Nature's Comfort GT-6000 User manual

Installation and Operating Manual For
GT-6000 Downdraft Gasification
Non-Pressurized Outdoor Wood oiler
Manufactured by Nature’s Comfort LLC.
Made In The USA
uilt Like A Tank
With Laser Precision
Full color and French manual available online at: / Couleur et manuel en français est disponible en ligne à:
www.naturescomfortllc.com
Revision 2012-1.3
Tested May 2012 to CSA- 366.1-2011 & UL 2523-2009
SAVE THESE INSTRUCTIONS!

ITRODUCTIO
Thank you and congratulations on the purchase of your new Nature’s Comfort GT Series
High Efficiency Downdraft Gasification boiler!
With the purchase of this Nature’s Comfort boiler, you can now appreciate the high degree of
craftsmanship and reliability that are a result of every boiler being carefully hand-built as well
as taking control of heating your home. Your choice shows the recognition you have for high
quality products.
We deem it important to provide you with this operation and maintenance manual, allowing
you to use your equipment under the best possible conditions and in the most optimal
manner and furthermore, to increase its operating life. Read through carefully before
beginning installation, follow all instructions and keep this manual handy.
THIS MA UAL I CLUDES IMPORTA T SAFETY I FORMATIO O PAGE 5
Again, thank you for purchasing a Nature’s Comfort oiler.
We appreciate your business!
If you are in need of insulated pex, heat exchangers or other parts for your new
boiler call your dealer, they have the lowest prices!
oiler water treatment and test required at time of installation and annually to
validate warranty. See warranty page for complete details.
For the most up to date installation, operation & warranty information, or if you
need to see any page in color, go to www.naturescomfortllc.com.
Please keep this manual with all other important papers. The information in this manual is
necessary for the installation, operation and proper use of the boiler. If you should ever have
a problem or question refer to this manual or call your dealer. If your dealer does not have
the information you need, request they contact Nature’s Comfort and your dealer will be
further educated to provide the best possible customer service. Please keep in mind that
Nature’s Comfort built the boiler but did not install it and has no control over the installation,
the efficiency of the building’s insulation or what is burned in the boiler.

Table of Contents
I. General Information
A. Terminology .....................................................................................4
B. Clearance to Combustibles Required ..................................4
C. Boiler Dimensions & Specs ......................................................4
D. Safety Precautions ................................................................. 5
E. Controls & Plumbing Connections ................................. 6
F. Heating the Home ................................................................... 7
II. Installing the Boiler
A. Location of Boiler ............................................................................8
B. Chimney, Extensions & Rain Cap ..........................................9
C. Underground Insulated Pex Pipe ............................................9
D. Plumbing Hookup ...................................................................... 10
E. Wiring the GT Boiler ................................................................... 10
F. Preconditioning Door Seals, Butterfly Air Spinners .... 10
G. Forced Air Systems -Thermostat Wiring ......................... 12
H. Adding Bypass Valves .............................................................. 13
I. Installing A Water-To-Air Heat Exchanger ................. 13
J. Installing In A Small Plenum ............................................ 14
K. Adjusting Plenum Air Flow .............................................. 15
L. Installing On An Existing Indoor Boiler ..................... 15
M. Filling GT Boiler with Water ............................................. 17
. Float Level ............................................................................... 17
O. Bleeding Air From Heat Exchangers .......................... 17
III. Heating Domestic Water, Pools and Spa’s
A. Sidearm Or Plate Heat Exchanger For Domestic Hot Water .................................................................................. 17
B. Heating a Pool or Spa .............................................................................................................................................................. 18
IV. Operation
A. Wood Requirements................................................................................................................................................................ 19
B. Starting A Fire .............................................................................................................................................................................. 19
C. Loading Wood ............................................................................................................................................................................ 19
D. Power Loss Procedure, Running On A Generator .................................................................................................... 20
E. Warm Weather Operation, Bypass For Domestic Hot Water Only .................................................................... 20
V. Maintenance
A. Cleaning ......................................................................................................................................................................................... 21
B. Disposal Of Ashes .................................................................................................................................................................... 21
C. Creosote – Formation And eed For Removal ........................................................................................................... 21
D. Actuator Backup Battery ........................................................................................................................................................ 22
E. Fuel Door & Cover Seals ........................................................................................................................................................ 22
F. Pump................................................................................................................................................................................................ 23
G. End of Season Care ................................................................................................................................................................. 24
Going Away ................................................................................................................................................................................... 25
Disclaimer ....................................................................................................................................................................................... 25
Trouble Shooting .................................................................................................................................................................... 26
Copy Of Safety Labels ....................................................................................................................................................... 27
Warranty .......................................................................................................................................................................................... 28
Warranty Cards ............................................................................................................................... 29

Page 4 of 30
I. General Information
A. Terminology In This Manual
oiler: Refers to the Nature’s Comfort GT oiler.
Furnace: Refers to the existing indoor gas or oil fired unit which heats the air or radiant water
heat for the home.
B. Clearance to Combustibles Required
Top, Front, Rear and Sides: 36”
Flooring: Non-Combustible
C. Boiler Dimensions & Specifications
Type of fuel: Only hard, cordwood that is cut & split, seasoned for 1-2 years.
Location: Outdoor use only.
Electrical Rating: 115 VAC, 5A (15A max when convenience outlet is used), 60 HZ
Min. Circuit reaker: 15 Amp
Draft lower: 300 CFM, 115 VAC
Water Pump: 115 VAC, 2A max.
Chimney: 6” inside diameter
GT-6000 250,000 TU, 250-gallon water tank, 6,000 sq ft.*
45" x 78" x 83" tall, 3,000 pounds
*Will heat up to (x) sq ft (This must include all heated areas of home as well
as basement.) with proper installation, properly insulated building and
when properly seasoned hardwood is used (20% moisture content).
Deduct a minimum of 500 sq ft if heating domestic hot water.
Firebox Size Cubic Feet Height Width Depth
GT-6000 15.8 30” 28” 40”
(w/firebrick) (--------------w/o firebrick--------------)
Steel thickness: Water Jacket Firebox
GT-6000 7ga. (approx. 3/16”) ¼”

Page 5 of 30
D. Safety Precautions
Do not operate this equipment for anything other than its intended purpose or for anything other
than in accordance with the instructions contained in this manual and all other instructions
accompanying the boiler. It is important to observe safety precautions to protect yourself and others
from possible injury. Observe all safety labels on the boiler.
All electrical and plumbing should be done by qualified personnel and conform to national,
state and local electrical, plumbing, fire and building codes.
1. DO NOT USE CHEMICALS OR FLUIDS TO START THE FIRE. Never use chemicals or any
type of petroleum based product, charcoal starter, lighter fluid, lantern fuel, kerosene or any other
flammable accelerant to start the fire in the firebox of the boiler. Keep all such liquids well away
from firebox.
2. If using antifreeze, use only non-toxic, follow manufacturer’s recommendations on mixing ratio
and test annually per manufacturer’s specs. Keep containers of antifreeze, which is flammable, well
away from the boiler.
3. The use of treated wood (painted, treated, etc.) and any other salvaged material can emit toxic
gases into the environment, is corrosive towards the components of the appliance, is not allowed
and voids the warranty.
4. DANGER! Risk of fire or explosion – DO NOT URN GAR AGE, GASOLINE, NAPHTHA,
ENGINE OIL OR OTHER INAPPREPRIATE MATERIALS. Flammable liquids household or yard
waste can reduce the life of the boiler, will void the warranty and is illegal in most areas. Also do not
burn trash, rubber, material treated with petroleum products (particle board, railroad ties, and
pressure treated wood), leaves, paper products, or cardboard. All of these are substances/materials
that should not be used as fuel in a hydronic heater.
5. Wait until boiler has shut down and idled for at least 5 minutes before opening the fire box door.
Pause for 30 seconds between the first latch and the safety latch to allow any combustion gases to
burn off. Always keep fueling and de-ashing doors closed and maintain all seals in good condition.
6. In the event of a runaway fire, make sure all doors are tightly shut, unplug the control power,
keep the pump running, make sure the blower damper is closed and keep the water jacket full.
7. WARNING! Risk of fire – Do not operate with fuel loading door or refractory channel door open.
Do not store fuel or other combustible material within the marked installation clearances. Leaving a
small crack or opening can cause over-heating in the firebox, boiling the water off, damage of the
unit and voiding the warranty. Inspect and clean the firebox, heat exchanger tubes, refractory and
chimney regularly.
8. CAUTION! Hot surfaces. Keep children away. Do not touch during operation. Always use proper
care when installing, operating and maintaining the boiler.
9. Always wear protective gloves and glasses and be aware that hanging and loose clothing can
catch fire.
10. All doors and covers must be maintained in place at all times, except during maintenance and
servicing.
11. Do not modify the boiler or controls. Do not connect this unit to a chimney flue serving another
appliance.
12. Failure to heed these warning or any additional warnings on the boiler may result in an accident
causing personal injury and damage and void the warranty.
All installation and operation must follow federal, provincial, state and local codes

Page 6 of 30
E. Controls & Plumbing Connections
The GT boiler uses a hot water thermostat (aquastat) with a sensor that is inserted into a brass
drywell for sensing the water temperature of the unit. When the temperature falls below the
differential setting on the aquastat, the blower turns on and the damper actuator opens, feeding
oxygen to burn wood in the firebox, heating the water jacket and remaining on until the water
temperature in the boiler reaches the set point of the aquastat.
The temperature is permanently set for 170F with a differential of 5 degrees for optimum operation
and performance and also provides for a long enough cycle time to burn off any creosote that
accumulated during idling.
There is also a safety thermal snap disc at the water output port that will shut off the boiler if output
temperature reaches 180F to ensure it never exceeds a safety standard of 204F as stored heat in
the refractory will continue to heat the water after shutdown. Differential is 20 degrees.
oiler shown is set up as a single-zone.
Porting for a 2
nd
zone is provided.
(Additional pumps & valves are available from your
dealer and can be ordered installed as well.)
1. Lower outlet for battery charger and control
plug that feeds power to the upper outlet
and controls
2. Upper outlet for circulation pump(s),
convenience load
3. Rear switch (front switch also shuts down
blower & closes firebox air damper)
4. Aqua-stat sensor for controlling blower and
firebox air damper
5. lower to feed oxygen to fire
6. Firebox air damper actuator
7. Output ports Please note! The pump that comes
with the boiler may not be the correct size for the
installation. Please consult your dealer for sizing as
water flow is essential to the proper & efficient
operation of the installation.
8. Rear access cover for refractory and rear
heat exchanger tubes
9. Output Temperature gauge
10. Drain Valve
11. Return ports (Use an additional valve here
for ease of servicing, not included.)
12. Rear access cover for upper and rear heat
exchanger tubes
13. Aquastat sensor

Page 7 of 30
F. Heating the Home
The GT series boiler saves energy and provides the most comfortable heating available. It heats
the home by burning seasoned hardwood in 2 stages to heat a firebox (1
st
burn stage), refractory
channel (2
nd
burn stage) and heat exchanger tubes surrounded by a steel tank filled with water. The
boiler is non-pressurized with an atmospheric vent and includes an easy-to-read water jacket float
indicator. The heated water must be circulated through insulated underground pex pipes to a heat
exchanger that must be installed in the existing furnace system.
If you have a forced-air system, a water-to-air heat coil must be installed in the ductwork. When air
travels through, heat is extracted and hot air is emitted out of the registers.
A water-to-water plate heat exchanger must be used if you have a hydronic radiant heating system.
When connecting to an in-floor heating system in concrete, a mixing valve is also required to keep
temperatures below 110F or damage to the concrete will occur over time from too much heat
expansion.
Complete parts packages at the lowest prices are available from Nature’s Comfort or your dealer!

Page 8 of 30
III. Installing Boiler
Installation is to be performed by a qualified installer and shall comply with all the
requirements of the authority having jurisdiction over the installation.
A. Location of Boiler
The GT boiler must be located to comply with the clearance requirements. Keep the firebox door
positioned so as not to point toward a structure so all fire danger is removed from the home. The
boiler may be installed as much as 250 feet away using an appropriately sized pump and piping
and still heat the house and hot water. However, if the boiler is located more than 100 feet away,
you may experience inefficiency and heat loss. A larger pump than the one supplied may be
needed for distances over 100 feet and/or any rise in elevation over 15 feet.
Locate the GT boiler where it will be convenient for refueling and wood storage. Pex pipe and
power lines are to be installed underground between the house and the boiler and must be buried
below frost lines.
1. It is recommended that the boiler be installed with chimney extensions for due consideration to
any neighboring residences and to the prevailing wind direction.
2. Do not locate the boiler within 100 ft of a residence not served by the boiler. e considerate of
neighboring residences, properties, parks, etc.
3. Do not locate the boiler near any combustible materials, gasoline or other flammable liquids or
gases.
4. The boiler should be located away from dry, grassy areas and any buildings
to minimize danger of fires.
5. Check with the insurance company and local codes or ordinances.
6. Do not install the boiler in an area where nearby structures or trees might cause down drafts.
7. Typically, outdoor wood burning boilers are located 40 to 100 ft down wind from the structure
served.
8. To aid in smoke dispersal, extra chimney lengths may be required depending on the distance to
surrounding structures.
Failure to keep the boiler area clear and free of combustible materials, gasoline and other
flammable liquids and vapors can result in severe personal injury, death or substantial
property damage.
A full concrete pad or footings just under the feet are not necessary for the installation for the boiler,
but is recommended to prevent frost heaving. Four concrete footing blocks 8” X 16” X 4” will suffice
if desired. You may add additional layers of blocks for ease of loading wood. The dotted line
represents the base dimension of the boiler for pouring a slab. If doing footings or blocks, follow the
footing dimension.

Page 9 of 30
B. Chimney:
A 6” stainless steel rain cap must be purchased separately for installation and can be
obtained from ature’s Comfort or your dealer.
The person operating the unit is responsible for operating in a manner that does not create a
public nuisance condition. The recommendations below may not always be adequate to
prevent nuisance conditions due to terrain or other factors.
If installing extensions, use supports as directed by pipe manufacturer. It is recommended that the
boiler be located with due consideration to the prevailing wind direction.
1 It is recommended that the stack be at least 2 feet higher than the peak roof line the nearest
residence.
2 If located more than 100 feet but no more than 150 feet to any residence, it is recommended
that the stack be at least 50% of the peak roof line of that residence, plus an additional 2 feet.
3 If located more than 150 feet but no more than 200 feet to any residence, it is recommended
that the stack be at least 25% of the height of the peak roof line of that residence, plus an additional
2 feet.
Example of chimney height relative to nearest downwind neighbor:
Always comply with all applicable state and local codes and laws.
C. Underground Insulated Pex Pipe
You must use underground insulated pex pipe for transferring the heated water from the boiler to
the home. Minimum pipe size permitted is 1”. 4” triple wrap & 6” 5 wrap insulated pipe is available
for purchase through Nature’s Comfort or your dealer. It may contain twine for pulling electrical wire.
If possible, do this with the pipe laid out straight for ease of pulling.
CALL YOUR LOCAL MISS DIG HOTLI E BEFORE YOU DIG TRE CHES!
ury the underground insulated pipe below frost lines (or just above water table level) and keep
underground as it enters the house. The depth of the trench varies in different regions of the
country. e completely sure about the correct depth needed before the insulated pex pipe is
installed underground. Contact your local building inspector’s office for this information. Make sure
to seal around the corrugated pipe to prevent water from entering. If conditions require the pipe to
be above ground for entering the home, make sure to insulate thoroughly.
ote: If only one color of PEX pipe is used, label the water lines or connect and test them before
back filling over pipe and lines. If you have rocky ground, make sure you use clean fill or place
straw or landscape fabric around the pipe before back filling, giving extra protection against
punctures.
If more than one building is to be heated, additional pipe and pump must be installed.

Page 10 of 30
D. Plumbing Hook Up
Plumbing connections should be well insulated after installation. Cover bottom access holes as
well.
Minimum pipe size permitted is 1”. Install the outgoing pex line on the pump flange that is already
mounted to the lower end of the circulation pump. Install the return line on the 1” 90 located to the
left of the rear upper heat exchanger tube access cover. Add a valve to the return line so if
repair or service is needed on lines or equipment, the water in the boiler can be isolated
without having to be drained. (Valves and PEX fittings can be purchased from NC or your dealer.)
Install a fill line from the domestic water into the return line using a T, 2 valves and a union to
disconnect or a backflow preventer when not using to keep 100% isolated so no boiler water can
ever enter the domestic side.
Use sweeping bends for PEX pipe keeping 90’s to a minimum (no more than 6) as each one adds 1
foot of head pressure, reducing the rate of water flow. For tight radiuses use ¾” rubber heater hose
in short lengths (fits 1” PEX fittings and is available from Nature’s Comfort or your dealer).
For a forced air system, run the line from the pump first to the heat exchanger for the domestic hot
water then to the one in the furnace plenum. For a hydronic radiant system, reverse this order.
ote: For larger homes, 1-¼ pipe may be needed for maximum TU output. A 1-¼” pipe can carry
up to 37% more TUs due to higher water flow. The fittings above would need to be changed to
accommodate 1-¼” Pex. The Armstrong E9.2 pump available from Nature’s Comfort or your dealer
has the ability to do this in a 1” pipe within distance & height limitations.
E. Wiring the GT Boiler
A qualified electrician must wire this boiler in accordance with the ational Electrical Code.
Using 14/2 with ground UF cable on a dedicated 15amp, 115vac circuit that is ground fault
protected, land power, neutral & ground wires to the L1, & G terminals on the top left of the
grey terminal strip. The small pair of red and black wires must be landed on the battery
charger and the charger plugged in. See controls section for an electrical diagram.
The size and type of electric wire to be installed depends on the distance from the boiler to the
house. If the boiler is less then 100 feet from the house, #14 AWG UF cable is the smallest wire
that may be used. If the distance is greater than 100 feet, #12 AWG UF cable must be used.
A maximum of 5 amps is used by the boiler if all standard equipment is running. The extra outlet will
provide a total of 10amps for convenience use.
F. Preconditioning Door Seals, Butterfly Air Spinners
Option 1: (Good) Wet the rope seals with WD-40 before firing the boiler to keep prevent hardening
from smoke and creosote and re-apply 1 or 2 times during the heating season or as needed.
Option 2: ( etter) Purchase a tube of high temperature caulk from your dealer or Nature’s Comfort
and lay a bead of caulk on the impression of the door jamb in the rope seals, placing a 2” strip of
wax paper over them. Over-extend the latch open and bounce the door/ash pan closed, then leave
open to fully cure before starting a fire to get a custom seal. Once cured, wet the rope seals with
WD-40 to prevent hardening from smoke and creosote and re-apply 1 or 2 times throughout the
heating season or as needed.
Option 3: ( est but more hassle and messy) Purchase a tube of high temperature caulk from your
dealer or Nature’s Comfort and brush over the entire surface area of the rope seals to permanently
seal out smoke and creosote. Place a 2” strip of wax paper over this. Over-extend the latch open

Page 11 of 30
and bounce the door/ash pan closed, then leave open to fully cure before starting a fire to get a
custom, long term seal.
NOTE! Adjust fuel door if you ever see any amount of smoke. See maintenance section.
Door adjustment is done at the factory but may be required again after installation and before
starting a fire as the seals compress over time. See maintenance section for complete
adjustment and care instructions.
Installation and placement of (12) GT-6000 Butterfly Air Spinners
Left Spin (qty 6) Right Spin (qty 6)
Verticle Tube Placement:
(as viewed from under vertical tubes)
Place the butterflies in the bottom of the tubes so the tips rest on the support
brackets.
Rear end of boiler
L R R
L L R
Front end of boiler
Horizontal Tube Placement:
(as viewed from rear control area)
Simply place the butterfly in the rear end of the tube.
L L L R R R

Page 12 of 30
G. Forced Air Systems - Thermostat Wiring
The next example drawings are for controlling the blower on a forced air system independently of
the existing heat source (i.e. propane, electric, fuel oil, etc). Nature’s Comfort can provide custom
diagrams for other types of control setups as well upon request.
Use this example diagram if you have a typical, basic 4 wire system:
Use the example drawing below if you have a 2 wire system or the thermostat is the advanced
computerized type that communicates back and forth between the furnace (typically found on heat
pump systems). Do not use this method if your HVAC system utilizes a multi-speed blower. All
of the parts below are available through your dealer or Nature’s Comfort.

Page 13 of 30
H. Adding Bypass Valves
Adding a bypass valve system (3 valves, 2 T’s and unions) at each heat exchanger is a good idea
so that if there is a potential problem such as a stopped up heat exchanger, it can be diagnosed &
serviced easily as well as being used for a summer bypass as explained in the “operation” section
of this manual.
I. Installing A Water-To-Air Heat Exchanger
The heat exchanger should be installed above an air conditioning condenser coil and must be
placed at least 2” above it so any ice that may from on the condenser due to improper operation
won’t touch the new heat exchanger.
No air can be allowed to flow around it or out of the ductwork. Use adhesive backed foam tape
(used for insulating doors and windows) to seal around the frame and foil tape to seal off the
opening you make in the plenum heat for the heat exchanger.
Make sure the fittings for the supply and return lines are easy to get to once the heat exchanger is
installed.
You should be able to find a heat exchanger to fit most popular sizes of plenums. If you are unable
to the ductwork must be modified to accept the heat exchanger. Wear proper protective gear.
(gloves, safety glasses, etc)
Measure the width of the heat exchanger (Dimension A in next diagram). Measure the thickness of
the heat exchanger (Dimension C).
Start by cutting a hole in the side of the ductwork the thickness of the heat exchanger (Dimension
C) and the full length of the ductwork (usually Dimension A).
WAR I G! Metal edges are very sharp! Wear protective gloves and use caution!

Page 14 of 30
Slide the heat exchanger into the hole for a test fit. Ideally the header and tubes (F) should stick out
of the plenum.
While test fitting try to determine how much tape is needed around the frame of the heat exchanger
to seal and keep air from flowing around it. A different amount (thickness) may be needed on
different sides.
The heat exchanger must be secured so it won’t move up or downstream in the plenum. Fabricate
some ‘L’ shaped braces and install the proper width apart as shown below (Dimension C). Secure
in place using pop rivets or self tapping screws.
Slide the heat exchanger carefully into the plenum to check the fit again. Once proper fitting is
verified, you can seal off the ends of the heat exchanger and the hole you made in the plenum with
foil or duct tape.
J. Installing In A Small Plenum
You can install a heat exchanger in a plenum that is smaller than the length of the heat exchanger
as follows. Make cuts at the top and bottom of the plenum, usually 4 inches long (the width of the
heat exchanger) as shown below. You may need to do this on both sides of the ductwork
depending on the heat exchanger size.
Slide the heat exchanger through the front hole to the back hole so it protrudes out the front and
back of the plenum the same amount. Ideally the core of the heat exchanger will be entirely within
the plenum.

Page 15 of 30
Crimp the sheet metal to the edge of the heat exchanger (item G) using channel-lock pliers. This
not only forms a virtually airtight seal, but also supports the heat exchanger as well.
K. Adjusting Plenum Air Flow
The motors on most force air furnaces have three speeds to provide various rates of air movement.
Please consult a local furnace specialist if you want to change the airflow of an existing furnace
system.
L. Installing On An Existing Indoor Boiler
The GT boiler may be connected to an existing boiler system. A water-to-water plate heat
exchanger is needed to transfer heat from the outdoor boiler to the indoor hydronic system so that
the two systems remain isolated (see next diagram).
As shown in the above figure, the two systems are totally isolated from each other so that the
existing hydronic system remains undisturbed and functions exactly as it did before. Water that
circulates through the outdoor boiler is never circulated through the home’s hydronic system or
vice-versa.
All pumps and controls remain essentially the same on the existing system but you will need to
keep the burner on the hydronic furnace from firing.
The electrical diagram on the next page shows a typical control setup for operating a 2 zone radiant
system for a new installation that does not use an existing hydronic furnace. Part numbers are
noted on each item for ordering from a Nature’s Comfort dealer.

Page 16 of 30

Page 17 of 30
M. Filling the GT Boiler with Water
Once all piping connections are complete, flush about 20 gallons of water into the float stack and
drain, repeating until it comes out clean. Close drain valve and pour Nature’s Comfort boiler
treatment in – required for warranty. Fill the boiler with a hose through the float stack or if you
have installed a fill line, open the valve and allow it to fill, stopping once the float starts to rise. Use
water that is softened and has low iron content if possible for maximum boiler and pump life.
Do not start circulation pump until boiler is FULL and the impeller and bearings have been
primed! After filling, remove the top screw on the pump until a steady stream of water flows and all
air has been purged. eing a wet-rotor unit, if the pump runs dry at all, it will seize up as the
bearings rely on lubrication from the water. See maintenance section for full details on pump
operation and care.
During the first heating cycle the water might expand and overflow. This is normal and will occur
anytime too much water has been added. Open the drain valve to keep the float indicator at the
bottom of the rubber cap. Any higher than this and hot water may push the float out and also cause
scalding water to spill out. (Over-fill when boiler is shut off and not in use)
. Float Level
After priming and starting the circulation pump and bleeding the heat exchanger (see next section),
let the boiler heat up and run for 24 hours then top off the water if needed. The ideal water level is
at the beginning of a heating cycle for the level indicator to be at the bottom of the rubber cap. The
water level will rise and fall during operation as water expands and contracts with temperature
changes. e sure to keep the boiler full of treated water at all times including through the summer
as this will keep the boiler free from corrosion and when in use, from overheating causing
circulation pump failure.
O. Bleeding the Heat Exchangers
With the pump running (prime and flush bearings first!), simply close a valve on the return side, hold
for 1 second then open quickly. Repeat the procedure four times or until you cannot hear air rushing
through the line.
III. Heating Domestic Water, Pools and Spa’s
A. Sidearm or Plate Heat Exchanger For Domestic Hot Water
For a sidearm heat exchanger, the hot line from boiler must first go to the top side port. This creates
twice the domestic water flow through the sidearm as opposed to coming in at the bottom side port.
For the fastest recovery, install a small circulation pump on the domestic side that is controlled by a
strap-on thermostat or thermal snap disc placed on bottom line on the domestic side. Hookups to
the domestic side must be connected to the drain and pressure relief ports. You cannot use a
sidearm if the pressure relief port is on top of the water heater tank. The domestic side will not
thermal siphon properly and will frequently air lock as well.
Make sure to keep drain & pressure relief in service & purge all air from piping and sidearm or it will
air lock.
The plate HX drawing shown is for a pre-heater setup. Leave utility energy on for this to maintain
the water temperature. As water is used it will then be heated by the plate HX for unlimited hot
water. You may also use a plate HX to bypass the water heater entirely for on-demand operation.
Always use a mixing valve to prevent scalding water temperatures.

Page 18 of 30
B. Heating a Pool or Spa
Please contact a local pool/spa specialist if this boiler is to be used to heat a pool or spa. A
stainless steel (or 90/10 copper/nickel alloy) tube & shell water-to-water heat exchanger must be
used to transfer heat from the boiler to a pool or spa since the chemicals used in a pool/spa are
destructive to the boiler. Pool heat exchangers are available from NC or your dealer. For sizing you
will need to know the volume of the pool in cubic feet or gallons. e sure to install isolation and
bypass valves for easy servicing and winter draining and also place before a chlorinator. Install a
separate line and pump on the boiler that is controlled to only run when the pool filter pump runs.

Page 19 of 30
IV. Operation
A. Wood Requirements
20% moisture content or lower is required for a GT boiler to achieve proper gasification.
Using unseasoned (“wet” or “green”) wood causes cooler burning temperatures preventing
gasification and severely reducing efficiency, causing the boiler to plug up with ash.
Only burn wood that has been cut, split and seasoned for 12-24 months, sheltered from rain and
snow. The wood should be split 6-8” in diameter and cut 12-16” for the fastest seasoning and
should be around 20% moisture content by weight before burning.
To test moisture content, use several pieces to get an average of a pile and first split the wood then
test using a moisture tester with pins suitable for wood (available from Nature’s Comfort or your
dealer), placing the pins in line with the wood grain. Testing the ends or outside of pieces will give
you a false, low reading.
Never burn driftwood, painted, stained or pressure treated wood. Do not burn trash, plastics,
gasoline, rubber, naphtha, household garbage, material treated with petroleum products (particle
board, railroad ties and pressure treated wood), leaves, paper products or cardboard.
The following are guidelines for wood:
Stack covered on rails off the ground, stored outside of clearance area and away from front and
back of stove for space required for fueling, ash removal & other routine maintenance
operations.
As rain and snow will greatly hamper seasoning, keep wood pile covered but open to the wind.
Wood will not dry out (season) properly until split.
Hardwoods burn longer than softwoods as they are denser and have more available TU’s.
Larger pieces burn longer than smaller pieces but take longer to season properly.
Wood with higher moisture content wastes energy to dry out wood and produces increased
amounts of creosote which, when mixed with ash and heat is corrosive and will shorten the life of
the boiler.
Higher moisture content also cools the exhaust gases, possibly eliminating complete gasification
which severely reduces efficiency and will also clog the refractory with ash. If you see moisture
oozing from the ends of burning pieces, this points to improper seasoning.
Rotten, old wood burns rapidly and does not have enough fuel mass for decent burn times.
B. Starting A Fire
Do not use combustible fluids or chemicals. Turn on the front and rear switch to run the blower.
Starting over the holes in the floor, criss-cross a small pile of sticks or pieces of split kindling about
the size of a dinner plate on top of several crumbled newspaper pages and light with a torch or
match and slowly add larger kindling pieces. Once this is sufficiently ignited, add 2-4 logs and close
the fuel door. Wait for these pieces to sufficiently ignite before loading the firebox full. Caution!
Follow procedures as outlined in “Loading Wood” (next section) for opening fuel door.
It can take up to 1-2 hours for the refractory channel to get hot enough for gasification to start and
the boiler to burn smokeless. There will also be a large amount of condensation created until the
water jacket comes up to temperature. This may drip from access doors and covers and will dry out
within 24 hours.

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C. Loading Wood
Caution! Doors, covers, coals & ashes are hot! Wear safety glasses and use heavy gloves.
Caution! ever open fuel door without first turning off the boiler at the front or rear switch
and allow idling for at least 10 minutes before opening or flame spillage may occur!
Caution! Flammable gases fill the firebox when idling. Pause at blowback catch for 30
seconds and then stand to the side when fully opening until smoke dissipates enough to see
inside. Failure to do this can result in possible flashback to the face from gases igniting.
Always move the previous load of wood over the hole in the floor before loading new wood.
Use care to avoid hitting air diverter! You will need to adjust an existing load if it doesn’t
automatically fall over the holes during burning as the coals burn away from the hole. This is
required so the exhaust gases are hot enough to ignite for the 2
nd
stage of burning in the
gasification chamber below the firebox for the most efficient and complete burn. It is ok for some
coals to drop through the exhaust hole in the floor as they will burn up. Make sure exhaust hole in
floor does not become jammed with coals or clogged with ash or operation will be affected.
Add wood before the previous load has burned down to 25% of firebox capacity to have enough hot
coals to maintain good gasification and dry out the next load of wood. Most often the boiler can be
loaded in the morning and at night. urn times vary from 6-24 hours depending on fuel being used
(wood with higher moisture content will require more frequent loading), installation, temperatures
maintained and size of area being heated. Nature’s Comfort makes no guarantees on burn times as
there are too many variables outside of its control.
D. Power Loss, Running On A Generator
If there is a loss of power while the unit is running the firebox air damper actuator will close on
battery power but boiling of the water jacket may occur due to the pump not circulating water. The
controls are designed for the control plug to be used on a generator or vehicle inverter if needed. If
the water jacket ever starts to overheat from lack of circulation during a power outage, first make
sure to keep the water level full then use this feature to keep the pump running.
***NOTE*** The battery will not charge until power is restored to the lower outlet unless you move
the battery charger to a live plug or outlet. The spare outlet has a total of 10amps available to be
used for an additional pump or convenience load if desired. Do not load more than this as
overloading of the supplying circuit will occur.
E. Warm Weather Operation, Bypass For Domestic Hot Water Only
Operation in warmer weather will result in larger amounts of creosote due to longer idle times and
can also be more difficult as too many coals may cause the water jacket to boil if not enough heat is
pulled from the water to heat the home. Use smaller loads of wood if this happens. Adequate water
circulation is critical for preventing water from boiling. Also make sure all rope seals are properly
sealed to prevent any extra air from feeding the fire. See the maintenance section for how to adjust
door seals.
For heating of domestic hot water without heating the home, install a 3-valve bypass system shown
in the next figure (shown on a water-to-air heat exchanger). This permits use of the boiler during the
spring, summer and fall seasons to heat domestic hot water when heating the home may not
needed or wanted. Use of union fittings between the isolation valves and the heat exchanger for
easy removal is recommended.