U.S. Boiler Company ALTAC-200 Service manual

110327-04 - 1/22
ALTA • Combi Boiler/Water Heater
• Condensing
• Direct Vent
• Gas Fired
Models:
• ALTAC-136
• ALTAC-200
WARNING
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 the gas supplier. Read these instruction carefully before installing.
!
Installation, Operating and Service Instructions for
Manual Contents Page
1. Installer Read Before Proceeding ...........3
2. Homeowner Read Before Proceeding........5
3. Specifications ...........................6
4. How It Works ............................8
5. Locating Boiler .........................10
6. Preparing Boiler ........................14
7. General Venting .........................17
8. Sidewall Direct Venting...................24
9. Vertical Direct Venting ...................30
10. Heating System Piping ...................36
11. Domestic Water Piping ...................39
12. Gas Piping.............................42
13. Field Wiring ............................43
14. Condensate Disposal ....................46
15. Start-up and Checkout ..................47
16. Operation ..............................53
17. Before Leaving Jobsite ..................65
18. Service and Maintenance .................66
19. Troubleshooting ........................71
20. Internal Wiring Diagrams .................86
21. Service Parts...........................89
Appendix
A. Combination Refrigeration/Heating System ..95
B. Water Quality and Boiler Additives .........96
C. Special Requirements In Massachusetts ....97
D. Code Required Text ......................99
TO THE INSTALLER:
Affix these instructions adjacent to boiler.
Provide model number and serial number when
seeking information and support.
TO THE HOMEOWNER:
Retain these instructions for future reference.
Contact heating installer or technician for all issues
and support.
Version en Español disponible en el web del fabricante. www.usboiler.net

2
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
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 Massachusetts Board of Plumbers and Gas Fitters has listed the Alta Boiler. See the Massachusetts Board of
Plumbers and Gas Fitters website 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 qualified installer, service agency or gas supplier.
• 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 boiler.
• Annually inspect all vent gaskets and replace any exhibiting damage or deterioration.
! !
!
!
!

3110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
1Installer or Qualified Service Agency Read Before Proceeding
1. Alta Combi boiler is a Direct Vent combination
space heating and DHW heating boiler.
2. A hot water boiler installed above radiation level
or as required by the authority having jurisdiction
must be provided with a low water cutoff (LWCO)
device. This boiler is equipped with a UL353
listed flow switch which provides low water
protection on this boiler. Where authority having
jurisdiction requires a separate LWCO, the
following kits are available:
• Auto reset LWCO: 105591-01
• Manual reset LWCO: 108182-01
Factory installed flow switch in this boiler meets
requirements of 248 CMR 5.00 Massachusetts
Amendments to NFPA 54 Section 5.10(6) 10.3.5
Safety Control.
3. Inspect shipment carefully for signs of damage.
See Figure 6-1 for location of parts shipped
loose with boiler. 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.
NOTICE: When replacing control, use boiler
control service part listed in Section 21 Service
Parts. Boiler control service part is compatible
for all models. Factory installed control is only
compatible with purchased boiler.
WARNING
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 gage when making
this judgement.
• Install all guards, cover plates, and
enclosures before leaving boiler in operation.
• Disconnect electrical supply before installing
or performing maintenance.
• Always use a combustion analyzer to verify
proper operation. See Section 15 Start-up and
Checkout for procedure and guidelines for
checking carbon monoxide (CO) levels. Failure
to use a combustion analyzer could cause
operation of boiler with elevated (CO) levels,
resulting in severe personal injury, death or
substantial property damage.
• Do not install at altitudes above 2,000 ft. (610
m).
!NOTICE: Size boiler properly relative to design
heat load or, if using DHW priority, the peak
hot water load, whichever is larger. A grossly
oversized boiler will cycle excessively leading to
premature failure of boiler and its components.
Warranty does not cover damage from excessive
cycling.
• For heating systems employing
convection radiation (baseboard
or radiators), use an industry
accepted sizing method such as
the I=B=R Guide RHH published
by the Air Conditioning, Heating and
Refrigeration Institute (AHRI).
• For new radiant heating systems,
refer to radiant tubing manufacturer's
boiler sizing guidelines.
• For system including indirect water
heater, ensure boiler has output
called for per indirect water
heater manufacturer's instructions.

4
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
SERVICE RECORD
SERVICE PERFORMED
DATE

5110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
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: Protect your home in freezing weather.
A power outage, safety lockout, 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: Boiler may leak water at the end of its
useful life. Be sure to protect walls, carpets, and
valuables from water that could leak from boiler.
WARNING
Asphyxiation Hazard. Fire Hazard.
• A qualified installer, service agency or
gas supplier should annually inspect boiler
including annually inspecting all vent gaskets
and replacing any exhibiting damage or
deterioration.
• 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. It is strongly recommended
that CO alarms be installed near bedrooms
and on all levels of building to warn you and
your family of potential CO exposure.
• Do not block air flow into or around boiler.
Insufficient air may cause the boiler to produce
carbon monoxide or start a fire.
!
BURN
HOT
• Water temperature over 125°F (52°C) can cause severe burns
instantly or death from scalds.
• Under certain conditions, this boiler can deliver domestic hot
water (DHW) at temperatures in excess of the DHW set point
on boiler control.
•
Children, disabled and elderly are at highest risk of being scalded.
• Feel water before bathing or showering.
• Installation of an ASSE 1017 or ASSE 1070 certified
tempering valve is REQUIRED as part of this boiler’s
installation. Consult manual for details on valve installation
and temperature adjustment.
• Additional temperature control valves
may also be required at fixtures.
Consult installation manual and
authority having jurisdiction for
additional details.
DANGER
!
110445-01
• Water temperature over 125°F (52°C) can cause
severe burns instantly or death from scalds.
• Under certain conditions, this boiler can deliver
hot water (DHW) at temperatures in excess of
the DHW set point on boiler control.
• Children, disabled and elderly are at highest
risk of being scalded.
• Feel water before bathing or showering.
• Installation of an ASSE 1017 or ASSE 1070
certified tempering valve is REQUIRED as
part of this boiler's installation. See Section11
Domestic Water Piping and authority
having jurisdiction for additional details.
• Additional temperature control valves may
also be required at fixtures. See Section 11
Domestic Water Piping and authority having
jurisdiction for additional details.

6
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
3Specifications
Space Heating Ratings Domestic Hot Water (DHW) Ratings1
Model
Number
Input2(MBH) DOE
Heating
Capacity
(MBH)
AHRI
Net
Rating3
(MBH)
AFUE
Input2(MBH) Hot Water Draw Limits GPM (L/min)2
Min Max Min Max
Max
Min4
70°F
(39°C)
Rise
77°
(43°C)
Rise
90°F
(50°C)
Rise
ALTAC-136 13.6 120 112 97 95.0 13.6 136 3.7 (14) 3.4 (13) 2.9 (11) 0.5 (2)
ALTAC-200 20 150 141 123 95.0 20 200 5.2 (19.6) 4.7 (17.8) 4.0 (15) 0.5 (2)
1DHW ratings are not AHRI certified.
2Input and DHW draw limits for elevations up to 2,000 ft. (610 m) with min vent length. See Table 3-3 for derate at
max vent length.
3 Net AHRI Water 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.
4Min DHW flow rate required through boiler to initiate DHW demand. Higher flow rate through fixture may be require
due to mixing at tempering valve and/or fixture itself.
Model
Number
Depth
in. (mm)
Width
in. (mm)
Height
in. (mm)
Space
Heating
Water
sweat, in.
Domestic
Water
sweat, in.
Gas
NPT
Relief
Valve NPT
Maximum
Allowable
Working
Pressure
psig (kPa)
ALTAC-136 16.3 (413) 17.8 (453) 29.8 (757) 1-1/4 3/4 1/2 3/4 50 (345)
ALTAC-200 20.4 (518) 17.8 (453) 29.8 (757) 1-1/4 3/4 1/2 3/4 50 (345)
Table 3-2: Dimensions and Connections
Table 3-1: Ratings
Table 3-3: Air Intake and Vent Lengths
Model Number Intake/Vent Size in. (mm) Min Length
ft. (m)
Max Length
ft. (m)
Approx. Derate at
Max. Length (%)
ALTAC-136 Standard 2 (60) 2.5 (0.76) 70 (21.3) 7
w/ increaser 3 (80) 2.5 (0.76) 135 (41.1) 1
ALTAC-200 Standard 2 (60) 2.5 (0.76) 70 (21.3) 9
w/ increaser 3 (80) 2.5 (0.76) 135 (41.1) 5
Table 3-4: Inlet Gas Pressure Range
Min in. wc (kPa) Max in. wc (kPa)
Natural Gas 2.5 (0.62) 14.0 (3.48)
LP Gas 8.0 (1.99)

7110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
Space Heating Ratings Domestic Hot Water (DHW) Ratings1
Model
Number
Input2(MBH) DOE
Heating
Capacity
(MBH)
AHRI
Net
Rating3
(MBH)
AFUE
Input2(MBH) Hot Water Draw Limits GPM (L/min)2
Min Max Min Max
Max
Min4
70°F
(39°C)
Rise
77°
(43°C)
Rise
90°F
(50°C)
Rise
ALTAC-136 13.6 120 112 97 95.0 13.6 136 3.7 (14) 3.4 (13) 2.9 (11) 0.5 (2)
ALTAC-200 20 150 141 123 95.0 20 200 5.2 (19.6) 4.7 (17.8) 4.0 (15) 0.5 (2)
Figure 3-6: Boiler Connections
3Specifications (continued)
Table 3-5: Weights and Volume
Model
Number
Shipping
Weight
lb (kg)
Empty Boiler
Weight
lb (kg)
Shipping
Crate D
in. (mm)
Shipping
Crate W
in. (mm)
Shipping
Crate H
in. (mm)
Water
Content
gal (L)
Heat
Exchanger
Surface
Area
ft.2(m2)
ALTAC-136 112 (51) 95 (43) 41.4 (1050) 20.0 (508) 18.3 (465) 1.0 (3.8) 11.99 (1.11)
ALTAC-200 135 (62) 116 (53) 41.4 (1050) 20.0 (508) 22.3 (567) 1.3 (4.9) 17.98 (1.67)
Electrical Requirements: 120 VAC, 60 Hz, 1-ph. 1.6A for boiler and internal pump + current draw of any external
pumps connected to boiler.
Controls: Boiler flow switch and integrated manual reset high limit provided with boiler are both UL-353 listed.
LP Gas Conversion: Boiler is shipped from factory configured for natural gas and is field convertible to LP gas. See
Section 15 Start-up and Checkout for instructions to convert to LP gas.
Altitude: Boiler is listed for 0 to 2,000 ft. (610 m). Do not install above 2,000 ft. (610 m).
Safety
Relief
Valve
Vent
Connector
Air Intake
Front View
120 VAC
Knockouts
Low Voltage
Knockouts
Domestic
Cold Water
Inlet
Boiler Return
Condensate Trap
Cleanout
Condensate Drain
Gas
Domestic
Hot Water
Outlet
Boiler
Supply
Bottom View
Combi Block Drain (hydronic side)

8
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
4How It Works
1. Heat exchanger
Water flows through heat exchanger's stainless
steel tubes. Heat is transferred to water as flue
products are cooled below point of condensation
for maximum heat transfer and efficiency. An
enclosure contains and directs flue products to
vent piping.
2. Blower
Pulls air and gas through venturi. Air and gas
mixture is then pushed into burner where it burns
inside combustion chamber.
3. Gas valve
Precisely controls gas flow rate in response to
electronic signal from control.
4. Venturi
Creates suction at gas valve outlet and mixes air
and gas before they flow into blower.
5. Burner (not shown)
Constructed of stainless steel, burner uses
pre-mixed air and gas to meet modulation
requirements.
6. Boiler control (not shown)
Monitors internal and external sensors and
controls blower, gas valve, 3-way valve and
pumps to meet heating and DHW demand.
Control is a "gas adaptive system" that regulates
air and gas flow mixture by measuring flame
ionization and adjusting gas valve to achieve a
target air-fuel ratio. This eliminates need to make
throttle screw or offset adjustments. System is
self-calibrating and continuously maintains air-fuel
ratio at desired value.
7. 120 VAC connection board
Provides field connections for line voltage and two
additional pumps (system pump and aux. pump).
8. Low voltage connection board
Provides field connections for thermostats,
external limits, remote firing devices (4-20mA
or 0-10V), header sensor, outdoor sensor and
LWCO.
9. Control enclosure
Houses boiler control and provides access to
installed fuses and spare fuses.
10. Local user display
Allows review of boiler status and parameter
adjustment. In event of fault condition, LCD
display turns red and fault condition is displayed.
11. Flue temperature sensor
Used to monitor flue gas exiting boiler. Boiler
control will alarm, reduce boiler firing rate and
shut down boiler if flue gas temperature is too
high.
12. Boiler supply temperature sensor (UL 353
Listed)
Dual element temperature sensor used to monitor
boiler water exiting heat exchanger. Boiler control
uses supply temperature to initiate CH burner
demand, adjust firing rate to maintain CH set point
temperature and shut down the boiler if supply
temperature is too high.
13. Boiler return temperature sensor
Used to monitor boiler water entering heat
exchanger.
14. Ignitor/flame sensor
A single ignitor/flame sensor is used to both
provide ignition energy and monitor flame.
15. Air pressure switch
Proves air flow (closes) prior to boiler ignition.
Switch is proven open prior to starting blower.
16. Boiler Pump
Internal boiler pump provides flow through heat
exchanger.
17. Automatic air vent
Connected to pump outlet, air vent helps remove
air from water system.
18. Boiler flow switch (UL 353 Listed)
Proves water is present in boiler and flow rate is
adequate prior to starting boiler.
19. DHW flow sensor
DHW flow sensor monitors DHW water demand.
When DHW detects DHW draw greater than 0.5
gpm, boiler control initiates a DHW heat demand.
20. Plate heat exchanger
Heats domestic water using boiler water.
21. 3-way valve
When DHW flow sensor detects flow and DHW
has priority, 3-way valve is positioned to direct all
boiler water to plate heat exchanger. When CH
demand has priority, valve is positioned to direct
all boiler water to CH zones. 3-way valve's default
position is DHW.
22. DHW temperature sensor
Used to monitor DHW water leaving plate heat
exchanger. Boiler control uses DHW water
temperature to initiate DHW burner demand and
adjusts boiler firing rate to maintain DHW setpoint
temperature.
23. Condensate trap (not shown)
Allows combustion chamber and vent condensate
to drain from boiler while retaining flue products in
boiler.
24. Combi Black Drain (not shown) used to drain
hydronic side water.

9110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
4How It Works (continued)
Figure 4-1: How it works
1
2
4
15
7
8
3
18
12
9
17 13
20 21
22 19 16
11
14
10

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ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
5Locating Boiler
Code Requirements
WARNING
Asphyxiation Hazard.
Adequate combustion and ventilation air must
be provided to assure proper combustion
and to prevent damage to boiler components.
Provide ventilation openings into boiler room as
described in "Air for Ventilation" in this manual.
Combustion air must be brought to boiler from
outdoors using an intake piping system meeting
requirements in Section 7.
!
2. All wiring must comply with National Electrical
Code ANSI/NFPA 70 (in the USA) or the
Canadian Electrical Code CSA C22.1 (in
Canada) and any local regulations.
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. If replacing an existing boiler, check for and
correct common system problems including:
A. System leaks, which can result 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
D. Incorrectly sized expansion tank
2. Boiler is listed for indoor installation only. Do
not install where boiler will be exposed to
freezing temperatures or ambient air temperatures
in excess of 104°F (40°C). Do not install in an
attic.
3. Protect gas ignition system components from
water (dripping, spraying, rain, etc.) during
appliance operation and service (circulator
replacement, condensate trap cleaning, control
replacement etc.).
4. 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.
5. Check for and remove any combustible
materials, gasoline, or other flammable liquids
from area around boiler.
6. Check for and remove any potential combustion
air contaminants from area around boiler and area
around vent/air termination. See Table 5-2.
WARNING
Explosion Hazard.
Do not store or use gasoline or other flammable
vapors or liquids in the vicinity of this or
any other appliance. Do not install vent/air
termination where gasoline or other flammable
vapors or liquids are stored. Avoid locating
vent/air termination near chemical products
containing chlorine, chlorine based salts,
chloro/fluorocarbons, paint removers, cleaning
solvents, and detergents. Boiler could ignite
vapors from flammable liquids resulting in
explosion or fire.
!
Wall Mounting
1. Wall must be plumb and comprised of cement,
brick, block, or wooden studs on 16 in. (406 mm)
centers.
2. If flooding is possible, elevate boiler to prevent
water reaching boiler.
3. Ensure boiler location minimizes risk of water
damage from valves, pumps, etc.
Clearances
1. Provide clearances between boiler jacket and
combustible material in accordance with
authority having jurisdiction. Minimum
clearances to combustible material shown in
Figure 5-1.
2. Provide practical service clearances. 24 in. (610
mm) service clearance are recommended from
left side, right side and front. If providing less
than 24 in. (610 mm) front clearance, ensure
access through a door. Minimum 6 in. (150 mm)
clearance required to remove side panels.
3. Boiler must not be installed on carpeting.
1. Installations must conform to the requirements
of the authority having jurisdiction or, in the
absence of such requirements, to the National
Fuel Gas Code, ANSI Z223.1/NFPA 54, or
Natural Fuel Gas and Propane Installation Code,
CAN/CSA B149.1.
NOTICE: If recommended service clearances
are not provided, it may be necessary to remove
boiler for service.

11110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
Figure 5-1 : Minimum Clearances to Combustible Construction
5Locating Boiler (continued)
Ventilation Air
1. Combustion air must be obtained directly
from outdoors, however ventilation openings
may still be required to prevent overheating of
boiler components if boiler is installed in small
space such as a closet.
2. If a 24" clearance from boiler sides, front, and
bottom can be maintained with all doors to the
boiler room closed, no ventilation openings are
required.
3. If 24" clearances described in (2) cannot be
maintained, provide two openings into
room, one near floor and other near ceiling.
Top of upper opening to be within 12 in. (305 mm)
of ceiling and bottom of lower opening within 12
in. (305 mm) of floor. Minimum free area 100 in.2
(650 cm2) for each opening. This free area takes
into account blocking effect of grills and louvers.
If using screens, minimum screen size 1/4 in. (6.4
mm).
1
4
" (6mm)
6"
(150mm)*
81
4"
(210mm)
1
2
" (13mm)* 1
2
" (13mm)*
Provide access to this area
for inspection and cleanout
of condensate trap
Vent Air
1
2
" (13mm)*
Closet Door
0-12" (0-305mm)
0-12" (0-305mm)
Closet Door
Ventilation Opening
(if required)
Ventilation Opening
(if required)
This boiler is listed for closet installation with
the following clearances from the boiler jacket
to combustible construction:
Top: 8
1
4
" (210mm), Sides:
1
2
" (13mm),
Front:
1
2
" (13mm), Bottom: 6" (150mm)
Clearances also apply to non-combustible
walls, doors, ceilings and floors.
Clearances from piping to combustible
construction:
Non-Concentric Vent (exhaust):
1
4
" (6mm)
Concentric Vent or Air Intake Piping: 0"
Hot Water Piping:
1
4
" (6mm)
*Recommended Service Clearances:
Sides, Front and Bottom: 24" (610mm)

12
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
4. If boiler is installed in room with other
appliances, provide adequate air for combustion
and/or ventilation in accordance with other
appliance manufacturer's instructions and
applicable code. If other appliance(s) require two
openings at least 100 in.2(650 cm2) each, no
additional openings are required for this
boiler.
Combustion Air and Venting
WARNING
Asphyxiation Hazard.
Boiler requires a special venting system
designed for positive pressure. Supplied vent
connector connects to CPVC, polypropylene,
and stainless steel venting listed in Section
7, General Venting. Failure to vent boiler in
accordance with these instructions could cause
products of combustion to enter the building
resulting in severe personal injury, death or
substantial property damage.
!
DANGER
Component Malfunction.
Outdoor combustion air must be piped directly
to boiler air connection. Ensure combustion air
does not contain contaminants and is not drawn
from an area likely to have contaminants per
Table 5-2. For example, never pipe combustion
air from areas near swimming pools or laundry
room exhaust vents. Contaminated combustion
air will damage boiler resulting in severe
personal injury, death or substantial property
damage.
!
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
Table 5-2: Corrosive Combustion Air
Contaminants and Sources
1. Use only vent and air piping and termination
methods listed in Section 7, General Venting. Vent
and air piping must terminate either horizontally
through a sidewall or vertically through a roof or
chase. Locate boiler so vent and air intake piping
can be routed through building and properly
terminated.
2. Ensure installation does not exceed maximum
air and vent pipe lengths and terminations
are located in acceptable location per these
instructions and all applicable local codes.
5Locating Boiler (continued)

13110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
1. If using existing vent system to vent new
boiler, check the following:
A. Material and manufacturer are listed in
Section 7 General Venting.
B. Proper size and length per Table 7-7.
C. Appropriate supports to prevent sagging and
vertical movement.
D. Minimum slope per Section 7 guidelines.
E. Terminations and their location comply with
Section 7 General Venting, Section 8 Sidewall
Direct Venting, or Section 9 Vertical Direct
Venting.
F. Seals and connections per Section 7
General Venting and /or vent system
manufacturer's instructions. System must be
tested per procedure Removing Existing
Boiler in this section.
G. Vent pipe and components should be
replaced if there is any question to their
integrity.
Removing Existing Boiler
5
Locating Boiler (continued)
DANGER
Asphyxiation Hazard.
Do not vent this boiler into a common vent with
any other appliance. Connecting this boiler to a
common vent will cause products of combustion
and/or carbon monoxide to enter living space
as well as appliance malfunction, resulting in
severe personal injury, death or substantial
property damage.
!
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 the appliances remaining connected to it.
At the time of removal of an existing boiler, the
following steps shall be followed with each
appliance remaining connected to the common
venting system placed in operation, while the
other appliances remaining connected to the
common venting system are not in operation:
1. Seal any unused openings in the common venting
system.
2. Visually inspect the venting system for proper size
and horizontal pitch and determine there is no
blockage or restriction, leakage, corrosion, and
other deficiencies which could cause an unsafe
condition.
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 the building. Turn on clothes dryers
and any appliance not connected to the common
venting system. Turn on any exhaust fans, such as
range hoods and bathroom exhausts, so they will
operate at maximum speed. Do not operate a
summer exhaust fan. Close fireplace dampers.
4. Place in operation the appliance being inspected.
Follow the Lighting (or Operating) Instructions.
Adjust thermostat so appliance will operate
continuously.
5. Test for spillage at the draft hood relief opening
after 5 minutes of main burner operation. Use
the 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
the minimum size as determined using the
appropriate tables in Chapter 13 of the National
Fuel Gas Code, ANSI Z223.1/NFPA 54.
Residential Garage Installation
1. If installing in residential garage or adjacent
space open to garage that is not part of living
space:
A. Burner and burner ignition devices must be a
minimum of 18 in. (46 cm) above floor.
B. Boiler must be located and/or protected to
prevent damage from moving vehicle.
2. Follow local codes for locating a residential boiler
in a garage or National Fuel Gas Code, ANSI
Z223.1/NFPA 54. in absence of such codes.
Connecting New Boiler to Existing Vent
System
WARNING
Asphyxiation Hazard.
If any of below conditions cannot be met,
existing vent system must be updated or
replaced. Failure to follow these instructions
could cause products of combustion and/ or
carbon monoxide to enter living space, resulting
in severe personal injury, death or substantial
property damage.
!

14
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
6
Preparing Boiler
Remove boiler and miscellaneous parts carton from
outer shipping carton.
CAUTION
Boiler Damage.
Do not attempt to lift boiler using water or gas
pipe connection as hand holds.
!
CAUTION
Boiler Damage.
Do not drop boiler. Damage to boiler can result.
CAUTION
Heavy Object.
Boiler weighs up to 130 lb (59 kg). Two people
are required to lift boiler onto wall mounting
bracket. Ensure wall bracket is anchored
to structure capable of supporting weight of
boiler and attached piping when filled with
water. Areas subject to earthquakes may have
special requirements that take precedence over
requirements in these instructions.
!
!
Unpack Boiler
Figure 6-1: What's in the Box
Boiler
Misc. Parts
Carton
Wall
Retaining
Clip (2X)
Wall Hook
DHW
Connector (2X)
Gasket (2X)
(1/2" Rubber)
Header
Gasket (2X)
(3/4" Rubber)
Gas Valve
Inlet Adapter
Gasket
(3/4" Paper)
Vent
Connector
Temp./Pressure
Gauge
Lag Screw (4X)
Screw (4X)
Drain
Valve
Safety
Relief
Valve
Gas
Shutoff
Valve
Washer (4X)
A A
B B
4
4
3
3
2
2
1
1

15110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
6
Preparing Boiler (continued)
1. Remove vent connector and screws from
miscellaneous parts carton.
2. Check vent reducer on top of heat exchanger to
ensure it is installed properly.
WARNING
Asphyxiation Hazard.
A boiler operating with an improperly installed
vent reducer (3" to 2") could cause unreliable
operation at elevated carbon monoxide levels
resulting in severe personal injury, death, or
substantial property damage.
3. Lubricate heat exchanger vent gasket with
soapy water.
4. Insert vent connector through jacket into heat
exchanger with flue gas sample port facing
forward. See Figure 6-2.
5. Tighten 4 screws.
Install Vent Connector
Figure 6-2: Installing Vent Connector
Flue gas sample
port facing front
of boiler
Vent Connector
Attach with
(4) screws
Figure 6-3: Gas Valve Fuel Setting
Preparing for Fuel Conversion
If using LP gas. LP conversion requires (2)
steps: gas valve setting adjustment and control
parameter change.
1. Use 2.5 mm hex wrench to adjust gas valve
setting from “1” to “2” (Figure 6-3). For easy
access to gas valve remove left side panel using
(2) Phillips screws. (136 combi only)
2. See Section 15 “Start-Up and Checkout” for
Control Parameter adjustment instructions.
!

16
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
2 X 4
Wood Stud
Drywall or other
sheathing
Boiler
Wall Bracket
(2X)
Retaining Clip
(4X) 5/16" X 2"
Lag Screw
(4X) 5/16" Flat Washer
See detail
Installed Retaining
Clip Detail
Support
Rail
Rear of
Boiler
Retaining
Clip
Figure 6-5: Mounting Boiler on Wall
6
Preparing Boiler (continued)
Figure 6-4: Wall Layout and Mounting Holes
18" (457mm)
30" (762mm)
16" (406mm)
1" (25mm)
.4" (10mm)
1" (25mm)
2.5" (64mm)
5" (127mm)
6" (152mm)
10" (254mm)
13" (330mm)
14" (356mm)
2.5" (64mm)
9" (229mm)
14" (356mm)
C D
Boiler Outline
Relief Valve
C
L
Vent
C
L
Air C
L
Boiler Supply
C
L
Gas
C
L
DHW Out
C
L
DCW In
C
L
Boiler Return
C
L
Condensate Drain
C
L
A B
1. Wall bracket is designed to mount on studs
with 16 in. (406 mm) centers or a masonry
wall. For other stud spacing, mount bracket
to 3/4 in. (19 mm) plywood or horizontal 2 x 4
anchored to studs.
CAUTION
Heavy object.
Do not mount boiler to a hollow wall. Boiler must
be anchored to studs.
2. Mark wall bracket hole locations using dimensions
shown in Figure 6-4. Ensure bracket is level.
3. For wood studs, drill 3/16 in. (4.8 mm) pilot holes
"A" and "B" and attach bracket using provided
5/16 in. x 2 in. lag screws and washers. For wood
studs with drywall or paneling greater than 1/2
in. (12 mm) thick, metal studs, or masonry wall,
use anchors suitable for boiler weight and
appropriate for wall material.
4. Hang boiler on wall bracket. See Figure 6-5.
5. Attach bottom retaining clips to boiler and mark
hole locations. Drill 3/16 in. (4.8 mm) pilot holes
"C" and "D" and attach to wall using provided 5/16
in. x 2 in. lag screws or other anchors appropriate
for wall material.
6. Verify boiler is level and plumb.
!
Mount Boiler

17110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
7General Venting
Figure 7-1: Sidewall
Termination with Fittings -
see Section 8 for details
Figure 7-2: Sidewall Low
Profile Termination - see
Section 8 for details
Figure 7-3: Sidewall
Concentric Termination -
see Section 8 for details
Direct Vent Sidewall Termination Options
Direct Vent Vertical Termination Options
Figure 7-4: Vertical
Termination with Fittings -
see Section 9 for details
Figure 7-6: Vertical Termination
with Abandoned B-vent or
Chimney Chase - see Section 9
for details
Figure 7-5: Vertical
Concentric Termination - see
Section 9 for details

18
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
7General Venting (continued)
Model
Number
Vent/Air
Size in.
(mm)
Min
Equivalent
Length ft.
(m)
Max
Equivalent
Length ft.
(m)
Approx.
Derate at
Max Length
(%)
ALTAC-136 2 (60) 2.5 (0.76) 70 (21.3) 7
3 (80) 2.5 (0.76) 135 (41.1) 1
ALTAC-200 2 (60) 2.5 (0.76) 70 (21.3) 9
3 (80) 2.5 (0.76) 135 (41.1) 5
Table 7-7: Vent and Air Sizing
1. Min and max lengths are calculated separately for
air and vent. For example, max length 135 ft. (41.1
m) means up to 135 ft. (41.1 m) air piping and up
to 135 ft. (41.1 m) vent piping.
Table 7-8: CPVC/PVC Fitting Equivalent Lengths
Fitting Equivalent Length ft. (m)
2 in. 3 in.
90° Short Elbow 6.0 (1.8) 10 (3.0)
90° Sanitary Elbow 2.6 (0.8) 4.0 (1.2)
45° Elbow 1.5 (0.5) 2 (0.6)
3. Maximum length of flexible polypropylene venting
is reduced due to higher pressure drop. See
Table 7-10.
4. If using B-vent air chase, 1 ft. (0.30 m) B-vent
equals 1 equivalent ft. ( 0.30 m).
WARNING
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 property damage.
• Vent installations shall be in accordance
with provisions of the National Fuel Gas Code,
ANSI Z223.1/NFPA 54, or "Natural Gas and
Propane Installation Code, CAN/CSA B149.1,
or applicable requirements of the local building
codes.
• This boiler requires a special venting system.
Use only CPVC, PVC, or polypropylene venting
systems listed in Tables 7-11 or 7-16.
• Thoroughly inspect finished vent and air
piping to ensure air-tightness and compliance
with provided instructions and code
requirements.
• Do not mix components from different venting
systems.
• Covering non-metallic vent pipe and fittings
with thermal insulation is prohibited.
• Follow all local codes for isolation of vent pipe
when passing through floors or walls.
• Do not use a barometric damper, draft hood,
or vent damper with this boiler.
• Do not connect any other appliance to vent
pipe or multiple boilers to a common vent pipe.
• Follow instructions in Section 5, Locating
Boiler, when removing a boiler from an existing
vent system.
• Failure to comply with any of the above
requirements could result in severe personal
injury, death or substantial property damage.
!
Vent and Air Sizing
2. If using 2 in. x 3 in. increaser, use max 12 in. (305
mm) of 2 in. pipe before increaser. For equivalent
length, count only 3 in. (80 mm) pipe starting from
increaser.
DuraVent
PolyPro
Centrotherm
InnoFlue
Selkirk
PolyFlue
2 in. (60 mm)
45° elbow 3 ft. (0.91 m) 3 ft. (0.91 m) 3.3 ft. (1.0 m)
2 in. (60 mm)
90° or 87°
elbow
5 ft. (1.5 m) 5 ft. (1.5 m) 4.8 ft.
(1.5 m)
3 in. (80 mm)
45° elbow 3 ft (0.91 m) 3 ft. (0.91 m) 3.6 ft. (1.1 m)
3 in. (80 mm)
90° or 87°
elbow
7 ft. (2.1 m) 7 ft. (2.1 m) 7.2 ft.
(2.2 m)
Table 7-9: Rigid PolyPro Fitting Equivalent Lengths
Table 7-10: Flexible Polypropylene Equivalent
Length for 1 ft. (0.30 m) Measured Length
DuraVent
PolyPro
Flex
Centrotherm
InnoFlue
Flex
Selkirk
Polyflue Flex
2 in.
(60 mm)
2 ft.
(0.61 m)
2.5 ft.
(0.76 m)
2.5 ft.
(0.76 m)
3 in.
(80 mm)
2 ft.
(0.61 m)
2.3 ft.
(0.70 m)
2.36 ft.
(0.70 m)

19110327-04 - 1/22
ALTA Combi Installation, Operating & Service Instructions
7General Venting (continued)
CPVC/PVC Venting
WARNING
Asphyxiation Hazard.
• Use only vent materials, primer, and cement
listed in Table 7-11 to make vent connections.
• Use of cellular core PVC (ASTM F891), cellular
core CPVC, or Radal® (polyphenolsulfone) in
venting systems is prohibited.
• PVC vent systems must include at least 30 in.
(760 mm) of CPVC pipe and one CPVC elbow
between boiler and PVC vent piping.
• CPVC is required within any interior space
where air cannot circulate freely, including a
vertical or horizontal chase, inside a stud wall, in
a closet, and through wall penetrations.
• Maintain clearances to vent piping per Figure
5-1.
• Failure to comply with venting instructions
could cause products of combustion and/or
carbon monoxide to enter the building, resulting
in severe personal injury, death or substantial
property damage.
!
NOTICE: PVC may not be used to penetrate
combustible or non-combustible walls unless all
of the following conditions are met. If any of these
conditions cannot be met, use CPVC for wall
penetration. See Figure 7-14.
• Wall penetration is at least 66 in. (1.7 m) from
boiler measuring along vent pipe.
• Wall is less than or equal to 12 in. (305 mm)
thick.
• Air space shown in Figure 7-14 is maintained
around outside diameter of vent.
1. Slope CPVC/PVC vent pipe not less than 1/4 in.
per foot (21 mm per m) upwards from boiler to
vent terminal for condensate drainage.
2. Support CPVC/PVC pipe at intervals not
exceeding 4 ft. (1.2 m).
3. Be sure to use appropriate primer and cement
when joining CPVC to PVC. The following or
equivalent may be used to join CPVC to PVC:
A. Primer: IPS P-70
B. Cement: IPS 790
Material Standard
Vent Pipe
CPVC, sched. 40 or 80 ASTM F441
PVC, sched. 40 or 80 ASTM D1785
PVC, DWV ASTM D2665
Vent
Fittings
CPVC, sched. 80 ASTM F439
PVC, sched. 40 ASTM D2466
PVC, sched.80 ASTM D2467
PVC, DWV ASTM D2665
Primer/
Cement
CPVC ASTM F493
PVC ASTM D2564
Table 7-11: Listed CPVC/PVC Vent Materials
4. Work from boiler towards vent or air
termination. Do not exceed maximum
equivalent lengths shown in Table 7-7. See
Table 7-8 for equivalent lengths of elbows
and fittings.
5. Starting from the boiler, first 30 in. (760 mm)
of vent pipe and first elbow must be CPVC.
30 in. (760 mm) CPVC pipe may be cut at any
location and CPVC elbow installed between
two resulting CPVC pipes before transitioning to
PVC. PVC coupling may be used to join CPVC to
PVC vent piping. See Figure 7-12.
WARNING
Asphyxiation Hazard.
All CPVC/PVC vent joints must be glued. Failure
to comply could cause products of combustion
and/or carbon monoxide to enter the building,
resulting in severe personal injury, death or
substantial property damage.
!
NOTICE: In Canada, CPVC and PVC vent pipe,
fittings, and cement/primer must be ULC-S636
listed.
5. Example equivalent length calculation for 2 in.
vent:
A. 1 ft. CPVC straight pipe =1 eq ft.
B. 90° CPVC short elbow = 6 eq ft.
C. 1.5 ft. CPVC straight pipe=1.5 eq ft.
D. Coupling = 0 eq ft.
E. 10 ft. PVC straight pipe = 10 eq ft.
F. 90° PVC sanitary elbow = 2.6 eq ft.
G. 15 ft. PVC straight pipe = 15 eq ft.
H. PVC coupling (terminal) = 0 eq ft.
I. Total vent length = 36.1 eq ft.
(acceptable length per Table 7-7)
6. Listed Air Piping Materials
A. PVC/CPVC
B. Polypropylene
C. B-vent double wall vent (with joints and
seams sealed with RTV silicone)
7. Listed Vent Materials
A. CPVC/PVC - See Table 7-11
B. Polypropylene - See Table 7-16

20
ALTA Combi Installation, Operating & Service Instructions
110327-04 - 1/22
7General Venting (continued)
6. CPVC/PVC vent starter kits are available. Kits
include 30 in. (760 mm) CPVC pipe, 90° short
CPVC elbow, PVC coupling (vent terminal), 90°
short PVC elbow (air terminal), and 2 terminal
screens. Components in these kits are not
ULC-S636 listed and are therefore not usable in
Canada.
A. 2 in. kit: 107039-01
B. 3 in. kit: 107039-02
7. Allow for 3/8 in. (9.5 mm) of thermal
expansion per 10 ft. (3.0 m) of CPVC/PVC pipe. If
a straight run of pipe exceeds 20 ft. (6.0 m) and
is restrained at both ends, an offset or expansion
loop is required per Figure 7-15. If a straight
horizontal run of pipe exceeds 20 ft. (6.0 m) and
is restrained at one end with an elbow at the other,
ensure hanger or guide is not less than Y in from
elbow per Figure 7-15. Thermal expansion fittings
not permitted.
8. All air piping may be PVC.
9. Vent and air can be up-sized to 3 in. for
longer runs. If up sizing to 3 in. vent material,
maximum length of 2 in. pipe is 12 in. (305 mm)
before transitioning with 2 x 3 CPVC increaser
for vent piping and similar PVC fittings for air.
Increaser must be installed in vertical section of
pipe. See Figure 7-13.
10. Cut pipe squarely and debur inside and
outside of pipe ends after cutting.
11. Dry fit all vent and air components before
cementing any joints.
12. Use field supplied primer and cement
appropriate for materials being joined. Follow
primer and cement instructions to join pipe
and fittings.
13. Clean all pipe ends and fittings with
appropriate primer before cement. Apply
primer to both pipe and fitting socket before
applying cement.
14. Boiler vent connector is gasketed. Lubricate
gasket with soapy water, insert pipe until it
bottoms out, and tighten clamp.
15. Boiler air connector in PVC socket fitting. Drill
7/32 in. (5.5 mm) hole in air connector. Drill
1/8 in. (3.2 mm) hole in air pipe to align with hole
in connector. Insert pipe into air connector and
use #10 x 1 in. sheet metal screw to secure. Seal
joint between air connector and pipe with RTV
silicone.
16. To the extent possible, slope horizontal air
piping towards outdoors.
At least 30in. (760mm)
of CPVC pipe and one
CPVC elbow required
between boiler and PVC
vent piping.
PVC coupling may
be used to join CPVC
to PVC vent pipe.
Clamp
To vent
termination
From air
termination
Max. 12in. (305mm)
2in. CPVC pipe
3in. X 2in. CPVC
Increaser
At least 30in. (760mm) of
CPVC pipe and one CPVC
elbow required between
boiler and PVC vent piping.
PVC coupling may
be used to join CPVC
to PVC vent piping.
3in. X 2in. PVC
Increaser
Clamp
Max. 12in. (305mm)
2in. PVC pipe
To vent
termination
From air
termination
Figure 7-12: Near Boiler CPVC/PVC Venting
Figure 7-13: Near Boiler CPVC/PVC Venting with
Increaser
Note: Length of 2 in. pipe is counted toward 30 in.
CPVC requirement.