Central Boiler MaXIM M255 PE User manual

WOOD PELLET FURNACE
OWNER’S MANUAL
M255 P; M255 PE
Portland
Oregon USA
OMNI-Test Laboratories, Inc.
Tested &
Listed By
US Save This Manual
For Future Reference
(p/n 9000311 - REV. A) - 15-MAY-2015
117-O-24-2

by Central Boiler, Inc.
20502 160th Street • Greenbush, MN 56726
CentralBoiler.com • MaximHeat.com
The Maxim Wood Pellet Furnace is listed by OMNI-Test Laboratories to the following standards: CAN/CSA B366.1-M91-2007 Solid
Fuel-Fired Central Heating Appliances, UL 391-2006 Solid Fuel and Combination Fuel Central and Supplementary Furnaces.
French Owner's Manual and decal set available upon request from your dealer.
(Manuel d'installation en français et décalcomanies disponible sur demande auprès de votre revendeur)
Manuel d'installation en français : p/n 9000269 Décalcomanies : p/n 9409
The Maxim Wood Pellet Furnace includes two 4-foot chimney sections (6" ASHT) listed to UL 103.
Maxim M255 P / M255 PE thermal output rating: 165,215 Btu/hr (47.5 kW) - maximum
Thermal Output Rating*: Manufacturer's Rated Heat Output Capacity: 180,000 Btu/hr
Annual Efciency Rating*: 89% (lower heating value), 82% (higher heating value)
*Performance is a product of the combustion rate, combustion efciency and heat exchange efciency with a single fuel load without refueling.
Results vary based on wood species, wood quality, wood quantity and moisture content. Efciencies are determined under the same test conditions
using higher heating value, lower heating value and annual fuel utilization efciency (AFUE).
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
• This heater is certied to comply with the 2015 U.S. Environmental Protection Agency's particulate emission standards for
wood heaters sold after May 15, 2015. Under specic test conditions this heater has been shown to deliver heat at rates
ranging from 0 to 165,215 Btu/hr.
• This wood heater has a manufacturer-set minimum low burn rate that must not be altered. This 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.
• This model is qualied for year-round use.
• 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. The person(s) operating a hydronic
heater is/are responsible for operation in a manner that does not create a public or private nuisance condition. Check State
and local regulations for stack height requirements, setback distances and for the time of the year the appliance may be
operated before installation. Meeting the 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.
• This outdoor furnace should not be installed in a building that could be damaged or where a nancial loss could occur from
smoke, soot or water.
Vermont certication is with wood pellets as a fuel source ONLY.
INSTALLATIONS IN MASSACHUSETTS:
1. All installation components must be products approved in the Commonwealth of Massachusetts by the
Gas and Plumbing Board.
2. The minimum 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).

Table of Contents
INTRODUCTION ..................................................................................... 4
SECTION 1 – GENERAL INFORMATION.................................................................. 7
Specications and Dimensions...................................................................... 7
Removing from Pallet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Shipping Slot Covers ............................................................................. 7
Potable Water ................................................................................... 8
Antifreeze ...................................................................................... 8
Corrosion Inhibitor Plus™.......................................................................... 8
Shut-Off Valves .................................................................................. 8
SECTION 2 – LOCATION AND FOUNDATION.............................................................. 9
Selecting a Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Foundation ..................................................................................... 9
Leveling the Outdoor Furnace ..................................................................... 10
Clearances .................................................................................... 11
SECTION 3 – ELECTRICAL ........................................................................... 12
Ground Rod ................................................................................... 12
SECTION 4 – GAS SUPPLY CONNECTION (P MODELS) AND IGNITOR OPERATION ............................ 13
Gas Supply Connection .......................................................................... 13
How to Operate the Gas Ignitor .................................................................... 13
Ignition Sequence - P Models...................................................................... 14
Ignition Sequence - PE Models..................................................................... 14
SECTION 5 – CHIMNEY .............................................................................. 15
Chimney Height ................................................................................ 15
Chimney Draft.................................................................................. 16
SECTION 6 – SYSTEM INSTALLATION.................................................................. 17
SUPPLY AND RETURN LINES .................................................................... 17
Above Ground or Winter Installations ................................................................ 17
Digging the Trench .............................................................................. 18
Underground Electric Wire ........................................................................ 18
Connecting to Existing Heating System .............................................................. 18
Backlling Water Line Enclosure ................................................................... 18
CIRCULATION PUMPS .......................................................................... 19
Water Flow .................................................................................... 19
Access to Ports on Furnace ....................................................................... 19
Installing Circulation Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Shut-Off Valves ................................................................................. 21
Filters ........................................................................................ 21
Thermostatic Valves ............................................................................. 21
MAXIM THERMOSTATIC VALVE - HOW IT WORKS ........................................................ 22
Purging Air from the System - Manual Air Bleeders ..................................................... 23
WATER HEATER INSTALLATION .................................................................. 23
EXISTING FORCED AIR INSTALLATION ............................................................ 24
Thermostatic Controls............................................................................ 27
HEATING MULTIPLE ZONES OR BUILDINGS ........................................................ 28
HYDRONIC INSTALLATIONS ..................................................................... 29
Pressurized Water System Installations .............................................................. 30
Water-to-Water Heat Transfer System ............................................................... 30
Vented System Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Direct Circulation Baseboard Installation ............................................................. 32
Radiant Floor System Installations .................................................................. 33
Pool and/or Hot Tub Heating....................................................................... 36
SECTION 7 – FILLING SYSTEM WITH WATER AND PURGING AIR ........................................... 37
FILLING OUTDOOR FURNACE WITH WATER AND PURGING AIR ....................................... 37
SECTION 8 – OPERATING INSTRUCTIONS .............................................................. 39
Fuel Quality and Storage ......................................................................... 39
FireStar Controller............................................................................... 39
Operating Precautions ........................................................................... 39
Filling the Hopper ............................................................................... 40
Smoke in Hopper ............................................................................... 40
SECTION 9 – ROUTINE MAINTENANCE................................................................. 41
ROUTINE MAINTENANCE........................................................................ 42
9.1 Water Level................................................................................. 42
9.2 Ash Removal................................................................................ 42
9.3 Firebox .................................................................................... 42
9.4 Gaskets.................................................................................... 43
9.5 Heat Exchangers and Chimney Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
9.6 Aerator and Burn Chamber..................................................................... 44
9.7 Door and Hopper ............................................................................ 45
9.8 Check Fuel Door Operation .................................................................... 45
9.9 Thermal Valve ............................................................................... 45
9.10 Test Thermal Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
9.11 Gas Ignitor................................................................................. 47
WATER QUALITY AND MAINTENANCE ............................................................. 48
POST HEATING SEASON MAINTENANCE .......................................................... 50
SECTION 10 – TROUBLESHOOTING ................................................................... 51
SECTION 11 – DECALS .............................................................................. 56
SECTION 12 – WIRING DIAGRAMS..................................................................... 57
SECTION 13 – PARTS LISTINGS ....................................................................... 59

4
Labeling and Terminology
The outdoor furnace and this owner's manual 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
furnace.
DANGER: Indicates an imminently hazardous situation
which, if not avoided, will result in death or serious
injury.
WARNING: Indicates presence of a hazard which
can cause severe personal injury, death, or substantial
property damage if ignored.
CAUTION: Indicates presence of a hazard which will
or 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 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.
Foreword
This manual is to be used as a guideline for the
installation, operation and maintenance of the Maxim
Wood Pellet Furnace. This manual is organized into
thirteen sections for easy reference.
Section 1 – General Information;
Section 2 – Location and Foundation;
Section 3 – Electrical;
Section 4 – Gas Supply Connection and
Ignitor Operation;
Section 5 – Chimney;
Section 6 – System Installation;
Section 7 – Filling System with Water and
Purging Air;
Section 8 – Operating Instructions;
Section 9 – Routine Maintenance;
Section 10 – Troubleshooting;
Section 11 – Decals;
Section 12 – Wiring Diagram;
Section 13 – Parts Listing.
Anyone owning or operating this outdoor furnace must
read, fully understand, and follow all of the information
in this manual.
NOTE: In higher populated areas, extend
the chimney to a height above the roofs of
surrounding buildings (see Chimney Height in
the Chimney section).
NOTE: The outdoor furnace may be connected
to an existing boiler system or hot water heating
system by a qualied installer only. However, the
outdoor furnace must not be pressurized.
INTRODUCTION

5
WARNING
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 system 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.
WARNING
This outdoor furnace is not intended or certied
to be installed inside habitable space. Do not
install the outdoor furnace inside your home.
CAUTION
This outdoor furnace should not be installed in
a building that could be damaged or where a
nancial loss could occur from smoke, soot or
water.
WARNING
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.
WARNING
Installation of the outdoor furnace is to be
performed by a qualied installer.
WARNING
When installing a heat exchanger on an existing
hot water boiler, be sure none of the existing
system safety controls are disabled.
WARNING
If this appliance is installed inside a building and
the LP tank capacity exceeds one pound, the tank
and regulator must be located outside.
WARNING
Maintain the following clearances from
combustibles for the outdoor 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
WARNING
Use only chimneys listed to UL 103 HT for
installation. The chimney and ue pipe must be
clean and in good condition.
WARNING
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 (Fig. 1).
Corrosion Inhibitor Plus™ must be added before
the initial ll (see Water Quality and Maintenance).
Fig. 1
WARNING
Do not allow combustible materials (straw, hay
or wood) near the outdoor furnace. Keep the
perimeter of the outdoor furnace clear and clean.
WARNING
Never leave the rebox door or hopper lid open
or ajar when unattended.
IMPORTANT PRECAUTIONARY INFORMATION
The information contained on this page appears throughout this manual. Be sure to read carefully and
understand these precautions before, during and after the installation, operation and maintenance
of the furnace.

6
WARNING
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.
WARNING
Burn premium quality wood pellets only.
WARNING
This heater is designed to burn premium quality
wood pellets only. Higher ef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, materials containing rubber,
waste petroleum products, 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 ineffective and cause smoke.
WARNING
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 the vent pipe. Do
not extend or restrict the vent pipe or opening.
DO NOT ALLOW THE OUTDOOR FURNACE TO
PRESSURIZE.
WARNING
Disconnect the electrical power to the furnace
and remove all ash from the rebox before
performing maintenance that requires draining
the water or replacing an electrical component.
WARNING
Allow the outdoor furnace to thoroughly cool
before draining water from the outdoor furnace.
Never drain water from the outdoor furnace with
live ash or re in the rebox. 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 Corrosion Inhibitor Plus™ (p/n
1650) must be maintained.
WARNING
When cleaning the outdoor furnace, be careful
not to spill any hot ash.
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.
CAUTION
Always wear the appropriate personal protective
gear when cleaning ash from the rebox.
WARNING
Sulfuric acid in the test kit is a corrosive acid.
Handle carefully. Carefully read and follow
precautions on test chemical labels. Keep test
chemicals away from children. Safely dispose of
tested samples.
NOTE: All installations and operations must be
in accordance with local and state codes which
may differ from the information in this manual.
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.
NOTE: Chloride or sulfurous gases can be
generated if plastic or rubber is burned and will
mix with the moisture from the wood pellets and
form hydrochloric or sulfuric acids in the rebox,
creating corrosion.
NOTE: If installed in a non-habitable building,
adequate combustion air and ventilation must be
provided.
IMPORTANT PRECAUTIONARY INFORMATION
The information contained on this page appears throughout this manual. Be sure to read carefully and
understand these precautions before, during and after the installation, operation and maintenance
of the furnace.

7
Anyone owning or operating this outdoor furnace must
read, fully understand, and follow all of the information
in this manual.
Specications and Dimensions
Fig. 2
Maxim M255 P; 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*
© 2014 Central Boiler
STAR
byCentral B oile r
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
NOTE: See Section 5 for chimney installation
guidelines.
NOTE: The Maxim Furnace includes two 4-foot
(1.2-meter) ASHT 6" in diameter chimney sections
listed to UL103HT. For chimney sections or
chimney replacement, use only genuine Central
Boiler chimney components. Parts are available
from an authorized Central Boiler dealer.
Removing from Pallet
The 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 by Fig. 3.
Fig. 3
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 (Fig. 4).
Fig. 4
SECTION 1 – GENERAL INFORMATION
Section 1 - General Information

8Section 1 - General Information
Options for Increasing Fuel Storage
An optional 48-Bushel Hopper is available (p/n 9660
or 9760) for increasing fuel storage. This 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. The 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.
Potable Water
If the outdoor furnace is to heat potable water associated
with commercial food preparation or for heating milk-
house hot water, it is recommended to install a double-
wall heat exchanger. Also, when lling the system with
water, a backow preventer must be installed in the line
used for lling.
Antifreeze
Most outdoor furnaces are installed without antifreeze
when an existing heating system is in place and there
is no anticipation of leaving the outdoor furnace
unattended for extended periods of time. If the building
being heated has an alternate heat source, system water
may be kept from freezing by running the circulating
pump(s) and drawing heat from the existing heat
emitter(s).
To prevent freezing if the outdoor furnace is not red for
extended time periods or if lengthy power outages are
anticipated during cold weather, a nontoxic propylene
glycol boiler-type may be used in the system. Some
types of antifreeze that contain various inhibitors
have been known to create problems like coagulation
and jelling. To prevent potential problems, do not
use propylene glycol that is premixed with unknown
inhibitors. Central Boiler Corrosion Inhibitor Plus (p/n
1650) is compatible with straight propylene glycol. It is
important to use Corrosion Inhibitor Plus with straight
propylene glycol for corrosion protection.
If adding antifreeze to the system, it is imperative
that the entire system contain at least 30% antifreeze
concentration mixed with softened water to prevent
bacterial growth and minimize minerals in the system.
Bacterial growth is likely to occur with low antifreeze
concentrations and can cause corrosion in the furnace
water jacket and/or clogging of heat exchangers. To
conrm the antifreeze solution is adequate, allow the
pumps to circulate for at least 24 hours and then obtain
a sample of the system water. Using an antifreeze tester,
the solution must be protected to 0˚F (-18˚C) or below.
NOTE: Be sure to adhere to all warnings and
precautions on the antifreeze label.
NOTE: Do not use automotive or RV types of
antifreeze.
NOTE: If using antifreeze, use Test Kit (p/n 597)
when testing the treated water in the outdoor
furnace (see Water Quality and Maintenance).
Corrosion Inhibitor Plus™
To aid in protecting the system from corrosion, it is
imperative to add Central Boiler Corrosion Inhibitor
Plus™ (p/n 1650). When initially lling the system (see
Finalizing the Installation), add the Corrosion Inhibitor
Plus™ before adding water to the system. Any time
water is added to the system, Corrosion Inhibitor Plus™
must be added if a tested water sample indicates it is
necessary (see Water Quality and Maintenance).
Corrosion Inhibitor Plus™ is composed of common
materials and is biodegradable. However, in keeping
with good safety and environmental practices, the
supplier recommends the following if draining treated
system water becomes necessary:
• You may drain the outdoor furnace to a home septic
system. Central Boiler Corrosion Inhibitor Plus™
is biodegradable and can be properly treated in a
residential septic system. If doing so, however, be
careful not to overow the septic system.
• Do not drain the outdoor furnace in such a manner
that the drain water could in any way contact
surface water, stream, river, estuary (where a river
meets a sea), lake, pond, ocean or other types of
waters.
• Do not drain to any location within 50 feet (15
meters) of any water well.
Shut-Off Valves
Shut-off valves must be installed on each hot supply
and return water line so each line can be shut off
individually for purging air from the system. Be sure all
valves and ttings are metal. Do not use plastic valves
or ttings.

9
Selecting a Location
To ensure the Maxim Furnace functions as designed,
careful planning and proper installation are imperative.
Be sure to read carefully and observe all of the
information in the entire owner's manual.
If any installation questions arise that cannot be
answered by the information in this manual, be sure to
contact your dealer.
• This outdoor furnace is not intended or certied to
be installed inside habitable space. Do not install
the outdoor furnace inside your home.
• This outdoor furnace may be installed outdoors or
in non-habitable structures and must be installed
in accordance with all applicable codes and
regulations.
• Check with your insurance company to see if they
have any location requirements.
• This outdoor furnace should not be installed in a
building that could be damaged or where a nancial
loss could occur from smoke, soot or water.
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.
❑The 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.
❑ThermoPEX 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 trafc unless
protected from excessive compression.
❑If the ground at the location 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
(see Fig. 6).
❑Carefully consider the location of, and the distance
to, the LP tank if one is to be used (see Gas Supply
Connection and Ignitor Operation section).
Foundation
The 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 as indicated in
Fig. 5. Another option is to pour a concrete foundation.
Fig. 5
SECTION 2 – LOCATION AND FOUNDATION
Section 2 - Location and Foundation

10
To install the outdoor furnace on a concrete foundation,
refer to Fig. 6 for dimensions and 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.
If installing on an existing slab, it may be necessary
to use patio blocks, bricks or pavers (Fig. 5) to allow
access to the water lines.
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 (see Fig. 6).
NOTE: The installation surface or foundation
must be noncombustible. The hot supply and
return lines must also be protected from possible
exposure to sunlight,  re or physical damage.
Foundations may consist of concrete, crushed
rock or patio blocks.
Leveling the Outdoor Furnace
CAUTION
The back of the outdoor furnace must not be
lower than the front of the outdoor furnace.
The 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.
WARNING
Disconnect the electrical power at the main
power source and turn off the gas supply at the
appliance service valve.
1. Disconnect the electrical power at the main power
source and turn off the gas supply at the appliance
service valve.
2. Remove the access panels from the back corner of
the furnace and set aside.
Section 2 - Location and Foundation
Maxim Foundation Dimensions
Shown without optional hopper.
48"
12"
72"
37"
14"
14"
2-1/2" Optional
Maxim
Furnace
Optional
Cement
Loading Area
Front
Base
18"
12"
52"
Do not use any combustible
materials for the foundation.
CAUTION
© 2014 Central Boiler
Outdoor 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 outdoor furnace enclosure. Foundation may consist of
concrete, crushed rock, or patio blocks.
Foundations dimensions are 1-1/2
in. beyond the outside perimeter
of the base.
Recommended
maintenance clearances
2" rigid foam insulation
(optional)
12"
18"
12"
48-Bushel
Fuel Hopper
Maxim
Furnace
51"
51"
87"
37"
52"
13"12"
12"
12"
12"
14"
14"
48"
72"
Front
2"
5-1/2-Foot
Transfer
Auger
Optional 48-Bushel
Hopper with Foundation
Optional Foundation
Fig. 6

11
Section 2 - Location and Foundation
3. Place a level on the back of the burner auger motor
as shown in Fig. 7. The 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.
Fig. 7
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
© 2014 Central Boiler
Foundation
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 and turn on the gas supply at the appliance
service valve.
7. Connect the electrical power at the main power
source and turn on the gas supply at the appliance
service valve.
Clearances
NOTE: Clearance to combustibles from the
chimney transition box is 8" (20 cm); HOWEVER,
if installing with the back of the outdoor furnace
facing an immovable wall, object, etc., you
must maintain 36" (91.5 cm) of clearance to the
wall, object, etc. in order to perform periodic
maintenance (see Fig. 8).
Fig. 8
WARNING
Maintain the following clearances from
combustibles for the outdoor 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

12
NOTE: Any electrical installation should be
done by a qualied installer in accordance with
applicable codes.
Ground Rod
The 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 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.
Fig. 9
SECTION 3 – ELECTRICAL
Section 3 - Electrical

13
Gas Supply Connection
The M255 P is designed so that a one-pound propane
cylinder may be connected to the gas ignitor. Thread
the cylinder on to the regulator installed on the gas
valve (Fig. 11). This conguration works well for all
temperatures.
Fig. 11
Other sizes of portable propane cylinders may be
connected to the regulator with the proper hose and
ttings.
Because liquid propane (LP) evaporates and turns to
gas at a slower rate when the temperature of the tank
is lower, sustained temperatures below 0˚F (-18˚C) will
lead to reduced gas pressure in small LP tanks. This
will lead to a drop in burner manifold pressure while
the burner is operating. If sustained temperatures below
0˚F (-18˚C) are expected, a properly installed tank of
at least 100-lb capacity must be installed (see Fig. 12).
Fig. 12
Temperatures below 0˚F (-18˚C) also will cause small
LP gas regulators to work incorrectly, outputting gas
pressures that are too high or too low. A two-regulator
system using a rst-stage and a second-stage regulator,
or a combination two-stage regulator (p/n 1930) such as
the one shown in Fig. 13 should be used.
Fig. 13
CAUTION
Make sure all covers for the gas ignition system
on the appliance are in place during operation
and service.
WARNING
Once the gas supply is connected, the appliance
and gas connection must be tested for leaks
before placing the appliance in operation.
For temperatures below 0˚F (-18˚C), use either the
conguration in Fig. 11 or the one in Fig. 13 with a
2-stage regulator system and a larger tank.
How to Operate the Gas Ignitor
The outdoor furnace utilizes a gas burner to ignite the
fuel in the burn chamber. The FireStar controller can
also be set to automatically relight the fuel if needed.
NOTE: For more detailed information, refer to
the FireStar Controller Operating Instructions
section.
There are two ways to start the gas burner:
1. Press and hold the Ignition button on the FireStar
controller until the LED display indicates and
the burner fan operates.
NOTE: The gas burner will start regardless of the
temperature of the burn chamber; however, if the
temperature of the burn chamber is greater than
350˚F (177˚C), the gas burner will immediately
shut off.
2. If Auto Relight is enabled and the controller is in
NORMAL or MEDIUM mode, the ignition process
will start if the burn chamber temperature falls below
300˚F (149˚C).
SECTION 4 – GAS SUPPLY CONNECTION (P Models) AND
IGNITOR OPERATION
Section 4 - Gas Supply Connection and Ignitor Operation

14 Section 4 - Gas Supply Connection and Ignitor Operation
Ignition Sequence - P Models
The ignition sequence is a series of steps that
automatically occur to ensure the gas ignitor starts
properly before the system begins to operate. During
ignition, the following will take place:
1. The burner fan will operate to provide air ow for
combustion.
2. Once the pressure switch senses air ow, it will
energize the gas ignition module.
3. The gas ignition module turns on the gas valve and
spark electrode, igniting the gas burner to light the
wood pellets in the burn chamber.
4. The feed and burner augers run for 60 seconds,
delivering fuel to the burn chamber.
5. The gas burner will continue to burn until the burn
chamber reaches a high enough temperature to
sustain burning the wood pellets, or for 10 minutes,
at which time the controller will turn off the gas
burner.
Ignition Sequence - PE Models
The ignition sequence follows a control logic to ensure
safe and effective ignition. The ignition sequence is as
follow:
1. The water temperature must be low enough for the
furnace to shift into demand mode.
2. The fan will start and operate at the ignition fan
speed and the Firestar control will send voltage to
the igniter relay.
3. The air proving switch will close, completing the
ignition relay control circuit.
4. The electric ignitor will warm up and heat the air
blowing across it into the burn chamber.
5. The 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. The 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 off.

15
Section 5 - Chimney
Chimney Height
The minimum recommended chimney length is eight
feet (2.4 m). Two 4-foot (1.2 m) sections are standard.
Additional sections may be needed (see Chimney Draft
section).
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 screws to stabilize the
extension.
Be considerate of neighbors when operating your
outdoor furnace. If you use your outdoor furnace in the
summer months, be certain your chimney exhaust is not
adversely affecting neighbors with open windows.
If located within 300 feet (91 m) of any residence not
served by the outdoor furnace, it is recommended that
the chimney be at least 2 feet (0.6 m) higher than the
peak of the residence served.
Fig. 14
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 in
Fig. 15.
If extensions are added to the standard eight feet (2.4 m) of
chimney, the chimney should be reinforced appropriately.
Fig. 15 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 (see Fig. 15).
NOTE: For chimney extensions or chimney
replacement, use only genuine Central Boiler
chimney components. Parts are available from
an authorized Central Boiler dealer.
The installation of a spark arrester is recommended,
particularly where there are dry conditions or where
there is combustible material near the unit, unless the
installation of a spark arrester is prohibited by local
requirements. Use common sense to avoid potential
res, including exercising caution when disposing of
ash, 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.
SECTION 5 – CHIMNEY
Fig. 15

16 Section 5 - Chimney
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. The 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
affect air ow in the chimney (see Fig. 16). Adding
chimney sections may overcome these factors.
Fig. 16

17
Section 6 - System Installation
SUPPLY AND RETURN LINES
Determine the conguration of the supply and return
lines from the outdoor furnace to where the supply and
return lines will connect to the existing heating system.
Central Boiler recommends using the ThermoPEX®
piping system.
ThermoPEX is a fully assembled, pre-insulated
piping system consisting of two 1" Central PEX lines
or two 1-1/4" PEX lines. The two lines (one a supply
and one a return line) are insulated with high-density
urethane insulation and a thick, durable, waterproof,
polyethylene outer jacket. One of the lines is marked
with a black stripe for identication.
NOTE: To prevent ground water from entering the
house, do not use drain tile, PVC pipe with bubble
wrap, or any other inferior material for insulating
the water lines.
NOTE: If the outdoor furnace supply and return
lines are not insulated properly, or if other
brands of insulated piping are used, there can be
excessive heat loss. This heat loss can greatly
increase the fuel consumption.
NOTE: If it is unavoidable that the supply and
return lines will run through an area of ponding
water, use ThermoPEX instead of other materials.
ThermoPEX should also be used for above-
ground or winter installations, and if the area is
likely to be affected by compaction.
Above Ground or Winter Installations
For above ground or winter installations in which
the supply and return lines can not immediately be
buried underground, Central Boiler recommends using
ThermoPEX. Be sure that both the insulation and the
supply and return lines will not be exposed to ultraviolet
rays. The ThermoPEX black exterior jacket has UV
protection but the insulation and water lines inside do
not. Use a ThermoPEX termination cap at each end of
the installation to protect and seal the insulation from
water.
If installed next to the building being heated, the supply
and return lines can be installed above ground provided
they are properly insulated and not exposed to ultraviolet
rays (see Fig. 17 as an example).
Fig. 17
NOTE: If an above ground installation is
temporary, bury the ThermoPEX as soon as
conditions permit (e.g., once the ground has
thawed).
NOTE: If ThermoPEX is installed temporarily
above ground, provisions should be made (i.e.,
a restop) to prevent possible risk of re coming
into contact with the ThermoPEX. ThermoPEX
is constructed of materials that can burn and
transfer a re.
CAUTION
If ThermoPEX is installed temporarily above
ground, do not cover with combustible materials
(e.g., stray, hay, leaves, etc.).
SECTION 6 – SYSTEM INSTALLATION

18 Section 6 - System Installation
Digging the Trench
WARNING
Before digging, be sure to call for utility locator
service.
The trench depth for ThermoPEX should be between
10" and 28" (25 and 71 cm).
Fig. 18
Underground Electric Wire
A 12-2 (two wires plus ground) underground rated wire
should supply the outdoor furnace with electricity. A
heavier gauge wire may be needed if the run is over 200
feet (61 meters). Check local codes and requirements. A
20-amp circuit is recommended.
Connecting to Existing Heating System
1. Make an entrance into the building(s) where the
supply and return lines are to enter.
2. Lay the ThermoPEX assembly in the trench and
feed one end into the building. Apply sealant around
the supply and return lines where they enter the
building.
3. Purge the supply and return lines before connecting
any ttings to ensure there is no debris or foreign
matter present.
NOTE: All holes made in basement or building
walls must be sealed completely to prevent water
from entering the building.
4. Close all valves on the outdoor furnace.
5. Install ttings to allow pressure-testing of both
supply and return lines. Pressurize with 50 psi (3.5
kg/cm2) of air; then check after 30 minutes to see if
pressure has dropped. A drop in pressure indicates a
leak; repair as necessary.
6. Connect the supply and return lines to the outdoor
furnace and the existing heat emitter(s). Fig. 19
shows some of the PEX ttings and tools used in
making connections.
NOTE: The base on the back of the outdoor
furnace is removable if necessary for connecting
the supply and return lines to the outdoor furnace.
Fig. 19
CAUTION
Allow for expansion and contraction of the
supply and return lines at each end. Without
an allowance for expansion and contraction,
the lines may kink or the ttings may be pulled
apart, causing an immediate water loss from the
outdoor furnace. Central PEX water lines can
have an expansion and contraction rate up to
.095" per each 100 ft and each 10°F (2.4 mm/30
m/5.5˚C).
7. Make sure there are no leaks in the supply and return
lines; then backll the trench.
NOTE: Do not backll the trench until the supply
and return lines have been tested to ensure there
are no leaks.
Backlling Water Line Enclosure
Using gravel or small rock, backll the perimeter of the
water line enclosure to the top, inner edge of the base
(Fig. 20) to keep out rodents. Install the back and side
panels.
Fig. 20

19
CIRCULATION PUMPS
NOTE: The direction of water  ow is very
important for the proper operation of the outdoor
furnace. Installing a swing check valve in the
return line can prevent possible reverse  ow.
Water Flow
For a single building using a water-to-air heat exchanger
system with a domestic water heater, the direction of
water  ow must go from the hot outlet on the outdoor
furnace to the lower side  tting of the domestic water
heater exchanger, to the lower  tting of the heat
exchanger on the existing furnace, and then to the return
port of the outdoor furnace.
NOTE: if there is a high heat draw with a single set
of lines, a wraparound pump (as shown in Fig. 21)
may be needed in order to keep the supply water
temperature the same temperature indicated by
the FireStar controller.
NOTE: Some systems may have different  ow
patterns.
Access to Ports on 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. There are two hot supply
and two return ports on the furnace. This con guration
allows for mounting the circulation pumps on the
furnace (Fig. 22).
Fig. 22
There are eight knock-out tabs on the  oor panel of
the furnace to accommodate the water lines. These
align with the hollowed-out area in the foundation
speci cations (Fig. 6). The pump access area in the back
right corner must align with the blocked out area of the
foundation.
Installing Circulation Pumps
The Taco 009 is a medium  ow, high head pressure
pump that requires an adequate amount of pressure on
the outlet side to prevent the motor from overloading.
Maxim
with Wrap-around-pump Installed
Side View Rear View
Area of Focus
RearSide
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
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
198 5871
380
410
171
224
1334
274
Qty p/n Description
Parts List
1 198 Ball Valve, 3/4"
2 171 Taco 007 Pump
1 410 Ball Valve, 1-1/4"
2 1330 PEX Adapter, 1" x 3/4"
2 224 Isolation Flange, 3/4"
1 225 Isolation Flange Kit, 1-1/4"
3 274 90° Street Elbow, 3/4"
2 380 MPT to PEX, 1-1/4"
2 556 Power Supply Cord, 32"
1 5871 Swing Check Valve, 1-1/4"
6 5926 Stainless Steel Clamp
Crimp Ring, 1"
2 1334 90° PEX Elbow, 1"
2 382 90°PEX Elbow, 1-1/4"
Parts and accessories sold separately.
Pump size may vary.
225
556
5926
382
Fig. 21
Section 6 - System Installation

20 Section 6 - System Installation
The Taco 014 is a high ow, high head pressure pump
that requires an adequate amount of head pressure on
the inlet side to prevent cavitation. Therefore, a Taco
014 may need to be mounted lower near the base of the
furnace, and on the 1-1/4" bung.
The Taco 007 is a medium to high ow, low head
pressure pump. In a very low-resistance system (e.g.,
short length of supply and return lines, only a at
plate heat exchanger, etc.), the 007 pump may need to
be mounted lower near the base of the furnace or on
the 1-1/4" bung to prevent cavitation at high water
temperatures.
NOTE: See the Hydronic Component Selection
Guide (p/n 2482) for more detailed information.
The following guidelines must be adhered to when
installing the circulation pump(s).
WARNING
Maximum load of the outlet on the outdoor
furnace is 10A, 120VAC, and 60Hz.
A. The pump motor must be installed in a horizontal
position.
B. The junction box must not be located below the
pump motor (see Fig. 23). If necessary, remove the
four screws and rotate the pump body.
Fig. 23
C. Do not operate the circulation pump until the entire
system has been lled with water and checked for
leaks or the pump may be damaged.
D. Insulate the areas around the supply and return lines
(Fig. 24) and pump(s) being careful not to block the
area around the louvers; then install and secure the
side and back panels.
Fig. 24
NOTE: At least one circulation pump must run
continuously to ensure proper operation of the
outdoor furnace.
The circulation pump(s) must be installed in the
supply line(s) with the arrow on each pump pointed
away from the outdoor furnace. In order to avoid
circulation problems, do not install the pump(s) in the
return line(s).
Fig. 25
The pump(s) must be located near the base of the
outdoor furnace if the system has a high-ow pump or
very low resistance on the outlet side of the pump. For
example, if the outdoor furnace is 20 feet (6 meters)
from the building and pumping water through one-
inch pipes, a heat exchanger, and back to the outdoor
furnace, the pump needs to be mounted with four feet of
water above the pump.
NOTE: See the Hydronic Component Selection
Guide (p/n 2482) for more detailed information.