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							2  Page
Installation Manual
Contents
CONTENTS
Installation Manual
SPECIFICATIONS                                    \
                            4
INTRODUCTION                                    \
                            5
SAFETY GUIDELINES                                                            \
  6
INSTALLATION                                     \
                              7
General                                     \
                                 7
Included accessories                                                          \
9
Clearances                                     \
                               9
Venting instructions                                                           10
Gas supply and gas pipe sizing                                    \
             20
Water connections                                                            \
22
Condensate drain                                                            \
 23
Electrical connections                                                        25
Temperature remote controller                                    \
            26
High-altitude installations                                                      28
APPLICATIONS                                    \
                            29
INITIAL OPERATION                                                          \
  31
OPTIONAL ITEMS                                                           \
    32
Owner's Guide
OPERATING SAFETY                                                          \
  35
NORMAL OPERATION                                                          \
37
Display of controller                                                           37
General                                     \
                                37
Temperature table of controller                                     \
            37
Temperature settings                                                          38
Additional features                                                          \
39
Flow                                     \
                                   40
Freeze protection system                                                     40
Maintenance and service                                                     41
Unit draining and filter cleaning                                     \
            41
Descaling the unit                                                          \
 42
TROUBLESHOOTING                                     \
                        43
General                                     \
                                43
Error codes                                                \
                  45
COMPONENTS DIAGRAM                                                       48
PARTS LIST                                               \
                    52
OUTPUT TEMPERATURE CHART                                     \
              54
LIMITED WARRANTY                                                          \
 55
This installation manual is approved for installation in the United States.  
						

							3  Page
Installation Manual
Installation Manual
CONGRATULATIONS
Congratulations and thank you for choosing our tankless water heater 
Before use, we recommend that you read through this safety manual 
carefully Please refer to the back of the manual for details about the 
warranty  Keep this manual for future reference
If you lose the manual, contact the manufacturer or your local 
distributor  When you call, please tell us the model number and the 
serial number of your unit written on the rating plate of the water 
heater   
						

							4  Page
Installation ManualSpecifications
SPECIFICATIONS
*40 psi (027 MPa) or above is recommended for maximum flow
** The Manif old Pressure is the factory setting and should not need adjustment
NOTE:
•	
Check the rating plate to ensure this product matches your specifications
•	The manufacturer reserves the right to discontinue, or change at any time, specifications or designs 
without notice and without incurring obligation.
Model
140
 Indoor
(T-H3M-DV)
140 
Outdoor
(T-H3M-OS)
Natural Gas Input 
(Operating Range) BTU/hMin: 15,000  
Max: 120,000
Propane Input 
(Operating Range)BTU/hMin: 15,000  
Max: 120,000
Gas Connection
1/2" NPT
Water Connection 3/4" NPT
Water Pressure* psi
(MPa)
15 - 150 (01 - 10)
Natural gas
Inlet Pressureinch WC 
(kPa)
Min 40 (10)
Max 105 (26)
Propane
Inlet Pressureinch WC
(kPa)
Min 80 (20)
Max 140 (35)
Manifold 
Pressure**
Natural
Gasinch WC 
(Pa)
330
(820)
200
(500)
Propaneinch WC
(Pa)
300
(750)
160
(400)
Weight
lbs (kg)50 (225)50 (225)
Dimension inch
H 21-3/4 x W 14 x D 9-1/4
H 552 x W 352 x D 236
mm
Ignition Electric Ignition
Electric
SupplyVAC / Hz120 / 60
Consumption
OperationW / A539 / 07
StandbyW / A32 / 005
Freeze-
Protection W / A2239 / 194  
						

							5  Page
Introduction
Installation Manual
INTRODUCTION
•	This manual provides information necessary for the installation, operation, and maintenance 
of the water heater
•	The model description is listed on the rating plate which is attached to the side panel of the 
water heater
•	Please read all installation instructions completely before installing this product
•	If you have any problems or questions regarding this equipment, consult the manufacturer or 
its local representative
•	This equipment is an on-demand, tankless water heater designed to efficiently supply endless 
hot water for your needs
•	These high efficiency models have a built-in secondary heat exchanger that absorbs latent 
heat from the exhaust gas
•	The 140 Indoor (T-H3M-DV) model is only to be installed indoors  The 140 Outdoor (T-H3M-
OS) model is only to be installed outdoors
•	The principle behind tankless water heaters is simple:
*This diagram illustrates tankless water heater design concepts only and does not accurately 
represent the water heater’s physical description
1 A hot water tap is turned on
2 Water enters the heater 
3 The water flow sensor detects the water flow 
4 The computer initiates the fan motor and sends a signal to the igniter to create an ignition 
spark
5 The gas ignites and flames appear within the burner chamber 
6 Water circulates through the heat exchanger and then gets hot
7 Using thermistors to measure temperatures throughout the water heater, the computer 
modulates the gas and water valves to ensure proper output water temperature
8 When the tap is turned off, the unit shuts down
Burners
Exhaust
Secondaryheat exchanger
Primaryheat exchanger
Igniter
Gas valve
Fan motor
Flow sensor
Condensatedrain port
Gas inlet
Cold water inletThermistor
Hot water outlet
Thermistor
Intake port
ExhaustThermistor
Water controlvalve
Computerboard  
						

							6  Page
SAFETY GUIDELINES
SAFETY DEFINITION
Indicates an imminently hazardous situation which, if not avoided, will result in 
death or serious injury
DANGER
WARNING
Indicates an imminently hazardous situation which, if not avoided, could result 
in death or serious injury 
CAUTION
Indicates an imminently hazardous situation which, if not avoided, could result 
in minor or moderate injury 
GENERAL
1. Follow all local codes, or in the absence of local codes, follow the current edition of the National 
Fuel Gas Code:  ANSI Z2231/NFPA 54 in the USA or B1491 Natural Gas, Propane Installation Code 
in Canada
2. Properly ground the water heater in accordance with all local codes or in the absence of local codes, 
with the National Electrical Codes:  ANSI/NFPA 70 in the USA or CSA standard C221 Canada Electrical 
Code Part 1 in Canada
3. Carefully plan where you intend to install the water heater  Please ensure:
•	Your water heater will have enough combustible air and proper ventilation
•	Locate your heater where water leakage will not damage surrounding areas (please refer to p 8)
4. Check the rating plate for the correct GAS TYPE, GAS PRESSURE, WATER PRESSURE and ELECTRIC 
RATING
*If this water heater does not match your requirements, do not install and consult with the manufac-
turer
5. If any problem should occur, turn off all hot water taps and turn off the gas Then call a trained 
technician or the Gas Company or the manufacturer
WARNING
•	Water temperatures over 125 °F (52 °C) can cause severe burns instantly or 
death from scalding  The water temperature is set at 120 °F (50 °C) from the 
factory to minimize any scalding risk  Before bathing or showering always 
check the water temperature
•	 Do not store or use gasoline or other flammables, vapors, or liquids in the 
vicinity of this appliance
•	 Do not reverse the water and/or gas connections as this will damage the gas 
valves and can cause severe injury or death  Follow the diagram on p 22 
when installing your water heater 
•	 Do not use this water heater if any part has been in contact with or been 
immersed in water   Immediately call a licensed plumber, a licensed gas fitter, 
or a professional service technician to inspect and/or service the water heater  
if necessary 
•	 Do not disconnect the electrical supply if the ambient temperature will drop 
below freezing   The Freeze Protection System only works if the water heater 
has electrical power   The heat exchanger will not be covered under warranty 
if it is damaged due to freezing  Refer to the section on the Freeze Protection 
System on p 40 for more information
Installation Manual
Safety Guidelines  
						

							7  Page
Installation Manual
INSTALLATION
GENERAL
1. Follow all local codes, or in the absence of local codes, follow the current edition of the National 
Fuel Gas Code: ANSI Z2231/NFPA 54 in the USA or B1491 Natural Gas, Propane Installation Code in 
Canada
2. All gas water heaters require careful and correct installation to ensure safe and efficient operation  
This manual must be followed exactly  Read the “Safety Guidelines” section
3. The manifold gas pressure is preset at the factory   It is computer controlled and should not need 
adjustment
4. Maintain proper space for servicing  Install the water heater so that it can be connected or removed 
easily Refer to the "Clearances" section on p 9 for proper clearances
5. The water heater must be installed in a location where the proper amount of combustible air will be 
available to it at all times without obstructions
6. The electrical connection requires a means of disconnection, to terminate power to the water heater 
for servicing and safety purposes
7. Do not install the water heater where the exhaust vent is pointing into any opening in a building or 
where the noise may disturb your neighbors  Make sure the vent termination meets the required 
distance by local code from any doorway or opening to prevent exhaust from entering a building (refer 
to p 17 to 19)
8. Particles from flour, aerosols, clothes dryers and other airborne contaminants may clog the air vent, 
build up and reduce the functions of the rotating fan, cause improper burning of the gas, or cause 
damage to the water heater   Regularly ensure that the area around the water heater is dust- or debris-
free  Regular maintenance is recommended for these types of environments  Sealed combustion is 
recommended too
9. The 140 Indoor (T-H3M-DV) model is to be installed indoors only   The model is equipped with a 
thermistor and hi-limit switch for the exhaust gas, detecting excess temperatures within the flue 
and enabling the water heater to safely stop operation if needed  These components are always 
monitoring exhaust gas conditions in order to prevent heat damage to ABS, PVC (solid core), CPVC 
(solid core), or Polypropylene (Plastic) venting if ABS, PVC, CPVC, or Polypropylene is used  If the 
exhaust gas temperature exceeds 140 °F (60 °C) these components will enable the water heater to 
safely stop operation  (These components are not installed on the outdoor model since the exhaust 
vent is built-in)
•	The Indoor model requires 3 inch, or 4 inch diameter intake air supply pipe  The intake pipe must 
be sealed airtight
•	Air supply pipe can be made of aluminum flexible tube, ABS, PVC (solid core), CPVC (solid core), 
Polypropylene, corrugated stainless steel, or Category lll / IV stainless steel  Regarding exhaust 
pipe, please refer to p11 for detailed information
•	Use of cellular core PVC (ASTM F891), cellular core CPVC, or Radel® (polyphenylsulfone) in non-
metallic venting systems is prohibited  Covering non-metallic vent pipe and fittings with thermal 
insulation is prohibited
•	Sidewall venting is recommended for the Indoor model  Vertical venting (roof termination) is 
acceptable
•	The manufacturer recommends running the exhaust vent and the intake pipe as parallel as possible
10.  The 140 Outdoor (T-H3M-OS) model is only to be installed outdoors and only in the area with mild, 
temperate climates
The Outdoor model shall be wall-mounted or mounted on a stand  Locate the Outdoor model in an 
open, unroofed area and maintain the minimum clearances (Refer to p9)
Installation  
						

							8  Page
Installation
Installation Manual
•	Installation and service must be performed by a qualified installer (for example, a 
licensed plumber or gas fitter), otherwise the warranty will be void.
•	The installer (licensed professional) is responsible for the correct installation of 
the water heater and for compliance with all national, state/provincial, and local 
codes.
•	The manufacturer does not recommend installing the water heater in a pit or 
location where gas and water can accumulate.
•	Do not have the vent terminal pointing toward any operating window, door, or 
opening into a building
•	Do not install the water heater next to any source of airborne debris, such as a 
clothes dryer and a vent that can cause debris to be trapped inside the combustion 
chamber, unless the system is direct-vented
•	The manufacturer does not recommend installing the water heater in an attic due 
to safety issues. If you install the water heater in an attic:
•	Make sure the water heater will have enough combustion air and proper 
ventilation
•	Keep the area around the water heater clean When dust collects on the flame 
sensor, the water heater will shut down on an error code
•	Place the water heater in a location that provides easy access for service and 
maintenance
•	A drain pan, or other means of protection against water damage, is required to 
be installed under the water heater in case of leaks
•	It is recommended to direct vent the heater
WARNING
•	Damage caused by water quality is not covered by the warranty.
•	Only potable water can be used with this water heater  Do not introduce pool 
or spa water, or any chemically treated water into the water heater 
•	Water hardness levels must not exceed 7 grains per gallon (120 ppm) for single 
family domestic applications or more than 4 grains per gallon (70 ppm) for 
all other types of applications Water hardness leads to scale formation and 
may affect / damage the water heater Hard water scaling must be avoided or 
controlled by proper water treatment
•	Water pH levels must be between 65 and 85
•	Well water must be treated
•	Do not install the water heater where water, debris, or flammable vapors may get 
into the flue terminal
•	Although the water heater is designed to operate with minimal sound, the 
manufacturer does not recommend installing the water heater on a wall adjacent 
to a bedroom, or a room that is intended for quiet study or meditation, etc
•	Locate your heater close to a drain where water leakage will not do damage to 
surrounding areas As with any water heating appliance, the potential for leakage 
at some time in the life of the product does exist The manufacturer will not be 
responsible for any water damage that may occur  If you install a drain pan under the 
water heater, ensure that it will not restrict the combustion air flow 
CAUTION  
						

							9  Page
Installation
Installation Manual
INCLUDED ACCESSORIES
Check that these items below are included with the water heater
Installation Manual
and Owner’s Guide Temperature Remote Controller kit*
Outdoor model only Bird Screen
Indoor model only
Qty: 1 Qty: 2
Qty: 1
*For more information on optional items, please refer to p32 to 33
CLEARANCES
Maintain all clearances around 
the water heater
Model To pBottom FrontBackSides
140 Indoor 
(T-H3M-DV ) 12 in
(305 mm) 12 in
(305 mm) 4 in*
(102 mm) 1 in
(25 mm) 3 in
(76 mm)
140 Outdoor  (T-H3M-OS) 36 in
(914 mm) 12 in
(305 mm) 24 in
(610 mm) 1 in
(25 mm) 3 in
(76 mm)
*24 inches recommended for maintenance
Top
Back
Side
Side
Front
Bottom
Do not install this water heater under an 
overhang less than 3 ft (914 mm) from its top, 
top of exhaust part, or eaves  The area under 
an overhang must be open to three sides 
(Outdoor models only)
Do not install the water heater exhaust port 
within 1 ft (305 mm), in the USA, of any air 
intake or building opening, and within 3 ft (914 
mm), in Canada, of any air intake or building 
opening  (Outdoor models only) (Refer to p17)
3 ft(914 mm)
exhaust portA 
A: 1 ft (305 mm) USA/ 3 ft (914 mm) Canada
A A   
						

							10  Page
Installation
Installation Manual
VENTING INSTRUCTIONS
For the 140 Indoor (T-H3M-DV) model
-General-
•	Improper venting of this appliance can result in excessive levels of carbon 
monoxide which can result in severe personal injury or death
•	 Improper installation can cause nausea or asphyxiation, severe injury or death 
from carbon monoxide and flue gases poisoning  Improper installation will 
void product warranty 
DANGER
When installing the vent system, all applicable national and local codes must be 
followed  If you install thimbles, fire stops or other protective devices and they 
penetrate any combustible or noncombustible construction, be sure to follow all  applicable national and local codes
CAUTION
The Indoor model must be vented in accordance with the section “Venting of Equipment" of the current 
edition of the National Fuel Gas Code: ANSI Z2231/NFPA 54 in the United States and/or Section 8 of the  
B1491 Natural Gas and Propane Installation Code in Canada, as well as applicable local building codes
The use of venting materials approved for Category III/IV appliances is recommended whenever possible 
However, the Indoor model may also be vented with plastic pipe materials such as ABS, PVC (solid core), 
CPVC (solid core), or Polypropylene  For details, please refer to the Exhaust Vent (ABS, PVC, CPVC, or 
Polypropylene Vent) section on p. 11.  Vent installations in Canada which utilize plastic vent systems must 
use venting that complies with ULC S636
General rules for venting water heaters are:
•	Place the water heater as close as possible to the vent termination
•	The vent collar of the water heater must be fastened directly to an unobstructed vent pipe
•	Do not weld the vent pipe to the water heater’s vent collar 
•	Do not cut or alter the vent collar of the water heater
•	The vent must be easily removable from the top of the water heater for normal service and 
inspection of the unit
•	The water heater vent must not be connected to any other gas appliance or vent stack
•	Avoid using an oversized vent pipe or using extremely long runs of the pipe
•	For rooftop venting, a rain cap or other form of termination that prevents rain water from 
entering into the water heater must be installed
•	Do not terminate the vent into a chimney  If the vent must go through the chimney, the vent 
must run all the way through the chimney with approved vent pipe
Water heater vent terminator must be at least 2 
ft (610 mm) away from an inside corner for both 
outdoor installation and direct-vent installation
InsideCorner
2 ft(610 mm)