimney or direct vented from the rear
flue opening.
26. Knockouts in jacket rear for electrical conduits
All electrical connections enter in conduits connected to these
knockouts.
27. Boiler relief valve
28. AFM (Advanced Features Module) — Optional
The boiler can be equipped with the Advanced Features
Module (AFM). The AFM is a system control that provides boiler
outdoor reset, a boiler setpoint temperature, domestic hot water
pump operation, and outdoor reset through the use of a mixing
valve or a variable speed injection pump. It also controls staging
and rotation of two boilers.
When equipped with an AFM, the boiler requires a 20-amp
service.
29. Electronic Aquastat
The boiler is equipped with a Honeywell L7248 electronic
aquastat. The L7248 senses boiler water temperature and call for
heat from the system thermostat or AFM to operate the burner
and boiler circulator.
30. Burner, with cover
31. Jacket front panel
32. Leveling legs

Part number 550-141-986/1005 3
water boiler — Boiler Manual
The waTer boiler

Part number 550-141-986/1005
water boiler — Boiler Manual
4
Commonwealth of Massachusetts
When the boiler is installed within the Common-
wealth of Massachusetts:
• This product must be installed by a licensed
plumber.
• If antifreeze is used, a reduced pressure back-
flow preventer device shall be used.
Contents
The waTer boiler — how iT works ......................................2–3
Please read before proceeding ...........................................................5
Boiler location checklist ......................................................................6
Prepare boiler location.........................................................................7
Connect breeching .............................................................................11
Connect water piping.........................................................................13
Connect wiring (Note 1).........................................................................18
Connect oil piping .............................................................................21
Startup procedure ..............................................................................22
Check-out procedure .........................................................................23
Annual service and start-up ..............................................................24
Appendix (removing/replacing boiler jacket, replacement parts,
dimensions and ratings)..................................................................... 29
Note 1: See burner manual for wiring and additional startup and operating information. Also
see AFM manual if used.
When calling or writing about the boil-
er— Please have the boiler model number
from the boiler rating label and the CP
number from the boiler jacket. You may
list the CP number in the space provided
on the Installation Certificate found on
page 23.
Consider piping and installation when
determining boiler location.
Any claims for damage or shortage in
shipment must be filed immediately
against the transportation company by
the consignee.
The terms below 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 ormaintenancethatareimportant
butnotrelatedtopersonalinjury orproperty
damage.

Part number 550-141-986/1005 5
water boiler — Boiler Manual
Please read before proceeding
Read all instructions —
• Read all instructions, including this manual, the burner
manual and any related supplements. Perform steps in
the order given. Failure to comply could result in severe
personal injury, death or substantial property damage.
When servicing boiler —
• To avoid electric shock, disconnect electrical supply before
performing maintenance.
• To avoid severe burns, allow boiler to cool before perform-
ing maintenance.
Boiler operation —
• Do not block flow of combustion or ventilation air to
burner.
• Should overheating occur or fuel supply fail to shut off, do
not turn off or disconnect electrical supply to circulator.
Instead, shut off the fuel supply at a location external to
the appliance.
• Do not use this boiler if any part has been under water.
Electrical and mechanical failures may cause electric
shock and fire risks. Immediately inspect chimney or vent,
boiler, burner and controls.Clean the boiler flueways and
replace all electrical and mechanical controls; all electrical
wiring; oil burner and controls; insulation and chamber
lining.
Boiler firing rate —
• Do not reduce the firing rate of the boiler. Use only the oil
nozzle size specified. Reduced input will cause condensa-
tion in the boiler and vent piping.
Ceramic fiber materials —
• The boiler contains ceramic fiber materials. Use care
when handling these materials per instructions on
page 25 of this manual. Failure to comply could result
in severe personal injury.
Boiler water —
• Thoroughly flush the system (without boiler con-
nected) to remove sediment.The boiler heat exchanger
can be damaged by build-up or corrosion due to sedi-
ment.
• Do not use petroleum-based cleaning or sealing
compounds in boiler system. Gaskets and seals in the
system may be damaged. This can result in substantial
property damage.
• Do not use“homemade cures”or“boiler patent medi-
cines.” Serious damage to boiler, personnel and/or
property may result.
• Continual fresh make-up water will reduce boiler
life. Mineral buildup in boiler sections reduces heat
transfer, overheats the sections, and causes failure.
Addition of oxygen carried in by make-up water can
cause internal corrosion. Leaks in boiler or piping
must be repaired at once to prevent make-up water.
• Do not add cold water to hot boiler. Thermal shock
can cause heat exchanger to crack.
Freeze protection fluids —
• When using antifreeze — Do not use automotive,
ethylene glycol, undiluted or petroleum-based an-
tifreeze. See the WARNING on page 22 for more
information.
Follow the guidelines below to prevent possible severe personal injury, death or substantial property damage.
Follow the guidelines below to prevent severe personal injury, death or substantial property damage.
Fuel
• Do not use crankcase drainings or any oil containing
gasoline. See burner manual for proper fuel oil.
• Never burn garbage or paper in the boiler. Never leave
combustible material around boiler.
Do not tamper with burner/controls
• Always follow specific instructions when starting up
boiler or performing routine maintenance or service.
Do not start burner if:
• Do not attempt to start burner when excess oil has ac-
cumulated in combustion chamber, when unit is full of
vapor, or when combustion chamber is very hot.
• Do not start burner unless breeching and burner mount-
ing door are secured in place.

Part number 550-141-986/1005
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Boiler location checklist
Before placing the boiler, verify:
❏
United States installations must
comply with all applicable U. S.
codes:
• Applicable state, local and national codes.
• National Electrical Code.
• Standard for Controls and Safety Devices for Automatically Fired Boilers, ANSI/
ASME CSD-1, when required.
Canadian installations must
comply with all applicable Cana-
dian codes:
• Canadian Standards Association CSA B139, Installation Code for Oil-Burning Equip-
ment.
• CSA C22.1 Canadian Electrical Code Part One.
• Applicable provincial and local codes.
❏Consider use of space
• The boiler area must be kept free of combustible materials, gasoline and other flam-
mable liquids.
• The boiler must be installed so that boiler and system components are protected from
dripping or spraying water or rain during operation or service.
❏Moving boiler to location
• See manual pages 38 and 39 for boiler dimensions and weights.
• If necessary, the boiler jacket can be removed if desired for handling. See manual
pages 30 and 31 for instructions.
❏Clearances
• Provide minimum clearances to combustible materials and for servicing boiler.
• Ensure that the swing-away burner door can swing open freely. (The hinge can be
mounted on right or left side.)
• See manual page 10 for instructions on changing door hinge location.
❏Flooring and foundation
• Provide level flooring (non-carpeted combustible flooring is acceptable if boiler level-
ing legs are installed).
• Provide foundation if necessary.
• See manual page 8.
❏Combustion and ventilation air
openings
• Boiler room must provide adequate combustion air and ventilation.
• Unless burner uses ducted outside air for combustion, the boiler room must provide
combustion air openings.
• See manual page 8.
❏Venting
Chimney venting:
• Ensure the vent pipe can be routed to the chimney, and that the chimney connection
is higher than the boiler flue outlet.
• Ensure the vent piping will provide minimum clearances shown on manual pages 7
and 11.
• See manual pages 11 and 12 for venting information.
Direct venting:
• The Ultra oil boiler can be direct vented, using the Field Controls Direct Vent Kit,
model number FDVS-46, and vent pipe model number FVOP-415. Verify that the vent
piping can be installed and routed to the outside wall as specified in the Field Con-
trols instruction manual.
• Ensure the vent piping will provide minimum clearances shown on manual page 7.
❏System water piping
• Check location of system water piping connections to be sure boiler can be properly
connected.
• See manual pages 13 through 17.
❏Fuel supply • See manual page 21 for routing of fuel lines.
❏Electrical power
• The boiler requires 120 vac power and connection to a room thermostat or other
device to initiate call for heat.
• If equipped with an AFM, the boiler requires a 20-amp service.
• See manual pages 18 through 20.
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.
If the Ultra boiler will replace an existing boiler, check for and correct system problems, such as: • System leaks causing
oxygen corrosion or heat exchanger cracks from hard water deposits; • Incorrectly-sized expansion tank; • Lack of freeze
protection in boiler water causing system and boiler to freeze and leak. Failure to correct such conditions could result in failure of
the new boiler.

Part number 550-141-986/1005 7
water boiler — Boiler Manual
Prepare boiler location
Figure 1 Minimum clearances to combustible surfaces and
Provide minimum clearances
From combustible materials (see Figure 1)
1. Hot water pipes
• All directions — ½ inch.
(not shown in Figure 1)
2. Double-wall vent pipe
• All directions — 6 inches.
3. Single-wall vent pipe.
• All directions — 18 inches.
4. Boiler jacket surfaces
• Top of Control Pod cover — 12 inches.
• Sides and back — 2 inches.
5. Burner cover
• All directions — 2 inches.
Combustible clearances always take pre-
cedence over service clearances.
For service access (see Figure 1)
If you do not provide the minimum
service clearances shown, it might not
be possible to service the boiler without
removing it from the space.
1. Recommended service clearances:
• Front of burner cover — 20 inches
• Jacket top — 24 inches
• Jacket sides and back — 6 inches
• Burner door swing clearance — 15 inches minimum
(door must swing fully open)

Part number 550-141-986/1005
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Air openings for combustion and
ventilation air
Adequate combustion and ventilation air
ensures proper combustion and 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.
Natural infiltration
Older buildings with single-pane windows, minimal
weather-stripping and no vapor barrier often provide
enough natural infiltration and ventilation without
dedicated openings.
Tight construction
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 code requirements
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 appli-
ances in area. A room 8 ft. high x 33.5 ft. x 33.5 ft. is
7200 cu. ft.).
Provide two permanent openings
Provide two permanent openings — one within 12
inches of ceiling, one within 12 inches of floor. Mini-
mum height or length dimension of each rectangular
opening should be at least 3 inches.
Air from inside the building
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 equip-
ment that can pull air from room (including clothes
dryer and fireplace).
Air from outside the building
When outside air is used — connect each opening
directly or by ducts to the outdoors or to crawl or at-
tic 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 (includ-
ing 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 equip-
ment to prove open before boiler operation.
Flooring and foundation
Flooring
1. Install on any level, properly-supported, and non-
carpeted surface. Flooring may be combustible if
boiler leveling legs are installed.
2. Ensure the flooring is capable of handling the boiler
weight (see page 39 for weight and water volume).
Residential garage installations
Install boiler so the burner is at least 18 inches above the
floor to avoid contact with gasoline fumes.
Foundation
Provide a level concrete, masonry or cement block
foundation if the flooring could become flooded or is
not level. See Table 1 for foundation size required.
Table 1 Boiler foundation size (when req’d)
Model Length
(inches)
Width
(inches)
Height, min.
(inches)
UO-3 49 23 2
UO-4 53 23 2
UO-5 57 23 2
Prepare boiler location (continued)

Part number 550-141-986/1005 9
water boiler — Boiler Manual
Prepare boiler location (continued)
Place the boiler:
Remove outer crate
1. Remove outer crate, leaving boiler on the crate base.
2. Remove the circulator and barometric damper cartons from the crate
base.
3. UO-3 boilers only — Remove the two flue baffles fastened to the crate
base behind the boiler.
4. Remove the two shipping channels by loosening and removing the four
nuts. Save the shipping channels for leveling leg installation.
5. Remove the jacket crosstie fastened to the crate base.
Install the leveling legs if used (required if boiler is placed on
combustible flooring)
The leveling legs must be installed if the boiler is placed on
combustible flooring.
A second person, or other means, is required to stabilize the
boiler during leveling leg installation. Failure to do so could
result in severe personal injury or property damage.
Wear heavy leather work gloves when handling the shipping
channels in the following steps to avoid potential severe per-
sonal injury.
1. (Figure 2a) Use one channel as a lever to raise the front of the boiler.
2. (Figure 2a) Insert the other channel between the boiler leg and crate
base. Place the channel directly over the crate base runner, as shown.
3. (Figure 2b) Lift the channel under the boiler leg slightly.
4. (Figure 2b) Slide the other channel under the other boiler leg. Place the
channel directly over the crate base runner, as shown.
5. (Figure 3) With the boiler resting securely on the two shipping chan-
nels, screw a leveling leg in each boiler leg hole. Screw leveling legs in
completely.
To avoid potential personal injury or property damage, DO
NOT attempt to insert leveling legs unless the boiler is securely
seated on both shipping channels.
6. Reverse steps 1 through 4 above to remove the shipping channels. Leave
the boiler on the crate base.
7. Follow steps 1 through 6 on the back side of the boiler to install leveling
legs in the rear section legs.
8. Leave the boiler on the crate base.
Remove boiler from crate base
Boilers may be top heavy. Use caution when handling to avoid
personal injury or property damage.
1. Attach the crosstie to the jacket side panels using the two screws located
in the barometric damper carton.Then remove the boiler from the crate
base.
Do not remove the boiler from the crate base without first
installing the jacket crosstie. The boiler wiring harnesses or
connectors could be damaged.
2. If necessary, the boiler jacket can be removed for handling. See pages 30
and 31 in this manual for the jacket removal/replacement procedure.
Figure 2a To install leveling legs: Insert first
shipping channel under boiler leg.
Figure 3 Inserting levelling legs
Figure 2b To install leveling legs: Insert
second shipping channel under

Part number 550-141-986/1005
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Perform hydrostatic pressure test:
See pages 2 and 3 for boiler feature locations.
1. Install air vent in relief valve tapping.
2. Plug supply and return tappings.
3. Install the boiler drain valve shipped with boiler.
4. Fill boiler.
5. Vent all air.
6. Pressure test boiler at 1½ times working pressure.
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 at least 10 minutes. Visually
check for leaks if gauge pressure drops.
8. Drain boiler. Repair leaks if found.
Do not use petroleum-based sealing compounds to repair
leaks. Damage to system components can result, causing
property damage.
9. Retest boiler after repairing leaks.
10. Remove air vent and plugs. Install the relief valve (shipped in barometric
damper carton).
Boiler preparation
Changing door hinge
The boiler is shipped with the burner door hinged on the left side.The hinge
bracket can be relocated to the right side if desired. See Figure 4.
1. Remove jacket front panel.
2. Remove and retain burner door screws and washers used to fasten the
burner door to the front section (one on each side of door).
3. Carefully lift the burner door so the door pins lift out of the hinge
bracket.
4. Set the burner door aside temporarily.
The burner door is heavy. Handle carefully to avoid potential
for personal injury.
Do not damage the burner door insulation when handling.
5. The hinge bracket has keyhole slots. Loosen the two screws securing
the hinge bracket to the front section. Remove the hinge bracket.
6. Loosen the two screws on the opposite side. Place the hinge bracket on
that side and tighten the two screws to secure the bracket. Also tighten
the two screws on the other side.
7. Carefully lift the burner door and position so the door pins slide into
the hinge bracket holes. The lower pin is longer than the upper. So align
the lower pin, then the upper.
8. Replace burner door screws and washers used to fasten the burner door
to the front section (one on each side of door).
Flue baffles —
UO-3 ONLY – 1.0 GPH firing rate ONLY
On UO-3 boilers fired at 1.0 GPH ONLY, install the two flue baffles sup-
plied with the boiler. See page 33 for location.
Figure 4 Burner door hinge installation
Prepare boiler location (continued)
DO NOT install baffles on UO-3 boilers
fired at 0.8 GPH. Flue gas condensation
will result, causing corrosion damage to
boiler and vent system.
Combustion chamber floor blanket —
UO-3 ONLY – 0.8 GPH firing rate ONLY
On UO-3 boilers fired at 0.8 GPH ONLY, place the ce-
ramic fiber floor blanket (supplied in the UO-3 low
firing rate kit) on the floor of the combustion chamber.
See page 33 for location.
If the boiler has flue baffles installed, you
must remove the baffles before changing
to the low firing rate. Flue gas condensa-
tion will result, causing corrosion damage
to boiler and vent system.
Check chamber and burner door
1. Check for secure placement of insulation on burner
door.
2. UO-3,0.8 GPH firing rate ONLY — Check for secure
placement of combustion chamber floor blanket.
3. Visually check burner mounting door and observation
port seals.
Verify gas-tight seal to prevent possible
flue gas leakage and carbon monoxide
emissions, which can lead to severe per-
sonal injury or death.

Part number 550-141-986/1005 11
water boiler — Boiler Manual
Connect breeching
Direct venting
The Ultra Oil boiler can be direct vented using the Field
Controls Direct Vent Kit, model number FDVS-46, and
vent pipe model number FVOP-415. Vent lengths are
limited to 15 feet. Air intake lengths are limited to 22
feet of rigid 4-inch pipe. Do not use flexible dryer vent.
Refer to instructions provided with the vent kit for vent
and air piping installation procedures.
Chimney venting
General chimney requirements:
The Ultra Oil boiler is designed for natural draft firing.
Connect boiler to vertical chimney.
• NFPA 211 requires chimney to be lined before con-
necting to boiler.
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:
• Type “L” doublewall vent — 6 inches
• Single wall vent — 18 inches
• Minimum chimney sizes should be used.
Oversized chimneys, outside masonry
chimneys and/or derated inputs can result
in condensation in chimney.
Table 2 Chimney venting — vent sizing
Model
Minimum
breeching
diameter
(inches)
Minimum I=B=R
chimney size
(inches)
Minimum
chimney
height
(feet)
Rect. Round
UO-3 58 x 8
(6¾ x 6¾
liner)
6 15UO-4 6
UO-5 6
Note: boiler flue connection is 6-inch diameter
Install the burner
1. Secure the burner flange to the burner door using
the three bolts provided.
2. Check for secure placement of insulation and sealing
rope on the burner door.
Prepare boiler location (continued)
3. Close the burner door and secure in place with the
burner door screws and washers.
4. Follow the burner manual and boiler manual
(pages 19 to 21) to wire the burner and connect fuel
lines.
• 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.
Insufficient draft can cause flue gas
leakage and carbon monoxide emis-
sions,which will lead to severe personal
injury or death.
Inspect existing chimney before install-
ing 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.

Part number 550-141-986/1005
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12
Connect breeching (continued)
Figure 5 Breech connection, typical, for gravity venting into chimney
Chimney venting (continued)
Connect breeching:
Long horizontal breechings, excessive
number of tees and elbows or other ob-
structions restricting combustion gas flow
can result in possibility of condensation,
flue gas leakage and carbon monoxide
emissions, which can lead to severe per-
sonal injury or death.
1. Connect full-sized breeching when possible. See
Table 2, page 11, and Figure 5, below.
2. Connection must be made above bottom of chimney
to avoid blockage. Breeching must not enter chim-
ney far enough to cause obstruction.Use thimble or
slip joint where breeching enters chimney to allow
removal for cleaning.
3. When burner and boiler are properly installed,
breeching draft will be approximately -0.01” to
-0.02” W.C. Install barometric control in breech-
ing, 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.
The Ultra Oil boiler is capable of being
pressure fired. Overfire pressure may be
positive even with a negative pressure
in the chimney. See the Ratings table on
page 39 for boiler draft loss.
The pressure in the breeching and chim-
ney must always be negative unless the
chimney and breeching are constructed
of vent piping designed for pressurized
venting.
4. An induced draft fan for the chimney may be neces-
sary if:
• Excessive resistance to flow of combustion gases can
be expected.
• Cross-sectional area of chimney is smaller than mini-
mum recommended.
• Chimney height is less than recommended.
5. When using an induced draft fan:
• Seal all vent joints.
• Interlock burner with fan operation.

Part number 550-141-986/1005 13
water boiler — Boiler Manual
General piping information:
ASME or Canadian requirements
• If installation is to comply with ASME or Canadian
requirements, an additional high temperature limit
is needed. Install control in supply piping between
boiler and isolation valve. Set control to a minimum
of 20 °F above set point of the boiler aquastat. Maxi-
mum allowable set point is 220 °F. Wire control as
shown on wiring diagram (page 20).
Low water cutoff devices
• Use a low water cutoff device when:
• Boiler is installed above radiation level.
• Required by certain state or local codes or insurance
companies.
• Use a low water cutoff designed for water installa-
tions.
• Probe-type is recommended.
• Purchase and install in tee in supply line above
boiler. Wire per wiring diagram, page 20.
Backflow prevention
• Use backflow check valve in cold water supply as
required by local codes.
Install piping:
Pipe sizing
• See Table 3 for pipe sizing for near-boiler piping and
single-zone piping.
Near-boiler piping
(with diaphragm expansion tank)
• See Figure 6, page 14.
Near-boiler piping
(with closed expansion tank)
• See Figure 7, page 14.
Multiple-zone piping
• See page 15.
Low-temperature system piping
• See page 16.
Chiller system piping
• See page 17.
For multiple-boiler piping
• Refer to Weil-McLain’s “Primary/Secondary Piping
Guide.”
Relief valve
• Install relief valve vertically in elbow supplied. See
Figure 6 or 7 for location.
• See WARNING at right.
• Also refer to tag attached to relief valve for manu-
facturer’s instructions.
Relief valve discharge piping: To
avoid water damage or scalding due to
relief valve operation:
• Discharge line must be connected to
relief valve outlet and run to a safe place
of disposal. Terminate the discharge
line to eliminate possibility of severe
burns should the valve discharge.
• Discharge line must be as short as pos-
sible and be the same size as the valve
discharge connection throughout its
entire length.
• Discharge line must pitch downward
from the valve and terminate at least
6” above the floor drain where any
discharge will be clearly visible.
• The discharge line shall terminate
plain, not threaded, with a material
serviceable for temperatures of 375 °F
or greater.
• Do not pipe the discharge to any place
where freezing could occur.
• No shutoff valve shall be installed be-
tween the relief valve and boiler, or in
the discharge line.Do not plug or place
any obstruction in the discharge line.
• Failure to comply with the above guide-
lines could result in failure of the relief
valve to operate, resulting in possibil-
ity of severe personal injury, death or
substantial property damage.
• Test the operation of the valve after
filling and pressurizing system by
lifting the lever. Make sure the valve
discharges freely. If the valve fails to
operate correctly, replace it with a new
relief valve.
Connect water piping
Table 3 Water piping sizing
Model
Piping to
system
(inches)
Piping from
system
(inches)
UO-3 1¼ 1¼
UO-4 1¼ 1¼
UO-5 1½ 1½
Note: sizing based on 20°F temperature rise through boiler.

Part number 550-141-986/1005
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14
Connect water piping (continued)
DIAPHRAGM expansion tank (Figure 6)
• Make sure expansion tank size will handle boiler and
system water volume and temperature. Tank must
be located near boiler before inlet to circulator. See
tank manufacturer’s instructions for details.
Undersized expansion tanks cause system
water to be lost from relief valve and
makeup water added through fill valve.
Eventual section failure can result.
CLOSED expansion tank (Figure 7)
• Ensure expansion tank size will handle boiler and
system water volume and temperature.
Undersized expansion tanks cause system
water to be lost from relief valve and
makeup water added through fill valve.
Eventual section failure can result.
• Pitch any horizontal piping up towards tank 1 inch
per 5 feet of piping.
Figure 6 Near-boiler piping, with diaphragm expansion tank
Figure 7 Near-boiler piping, with closed expansion tank

Part number 550-141-986/1005 15
water boiler — Boiler Manual
Connect water piping (continued)
Piping MULTIPLE ZONES — System temperature 140 °F or higher
1. Follow instructions on page 13 and 14 to install
piping near boiler.
2. Zoning with circulators (Figure 8)
a. Size each circulator to individual circuit require-
ments.
b. Remove circulator (when furnished as standard equip-
ment).
c. Install balancing valves to adjust flow to distribute heat
to all zones.
Figure 8 Multiple zoning with circulators – Figure 9 Multiple zoning with zone valves –
Temperatures 140 °F and higher
d. Separate relay is required for each circulator.
3. Zoning with zone valves (Figure 9)
a. Install balancing valves to adjust flow to distribute
heat to all zones.
b. Separate transformer is required to power zone valves.
Refer to “Weil-McLain Zone Valve Wiring
Guide” for details.
1 Isolation valve
2 Flow control valve
3 Circulator
4 Zone valve
5 Drain valve

Part number 550-141-986/1005
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16
Connect water piping (continued)
Figure 11 Multiple zoning with zone valves –Figure 10 Multiple zoning with circulators –
1. If system water temperature requirements are less
than 140 °F, such as radiant panels or converted
gravity systems, use piping as shown in Figure 10
or 11.
2. If system piping is plastic without an oxygen barrier,
a heat exchanger must be used.
3. Follow instructions on page 13 and 14 to install
near-boiler piping.
4. Zoning with circulators (Figure 10)
a. Size each circulator to individual circuit require-
ments.
b. Remove circulator (when furnished as standard equip-
ment).
c. Install balancing valves to adjust flow to distribute heat
to all zones.
d. Separate relay is required for each circulator.
5. Zoning with zone valves (Figure 11)
a. Install balancing valves to adjust flow to distribute heat
to all zones.
b. Separate transformer is required to power zone valves.
Refer to “Weil-McLain Zone Valve Wiring
Guide” for details.
6. To set the valves, 7a and 7b:
a. Set the valves while the system is cool, setting for the
coldest expected water temperature (usually 60 °F
since the system will often drop to room temperature
between cycles).
b. Start with valve 7a fully closed and 7b fully open.
c. Gradually open valve 7a while closing 7b until the
temperature at gauge 8reads 130 °F when gauge 4a
reads 60 °F.
d. Note that valve 7a regulates the amount of hot water
from the boiler supply, which mixes with return water.
Valve 7b regulates the amount of system water flowing
through the boiler secondary loop.
Piping MULTIPLE ZONES — System temperature below 140 °F
1 Isolation valve
2 Flow control valve
3 Circulator
4 System temperature gauges
5 Zone valve
6 Drain valve
7 System temperature valves. Adjust valves
8 Blend temperature gauge
9 Boiler temperature gauge (not shown)

Part number 550-141-986/1005 17
water boiler — Boiler Manual
Connect water piping (continued)
Piping boiler in refrigeration systems (Figure 12)
• Install boiler so that chilled medium is piped in parallel with heating
boiler. Use appropriate valves to prevent chilled medium from entering
boiler. 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, use flow control valves or other
automatic means to prevent gravity circulation during cooling cycle.
Figure 12 Piping boiler in a system with chiller

Part number 550-141-986/1005
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18
Connect wiring
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 servic-
ing.
Installations must follow these codes:
• United States:
National Electrical Code, ANSI/NFPA 70, latest
edition and any additional national, state or local
codes.
• Canada:
CSA C22.1 Canadian Electrical Code Part 1 and any
local codes.
Wire requirements
• Wiring must be N.E.C. Class 1.
• If original wire supplied with boiler must be re-
placed, type 105 °C wire or equivalent must be
used.
• Supply wiring:
• Boiler only — 14 gauge or heavier.
• Boiler with optional AFM — 12 gauge.
Electrical requirements
• Boilers not equipped with an AFM can be supplied
by a 15-amp service.
• Boilers equipped with an AFM require a 20-amp
service.
Electrical grounding
• Provide electrical ground at boiler as required by
codes.
Wiring entrances (see Figure 13)
Terminal strip access
• Remove the two retainer screws in the jacket top
panel (at rear of the boiler) and remove the jacket
top panel.
• Release the Control Pod cover by loosening the
retainer screw in the top center of the cover. Swing
the cover open to reveal the boiler terminal strip.
• Remove the Control Pod cover to facilitate wire
routing. (To remove, push the Control Pod cover to
one side, and gently work the cover retainer hinge
on the other side out of the jacket slot.)
Figure 13 Terminal strip access
120-volt wiring
Conduits
• Connect each conduit supplying line-voltage wiring
to or from the boiler to a conduit opening in the
upper portion of the jacket rear panel.
• All field-provided line-voltage wiring must be
sheathed in flexible metal conduit.
Additional limits
• If required by state or local codes,provide additional
limits as needed.
• When using additional limits, remove the factory-
installed jumper between boiler terminal strip ter-
minals 18 and 19.
• Connect the additional limits in series and wire to
boiler terminal strip terminals 18 and 19.

Part number 550-141-986/1005 19
water boiler — Boiler Manual
Circulator
• The circulator is shipped with the boiler, but not
installed or wired.
• Wire the circulator to the boiler terminal strip as
shown on the boiler wiring diagram. Provide hot,
neutral and ground wires, routed in metal con-
duit.
Thermostat wiring
• Install thermostat on inside wall away from influ-
ences of drafts, hot or cold water pipes, lighting
fixtures, televisions, sun rays or fireplaces.
• Follow instructions with thermostat.
• If the thermostat has a heat anticipator, set the heat
anticipator per the limit control manufacturer’s
recommendation.
Burner wiring (see Figure 14)
• The burner harnesses incorporate disconnect plugs,
providing a convenient way to disconnect wiring
when burner mounting door is opened.
Failure to disconnect the burner wiring har-
nesses before opening the burner door can
cause damage to the burner and boiler wir-
ing.
Optional AFM installation
• See separate AFM instructions when used.
When wiring is completed:
• Reinstall the Control Pod cover, close cover and
tighten the retainer screw.
• Replace jacket top and secure with screws.
Figure 14 Burner harness and EnviraCOM®
Connect wiring (continued)

Part number 550-141-986/1005
water boiler — Boiler Manual
20
Connect wiring (continued)
Figure 15 Boiler and burner wiring, standard equipment This wiring diagram is for standard boiler
equipment. For wiring with optional AFM,
see AFM instructions.