Central Boiler MaXIM M255 PE User manual

OWNER’S MANUAL
SAVE THESE
INSTRUCTIONS
(p/n 9001003 - REV. A)
WARNING: If the information in this manual is not followed exactly, a re or explosion may result causing
property damage, personal injury or loss of life.
– Do not store or use gasoline or other ammable vapors and liquids in the vicinity of this or any other appliance.
– WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch.
• Immediately call your gas supplier. Follow the supplier’s instructions.
• If you cannot reach your gas supplier, call the re department.
– Installation and service must be performed by a qualied installer, service agency or the gas supplier.
0117PS024S
0117PS024E
M255 PE
WOOD PELLET FURNACE

CentralBoiler, Inc. • 20502 160th Street • Greenbush, MN 56726
CentralBoiler.com
For parts and accessories, service or repairs, call your authorized Central Boiler dealer or heating contractor. Record
the information below for future reference.
Model Serial Number Installation Date
Dealership Name Phone Number
Owner Name
e Maxim Wood Pellet Furnace is listed by OMNI-Test Laboratories to the applicable portions of the following standards: UL 2523-
2018 Solid Fuel-Fired Hydronic Heating Appliances, Water Heaters and Boilers, CAN/CSA B415.1-10 (R2015) Performance Testing
of Solid-Fuel-Burning Heating Appliances, CSA-B366.1-11 (R2015) Solid-Fuel-Fired Central Heating Appliance, ASTM E2618-
13 Standard Test Method for Measurement of Particulate Emissions and Heating Eciency of Solid Fuel-Fired Hydronic Heating
Appliances, ASTM E2515-11 Standard Test Method for Determination of Particulate Matter Emissions Collected by a Dilution
Tunnel.
e Maxim Wood Pellet Furnace includes two 4-foot stainless steel insulated chimney sections. Use only stainless steel solid fuel
chimneys specied by CentralBoiler. Maximum draft is marked on nameplate.
French Owner's Manual is available at CentralBoiler.com/support or upon request from your dealer
(Manuel d'installation en français disponible sur demande auprès de votre revendeur)
MAXIM M255 PE Annual Eciency Rating*: 96.2% (lower heating value), 89.22% (higher heating value)
Manufacturer's Rated Heat Output Capacity: 190,000 Btu/hr
ermal Output Rating: 182,504 Btu/hr (53.5 kW) - maximum
Water Capacity: 90 gal. | Weight: 1,297 lbs
*Performance is a product of the combustion rate, combustion eciency and heat exchange eciency with a single fuel load without refueling. Results
vary based on wood species, wood quality, wood quantity and moisture content. Eciencies are determined under the same test conditions using
higher heating value, lower heating value and annual fuel utilization eciency (AFUE).
• is heater meets the 2020 U.S. Environmental Protection Agency's cord wood emission limits for wood heaters sold after May 15, 2020.
Under specic test conditions this heater has been shown to deliver heat at rates ranging from 0 to 182,504 Btu/hr.
• is wood heater has a manufacturer-set minimum low burn rate that must not be altered. is wood heater needs periodic inspection and
repair for proper operation. It is against federal regulations to operate this wood heater in a manner inconsistent with operating instructions in
this manual.
• DO NOT OVERFIRE THIS HEATER. Attempts to achieve heat output rates that exceed heater design specications can result in permanent
damage to the heater.
• Any person(s) operating a hydronic heater must comply with all applicable laws, including but not limited to local ordinances.
• Improper use or failure to maintain the hydronic heater may cause nuisance conditions. e person(s) operating a hydronic heater is/
are responsible for operation in a manner that does not create a nuisance condition. Meeting the setback distance and stack height
recommendations from the manufacturer and requirements in applicable State and local regulations may not always be adequate to prevent
nuisance conditions in some areas due to terrain or other factors.
• Operating an outdoor furnace may not be suitable to some individuals' abilities or lifestyles. Be sure to review the Owner's Manual for the
appliance with your dealer.
- Register at time of purchase for FREE 5 Year Limited Warranty -
Verify your warranty at: CentralBoiler.com/w25

Contents
How to Use This Guide
e guide is divided into sections
to help with the operation and
maintenance of the outdoor furnace.
If questions arise that are not
answered with this manual, consult
with your authorized CentralBoiler
dealer.
Central Boiler Online Resources................................................................. Iv
EPA Resources ............................................................................... Iv
Labeling and Terminology ......................................................................1
Important Precautionary Information ................................................. 2
Removing from Pallet..........................................................................4
Shipping Slot Covers ...........................................................................4
Selecting a Location ...........................................................................5
Foundation...................................................................................5
Levelling the Outdoor Furnace ..................................................................6
Clearances ...................................................................................6
Electrical - Grounding Rod ......................................................................7
Access to Ports on Outdoor Furnace ..............................................................8
Furnace Installation - Connecting toYour Existing System ...........................................9
Outdoor Furnace Best Burn Practices ............................................................11
Chimney Recommendations ...................................................................11
Assembling Chimney Transition Box and Insert / Chimney Installation................................11
Maxim Chimney Transition Box and Insert........................................................12
Chimney Draft ...............................................................................12
Water Quality and Maintenance ..................................................... 14
Test Supply Water ............................................................................14
Add Initial Water Treatment....................................................................14
Fill withWater and Purge Air...................................................................15
Immediately Start the Pump(s) and Heat the System Water to 185˚F (85˚C)...........................17
Test the Treated System Water..................................................................18
System Maintenance .........................................................................19
Water Test Kits and Test Results.................................................................19
Flushing the System ..........................................................................21
Adding Antifreeze to Outdoor Furnace System ....................................................22
Fuel Selection ..................................................................... 23
Fuel Quality and Storage ......................................................................23
Other Important Information About Fuels........................................................23
Operating Instructions ............................................................. 24
Filling the Hopper ............................................................................24
Power Up ...................................................................................24
Basic Operation ..............................................................................24
Lighting Instructions .........................................................................24
Auger Prime.................................................................................24
Relighting after a Fire Out .....................................................................25
Operating Precautions ........................................................................26
Smoke in Hopper.............................................................................27
Routine Maintenance .............................................................. 28
Maintenance Sections .............................................................. 28
Section 1 - Water Level ........................................................................28
Section 2 - Ash Removal.......................................................................28
Section 3 - Firebox............................................................................30
Section 4 - Gaskets ...........................................................................30
Section 5 - Heat Exchangers and ChimneyTransition...............................................31
Section 6 - Aerator and Burn Chamber...........................................................32
Section 7 - Door and Hopper ...................................................................34
Section 8 - Check Fuel Door Operation ...........................................................34
Section 9 - Thermal Valve......................................................................35
Section 10 - Test Thermal Valve .................................................................39
Troubleshooting................................................................... 40
General Information ............................................................... 46
Wiring Diagram ................................................................... 47

MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
INSTALLATIONS IN MASSACHUSETTS:
1. All installation components must be products approved in the Commonwealth of Massachusetts by the Gas and Plumbing Board.
2. e maximum run of tubing from the water heater to a fan coil is 50 linear feet.
3. Persons operating this hydronic heater are responsible for operation of the hydronic heater so as not to cause a condition of air pollution as
dened in 310 CMR 7.01(1).
Videos to supplement the Owner's Manual are available at
www.youtube.com/centralboilerinc
Watch tips on initial startup, testing system water and more.
CentralBoiler.com/Support
Online Support Center
Write your serial number here for future reference.
EPA RESOURCES
EPA's Burnwise Program - https://www.epa.gov/burnwise
NOTE: The warranty can be voided by operating a residential hydronic heater in a manner inconsistent with the Owner's Manual.
CENTRAL BOILER ONLINE RESOURCES
Enter CentralBoiler.com in your browser or scan the code using any QR code reader app on your smartphone to access
CentralBoiler's library of information to help with installation, operation and maintenance of your CentralBoiler outdoor furnace.
Detailed Furnace Installation Variations - https://www.CentralBoiler.com/explore/furnace-installation/
View and/or download PDFs to assist in installation of your outdoor furnace. Information and examples
regarding pumps, foundations, chimneys and support structures, ermoPEX piping, and example congurations
for a variety of heating congurations.
Online Support Center
https://www.CentralBoiler.com/Support/
Enter your furnace serial number and nd articles,
answers, parts and more information.

1
MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Labeling and Terminology
e outdoor furnace and this guide use the following terms and symbols to
bring attention to the presence of hazards of various risk levels and important
information concerning the use and maintenance of the outdoor furnace.
This symbol and text indicate an imminently hazardous situation which, if ignored,
will result in death or serious injury.
This symbol and text indicate the presence of a hazard which can cause severe personal
injury or death to an operator or bystander, or substantial property damage if ignored.
CAUTION
This symbol and text indicate the presence of a hazard which can cause minor personal
injury or property damage if ignored.
NOTE: Indicates supplementary information worthy of particular attention relating
to installation, operation, or maintenance of the outdoor furnace but is not related to a
hazardous condition.
Be sure to follow all instructions and related precautions as they are meant for
your safety and protection. Store this manual in a readily accessible location for
future reference.
Maxim M255 PE Measurements
A B C D E F G
117.5**34
86
in.
cm
57 49.5 36 48 59.5*
298.5**145 126 91.5 122
H
14.5
37151*
STAR
byCentral Bo iler
FIRE
WaterTemp
CleanOut
Mode
Hold
toLight
Press
Twice
forAuto
Relight
Holdto
Prime
Press
Twice
toClean
Power
TM
Ignition
AutoRelight
Enabled
p/n9507
Auger
AirAdjust
5%100% 60%
HeatOutput
20%65% 1%
HIGH MEDIUM LOW
D
A
B
E
C
G
F
Measurement (G) with two 4-foot chimney sections.
Measurement (F) is from firebox door to chimney
inspection cover.
*
**
H

2MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Important Precautionary Information
Be sure to read carefully and understand these precautions before, during and after the installation, operation and
maintenance of the furnace.
NOTE: All operations must be in accordance with local and state
codes which may dier from the information in this manual.
NOTE: Installation of the outdoor furnace is to be performed by a
qualied installer.
NOTE: Check with your insurance company to see if they have any
location requirements.
NOTE: Any changes to an existing boiler should be done by a
qualied installer in accordance with applicable codes.
NOTE: Do not connect this outdoor furnace to a chimney ue
serving another appliance.
CAUTION
This outdoor furnace is not intended to be the only source of
heat. In the event of a prolonged power failure, a generator
may be used to prevent lines from freezing. Should the outdoor
furnace be left unattended, run out of fuel or require service, an
alternate heating source in the building being heated should
be in place to prevent damage caused by freezing.
This outdoor furnace is not intended or certied to be installed
inside habitable space. Do not install the outdoor furnace
inside your home.
NOTE: If installed in a non-habitable building, adequate
combustion air and ventilation must be provided.
This outdoor furnace and/or chimney is not intended or safety
tested to be used or installed in a building where contents of
that building could be damaged or where a nancial loss could
occur from smoke, soot, re or water.
This outdoor furnace and/or chimney must not be installed
inside or under any conguration or construction that contains
combustible materials as part of the structure or conguration.
The chimney is not intended or safety tested to be used or
installed other than on the furnace located outside of any
structure or enclosure.
CAUTION
This outdoor furnace is not to be connected to a chimney ue
serving another appliance.
The outdoor furnace vent cap must t loosely on the vent
opening. Do not force the cap down or try to seal it tightly onto
theventpipe.Donotextendorrestrictthe ventpipe or opening.
DO NOT ALLOW THE OUTDOOR FURNACE TO BE PRESSURIZED.
Be sure the outdoor furnace is lled with water before ring.
Water level is safe when the water level indicator rod is above
the vent cap. MolyArmor 350 must be added before the initial
ll (see Water Quality and Maintenance).
Water level is safe when water level
indicator is above vent cap.
Disconnect the electrical power to the outdoor furnace and
remove all ashfrom thereboxbefore performingmaintenance
that requires draining the water or replacing an electrical
component.
Do not attempt service inside the electrical control panel
without rst disconnecting the electrical power at the main
power source.
NOTE: Any electrical installation should be done by a qualied
installer in accordance with applicable codes.

3
MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Use only chimneys listed to UL 103 HT for installation. The
chimney and ue pipe must be clean and in good condition.
Allow the outdoor furnace to thoroughly cool and completely
clean out the rebox before draining water from the outdoor
furnace. If the water in the outdoor furnace ever boils, be sure
to check the water level and restore to full. If water is added,
the proper level of MolyArmor 350 Corrosion Inhibitor (p/n
2900630) must be maintained.
When cleaning the outdoor furnace, be careful not to spill any
hot ash.
ALWAYS store ash in a covered non-combustible container.
Maintain the following clearances from combustibles for the
furnace installation:
• 8" (20 cm) from the transition box
• 6" (15 cm) from the sides
• 48" (122 cm) from the front
• 8" (20 cm) from the chimney
• 27" (68.5 cm) from the top
• The foundation must be noncombustible
Do not allow combustible materials (straw, hay or wood) near
the outdoor furnace. Keep the perimeter of the outdoor furnace
clear and clean.
All covers must be maintained at all times except during
maintenance, inspection and service.
Never leave the rebox door or hopper lid open or ajar when
unattended.
This heater is designed to burn premium quality wood pellets
only.* Higher eciencies and lower emissions generally result
when burning premium quality wood pellets, as compared to
standard pellets. DO NOT BURN: unseasoned wood, garbage,
tires, lawn clippings, leaves, brush trimmings or general yard
waste, materials containing asbestos, materials containing
lead, mercury or other heavy toxic metals, materials containing
plastic,materialscontaining rubber, wastepetroleumproducts,
paints and paint thinners, asphalt products, chemicals, coal,
glossy or colored paper, construction and demolition debris,
plywood, particleboard, salt water driftwood and other
previously salt water saturated materials, manure, animal
carcasses and asphalt products. Burning these materials may
result in release of toxic fumes or render the heater ineective
and cause smoke.
CAUTION
Never use gasoline, gasoline-type lantern fuel, kerosene,
charcoal lighter uid, or similar liquids to start or ‘freshen up’a
re in this outdoor furnace. Keep all such liquids well away from
the outdoor furnace while it is in use.
Use only those listed fuels recommended by the manufacturer
of your unit. Never use the following: trash, plastics, gasoline,
rubber, naptha, household garbage, material treated with
petroleum products (particle board, railroad ties and pressure
treated wood), leaves, paper products, and cardboard.
NOTE: Chloride or sulfurous gases can be generated if plastic or
rubber is burned and will mix with the moisture from the wood
and form hydrochloric or sulfuric acids in the rebox, creating
corrosion.
CAUTION
Always wear the appropriate personal protective gear when
cleaning ash from the rebox.
CAUTION
Failure to maintain and clean heat exchangers properly can
result in the thermal valve activating.
NOTE: At least one circulation pump must run continuously to
ensure proper operation of the outdoor furnace.

4MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Removing from Pallet
e outdoor furnace is secured to the shipping pallet with four brackets. To
remove these brackets, loosen (but do not remove) the two screws securing
each shipping slot cover and slide the cover up. Remove the bolts securing the
bracket to the pallet and remove the bracket.
NOTE: Lift the outdoor furnace only where specied in the illustration.
STAR
byCentralBoiler
FIRE
WaterTemp
CleanOut
Mode
Hold
toLight
Press
Twice
forAuto
Relight
Holdto
Prime
Press
Twice
toClean
Power
TM
Ignition
AutoRelight
Enabled
p
Auger
AirAdjust
5%100%60%
HeatOutput
20%
65% 1%
HIGHMEDIUMLOW
Place forklift tines
under furnace within
areas shown.
No
Forks
OPTION #1
OPTION #2
Use forklift, chain
and hook here.
No
Forks
30"
30"
Shipping Slot Covers
Position each shipping slot cover so it is ush with the bottom of the outdoor
furnace; then secure the cover by tightening the two screws. Make sure all four
covers are properly positioned and secured.
Tools/Ground Rod Kit
Included with each new furnace are
tools that are invaluable for maintenance
and cleaning and a Ground Rod Kit
for electrically grounding the furnace.
Use the ue brush kit to clean the ue
passageways. e cleaning rod can be
used to clean the rebox. It is also used to
clean the heat exchangers.
Refer to the Maintenance section for more
information.
Cleaning Rod
Ground Rod Kit
Flue Brush Kit
Options for Increasing Fuel Storage
An optional 48-Bushel Hopper is
available (p/n 9660 or 9760) for
increasing fuel storage. is hopper
can be positioned to the side of the
furnace using a 5-1/2' Auxiliary Auger
Kit (p/n 9440).
A 6' Auxiliary Auger Kit (p/n 6453)
and an 8' Auxiliary Auger Kit (p/n
9454) are also available for other
applications. e auxiliary augers can
also be used with larger external bins.
An optional Auxiliary Auger Vibrator
with Timer Kit (p/n 9458) can
be installed on the auxiliary auger
connected to an external hopper.
Vibration occurs based on a timer
setting.

5
MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Foundation
e outdoor furnace may be installed directly on stable, level ground without
the necessity of a foundation. If the ground is unstable, one option is to use
patio blocks, bricks or pavers under the base. Another option is to pour a
concrete foundation. If installing on an existing slab, it may be necessary to use
patio blocks, bricks or pavers to allow access to the water lines.
Front
Top View
Side View
Internal
Frame Support
Patio Blocks, Bricks or Pavers
Patio Blocks, Bricks or Pavers
To install the outdoor furnace on a concrete foundation, account for the
location of the hollowed-out area. A 4" to 6" (10 cm to 15 cm) thick concrete
slab works well; however, a thicker slab may be used to obtain the desired
rebox door opening height.
Maxim Furnace Base Dimensions
Optional 48-Bushel
Hopper with Furnace Base Dimensions
Furnace Base Dimensions
Do not use any combustible
materials for the foundation.
CAUTION
Optional 48-Bushel
Fuel Hopper
48"
48"
34"
12"
12.5"
Maxim
Furnace
Front
49.5"
37"
34"
12"
12"
Maxim
Furnace
Front
49.5"
37"
NOTE
Furnace must be installed on a noncombustible
surface or foundation that incorporates an enclosure
that will prevent supply and return lines from possible
exposure to sunlight, fire, or physical damage that
may be caused by an occurrence outside the furnace
enclosure.
NOTE: In all installations, the outdoor furnace must not be operated with the back panels
removed. Make necessary allowances for access to the back of the outdoor furnace.
If the area for the concrete slab is unstable or subject to frost heaving, consider
installing 2" closed-cell insulation under the front portion of the concrete slab
the outdoor furnace will be installed on, and under the area around the slab
used for walking.
Selecting a Location
To ensure the Maxim Furnace
functions as designed, careful
planning and proper installation
are imperative. If any installation
questions arise that cannot be
answered by the information in this
manual, be sure to contact your
dealer.
When selecting a suitable location,
carefully consider each of the
following:
❑Must be installed in accordance
with all applicable codes and
regulations.
❑A qualied installer must
perform the installation of this
supplementary outdoor furnace
and must determine how to
install it to be compatible with
the existing heating source.
❑Consider prevailing winds and
the direction exhaust from the
chimney will travel.
❑e shorter the distance
between the outdoor furnace
and building(s) being heated,
the lower the cost will be for the
installation of the hot supply
and return water lines and
insulation.
❑Be sure to maintain the required
clearances to combustibles and
recommended maintenance
clearances.
❑ermoPEX pre-insulated
piping is recommended for
all underground installations.
Other types of piping should
not be buried in low-lying areas
with standing water or with a
very high water table, or under
an area of heavy vehicle trac
unless protected from excessive
compression.

6MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Levelling the Outdoor Furnace
CAUTION
The back of the furnace must not be lower than the front of the furnace.
e Maxim should be leveled so that the back of the transition box (i.e., the
burner auger motor end) is slightly higher than the front. Smoke can condense
into creosote inside the burner auger tube. If the burner auger is not sloped
down toward the front of the furnace, condensation can form in the burner
auger tube and drip into the transition box.
Disconnect the electrical power at the main power source.
1. Disconnect the electrical power at the main power source.
2. Remove the access panels from the back corner of the furnace and set aside.
3. Place a level on the back of the burner auger motor as shown. e back of
the transition box should be slightly higher than the front, indicated when
the level is vertical and there is a small gap (from 1/16" to 3/32", or 1.6
mm to 2.4 mm) between the level and the top of the burner auger motor
and no gap between the level and the bottom of the burner auger motor.
4. Use shims as necessary under the outdoor furnace in the locations shown
until the procedure in Step 3 indicates that the back of the transition box
is slightly higher than the front.
NOTE: Periodically check that the outdoor furnace is leveled as described in these
instructions because frost can cause the foundation to move.
5. Install the access panels on the back corner of the furnace.
6. Connect the electrical power at the main power source.
Clearances
NOTE: Clearance to combustibles from the chimney transition box is 8" (20 cm);
HOWEVER, if installing with the back of the furnace facing an immovable wall, object,
etc., you must maintain 36" (91.5 cm) of clearance to perform periodic maintenance.
Maintain the following clearances from combustibles for the installation:
• 8" (20 cm) from the transition box
• 6" (15 cm) from the sides
• 48" (122 cm) from the front
• 8" (20 cm) from the chimney
• 27" (68.5 cm) from the top
• The foundation must be noncombustible
3/4
1" CENTRAL PEX
Small Gap
(No less
than 1/16")
Place Decal
Here
No Gap
Centered
Shims
Use shims to position
feed assembly as shown.
NOTE
Foundation Foundation
Shim
(Shown in black)
Maxim Leveling Procedure
Foundation
Wall
36 in. Min.
(91.5 cm) Min.

7
MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Electrical - Grounding Rod
NOTE: Any electrical installation should be done by a qualied installer in accordance with
applicable codes.
e outdoor furnace must be electrically bonded to ground in accordance with
the requirements of the authority having jurisdiction or, in absence of such
requirements, with the National Electrical Code, ANSI/NFPA 70 and/or the
Canadian Electrical Code Part 1, CSA C22.1 Electrical Code.
Install the ground rod included with the outdoor furnace and connect it to the
outdoor furnace.
1. In the water line trench near the outdoor furnace, drive the ground rod
into the ground until the top of the ground rod is below the ground
surface.
2. Remove the side and back panels; then route the ground wire from the
ground rod under the outdoor furnace base and over to the bottom left
corner at the back of the outdoor furnace.
3. Secure the ground terminal with the self-drilling screw provided. Secure
the ground wire to the terminal; then secure the ground wire to the
ground rod with the clamp. Tighten all hardware securely.
Ignitor Operation - Ignition Sequence
e ignition sequence follows a control logic to ensure safe and eective
ignition. e ignition sequence is as follow:
1. e water temperature must be low enough for the furnace to shift into
demand mode.
2. e fan will start and operate at the ignition fan speed and the Firestar
control will send voltage to the igniter relay.
3. e air proving switch will close, completing the ignition relay control
circuit.
4. e electric ignitor will warm up and heat the air blowing across it into
the burn chamber.
5. e auger will cycle periodically to feed the required amount of fuel into
the burn chamber, and to agitate any pellets already present in the burn
chamber.
6. e ignitor will operate until the burn chamber reaches a temperature
that is high enough to sustain itself, or for ten minutes, at which time the
ignitor will turn o.
3/4
1" CENTRALPEX
3/4
1" CENTRALPEX
1" CENTRALPEX
Side View of Pump
Access Area
Ground
Terminal
Ground Rod
Clamp
NOTE: Incoming
power, Handy box,
duplex and cover
must be wired by a
certified electrician
or qualified installer.
NOTE: Must be
earth-grounded for
furnace to function
properly. Install the
ground rod. The
ground terminal
can be mounted to
any galvanized tin
withing the pump
acces area.

8MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Access to Ports on Outdoor Furnace
Access to the hot supply and return ports is gained by removing the access
panels on the lower right-hand side and back of the furnace. ere are two
hot supply and two return ports on the furnace. is conguration allows for
mounting the circulation pumps on the furnace.
1" CENTRAL PEX
3/4
1" CENTRAL PEX
3/4
1" CENTRAL PEX
1" CENTRAL PEX
1" CENTRAL PEX
1" CENTRAL PEX
Side View Rear View
ReturnReturn SupplySupply
ere are eight knock-out tabs on the oor panel of the furnace to
accommodate the water lines. ese align with the hollowed-out area in the
foundation specications. e pump access area in the back right corner must
align with the blocked out area of the foundation.
NOTE: The Installation Guide provides more information on pump selection. For even more
detailed information, see the Hydronic Component Selection Guide (p/n 2482), available
from your CentralBoiler dealer.
Maxim
with Wrap-around-pump Installed
1" CENTRAL PEX
3/4
1" CENTRAL PEX
3/4
1" CENTRAL PEX
1" CENTRAL PEX
1" CENTRAL PEX
1" CENTRAL PEX
Area of Focus
Side Rear
Side
3/4
1"CENTRAL PEX
3/4
1"CENTRAL PEX
1"CENTRAL PEX
1"CENTRAL PEX
1"CENTRAL PEX
1"CENTRAL PEX
198
410 388
5800004
225
119
556
224
296
1334 5926
1330
118
Qty p/n Description
Parts List
1 198 Ball Valve, 3/4"
2 5800004 Taco 007 Pump
2 118 Close Nipple, 3/4"
1 119 Pump Flange Kit, 3/4"
1 410 Ball Valve, 1-1/4"
4 1330 PEX Adapter, 1" x 3/4"
1 224 Isolation Flange, 3/4"
1 225 Isolation Flange, 1-1/4"
1 388 Hex Bushing, 1-1/4" x 3/4"
2 556 Power Supply Cord, 32"
2 296 Swing Check Valve, 3/4"
4 1334 PEX 90° Elbow, 1"
12 5926 Stainless Steel Clamp, 1"
Parts and accessories sold separately.
Pump size may vary.
Side View Rear View
NOTE: At least one circulation pump
must run continuously to ensure proper
operation of the outdoor furnace.

9
MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Furnace Installation - Connecting to Your Existing System
A common installation is to connect the outdoor furnace to an existing water
heater and then to an existing forced air system. A water-to-air heat exchanger
is mounted in the plenum or duct work of the existing furnace. Heated water
from the outdoor furnace either continuously ows through the water-to-air
heat exchanger or is diverted through a 3-way zone valve. When the thermostat
senses the need for heat, the fan on the existing furnace forces air through the
heat exchanger, transferring heat throughout the existing ductwork.
NOTE: There are numerous ways to connect to your heating system. Refer to the
CentralBoiler Outdoor Furnace Installation Guide for other installations.
Detailed Furnace Installation Variations
Visit CentralBoiler.com to access
a library of detailed illustrations
for connecting to a wide variety of
existing heating systems and for
other heating options.
H
C
M
R
Hot Supply
Water-to-Water
Heat Exchanger
Bypass Line
Thermostatic
Mixing Valve
This horizontal assembly
must not exceed a height
of 4 inches (10 cm) above top
of water heater.
Existing
Water
Heater
1"
Central
PEX®
Optional Bypass
Valve
Heat
Exchanger
Plenum
Existing
Forced Air
Furnace
For illustration purposes only,
water heater styles may vary.
NOTE
A pump must be installed in the hot
supply line between the outdoor furnace
and thermostatic valve. Outdoor furnace
water temperature setpoint should be
set at 185˚F (85˚C) minimum.
NOTE
Installer must comply with all
applicable codes and regulations.
NOTE
Any electrical installation should
be done by a qualified installer
in accordance with applicable
codes.
NOTE: A certified electrician must
do the electrical installation.
Typical Installation
Connecting to Water Heater and Forced Air Furnace
Hot Supply from Pump
on Outdoor Furnace
Return to Outdoor Furnace
Optional Thermostatic Valve

10 MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
To Heating
System
From Heating
System
Hot Supply from Pump
on Outdoor Furnace
Return to
Outdoor Furnace
Remote
Thermal
Storage
Tank
For illustration purposes only;
system components may vary.
NOTE
Installer must comply with all
applicable codes and regulations.
Remote Thermal Storage Installation
Connecting to Remote Thermal Storage Tank

11
MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Chimney Recommendations
In higher populated areas, extend the chimney to a height above the roofs
of surrounding buildings. Use CentralBoiler Chimney Extensions when
extending the chimney. When only the standard eight feet (2.4 m) of chimney
are used, the sections must be secured at the connection joint with four (4)
screws to stabilize the extension.
Assembling Chimney Transition Box and Insert /
Chimney Installation
NOTE: Instructions are also provided with the furnace. For these steps, refer to the
illustration on the next page.
1. Place the Chimney Transition Box into position on the back of the
furnace. Secure with hardware provided.
2. Using the #8-18 x 1/2" Self-tapping Screws provided, assemble the
Chimney Transition Box Insert sides to the insert top and insert bottom
as shown in Fig. 1. e screws are installed from the inside. Make sure the
insert sides are assembled inside the anges on the insert top and bottom
and the anges on the insert sides are positioned to the outside. e hole
on the insert top must be positioned toward the back as shown.
3. Cut the 2-foot length of foil tape provided into six pieces approximately
4" long each. Wrap the assembled Chimney Transition Box Insert with the
insulation as shown.
4. Secure the top and rear edges of the insulation to the assembly with the
pieces of foil tape. e tape will hold the insulation in place when the
insert is installed in the chimney transition box.
5. Carefully slide the assembly with insulation into the Chimney Transition
Box.
6. Using the screws provided, install the latch to the bottom of the chimney
box as shown.
7. Install the Chimney Transition Box Cover and secure with the latch.
Outdoor Furnace
Best Burn Practices
1. Read and follow all operating
instructions supplied by the
manufacturer.
2. FUEL USED: Only those
listed fuels recommended by the
manufacturer of your unit. Never
use the following: trash, plastics,
gasoline, rubber, naphtha,
household garbage, material
treated with petroleum products
(particle board, railroad ties and
pressure treated wood), leaves,
paper products, and cardboard.
3. LOADING FUEL: For
a more ecient burn, pay
careful attention to loading
times and amounts. Follow
the manufacturer’s written
instructions for recommended
loading times and amounts.
4. STARTERS: Do not use lighter
uids, gasoline, or chemicals.
5. CHIMNEY
RECOMMENDATIONS:
In higher populated areas,
extend the chimney to a height
above the roofs of surrounding
buildings.
6. Always remember to comply
with all applicable state and local
codes.
Be considerate of neighbors when
operating your furnace. If you
use your furnace in the summer
months, be certain your chimney
exhaust is not adversely aecting
neighbors with open windows.

12 MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Maxim Chimney Transition Box and Insert
Chimney Draft
Proper draft is necessary for the Maxim to operate
optimally. Draft occurs when the temperature in the
chimney is high enough and/or the chimney is high enough
to cause a negative pressure that "pulls" the exhaust up and
out the chimney. e higher the burn rate and fan settings,
the more sections of chimney that will be required to
provide proper draft.
NOTE: Adding more chimney sections increases the amount of
negative pressure in the chimney.
NOTE: A qualied installer may perform the following test to check
for proper draft.
1. Drill a hole in the chimney inspection cover; then with
the outdoor furnace and chimney at normal operating
temperature, use a manometer to check draft. Flue draft
should be between -0.02 in. WC (-5 Pa) and -0.05 in.
WC (-12.45 Pa). If the ue draft is lower, add more
chimney sections.
2. After the test, ll the hole in the chimney inspection
cover with high-temp silicone.
3. If a spark arrestor is being used, make sure it is clean
and unobstructed.
4. Objects like buildings and trees in close proximity or
nearby terrain (e.g., hills, valleys, etc.) can adversely
aect air ow in the chimney. Adding chimney
sections may overcome these factors.
May cause poor draft.
Allows for better draft.

13
MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
If extensions are added to the standard eight feet (2.4m) of chimney, the chimney
should be reinforced appropriately. e illustration shows chimney support
recommendations when three or more sections are used. When adding sections
of chimney, make sure that there is nothing within the fall zone of the chimney
that could be damaged. If something is located within the fall zone and cannot be
removed, guy wires or braces may need to be installed to prevent a falling chimney
from causing damage.
NOTE: If more than three 4-foot (1.2-m) sections of chimney are used, a support (e.g., a pole, pipe
or other structural support) may be installed from the ground that can withstand wind. Other
reinforcement recommendations are shown.
NOTE: For chimney extensions or chimney replacement, use only genuine Central Boiler
chimney components. Parts are available from an authorized CentralBoiler dealer.
e installation of a spark arrestor is recommended, particularly where there are
dry conditions or where there is combustible material near the unit, unless the
installation of a spark arrestor is prohibited by local requirements.
NOTE: If the screen is left on the chimney cap, the spark arrestor should be inspected and
cleaned as needed.
Use common sense to avoid potential res, including exercising caution when
disposing of ashes, cleaning and refueling. Keep all highly combustible materials
(e.g., gasoline, propane, leaves, pine needles, etc.) away from an operating unit at
all times. Take special precautions in windy conditions.
NOTE: You may need to increase the chimney height if conditions occur that force exhaust to
low levels.
Chimney Reinforcement Recommendations
for Maxim M255 Models
STAR
byCentralBoiler
FIRE
WaterTemp
CleanOut
Mode
Hold
toLight
Press
Twice
forAuto
Relight
Holdto
Prime
Press
Twice
toClean
Power
TM
Ignition
AutoRelight
Enabled
p/n9507
Auger
AirAdjust
5%100% 60%
HeatOutput
20%65% 1%
HIGH MEDIUM LOW
Chimney
Guy-Wire
Band Kit
(p/n 776)
Fall Zone
If objects are placed in the fall zone of the chimney, a
Chimney Guy-Wire Band Kit (p/n 776) or additional bracing
is recommended.
Additional bracing may be necessary in
certain areas such as those subject to severe
weather, winds, freezing rain, etc.
Inspect all bracing bi-annually for integrity.
•
•
NOTE
STAR
byCentralBoiler
FIRE
WaterTemp
CleanOut
Mode
Hold
toLight
Press
Twice
forAuto
Relight
Holdto
Prime
Press
Twice
toClean
Power
TM
Ignition
AutoRelight
Enabled
p/n9507
Auger
AirAdjust
5%100% 60%
HeatOutput
20%65% 1%
HIGH MEDIUM LOW
STAR
byCentralBoiler
FIRE
WaterTemp
CleanOut
Mode
Hold
toLight
Press
Twice
forAuto
Relight
Holdto
Prime
Press
Twice
toClean
Power
TM
Ignition
AutoRelight
Enabled
p/n9507
Auger
AirAdjust
5%100% 60%
HeatOutput
20%65% 1%
HIGH MEDIUM LOW
Two 1" electrical
conduit sections
(not supplied)
Chimney Attachment
Ring (p/n 774)
Must be located directly
below Chimney Band
Clamp to reduce stress
on the joint.
Five or More Sections
When five or more sections of
chimney are being used, a Chimney
Band Clamp Kit for each joint and a
Chimney Attachment Ring
(p/n 774) are recommended.
Three or Four Sections
When three or four sections of
chimney are being used, a Chimney
Snaplock Clamp (p/n 6500011) for
each joint is recommended.
Two 3/4"electrical
conduit sections
(not supplied)
Chimney
Snaplock Clamp
(p/n 6500011)

14 MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
WATER QUALITY AND MAINTENANCE
Test Supply Water
Test a sample of the supply water (makeup water) that will be used to ll the
outdoor furnace (softened water is recommended). Test strips for testing pH
are included in the water test kit which is provided with the outdoor furnace.
1. Collect a small sample of the water to be used to ll the outdoor furnace
in a clean container.
2. Dip a test strip from the test kit in the water sample for 1 second and
remove. Shake o excess liquid (very important to prevent water bleed
from one pad to the other). Compare the pH test pad to the color chart at
30 seconds.
3. If the pH level is between 6.5 and 8.0 and there are no other known water
quality problems, then the outdoor furnace may be lled with this water.
4. Water that has a pH level of less than 6.5 or greater than 8.0, or that
has other known water quality problems, should not be used to ll the
furnace. Instead, water should be supplied from a dierent source.
Add Initial Water Treatment
CAUTION
Avoid damaging your furnace and voiding your warranty. Add water treatment
BEFORE adding water to the system.Water treatment in your outdoor furnace is just as
important as the oil in a car's engine.
MolyArmor 350 Corrosion Inhibitor (p/n 2900630) gives optimum protection
for the furnace water jacket and system parts when it is used to initially treat
the water and is maintained at a minimum of 350 ppm of moly and pH level
between 8.0 and 9.5. One unit of MolyArmor 350 is a 1-gallon (3.78-liter)
container.
MOLYARMOR 350 TREATMENT AMOUNTS
Maxim M255 PE 1/2 gallons
Add the recommended amount of MolyArmor 350 to the outdoor furnace.
NOTE: If the system has a larger than normal water capacity, more MolyArmor 350 should
be added at a recommended rate of 6.5 oz. (190 ml) per 10 gallons (37.8 liters) of system
water. One unit (1 gallon or 3.78 liters) of MolyArmor 350 will treat 200 gallons (757 liters)
of system water.
SEE HOW IT'S DONE
CentralBoiler.com > Support

15
MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
Fill with Water and Purge Air
NOTE: The items referred to in this procedure correspond to the items in the illustration
below.
All air must be purged from the water lines when lling the system. Also, the
circulation pump(s) must be installed in the hot supply line(s).
NOTE: If using the valve on the water heater to ll the outdoor furnace, ush the water
heater to remove all sediment before lling the outdoor furnace.
NOTE: If the outdoor furnace is being lled with water when the temperature is below
freezing, circulate the water immediately after lling to prevent freezing the water lines.
NOTE: Be sure to ll the outdoor furnace with water of good quality (softened water, if
possible). See Water Quality and Maintenance section.
Use the procedure in this section to ll the outdoor furnace with water and
purge the air from the system. All valves in the outdoor furnace system that
allow circulation through each circuit should be open before starting. Perform
this procedure on each pump circuit from the outdoor furnace.
NOTE: Add MolyArmor 350 (p/n 2900630) through the vent pipe BEFORE lling with water
to immediately begin to protect the steel.
1. Connect the male end of garden hose A to valve #1 using the backow
preventer and two 3/4" female hose x 3/4" male pipe adapters (p/n 4928).
Connect the female end of the garden hose to valve #2.
2. Close the valves on the hot supply and return lines of the outdoor furnace.
H
C
M
R
Hot
Supply
Backflow
Preventer
Hot
Supply
Valve #1
1" Central
PEX®
Bypass
Line
Plenum
Forced Air
Furnace
Return Line
NOTE: For illustration purposes only.
Actual configuration may vary.
NOTE
Installer must comply with
all applicable codes and
regulations.
NOTE
A pump must be installed in the hot
supply line between the outdoor furnace
and thermostatic valve.
Valve #2
Valve #5
Optional
Thermostatic
Valve
Valve #3
Hose A
Valve #4 Valve #6
(Seasonal Manual
Bypass Valve)
Water
Heater
NOTE
Outdoor furnace water temp
setpoint should be set at
185˚F (85˚C) minimum.
Filling Outdoor Furnace and Purging Air
Using Pressurized Domestic Water

16 MAXIM OUTDOORWOOD PELLET FURNACE • OWNER'S MANUAL
3. Close valve #4 and valve #5.
4. Open valve #1 and valve #2. is step begins lling the system with
domestic water and purging the hot supply line and thermostatic valve.
5. Remove cap from valve #3 and open valve #3 slightly to purge air from
valve body. Close valve #3 when air is purged.
6. Open valve #5.
7. Open the valve on the hot supply line of the outdoor furnace for 5
minutes; then close the valve. Water will purge air from the hot supply
line. e valve and attached ttings on the outdoor furnace will become
cold as water starts lling into outdoor furnace.
8. Close valve #5, #1 and #2.
9. Move hose A from valve #2 to valve #3.
10. Open valves #1, #3 and #4.
NOTE: Skip to Step 12 if your system does not have a seasonal manual bypass valve (valve
#6 shown in Fig. 35).
11. Valve #6 (seasonal manual bypass valve) should be positioned to direct
water through the heat exchanger rst.
12. Open the valve on the return line of the outdoor furnace.
NOTE: Skip to Step 14 if your system does not have a seasonal manual bypass valve (valve
#6 shown in Fig. 35).
13. As soon as the valve on the return line of the outdoor furnace is opened,
turn valve #6 to the bypass direction for 30 seconds; then turn valve #6
back to previous position.
NOTE: The heat exchanger manifold (lower manifold rst) and ttings will become cold as
water ows through the heat exchanger to the outdoor furnace.
14. Allow outdoor furnace to ll until the controller no longer indicates
.
15. Close valves #1 and #3. Disconnect hose A and replace caps on valves #1,
#2 and #3.
16. Open the valve on the hot supply line of the outdoor furnace and valve
#5.
NOTE: The valves on the hot supply and return lines of the outdoor furnace, and valves
#4 and #5 should all be open, allowing the pump to circulate heated water in the system.
Start pump.
NOTE: If there are multiple circuits connected to the outdoor furnace, repeat the process
for each circuit.