U.S. Boiler Company X-202 Service manual

106636-04 - 8/22
9700609
X-2 TM
Installation, Operating and Service Instructions for
• Water Boiler
• Cast Iron
• Chimney Vent
• Gas Fired
Models:
• X-202
• X-203
• X-204
• X-205
WARNING
Read these instructions carefully before installing. This boiler must only be installed, serviced, or repaired
by a qualified installer, service agency or gas supplier. Improper installation, adjustment, alteration, service,
or maintenance can cause severe personal injury, death, or substantial property damage. For assistance or
additional information, consult a qualified installer, service agency or gas supplier.
!
Manual Contents Page
1. Qualified Installer, Service Agency or Gas Supplier
Read Before Proceeding .........................3
2. User/Homeowner Read Before Proceeding ..........4
3. Specifications ..................................5
4. Locating Boiler .................................6
5. Preparing Boiler.................................9
6. Venting ........................................9
7. Water Piping...................................12
8. Gas Piping ....................................16
9. Electrical .....................................17
10. System Start-up and Checkout ...................21
11. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
12. Before Leaving Jobsite ..........................30
13. Service and Maintenance ........................31
14. How it Works ..................................34
15. Troubleshooting ...............................36
16. Service Parts ..................................41
Appendix A Combination Refrigeration/Heating System..48
Appendix B Water Quality and Boiler Additives .........49
Appendix C Low Water Return Temperature ............50
WARNING
Attention Installer - Affix these instructions
adjacent to boiler. Provide model number and
serial number when seeking information and
support.
Attention Building Owner - Retain these
instructions for future reference. Contact a
qualified installer, service agency or gas
supplier for all issues and support.
• X-206
• X-207
• X-208
• X-209
!

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X-2 Installation, Operating & Service Manual
The following terms are used throughout this manual to bring attention to the presence of hazards of various
risk levels, or to important information concerning product life.
The City of New York requires a Licensed Master Plumber supervise the installation of this product.
The Massachusetts Board of Plumbers and Gas Fitters has listed the X-2TM Series Boiler. See the Massachusetts
Board of Plumbers and Gas Fitters website,
https://licensing.reg.state.ma.us/pubLic/pl_products/pb_pre_form.asp for the latest Approval Code or ask your
local Sales Representative.
The Commonwealth of Massachusetts requires this product to be installed by a licensed Plumber or Gas fitter.
NOTICE: Indicates special instructions on
installation, operation, or service which are
important but not related to personal injury
hazards.
DANGER
Indicates a hazardous situation that, if not
avoided, will result in death or serious injury.
CAUTION
Indicates a hazardous situation that, if not
avoided, could result in minor or moderate
injury.
WARNING
Indicates a hazardous situation that, if not
avoided, could result in death or serious injury.
DANGER
Explosion Hazard. DO NOT store or use gasoline or other flammable vapors or liquids in the vicinity of
this or any other appliance.
If you smell gas vapors, DO NOT try to operate any appliance - DO NOT touch any electrical switch or
use any phone in the building. Immediately, call the gas supplier from a remotely located phone.
Follow the gas supplier’s instructions or if the supplier is unavailable, contact the fire department.
WARNING
This boiler must only be serviced and repaired by skilled and experienced service technicians.
• If any controls are replaced, they must be replaced with identical models.
• Read, understand and follow all the instructions and warnings contained in all the sections of this
manual.
• If any electrical wires are disconnected during service, clearly label the wires and assure that the wires
are reconnected properly.
• Never jump out or bypass any safety or operating control or component of this boiler.
• Assure that all safety and operating controls and components are operating properly before placing
the boiler back in service.
• Annually inspect all vent systems and replace any exhibiting damage or deterioration.
! !
!
!
!

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X-2 Installation, Operating & Service Manual
DANGER
Asphyxiation Hazard, Burn Hazard, Electrical
Shock Hazard.
• Carefully read all instructions in literature
packet and posted on boiler before attempting
installation, startup, or service of this boiler.
Perform steps in order given. Failure to follow
all instructions in proper order could result in
severe personal injury, death or substantial
property damage.
• Use proper personal protective equipment
when installing, servicing, or working near this
boiler. Materials of construction, flue products,
and fuel contain alumina, silica, heavy metals,
carbon monoxide, nitrogen oxides, and/or
other toxic or harmful substances that can be
hazardous to health and life and that are known
to the State of California to cause cancer, birth
defects, and other reproductive harm.
• Do not disconnect pipe fittings on boiler or
in heating system without first verifying system
is cool and free of pressure and that your
clothing will protect you from a release of hot
water or steam. Do not rely solely on boiler
temperature and pressure gauge when making
this judgement.
• Install all guards, cover plates, and
enclosures before leaving boiler in operation.
• Disconnect electrical supply before installing
or performing maintenance.
!NOTICE:
1. Size boiler properly. A grossly oversized boiler
will cycle excessively leading to premature
failure of boiler and its components. Warranty
does not cover damage from excessive
cycling.
2. Systems employing baseboard and/or
radiators, use an industry accepted
sizing method such as the I=B=R "Residential
Hydronic Heating Installation and Design"
guide published by the Air Conditioning,
Heating and Refrigeration Institute (AHRI).
3. Inspect shipment carefully for signs of
damage. Any claim for damage or shortage
in shipment must be filed immediately against
carrier by consignee. No claims for variances
or shortages will be allowed by boiler
manufacturer, unless presented within 60
days after receipt of equipment.
1Qualified Installer, Service Agency or Gas Supplier Read Before Proceeding

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X-2 Installation, Operating & Service Manual
2User/Homeowner Read Before Proceeding
CAUTION
Burn Hazard.
Keep children and pets away from hot surfaces
of the boiler including boiler piping, vent piping,
and vent terminals.
!
NOTICE: Boiler may leak water or steam at the
end of its useful life. Be sure to protect walls,
carpets, and valuables from water or steam that
could leak from boiler.
WARNING
Asphyxiation Hazard. Fire Hazard.
• A qualified installer, service agency or gas
supplier should annually inspect boiler.
• If you are not qualified to install or service
boilers, do not install or service this one.
• Carbon monoxide is an odorless, deadly gas
that may be introduced into your home by any
malfunctioning fuel burning product or vent
system failure. Consider installing CO alarms
near bedrooms in all levels of building to
warn you and your family of potential CO
exposure.
• Do not block air flow into or around boiler
or opening for fresh air into boiler room.
Insufficient air may cause the boiler to produce
carbon monoxide or start a fire.
!
NOTICE: Protect your home in freezing weather.
A power outage, operating control, or component
failure will prevent your boiler from lighting. In
winter your pipes may freeze and cause extensive
property damage. Do not leave heating system
unattended during cold weather unless alarms
or other safeguards are in place to prevent such
property damage.
NOTICE: This boiler contains controls which
may cause the boiler to shut down and not restart
without service. If damage due to frozen pipes
is a possibility, heating system should not be
left unattended in cold weather; or appropriate
safeguards and alarms should be installed on
heating system to prevent damage if boiler is
inoperative.

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X-2 Installation, Operating & Service Manual
Table 3-2: Dimensions and Connections
Boiler
Model Depth Width Height Supply NPT (in.)
Return NPT
(in.)
Vent
(in.)
Gas NPT
(in.)
Relief Valve
NPT (in.)
Drain
NPT (in.)
X-202 32 14 40 1¼ 1¼ 4 ½ ¾ ¾
X-203 32 14 40 1¼ 1¼ 4 ½ ¾ ¾
X-204 32 16 40 1¼ 1¼ 5 ½ ¾ ¾
X-205 32 19 40 1¼ 1¼ 6 ½ ¾ ¾
X-206 32 22 40 1¼ 1¼ 6 ½ ¾ ¾
X-207 32 25 40 1¼ 1¼ 7 ¾ ¾ ¾
X-208 32 28 40 1¼ 1¼ 7 ¾ ¾ ¾
X-209 32 31 40 1¼ 1¼ 8 ¾ ¾ ¾
Electrical Requirements: 120 VAC, 60 Hz, 1-ph, Less than 12A
Maximum Allowable Working Pressure - 50 psi. Boiler shipped from factory with a 30 psi safety relief valve.
Boiler
Model
Shipping Weight
(lbs)
Empty Weight
(lbs)
Shipping Crate
Depth (in.)
Shipping Crate
Width (in.)
Shipping
Crate Height
(in.)
Water Content
(gal)
X-202 202 143 39 26 47 1
X-203 254 180 39 26 47 2
X-204 304 231 39 26 47 3
X-205 357 284 39 26 47 4
X-206 405 332 39 26 47 5
X-207 462 382 39 35 47 6
X-208 518 438 39 35 47 7
X-209 564 484 39 35 47 8
Table 3-3: Weights and Volume
3Specifications
Table 3-1: Ratings
Model
Number AFUE % Input (MBH)(1)
DOE Heating
Capacity
(MBH)
Net AHRI (MBH)(2)
X-202 84.0 38 32 28
X-203 84.0 70 59 51
X-204 84.0 105 88 77
X-205 84.0 140 117 102
X-206 84.0 175 146 127
X-207 84.0 210 176 153
X-208 84.0 245 205 178
X-209 84.0 280 234 203
(1) Input ratings can be used for elevations up to 2,000 ft. Refer to System Start-Up and Checkout Sections for
elevations 2,000 ft. or higher.
(2) Net AHRI Ratings shown are based on a piping and pickup allowance of 1.15. The manufacturer should be
consulted before selecting a boiler for installations having unusual piping and pickup requirements, such as
intermittent operation, extensive piping systems, etc.

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X-2 Installation, Operating & Service Manual
4 Locating Boiler
Code Requirements
2. All wiring must comply with National Electrical
Code ANSI/NFPA 70.
3. Where required by authority having
jurisdiction, installation must conform to
Standard for Controls and Safety Devices for
Automatically Fired Boilers, ANSI/ASME CSD-1.
Location Considerations
1. Provide combustion and ventilation air in
accordance with section "Air for Combustion and
Ventilation," of National Fuel Gas Code, ANSI
Z223.1/NFPA 54, or applicable provisions of local
building codes.
2. If replacing an existing boiler, check for and
correct common system problems including:
A. System leaks resulting in premature heat
exchanger failure from oxygen corrosion or
hardness deposits.
B. Inadequate freeze protection resulting in
system freezing and leaking.
C. Dirt or debris left in existing piping if it has not
been properly flushed or cleaned.
3. Appliance is listed for installation on combustible
flooring and must not be installed on carpeting.
4. Install on level floor. For basement installation
provide concrete base if floor is not level or if
water may be encountered on floor around boiler.
5. Protect gas ignition system components from
water (dripping, spraying, etc.) during appliance
operation and service.
6. Locate boiler to avoid water damage in case
there is a leak. If boiler must be located in an
area sensitive to water damage, install drain
pan underneath boiler and pipe to a suitable
drain location. Manufacturer will not be held
responsible for water damage resulting from
this appliance or any of its components.
7. Check for and remove any combustible
materials, gasoline, or other flammable liquids
from area around boiler.
8. Check for and remove any potential combustion
air contaminants from area around boiler. See
Table 4-1.
Clearances
1. Provide clearances between boiler jacket and
combustible material in accordance with
authority having jurisdiction. Minimum
clearances to combustible material shown in
Figure 4-1 and 4-2.
2. Recommend 24 in. service clearance from left
side, right side and front.
NOTICE: If recommended service clearances
are not provided, it may be necessary to remove
boiler for service.
3. Boiler must not be installed on carpeting.
1. Installations must conform to requirements of
authority having jurisdiction or, in the
absence of such requirements, to National Fuel
Gas Code, ANSI Z223.1/NFPA 54.
Table 4-1: Corrosive Combustion Contaminants
and Sources
Contaminants to avoid:
Spray cans containing chloro/fluorocarbons (CFC’s)
Permanent wave solutions
Chlorinated waxes/cleaners
Chlorine-based swimming pool chemicals
Calcium chloride used for thawing
Sodium chloride used for water softening
Refrigerant leaks
Paint or varnish removers
Hydrochloric acid/muriatic acid
Cements and glues
Antistatic fabric softeners used in clothes dryers
Chlorine-type bleaches, detergents, and cleaning
solvents found in household laundry rooms.
Adhesives used to fasten building products and
other similar products
Excessive dust and dirt
Areas likely to have contaminants:
Dry cleaning/laundry areas and establishments
Swimming pools
Metal fabrication plants
Beauty shops
Refrigeration repair shops
Photo processing plants
Auto body shops
Plastic manufacturing plants
Furniture refinishing areas and establishments
New building construction
Remodeling areas
Garages with workshops
NOTICE: Flue side corrosion caused by
contaminants is not covered by warranty.

106636-04 - 8/22 7
X-2 Installation, Operating & Service Manual
After Removing Existing Boiler
When an existing boiler is removed from a
common venting system, the common venting
system is likely to be too large for proper venting
of appliances remaining connected to it.
At 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:
1. Seal any unused openings in the common venting
system.
2. Visually inspect 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.
3. 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 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.
Before Removing Existing Boiler
Take pictures and measure and/or mark existing
steam and condensate return piping to ensure
proper re-piping of new boiler. Support existing
piping before disconnecting to prevent change in
pitch.
4. Place in operation appliance being inspected.
Follow Operating Instructions. See Figure 10-
1. Adjust thermostat so appliance will operate
continuously.
5. Test for spillage at draft hood relief opening after 5
minutes of main burner operation. Use flame of a
match or candle, or smoke from a cigarette, cigar
or pipe.
6. 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 condition of use.
7. Any improper operation of the common venting
system should be corrected so the installation
conforms with the National Fuel Gas Code, ANSI
Z223.1/NFPA 54. When resizing any portion of the
common venting system, the common venting
system should be resized to approach minimum
size as determined using appropriate tables in
Chapter 13 of the National Fuel Gas Code, ANSI
Z223.1/NFPA 54.
4 Locating Boiler (continued)

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X-2 Installation, Operating & Service Manual
4 Locating Boiler (continued)
Figure 4-2: Minimum Alcove Clearances
Figure 4-1: Minimum Closet Clearances
* Minimum radial clearance around vent pipe and breeching for single-wall metal pipe vent connector.
Otherwise, follow vent connector manufacturer's recommended clearances.
** Additional height required to maintain 6 in. clearance from all breeching components. Vent damper may
be installed in vertical or horizontal section of vent connector within reach of vent damper harness.
*** Area of each opening to be 1 sq. inch for each 1,000 BTU/hr (1 MBH) input - with minimum of 100 sq.
inches. Height of opening should be half of width. 3 in. minimum dimension for air openings.
Model "W"
X-202 14 in.
X-203 14 in.
X-204 16 in.
X-205 19 in.
X-206 22 in.
X-207 25 in.
X-208 28 in.
Model "W"
X-209 31 in.
WARNING
Adequate combustion and ventilation air must
be provided to assure proper combustion.
WARNING
ASSURE THAT THE FRONT AIR DAM is in place
and undamaged. A damaged front air dam will
negatively affect the performance of this boiler,
which can cause serious property damage,
personal injury or death.
! !

106636-04 - 8/22 9
X-2 Installation, Operating & Service Manual
CAUTION
Do not drop boiler. Do not bump boiler jacket
against floor.
Unpack boiler
1. Move boiler to approximate installed position.
2. Remove all crate fasteners.
3. Lift outside container and remove with all other
inside protective spacers and bracing. Save two
of the wooden slats from the container sleeve for
use in Steps E and F.
4. Remove all boiler hold-down fasteners.
5. Tilt the boiler to one side and slide a wooden slat
under the two raised feet.
6. Tilt the boiler to the other side and slide another
wooden slat under the two raised feet.
7. Slide the boiler forward or backward off the skid
using the two wooden slats as runners.
8. Move boiler to its permanent location.
!
5 Preparing Boiler
DANGER
Use precautions and appropriate rigging
apparatus when moving heavy objects.
!
DANGER
Asphyxiation Hazard.
• Failure to vent this boiler in accordance with
these instructions could cause products of
combustion and/or carbon monoxide to enter
living space, resulting in severe personal injury,
death or substantial proper damage.
• Vent installation shall be in accordance with local
codes, authority having jurisdiction or National
Fuel Code, ANSI Z223.1/NFPA 54 or applicable
requirements of the local building codes.
• Follow instructions in Section 4 Locating Boiler
when removing a boiler from an existing vent
system.
• Maintain clearances to vent piping and draft
hood per Figures 4-1 and 4-2.
• Do not use CPVC, PVC, Polypropylene or any
other non-metallic vent pipe.
!
6 Venting
General
1. Locate boiler as close to chimney as possible.
See Figure 4-1 and 4-2 for minimum clearances.
2. Install vent system in accordance with local
codes, authority having jurisdiction or National
Fuel Gas Code, ANSI Z223.1/NFPA 54. X-2 boilers
are Category I, draft hood equipped appliances.
A. Acceptable Chimneys.
i. Listed Type B or Type L gas
vent. Install in accordance with
manufacturer's installation
instructions, local codes, authority
having jurisdiction or National Fuel
Gas Code, ANSI Z223.1/NFPA 54.
ii. Masonry chimney. Build and install
in accordance with local codes,
authority having jurisdiction or
Standard for Chimney's Fireplaces,
Vents and Solid Fuel Burning
Appliances, NFPA 211.
B. Acceptable Vent Connections.
i. Listed Type B or Type L gas vent.
ii. Single wall galvanized vent. Use
0.018 in. (26 gauge or heavier). The
size and location of the chimney
may not permit the use of a single
wall connector in some cases. See
National Fuel Gas Code, ANSI
Z223.1/NFPA 54.
Do not use single wall pipe for vent
connections in attics.
C. Size chimney and vent connector in
accordance with National Fuel Gas Code,
ANSI Z223.1/NFPA 54.
D. Do not connect vent of this appliance into any
portion of a mechanical vent system
operating under positive pressure.

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X-2 Installation, Operating & Service Manual
E. Do not connect boiler into a chimney flue
servicing an open fireplace or other solid fuel
appliance.
F. Prior to boiler installation, inspect chimney
for obstructions or other defects and correct
as required. Clean chimney as necessary.
G. The vertical section of vent pipe coming off
boiler should be as tall as possible, while
still maintaining the proper clearance from
horizontal vent connector to combustibles.
H. Vent pipe should slope upward from draft
hood not less than one inch in four feet. No
portion of vent pipe should run downward or
have sags. Vent pipe must be securely
supported.
I. Vent pipe should be installed above bottom of
chimney to prevent blockage.
J. Vent pipe must be inserted flush with inside
face of chimney liner and the space between
vent pipe and chimney sealed tight.
K. Do not install vent damper in any portion of
vent system which is used by appliances
other than the boiler being installed.
6 Venting (continued)
Figure 6-1: Vent Damper Installation
Figure 6-2: Vent Damper Position Indicator
A. Vent damper must be same size as outlet
of vent supplied with boiler (see Table 3-2).
Unpack damper carefully - DO NOT FORCE IT
CLOSED! Forcing damper may damage motor
and is not covered by warranty.
Insert pilot vent plug into gate and fold over
tabs.
B. Mount the vent damper assembly onto diverter.
See damper manufacturer instructions for more
information. Do not modify either diverter or
vent damper. See Figure 6-1.
NOTICE: Provide adequate access for
servicing.
C. Locate vent damper position indicator to be
visible following installation. See Figure 6-2.
D. Plug vent damper connector into damper
motor polarized receptacle.
2. Install vent piping.
A. See Figure 3-4 for vent sizes and locations.
See Figure 4-2 for clearances.
B. Install vent piping from vent damper outlet
to chimney. See Figure 6-3 for typical vent
installation.
CAUTION
Do not use one vent damper to control more
than one heating appliance.
!
Install Vent Piping
1. Install vent damper.
OPEN VENT DAMPER CARTON and remove
Installation Instructions. READ INSTALLATION
INSTRUCTIONS THOROUGHLY before
proceeding.

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X-2 Installation, Operating & Service Manual
6 Venting (continued)
DANGER
Inspect existing chimney before installing
boiler. Look for corrosion holes. Failure to clean
chimney or replace corroded pipe or tile lining
will cause severe injury or death. Do not connect
into same flue of chimney serving an open
fireplace.
C. Vent pipe to chimney must not be smaller
than outlet on draft hood or vent damper.
Arrange venting system so boiler is
served by vent damper device.
Exception: National Fuel Gas Code,
ANSI Z223.1/NFPA 54, and allow vent
downsizing when vent size
determined by their Vent Sizing
Tables is smaller than draft hood
outlet/vent damper. These codes
require all of following:
i. Total vent height (H) is at least
10 ft.;
ii. Vent not reduced more than one
table size;
and
iii. Draft hood outlet/vent damper is
greater than 4 in. in diameter.
D. Vent pipe should have greatest possible
initial rise above draft hood consistent
with head room available and required
clearance from adjacent combustible
building structure. Vent pipe should be
installed above bottom of chimney to prevent
blockage.
E. Slope vent pipe upward from draft hood to
vent terminal not less than 1/4 in. per foot.
F. Support horizontal portions of venting
system to prevent sagging. Use pipe
straps, brackets or hangers spaced 4 ft. or
less.
G. Vent pipe must be inserted into but not
beyond inside wall of chimney liner. Seal tight
between vent pipe and chimney.
!4. Install vent termination (masonry chimney and
single wall metal pipe).
A. Termination shall extend at least 5 ft.
in vertical height above highest connected
appliance vent outlet.
B. Termination shall extend at least 3 ft. (2 ft. for
single wall metal pipe) above roof penetration
and at least 2 ft. above any portion of building
within horizontal distance of 10 ft.
5. Install vent termination: (Gas Vent).
A. Termination shall extend at least 5 ft.
in vertical height above highest connected
appliance vent outlet.
B. For terminations located at least 8 ft. from
vertical wall or similar obstruction, termination
shall extend above roof in accordance with
Figure 6-4.
C. For terminations located less than 8 ft. from
vertical wall or similar obstruction, termination
shall extend at least 2 ft. above roof
penetration and at least 2 ft. above any
portion of building within horizontal distance
of 10 ft.
D. Termination shall be at least 3 ft. above forced
air inlet located within 10 ft.
Figure 6-3: Typical Single Draft Hood Installation
Bottom
of Boiler
Air Gap
Front
of Boiler
Cleanout
Thimble
Chimney
Slope Up

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X-2 Installation, Operating & Service Manual
6 Venting (continued)
Figure 6-4: Termination Location for Gas Vent
Roof Slope Heights (H)
Roof Slope ft.
Flat to 6/12 1.0
Over 6/12 to 7/12 1.25
Over 7/12 to 8/12 1.5
Over 8/12 to 9/12 2.0
Over 9/12 to 10/12 2.5
Over 10/12 to 11/12 3.25
Over 11/12 to 12/12 4.0
Over 12/12 to 14/12 5.0
Over 14/12 to 16/12 6.0
Over 16/12 to 18/12 7.0
Over 18/12 t 20/12 7.5
Over 20/12 to 21/12 8.0
7 Water Piping
WARNING
Failure to properly pipe boiler may result in
improper operation and damage to boiler or
building.
!
1. Design and install boiler and system piping to
prevent oxygen contamination of boiler water.
Oxygen contamination sources are system leaks
requiring addition of makeup water, fittings,
and oxygen permeable materials in distribution
system. Eliminate oxygen contamination by
repairing system leaks, repairing fittings, and
using non-permeable materials in distribution
system.
2. Install circulator with flanges, gaskets and bolts
provided.
3. Install Safety Relief Valve. See Figure 7-1. Safety
Relief Valve must be installed with spindle in
vertical position.
DANGER
• Pipe relief valve discharge to a safe location.
• Do not install any valves between boiler and
relief valve.
• Do not install any valves between relief valve and
discharge.
• Do not move relief valve from factory location.
• Do not plug relief valve discharge.
• Do not install a relief valve with a setting greater
than 30 psi.
!
WARNING
• Pipe discharge of relief valve to a location where
water will not create a hazard or cause property
damage if the relief valve opens.
• End of discharge pipe must terminate in an
unthreaded pipe.
• Relief valve must terminate no greater than 6
inches above floor.
• Termination of the relief valve discharge piping
must be in an area where it is not likely to
become plugged by debris or subjected to
freezing.
• Union may be installed in safety relief valve
piping.
!

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7 Water Piping (continued)
4. Connect system supply and return piping to
boiler. Refer to Figures 7-1, 7-2, and 7-3. Also
consult Residential Hydronic Heating Installation
and Design I=B=R Guide. Maintain minimum
½ inch clearance from hot water piping to
combustible materials.
5. If boiler is used in connection with refrigeration
systems, See Appendix: "Combination
Refrigeration/Heating System".
6. Use a boiler bypass if boiler is to be operated in
a system which has a large volume or excessive
radiation where low boiler water temperatures may
be encountered (i.e. converted gravity circulation
system, etc.). See Appendix: "Low Return Water
Temperatures".
7. Perform a long term pressure test of hydronic
system, isolate boiler to avoid a pressure loss due
to escape of air trapped in boiler.
To perform a long term pressure test including the
boiler, ALL trapped air must first be removed from
the boiler.
A loss of pressure during such a test, with no
visible water leakage, is an indication that the
boiler contained trapped air.
Figure 7-1: Near Boiler Piping

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X-2 Installation, Operating & Service Manual
Figure 7-2: Recommended Water Piping for Direct Connection Systems
At least 18"
of straight pipe
for conventional
air separator
To
System
To
System
Optional Circulator Zone
Controlled System
Optional Zone Valve
Controlled System
System
Circulator
System
Zone
Valves
Zone Circulators
Full Port Isolation Valves
Flow Check
From System
Full Port Isolation Valves
Drain Valve
Safety Relief Valve
Pipe within 6" of floor or drain
Drain Valve
IWH
Return
IWH
Supply
Indirect Water Heater (IWH)
Air Separator
& Air Vent
Expansion Tank
Backflow Preventer
Fill Valve
Cold
Water
Return
Full Port Isolation Valves
Unions
Flow Check
IWH Circulator
Full Port Isolation Valve
Unions
Full Port Isolation Valve
7 Water Piping (continued)
Pipe no greater than 6 in. of floor or drain

106636-04 - 8/22 15
X-2 Installation, Operating & Service Manual
7 Water Piping (continued)
'C'
'B' 'A'
To
System
To
System
Optional Circulator Zone
Controlled System
Optional Zone Valve
Controlled System
System
Circulator
System
Zone
Valves
Zone Circulators
Full Port Isolation Valves
Flow Check
From System
Full Port Isolation Valves
Drain Valve
Safety Relief Valve
Pipe within 6" of floor or drain
Drain Valve
IWH
Return
IWH
Supply
Indirect Water Heater (IWH)
Air Separator
& Air Vent
Expansion Tank
Backflow Preventer
Fill Valve
Cold
Water
Return
Full Port Isolation Valves
Unions
Flow Check
IWH Circulator
Full Port Isolation Valve
Unions
Full Port Isolation Valve
A. At least eight pipe diameters upstream of boiler return tee. B. No further apart than 12" (~30cm) or four pipe diameters, whichever is smaller. C. At least 18" (~46cm) of straight pipe for
Conventional Air Scoop.
Circulator
Figure 7-3: Recommended Water Piping for Primary/Secondary Systems
Pipe no greater than 6 in. of floor or drain

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X-2 Installation, Operating & Service Manual
Figure 8-2: Pilot and Gas Piping
1. Size gas piping. Design system to provide
adequate gas supply to boiler. Consider these
factors:
A. Allowable pressure drop from point of delivery
to boiler. Maximum allowable system pressure
is ½ psig. Minimum gas valve inlet pressure is
listed on rating label. See Table 8-1.
Table 8-1: Gas Pressure
Natural
Gas
Inlet Min
(in w.c.)
Inlet Max
(in w.c.)
Manifold
(in w.c.)
All Sizes 4.5 14.0 3.5
LP Gas Inlet Min
(in w.c.)
Inlet Max
(in w.c.)
Manifold
(in w.c.)
All Sizes 11.0 14.0 10.0
B. Maximum gas demand. Consider existing and
expected future gas utilization equipment (i.e.
water heater, cooking equipment).
2. Connect boiler gas valve to gas supply system.
A. Use methods and materials in accordance with
local plumbing codes and requirements of gas
supplier. In absence of such requirements,
follow National Fuel Gas Code, ANSI Z223.1/
NFPA 54.
B. Use thread compounds (pipe dope) resistant
to action of liquefied petroleum gas.
C. Install sediment trap, ground-joint union and
manual shut-off valve upstream of boiler gas
control valve. See Figure 8-2 (within 6 ft. of
boiler).
D. All above ground gas piping upstream from
manual shut-off valve must be electrically
continuous and bonded to a grounding
electrode. Do not use gas piping as grounding
electrode. Refer to National Electrical Code,
ANSI/NFPA 70.
3. Pressure test. Boiler and its gas connection must
be leak tested before placing boiler in operation.
See "System Start-Up and Checkout" section and
"Gas Leak Test" for guidance. Follow National Fuel
Gas Code, ANSI Z223.1/NFPA 54.
8 Gas Piping
WARNING
Explosion Hazard.
• Failure to properly pipe gas supply to boiler
could cause improper operation if leaks of
flammable gas resulting in severe personal
injury, death, or substantial property damage.
• Gas supply to boiler and system must be shut off
prior to installing or servicing boiler gas piping.
!
DANGER
Explosion Hazard.
• Do not use matches, candles, open flames, or
other ignition sources to check for leaks. Failure
to comply could result in severe personal injury,
death, or substantial property damage.
!
Figure 8-3: Gas Manifold and Control Assembly

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X-2 Installation, Operating & Service Manual
1. Install wiring so boiler is electrically bonded
to ground in accordance with requirements of
authority having jurisdiction, or in absence of such
requirements, with the National Electrical Code,
ANSI/NFPA 70.
2. Install thermostat. Locate on inside wall
approximately 4 feet above floor. Do not install on
outside wall, near fireplace, or where influenced
by drafts or restricted air flow, hot or cold water
pipes, lighting fixtures, television, or sunlight.
Allow free air movement by avoiding placement of
furniture near thermostat.
3. Wire boiler. Boiler is rated for 120 VAC, 60 hertz,
less than 12 A. A separate electrical circuit must
be run from main electrical service with an over-
current device/disconnect in circuit. A service
switch is recommended and may be required by
some local jurisdictions. Connect to black and
white wires and green ground screw. See Figures
9-1 and 9-2.
4. For installations using zone valves, provide
separate transformer for zone valve wiring.
Consult zone valve manufacturer for assistance.
See Figure 9-3.
9 Electrical
WARNING
Electrical Shock Hazard. Wiring errors can
cause improper or dangerous operation. Verify
proper operation after installation.
!DANGER
Electrical Shock Hazard.
• Disconnect electrical supply before installing or
performing maintenance.
• Electrical power may be supplied from more
than one circuit.
• Lock out all electrical boxes with padlock once
power is turned off.
!
WARNING
Electrical Shock Hazard.
• All wiring and grounding must conform to
requirements of authority having jurisdiction or,
in the absence of such requirement, to National
Electrical Code/NFPA 70.
• Make electrical connections according to boiler's
wiring diagram and instructions. Failure to
properly wire electrical connections to the boiler
may result in severe personal injury, death, or
substantial property damage.
• Protect each boiler circuit with a properly sized
over-current device.
• Never jump out or bypass any operating control
or component of this boiler.
!

106636-04 - 8/22
18
X-2 Installation, Operating & Service Manual
Figure 9-1: Wiring Connection Diagram
9
Electrical (continued)

106636-04 - 8/22 19
X-2 Installation, Operating & Service Manual
Figure 9-2: Schematic Ladder Diagram
9 Electrical
(continued)

106636-04 - 8/22
20
X-2 Installation, Operating & Service Manual
9
Electrical (continued)
Figure 9-3: Wiring Schematic, Zone Valves
Figure 9-4: Wiring Schematic, Zone Circulators