American Water Heater 160X3P User manual

Condensing Models
On-Demand Water Heater
Service Handbook
DIR 2000585401 Rev. B
March 2020
MODELS:
160X3P 180X3P 199X3P
(Indoor/Outdoor) (Indoor/Outdoor) (Indoor/Outdoor)
Series 100 Series 100 Series 100
THIS SERVICE HANDBOOK IS FOR USE BY QUALIFIED SERVICE PROFESSIONALS ONLY.
IF YOU NEED ASSISTANCE, CALL TECHNICAL SUPPORT.
IN USA, CALL AT 8777372840. IN CANADA, CALL 8884798324.

2 • On-Demand Water Heater Service Handbook for X3P Models
TABLE OF CONTENTS
SPECIFICATIONS............................................................................................................................................................................................4
INTRODUCTION ............................................................................................................................................................................................5
General Installation Guidelines...................................................................................................................................................................................................5
NORMAL OPERATION ...................................................................................................................................................................................6
Activation ..................................................................................................................................................................................................6
Operation ..................................................................................................................................................................................................6
Shutdown ..................................................................................................................................................................................................6
Preliminary Checklist .................................................................................................................................................................................6
Gas/Water/Electric: .................................................................................................................................................................. 6
TROUBLESHOOTING .....................................................................................................................................................................................7
Remote Controller: ................................................................................................................................................................... 7
High Altitude: ............................................................................................................................................................................ 7
Vent Length: ................................................................................................................................................................................ 7
X3TM Technology: ....................................................................................................................................................................... 7
New Installations: ..................................................................................................................................................................... 7
Test to determine if the problem is related to plumbing or the water heater: ........................................................................ 7
Next Step: ................................................................................................................................................................................. 8
General Issues ...........................................................................................................................................................................................8
Water is too hot or not hot enough. ......................................................................................................................................... 8
Temperature fluctuates when a fixture is opened..................................................................................................................... 8
Unit does not operate when water goes through it. ..................................................................................................... 8
Abnormal sounds come from the unit....................................................................................................................................... 9
ERROR CODES..........................................................................................................................................................................................11
Code 031: Incorrect DIP Switch Settings ................................................................................................................................. 16
Code 051 or 101: Combustion Air and/or Exhaust Gas Blockage ............................................................................................ 16
Code 111 or 121: Ignition Failure / Flame Loss ....................................................................................................................... 16
Code 201: Combustion Air and Gas Line Failure...................................................................................................................... 17
Code 211: Air Pressure Sensor Failure..................................................................................................................................... 17
Code 311, 321, 331, 341 or 351: Thermistor Failure ............................................................................................................... 18
Code 391: Flame Rod Failure .................................................................................................................................................. 19
Code 441: Flow Sensor Failure ................................................................................................................................................ 19
Code 511: Abnormal Main Gas Valve (MV) ............................................................................................................................ 19
Code 521: Air Damper Failure.................................................................................................................................................. 19
Code 551: Abnormal Solenoid Gas Valve (SV1, SV2, and/or SV3) ........................................................................................... 19
Code 611: Abnormal Fan Motor ............................................................................................................................................. 20
Code 631: Pump Fault ............................................................................................................................................................................................ 20
Code 651: Flow Adjustment Valve Fault .............................................................................................................................................................. 20
Code 661: Bypass valve fault ................................................................................................................................................................................. 21
Code 701: Computer Board Fault ........................................................................................................................................... 21
Code 711: High Limit Switch / Overheat Cutoff Fuse Circuit is Compromised ........................................................................ 21
Code 721: False Flame Detection ............................................................................................................................................ 22
Code 741: Remote Control Problem ....................................................................................................................................... 22
Code 751: Temperature Controller Problem .......................................................................................................................... 22
Code 761: Communication Error in Easy-Link System ............................................................................................................. 22
Code 991: Combustion Air and/or Exhaust Gas Blockage (also Code 051 and 101) ............................................................... 22

On-Demand Water Heater Service Handbook for X3P Models • 3
DIP SWITCH SETTINGS ...............................................................................................................................................................................25
WIRING DIAGRAM ..................................................................................................................................................................................... 28
SERVICE PROCEDURES ...............................................................................................................................................................................29
Filter/Drain Plugs Cleaning .....................................................................................................................................................................29
Checking for a Crossed Connection .........................................................................................................................................................30
Checking for a Reversed Connection .......................................................................................................................................................30
Checking the Inlet Gas Pressure and Pressure Drop................................................................................................................................30
Adjusting the Manifold Gas Pressure and Firing Rate .............................................................................................................................31
Checking the Manifold Gas Pressure ....................................................................................................................................... 31
Adjusting Manifold Pressure.................................................................................................................................................... 31
Checking the Overheat Cutoff Fuse (OHCF).............................................................................................................................................32
Checking the Flow Sensor........................................................................................................................................................................32
Cleaning the Flame Sensor and Igniter Rod.............................................................................................................................................33
Easy-Link Connections with Previous Models..........................................................................................................................................34
DIP Switch Setting Easy-Link on the Computer Board ............................................................................................................. 34
Easy-Link Unit Number Display and Renumbering Procedure (for 199X3P Models Only)....................................................... 35
Diagnostic Mode......................................................................................................................................................................................36
Individual Unit ......................................................................................................................................................................... 36
Multiple Units in a Linked System ........................................................................................................................................... 37
MAINTENANCE ..........................................................................................................................................................................................40
REMOVING AND REPLACING THE EXHAUST PORT CAP ............................................................................................................................42
REMOVING AND REPLACING THE FAN ASSEMBLY ....................................................................................................................................42
REMOVING AND REPLACING THE COPPER GAS PIPE ................................................................................................................................45
REMOVING AND REPLACING THE VENTURI ASSEMBLY ............................................................................................................................46
REMOVING, REPLACING, AND VERIFYING THE GAS ORIFICE ASSEMBLY .................................................................................................47
REMOVING AND REPLACING THE MAIN GAS VALVE MVASSEMBLY......................................................................................................49
REMOVING AND REPLACING THE PRIMARY HEAT EXCHANGER...............................................................................................................50
REMOVING AND REPLACING SECONDARY HEAT EXCHANGER.................................................................................................................. 55
REMOVING AND REPLACING THE IGNITER FLAME ROD ASSEMBLY.......................................................................................................59
REMOVING AND REPLACING THE THERMISTORS ..................................................................................................................................... 60
REMOVING AND REPLACING THE WATER PIPING SYSTEM COMPONENTS ..............................................................................................61
REMOVING AND REPLACING THE RECIRCULATION PUMP........................................................................................................................64
REMOVING AND REPLACING THE DRAIN PORT AND DRAIN TUBE..........................................................................................................65
REMOVING AND REPLACING THE THERMISTOR INLET PLUG ...................................................................................................................67
COMPONENT DIAGRAMS...........................................................................................................................................................................68
COMPONENT DIAGRAMS/ITEM NUMBERS...............................................................................................................................................73

BASICSBASICS
4 • On-Demand Water Heater Service Handbook for X3P Models
SPECIFICATIONS
Table 1:
Model 160X3P
Indoor
160X3P
Outdoor
180X3P
Indoor
180X3P
Outdoor
199X3P
Indoor
199X3P
Outdoor
Natural Gas Input
(Operating Range) BTU/h MIN: 9,000 160,000
9,000
180,000
9,000
199,000
MAX:
Propane Input
(Operating Range) BTU/h MIN: 9,000 160,000
9,000
180,000
9,000
199,000
MAX:
Gas Connection 1/2” NPT
Water Connections 3/4” NPT
Water Pressure* psi (MPa) 15 - 150 (0.1 - 1)
Max. water flow rate GPM (L/min) 6.5 (25) 8.0 (30) 10.0 (38)
Natural gas
lnlet Pressure inch W.C. (kPa) Min. 3.5 (0.87) Max. 10.5 (2.62)
Propane
lnlet Pressure inch W.C. (kPa) Min. 8.0 (1.99) Max. 13.0 (3.24)
Manifold
Pressure**
NG inch W.C. (Pa) MIN: 0.05 (12.5)
-0.4 (-99.6)
0.05 (12.5)
-1.12 (-279)
0.05 (12.5)
-1.12 (-279)
MAX:
LP inch W.C. (Pa) MIN: -0.06 (-14.9)
-0.5 (-124.5)
-0.06 (-14.9)
-1.26 (-313.8)
-0.06 (-14.9)
-1.26 (-313.8)
MAX:
Weight lbs. (kg) 68.8 (31.0)
Dimension inches H 27.4 x W 17.7 x D 11.2
mm H 696 x W 450 x D 285
Ignition Electric Ignition
Electric
Supply VAC/Hz 120/60
Consumption
Operation W/Pump W/A 126.7/1.55
W/O Pump W/A 113.8/1.41 107.0/1.30 113.8/1.41 107.0/1.30 113.8/1.41 107.0/1.30
Standby W/A 1.2/0.04
Freeze-Protection W/A 129.5/1.10
Water Heater Vent Category*** Category
IV N/A Category IV N/A Category IV N/A
Maximum Pipe Length****
(Hot Water supply line and
Dedicated Return line)
Pipe
Diameter
3/4” 500 ft (152.4 m)
1/2” 200 ft (61 m)
* 40 psi (0.27 MPa) or above is recommended for maximum flow.
** The Manifold Pressure is the factory setting and should not need adjustment. NOTE: Manifold Pressure readings are taken
with the front cover removed.
*** Water Heater Vent Category - Does not apply to Outdoor or Direct Vent Installations.
Category IV - a water heater that operates with a positive vent static pressure and with a vent gas temperature that may
cause excessive condensate production in the vent.
**** Refer to page 36 in the Installation Manual for additional information on pipe lengths.
NOTE:
• Check the rang plate to ensure this product matches your specificaons.
• The manufacturer reserves the right to disconnue, or change at any me, specificaons or designs without noce and without
incurring obligaon.

BASICS
On-Demand Water Heater Service Handbook for X3P Models • 5
BASICS
INTRODUCTION
Read and follow all safety messages
and instructions in this handbook and
on the product labeling.
This is the safety alert
symbol. It is used to alert
you to potential physical
injury hazards. Obey all safety
messages that follow this symbol to
avoid possible property damage,
serious injury or death. Do not remove
any permanent instructions, labels, or
the rating plate from either the outside
of the water heater or the inside of the
access panels.
DANGER indicates a hazardous
situation that, if not avoided, will
result in death or serious injury.
WARNING indicates a hazardous
situation that, if not avoided, could
result in death or serious injury.
CAUTION indicates a hazardous
situation that, if not avoided, could
result in minor or moderate injury.
NOTICE indicates practices not
related to physical injury.
WARNING
●Installation and service must be
performed by a qualified installer
(such as a licensed plumber or gas
fitter).
●The installer/service agent (licensed
professional) is responsible for
correctly installing or servicing your
water heater and for compliance with
all national, state/provincial, and local
codes.
●Failure to comply with these warnings
could result in death, explosion, fire,
or carbon monoxide poisoning.
CAUTION
Wear eye protection during water
heater assembly or disassembly.
Failure to do so could lead to personal
injury.
This handbook provides the necessary
information for troubleshooting the
160X3P, 180X3P and 199X3P tankless
water heaters. It will be effective in
helping your troubleshooting needs as
long as the instructions are followed in
the intended order. Here is how to use
this manual:
●First, refer to the Installation
Manual as the primary source
of information. Refer to it along
side this manual throughout the
troubleshooting process.
●Before troubleshooting, if you are
unfamiliar with how a tankless unit
operates, read “Normal Operation”
on page 6.
●Before troubleshooting a new
installation, use the installation
manual.
●Before troubleshooting, first go
through the “Preliminary Checklist”
on page 6. It will identify the most
common and frequent problems and
provide you with general knowledge
to help narrow down the information
you need.
●If the water heater is in fault and
is displaying an error code, refer
to “Error Codes” on page 11. If
you have not received an error
code, refer to “General Issues” on
page 8.
If you have any problems or questions
regarding this equipment, consult the
technical service department or the local
service agent.
General Installaon
Guidelines
1. Follow all local codes, or in the
absence of local codes, follow the
current edition of the National Fuel
Gas Code: ANSI Z223.1/NFPA 54 in
the USA or B149.1 (Natural Gas and
Propane Installation Code) in Canada.
2. Properly ground the unit 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 C22.1, Canada Electrical
Code, Part 1 in Canada.
3. Carefully plan where you intend to
install your water heater.
4. Check the rating plate located on
the right side of the water heater for
the correct GAS PRESSURE, WATER
PRESSURE, ELECTRIC RATING and GAS
TYPE. NOTE: This water heater’s gas
type is field convertible, confirm the
orifice installed matches the gas type
supplied. See Removing, Replacing,
and Verifying the Gas Orifice
Assembly on page 47.
NOTE: If this unit does not match your
requirements, do not install.
If any problem occurs, turn off all hot
water taps and turn off the gas. Then
call a trained technician or the gas
company.

BASICS
6 • On-Demand Water Heater Service Handbook for X3P Models
Becoming familiar with how a tankless
water heater normally operates may
help to troubleshoot it. Assuming it
is properly installed with appropriate
gas, water, and electrical connections,
it should operate as follows:
Acvaon
1. A hot water fixture is opened. The
flow sensor must detect a flow rate
through the heater that is greater
than the 0.4 GPM before the
heater will begin operation. The
temperature rise must be great
enough to meet the minimum input
requirement which is 9,000 Btu/h
for NG and LP. Otherwise, the
heater will remain in standby.
2. The fan activates to purge the system.
3. The Igniter generates a spark to
ignite the gas.
4. The gas valve will open. You will
hear a deep “clunk clunk” noise.
5. Once a flame is detected, the
green “In Use” LED will activate.
(This green LED is located on the
temperature controller or remote
controller.)
Operaon
6. The fan will modulate and the
gas solenoid valve assembly will
adjust based on the amount of
energy input required to meet the
demand.
7. If the water flow exceeds the water
heater’s capabilities to heat to the
desired temperature, the flow control
valve will restrict the flow to ensure
delivery of water at the desired
temperature. This will result in a
loss of pressure at hot water fixtures
whenever flow is restricted through
the water heater.
NOTICE: The bypass component acts
like a mixing valve. It helps to maintain
the desired outlet temperature and
reduce damage to the heat exchangers
due to corrosion and erosion. The
bypass valve is also used when
multiple water heaters are linked
together.
Shutdown
8. The heater will stop heating when
the water flow rate drops below
the deactivation point of 0.26 GPM.
9. The heater will close the main
gas valve and solenoid gas valves,
extinguishing the flame.
Pressure sensor
Exhaust duct
Primary heat exchanger
Igniter
PCB
Secondary heat exchanger
Exhaust thermistor
Venturi
KƌŝĮĐĞ
Thermistor
Gas valve
Bypass valve
Thermistor
Water control valve
/Flow sensor
Thermistor
Thermistor
X3
TM
Filter
Intake Exhaust
Air adjustment valve
Stepping motor
Metal knit burner
;ŽŵďƵƐƟŽŶĐŚĂŵďĞƌĂƐƐĞŵďůLJͿ
Cold water
Gas
Hot water
Return line
Condensate drain port
Hi-limit
Flame rod
Heater
Igniter rod
Gas solenoid valve
Fan motor
Thermo switch
KǀĞƌŚĞĂƚƵƚŽī&ƵƐĞ;K.H.&Ϳ
ZĞĐŝƌĐƵůĂƟŽŶWƵŵƉ
Figure 1: The purpose of this diagram is to illustrate tankless water heater design concepts, and may
not be accurate to the unit’s physical description.
10. When the flame sensor no longer
detects a flame, the green “In Use”
LED will turn off.
11. The fan will increase in speed to
purge any remaining exhaust gases.
The length of post-purge can last up
to 1-½ minutes.
12. The heater will enter standby
mode.
Preliminary
Checklist
To get started, review the following
topics. You may also refer to “General
Issues,” if necessary.
Gas/Water/Electric:
• Verify that the correct gas type
is being used. Check the supply
gas, the gas type DIP switch,
and the gas type shown on the
NORMAL OPERATION

On-Demand Water Heater Service Handbook for X3P Models • 7
TROUBLESHOOTING
rating plate. All four must be
the same in terms of gas type,
and your water heater model
must be converted for use with
that type of gas (natural gas or
LP). NOTE: This water heater’s gas
type is field convertible, confirm the
orifice installed matches the gas type
supplied. See Removing, Replacing,
and Verifying the Gas Orifice
Assembly on page 47.
• The gas supply valve should be
fully open and the gas line purged
of air and debris.
• The water supply valve should be
fully open and purged of air and
debris.
• The unit must be connected to a
120 VAC 60 Hz power supply.
• There is a power switch inside
the heater, located to the left of
the control board, that must be
turned on before the heater can
operate.
Remote Controller:
If you are using a remote controller,
the remote’s ON/OFF button must be
turned on. Press the ON/OFF button
on the remote until the amber Stand-
By LED is lit.
High Altude:
If the heater is installed at an altitude of
over 2,000 feet, it may cause a lack of air
and incomplete combustion. See “DIP
Switch Settings” on page 25.
Vent Length
The length of your vent run may
require changes to your DIP switch
settings. See “DIP Switch Settings” on
page 25. Also, see the installation
manual for venting requirements.
Incorrect vent length settings may
result in the reduced output from the
water heater.
X3TM Technology:
This water heater is equipped with
X3™ Scale Reduction Technology to
inhibit scale formation within the heat
exchanger tubing of this unit. Part
of the X3™ Technology’s anti-scale
protection comes from the special X3™
cartridge. The X3™ cartridge must be
installed into the manifold located on
the underside of the heater cabinet
prior to operation of the unit). The
X3™ system is designed to be hassle-
free; eliminating the need to drain
the heater for installation, removal,
or replacement of the cartridge. X3™
Scale Reduction Technology reduces
the formation of scale in the heat
exchanger, extending the operating
life of the unit in typical potable water
installations. Specific water conditions
may impact the efficacy of X3™,
such as excessive iron or manganese
levels. Refer to the guidelines below
and consult a water quality expert
to determine if your water is within
acceptable X3™ and EPA guidelines.
New Installaons:
If a newly installed water heater won’t
operate at all or operates erratically,
check for the following:
◦Reversed hot and cold
plumbing connections. The
water heater must sense
water flow to initialize
operations. Water flowing
through the heater backwards
will not activate the flow
sensor.
◦Cross-connections may be
related to a recirculation
pump, a defective mixing
valve, a bad check valve, a
missing check valve, or a
cartridge in a single-handle
faucet that needs to be
replaced.
◦A dirty inlet filter. A dirty
inlet filter can either prevent
water from flowing through
the water heater entirely, or
create turbulence that can
prevent the flow sensor from
measuring the water flow.
◦Misconfiguration of the Easy-
Link system (if applicable).
◦Gas line that has not been
purged of air correctly.
Test to determine if the
problem is related to plumbing
or the water heater:
1. Test whether the problem is
within the unit or external to the
unit (i.e., in the plumbing system)
by attempting to run hot water
locally through the isolation valve
(if installed). Ensure that the hot
water shutoff is closed on the hot
and return lines while running
water through the pressure relief
valve or hot isolation valve drain
port. See Figure 2 on page 8.
2. Does the heater ignite and continue
to run properly? If it runs properly,
the plumbing system is at fault. If
the heater shuts down with an
error code or no operation occurs,
the problem is with the water
heater. NOTICE: If no error code is
displayed, you can use Diagnostic
Mode to review stored error codes.
See “ERROR CODES” on page 11
TROUBLESHOOTINGNORMAL OPERATION /

TROUBLESHOOTING
8 • On-Demand Water Heater Service Handbook for X3P Models
Figure 2: Water flow test.
Next Step:
Finally, check to see if the unit has an error
code. The error code will be displayed on
the temperature controller (or remote
controller) and by flash codes on the green
LED on the computer board. See Figure 3,
page 11. See also the error code chart in
Table 2 starting on page 11.
• If it is displaying an error code, proceed
to “ERROR CODES” on page 11.
• If there is no error code, proceed
to “General Issues.”
General Issues
Proceed to the “Error Codes” section
if an error code is identified. For other
common problems that do not involve
error codes, see if the following items
help:
Water is too hot or not hot
enough.
• What is the set temperature
of the water heater? The
temperature setting may be set
too high or low. The temperature
can be adjusted using the
temperature or remote controller.
Solar installation can have higher
inlet water temperatures. NOTE:
To reduce the risk of scalding,
install Thermostatic Mixing Valves
(temperature limiting valves) at
each point-of-use.
• If a mixing valve is installed, verify
proper installation and check
temperature setting at the valve.
The mixing valve may need to
be adjusted or cleaned. Refer to
the mixing valve manufacturer’s
instructions.
• The output thermistor could be
malfunctioning or debris may be
present on the thermistor. This
could cause it to read incorrectly.
Clean the thermistor and recheck.
• Cross plumbing between cold
water lines and hot water lines.
• Incorrect gas supply line and/or
regulator sizing.
• Easy-Link misconfiguration in multi
unit system.
Temperature fluctuates when a
fixture is opened.
• Check DIP switches for correct
setting. Incorrect settings for
altitude and vent length can result
in fluctuating outlet temperature.
• Test whether the problem is
within the unit or external to the
unit (i.e., plumbing system).
• If the unit is installed in a multi-
unit system, verify that the Easy-
Link system is set up correctly.
Refer to the installation manual.
• The filter on the cold water inlet
should be clean. See”Filter/Drain Plugs
Cleaning” on page 29.
• Fluctuations in pressure of the
supply water system will result in
outlet temperature fluctuations.
On well systems, the heater’s
operation will fluctuate when the
well pump is charging the bladder
tank. Check the pressure settings
to see if an adjustment can reduce
the pressure difference and/
or consider a constant pressure
pump.
Unit does not operate when
water goes through it.
• Check to see if the water heater is
in standby. This can be verified by
observing the amber LED on the
temperature/remote controller.
If is not lit, press the ON/OFF
button on the controller to see if
it will turn on. If not, then check
to see if the ON/OFF button to the
right of the temperature controller
is set to the on position, or if the
fuse in the fuse box assembly is
blown.
• Is the flow rate over 0.4 GPM?
See if the unit initiates when you
increase demand of water being
drawn through the unit (e.g.,
opening up more hot fixtures).
You can verify the flow rate by
pressing the info button on the
front of the unit until the arrow
lights up beside “flow.” See”Filter/
Drain Plugs Cleaning” on page
29.
On-Demand
Water
Heater
HC
AB
CD
Outlet Hose
(Hot)
Bucket
“A” Open
“C” Closed
“B” Closed
“D” Open
NOTE: Close
valve on
return line.

TROUBLESHOOTING
On-Demand Water Heater Service Handbook for X3P Models • 9
• Make sure that a check valve
is installed on the return line.
A malfunctioning or missing
check valve will cause a cross
connection, allowing cold water to
back-feed into the system.
• Check that the filters on the cold
and return lines are clean.
• Is the inlet water temperature
is too close to the set point
temperature. Verify by opening
multiple faucets and check to
see if the water heater operates.
If the water heater operates
this may indicate a seasonal/
geographic condition causing
warmer inlet water that is too
close to the water heater’s set
point. The minimum input is
9,000 btu/h which means the
heater will not activate if the
energy input is below this. For
recirculation systems, review and
adjust the temperature differential
setting as necessary.
• New installations only: Are the hot
and cold water connections to the
water heater reversed (hooked
up backwards)? Water flowing in
reverse through the heater will not be
detected by the flow sensor and the
water heater will not operate. See
“Checking for a Reversed Connection”
on page 30 for details on checking
for a reversed connection.
• If the fan does not initiate at all and
it is verified that there is power to
the unit, the flow sensor may not
be working properly. Check the
flow sensor for proper impeller
functionality See “Checking the
Flow Sensor,” page 32.
Abnormal sounds come from
the unit.
• Check the fan for debris.
• Check for blockages in the exhaust
vent and intake air line.
• Check terminations for proper
clearances to ensure flue gases
are not being drawn into the
combustion air intake.
• Check for proper gas supply
pressure and allowable pressure
drop.
• Check the rating plate to ensure
that the correct gas type is applied
to the unit. NOTE: This water
heater’s gas type is field convertible,
confirm the orifice installed matches
the gas type supplied. See Removing,
Replacing, and Verifying the Gas
Orifice Assembly on page 47.
• Check the DIP switch settings for
vent length, altitude and gas type.
• If you cannot identify the source
of this issue, contact the technical
service department.

TROUBLESHOOTINGTROUBLESHOOTING
10 • On-Demand Water Heater Service Handbook for X3P Models
THIS PAGE IS INTENTIONALLY BLANK

TROUBLESHOOTING
On-Demand Water Heater Service Handbook for X3P Models • 11
TROUBLESHOOTING
ERROR CODES
All units have self-diagnostics. If there is a problem with the unit, a numerical error code will display on the temperature controller
of indoor models or on the TM-RE43 Remote Controller (if installed). Installation related problems can also produce an error
code(s). If the remote/temperature controllers are not working, the green LED on the computer board will flash a code pattern.
(The green LED is located beside the DIP switches as shown in Figure 3).
Computer board
Error code indicator on
the remote controller
Error code indicator on
the built-in controller
Figure 3: Error Code Indicators.
Table 2: Error and Flash Codes
ERROR CODE GREEN LED ON
COMPUTER BOARD
SYMPTOM OR ISSUE TROUBLESHOOTING PROCEDURE
031 One Flash Incorrect DIP switch
setting
Check the DIP switch settings on the PCB (Part #701).
051 Three Flashes Combustion Air and/or
Exhaust Gas Blockage See Error Code 991
101 Five Flashes Combustion Air and/or
Exhaust Gas Blockage See Error Code 991
If you are working with a water heater that is part of an Easy-
Link system, we recommend that you troubleshoot the unit as
an individual unit and not as part of the system. Follow these
steps prior to troubleshooting a child unit:
1. Disconnect power to all the water heaters in the Easy-
Link system. The ON/OFF button on the water heater and
remote does NOT disconnect power to the water heater.
You must physically disconnect power to the water heater.
2. Close isolation valves to the water heater.
3. Disconnect both linking wires from the bottom of the
heater.
4. If the unit is not an end unit, take the ends of both linking
wires which you unplugged and connect them together.
One end is male and the other is female; they will connect
together.
5. Turn power to the water heaters back on, then
troubleshoot as necessary.

TROUBLESHOOTINGTROUBLESHOOTING
12 • On-Demand Water Heater Service Handbook for X3P Models
ERROR CODE GREEN LED ON
COMPUTER BOARD
SYMPTOM OR ISSUE TROUBLESHOOTING PROCEDURE
111 or 121 Three Flashes Ignition failure / Loss of
flame
• Check for connection/breakage of wires, burn marks
on the computer board (Part #701), and/or soot on the
flame rod (Part #108).
• A “buzzing” ignition sound should be coming from the
burner (Part #101) when the water heater prepares for
combustion, if not heard then the igniter (Part #710)
maybe the issue.
• Listen for the “clunk” sound coming from gas solenoid
valve assembly (Part #130) when water heater goes
into combustion. If nothing is heard, then check the
hi-limit switch (Part #412), overheat-cut-off fuse (Part
#413) and connections to the gas valve Part #102).
• Check if the Hi-limit switch (Part #412) is functioning
properly. The switch has a button in its center, pressing
the button will reset the switch. If tripped, you will hear
and feel it click when resetting. If the high limit switch
continues to trip contact a qualified service technician.
201 One Flash Combustion air
and gas line failure
• Check if the pressure sensor (Part # 123) is functioning
properly.
• Check if the fan motor (Part #103) is functioning
properly.
• Check for connection/breakage of wires, burn marks
on the computer board (Part #701).
211 Three Flashes Air pressure
sensor failure
Check for connection/breakage of wires (Part #123,
715), burn marks on the computer board (Part #701).
311 Two Flashes Heat Exchanger
Thermistor Failure • Check for connection/breakage of wires and/or debris on
thermistor (Part #407, 408, 411, 715, 718, 731).
• Verify thermistor resistances, see page 18 for thermistor
troubleshooting.
321 Two Flashes Inlet thermistor failure
331 Two Flashes Outlet thermistor failure
341 Two Flashes Exhaust thermistor
failure
351 Two Flashes Return thermistor
failure

TROUBLESHOOTING
On-Demand Water Heater Service Handbook for X3P Models • 13
ERROR CODE GREEN LED ON
COMPUTER BOARD
SYMPTOM OR ISSUE TROUBLESHOOTING PROCEDURE
391 Two Flashes Flame Rod Failure Check for connection/breakage of wires (Part #709)
and/or soot on the Flame rod (Part #108).
441
Two Flashes
Flow Sensor Failure • Check for connection/breakage of wires (Part #402,
715).
• Check for debris on the flow sensor impeller (Part
#402).
• If a check valve(s) is installed in the water lines, verify
that they are operating properly.
• The circulation lines may have more pressure drop
than the pump is designed to push through. A Qualified
Service Technician will need to perform a pressure drop
calculation.
• If a cross over valve is installed, check if the DIP switch
setting is correct. (Refer to p. 25.)
511
Six Flashes
Abnormal main gas
valve (MV)
Check for connection/breakage of blue and brown
wires going to gas valve assembly and/or burn marks
on the computer board (Part #701).
521
Six Flashes Air damper failure
• Check if the air damper assembly (Part #122) is
functioning properly.
• Check for connection/breakage of wires (Part #122,
715), burn marks on the computer board (Part #701).
551
Six Flashes
Abnormal gas solenoid
valve (SV1, SV2, and/
or SV3)
Check for connection/breakage of the blue and green,
light blue, and red wires going to gas valve assembly
and/or burn marks on the computer board (Part #701).
611 Four Flashes Fan motor fault
• Check for connection/breakage of wires, dust buildup
in the fan motor (Part #103) and/or burn marks on the
computer board (Part #701).
• Check for corrosion/damage of the wire connectors
(Part #103).
• Inspect your exhaust air intake for any blockages,
clear if any are found.
631 Four Flashes Pump fault
• Check for connection/breakage of wires in the pump
(Part #726, 738).
• Check for the reverse water flow through the pump.
Install a check valve on the return line to the water
heater. Verify proper operation.

TROUBLESHOOTING
14 • On-Demand Water Heater Service Handbook for X3P Models
ERROR CODE GREEN LED ON
COMPUTER BOARD
SYMPTOM OR ISSUE TROUBLESHOOTING PROCEDURE
651 Four Flashes Flow adjustment
valve fault
• Inspect the flow adjustment valve (Part #402), for
connection/breakage of wires
• Inspect the control valve for debris that may be
blocking it.
661 Four Flashes Bypass valve fault
• Inspect the bypass valve (Part #403), for connection/
breakage of wires.
• Inspect the control valve for debris that may be
blocking
701 One Flash Computer board fault Check for connection/breakage of wires or burn marks
(Part #701, 714).
711 One Flash Gas solenoid valve drive
circuit failure Refer to the 111 and 121 error codes.
721 Six Flashes False flame detection Check the flame rod (Part #108) for corrosion/soot
buildup.
741 N/A
Communication error
between water heater
and remote controller
• Verify the correct model/type of remote is installed.
• Inspect the connections between the water heater
and remote controller.
• The code will appear if you disconnect the remote
from the water heater without first turning off power
to the water heater. Turn the water heater OFF then ON
to reset.
751 N/A
Communication error
between water heater
and built-in controller
• Inspect the connections between the water heater
and built-in controller.
• The code will appear if you disconnect the remote
from the water heater without first turning off power
to the water heater. Turn the water heater OFF then ON
to reset.
761 N/A Communication error in
Easy-Link
• Check if the connections between the parent unit and
the child units are correct. Refer to pp. 34 and 37.
• Check the Child units for power. Troubleshoot any
Child units without power.
• The code will only appear on the Parent water heater
if you disconnect an Easy Link wire from a Child water
heater without first turning off power to the Easy Link
System. Turn the Parent water heater OFF then ON to
reset.

TROUBLESHOOTING
On-Demand Water Heater Service Handbook for X3P Models • 15
ERROR CODE GREEN LED ON
COMPUTER BOARD
SYMPTOM OR ISSUE TROUBLESHOOTING PROCEDURE
991 Five Flashes Combustion Air and/or
Exhaust Gas Blockage
• Verify the gas type supplied to the water heater
matches gas type orifice plate installed. DO NOT
operate the water heater if they do not match;
correct immediately.
• Inspect the environment around the water heater.
• Check the altitude/elevation of the area where the
water heater is installed, and verify the DIP switches
are set to the proper elevation.
• Verify the vent length DIP switches match the
equivalent vent length of the installed venting
system. Refer to See Table 5 on page 27.
• Inspect your exhaust air intake for any blockages,
clear if any are found.
• If the water heater is installed as a direct-vent system,
check whether there is proper clearance between the
intake air terminal and the exhaust terminal. Refer to
pp. 26 to 28 of the Installation Instructions and Use &
Care Guide.
• Check for dust and dirt on the air screen of the rain
protection tray (Part #007) and verify air intake is not
blocked.
• Check for connection/breakage of wires and/or burn
marks on the computer board (Part #701)

TROUBLESHOOTING
16 • On-Demand Water Heater Service Handbook for X3P Models
Code 031: Incorrect DIP Switch
Sengs
The system displays this code when an
incorrect DIP switch setting is detected
or DIP switches were changed when
the heater power was on.
1. Turn off the power supply.
2. Remove front cover and locate
the DIP switches at the side of the
computer board.
Refer to “DIP Switch Settings” on
page 25. The correct DIP switch
positions are illustrated in that
section.
For specific DIP switch settings
related to vent length or high-
altitude installations, refer to
the tables that start on page 25.
Additional information is provided
in the Installation Manual/Owner’s
Guide.
3. After setting the DIP switches, turn
power to the water heater back on.
Code 051 or 101: Combuson
Air and/or Exhaust Gas
Blockage
Refer to “Error Code: 991,“ page 22.
Code 111 or 121: Ignion
Failure / Flame Loss
Either the water heater will not fire
after three failed ignition attempts
(code 111) or it lost the flame signal
during a heating cycle and was not
able to establish a flame after three
failed ignition attempts (code 121).
These codes can appear due to a
component in the heater or due to an
external cause, such as no gas supply.
1. Verify that the gas supply pressure is
within specifications when the heater is
in standby, and verify the gas pressure
does not drop below the minimum
specified supply pressure when all
gas appliances are in operation. Also,
verify that the gas line is cleared of
debris.
• It is possible that there is a faulty
pressure regulator at the gas meter.
• If a second stage regulator is
installed, verify the following:
that it is sized properly for the
application; that it is installed per
the manufacturer’s instruction
(pay close attention if an indoor
vent limiter is installed); the vent
line (if installed) is sized properly.
Note: Some manufacturer’s
may recommend that a specific
amount of straight pipe is
installed on the outlet before any
changes in direction. Refer to the
regulator’s manufacturer. See
“Checking the Inlet Gas Pressure
and Pressure Drop” on page
30.
2. Check the High Limit Switch and
Overheat Cutoff Fuse (OHCF) as follows:
2.1 Turn offpower to the water
heater, then turn it back on.
(Use the switch above the
computer board.) Listen for
the “clunking” noises of the
gas solenoid valves. If you
DO hear them, go directly to
step 3. The water heater may
show error code 711, if this
occurs proceed to the next
step.
2.2 Turn offpower to the heater
by disconnecng the power
cord or external switch.
2.3 Locate the high limit switch
(item 412, p. 74). See also
Figure 21 (p. 40) and Table
8 (p. 41).
2.3.1 Push the buon in the
middle of it. The switch was
reset if you heard and felt
the buon click.
2.3.2 Turn the power back on
and test the heater. If the
burner lights, the cause of
the high limit trip must be
determined. Connue with
the troubleshoong process.
Also, be sure to check the
temperature of the incoming
water supply. If the unit is
supplied with pre-heated
water, such as from a solar
system, the incoming water
temperature may be too
high.
2.3.3 If the high limit switch is
operang properly and you
don’t hear the “clunking”
noises of the gas valves, then
check the overheat cutoff
fuse (OHCF) for connuity. If
there is no connuity, or for
instrucons on how to test
the OHCF for connuity, refer
to “Checking the Overheat
CutoffFuse (OHCF)” on page
32.
3. Check for blockages in venting, such
as bird nests, animals, or trash. A
blockage will cause improper operation
leading reduced capacity and inability
to maintain combustion.
4. Check for a spark inside the burner
chamber between the igniter rods.
The spark may be viewed through
the sight glass located next to the
igniter and flame sensor. A strong
blue spark will remain steady and in
place, while a weak spark will jump
around.
4.1 If no spark or a weak spark is
observed, check the purple
igniter wire connecons at

TROUBLESHOOTING
On-Demand Water Heater Service Handbook for X3P Models • 17
both the igniter and at the
computer board. Unplug and
reconnect them to clean the
electrical connecons.
4.2 Check the igniter rod to
make sure the black wire is
properly aached and that
the rod doesn’t move. If
the rod moves, replace the
igniter rod. You will also need
a rod holder gasket.
4.3 When the igniter is sparking,
check the voltage across the
purple wires coming to the
igniter. Normal voltage is
108-132 VAC. If voltage is
outside of this range, then
replace the computer board.
(See item 701 on page 77 for
the correct part number.)
4.4 If the previous steps sll
don’t result in a spark being
generated, replace the igniter.
5. If flame comes on for only 1-2
seconds before going out, verify
that the green IN USE LED on
the built-in controller or remote
controller did not turn on. If the
LED stayed off, then inspect the
flame sensor. Clean it if necessary.
Replace it if any damage (chips or
cracks in the ceramic) is seen or
if the metal rod can move freely
in the ceramic insulator. See
“Cleaning the Flame Sensor and
Igniter Rod)” on page 33.
Unplug both ends of the wiring
harness from the igniter assembly
and control board, then reconnect
them to ensure good connection.
Also, verify that the green wire that
is part of the circuit is attached
to one of the screw connections
around the manifold.
6. Verify proper operation of the
main gas valve (MV). To do so,
turn the power off, then check the
resistance of the MV. A normal
resistance is 1.15-1.65 kΩ. If the
resistance is out of range, replace
the gas valve.
7. Verify proper operation of the gas
solenoid valves. To do so, turn
the power off, then check the
resistance of the valves. A normal
resistance reading for SV1 is 1.35-
1.65 kΩ. Normal resistance for SV2
and SV3 is 2.07-2.53 kΩ. If the
resistance is out of range, replace
the gas valve.
Code 201: Combuson Air and
Gas Line Failure
• Check if the pressure sensor is
functioning properly.
• Check if the fan motor is functioning
properly.
• Check for connection /breakage of
wires, burn marks on the PCB.
Code 211: Air Pressure Sensor
Failure
• Check the voltage between the
black and red wires. Normal: 4 to 6
VDC between black & red (during
operation)
• Replace the pressure sensor if
the voltage is outside of the range.
Replace the PCB if the voltage is within
the normal voltage range.

TROUBLESHOOTING
18 • On-Demand Water Heater Service Handbook for X3P Models
Code 311, 321, 331, 341 or 351:
Thermistor Failure
The system displays this code when it
detects a thermistor failure.
1. Turn off power to the water heater.
2. Identify the row in Table 3 that
applies to you, then follow its
instructions.
3. After you have located the correct
thermistor, verify that the wire
connections are secure and free of
burns or cuts.
4. Check the thermistor’s resistance
value. See Figure 4 for a list of
normal resistance values. Run
water through the heater for
several minutes to get all the
thermistors in approximately the
same temperature range.
5. Clean the thermistor as follows:
a. Drain the unit of water. (See
“Unit Draining and Filter
Cleaning” on p. 29.)
b. Remove the screw or clip
that secures the thermistor,
then pull the sensor probe
out by grabbing the metal
base. Do not pull the wire
as you may cause the wire to
separate from the probe.
c. Clean the probe to a silver
finish. Do not lose the red
rubber o-ring that wraps
around this sensor.
d. Reinstall the thermistor.
6. Return the water heater to service.
7. If the error code persists, replace
the thermistor.
30.04
24.12
19.50
15.87
13.00
10.71
8.87
7.39 6.19 5.21 4.41 3.74 3.19 2.73 2.35 2.03 1.76 1.53 1.33 1.16 1.02
19.08
15.43
12.56
10.28
8.47
7.02 5.85 4.90 4.12 3.49 2.96 2.53 2.16 1.86 1.60 1.39 1.21 1.05 0.92 0.81
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
0°C 5°C 10°C 15°C 20°C 25°C 30°C 35°C 40°C 45°C 50°C 55°C 60°C 65°C 70°C 75°C 80°C 85°C 90°C 95°C 100°C
32°F 41°F 50°F 59°F 68°F 77°F 86°F 95°F 104°F 113°F 122°F 131°F 140°F 149°F 158°F 167°F 176°F 185°F 194°F 203°F 212°F
Temperature vs Resistance
Exhaust Thermistor Temperature Thermistor
ZĞƐŝƐƚĂŶĐĞ;ŬɏͿ
23.76
Figure 4: Temperature vs Resistance Graph

TROUBLESHOOTING
On-Demand Water Heater Service Handbook for X3P Models • 19
Code 391: Flame Rod Failure
1. Ensure that the unit is plugged into
a socket that is properly grounded.
A floating ground can cause this
error.
2. Check that the wire connections are
secure and free of burns or cuts.
Verify that the green ground wire is
installed properly and is making an
electrical connection. This ground
wire is part of the connector to the
PCB. The green wire is secured to
the metal plate to the right of the
surge box.
3. Clean the flame rod. See “Cleaning
the Rod Assembly (Flame Sensor
and Igniter Rod)” on page 33.
Code 441: Flow Sensor Failure
This code is displayed when the
computer doesn’t detect a signal from
the flow sensor when the pump is
running or when a heater in the Easy-
Link System is running.
1. If the code appears when the pump
should be operating, then:
• Inspect the filter on the
return connection and clean
as necessary.
• Inspect the pump for
any debris in the pump
connections and clean as
needed.
• If using a crossover valve,
check to make sure the
crossover valve DIP switch
setting is in the ON position
(DIP switch #5, top bank).
2. Disconnect the water heater
from the linked system before
you advance to step 2. The water
heater must be tested as an
individual unit.
3. Ensure that the water supply is
turned on.
4. Check the flow sensor/control valve
wires to see if they are broken or
disconnected.
5. Verify the flow rate using the water
heater’s controller. To do so, select
Flow Rate by pushing the INFO
button until the arrow on the left
side of the display points toward
“Flow.” Ensure that the controller
displays a flow rate during
operation. If a flow rate is not
indicated, proceed to the next step.
6. Check the inline water filter for
debris.
7. Turn off the gas supply and
electrical power to the heater, then
remove the flow sensor/control
valve (p. 61). Check the flow
sensor as described in “Checking
the Flow Sensor,” page 32. Clean
or replace as necessary.
Code 511: Abnormal Main Gas
Valve (MV)
This code indicates a fault in the main
gas valve (MV) circuit.
1. If the hot water is shut off, but
flames are still visible through the
burner sight window, immediately
shut off gas and power to the unit
and contact the technical service
department.
2. Check the wire connections to the
main gas valve for burns or cuts.
3. If the unit was serviced recently
and the gas valve had to be
removed, make sure that each gas
valve wire is fully plugged into the
connector.
4. Verify that the gas supply pressure
is within the specified limits. An
inlet gas pressure that is too high
can jam or damage the main gas
valve.
5. With the power off, check the
resistance of the valve. Normal
resistance reading is 1.15-1.65 kΩ.
If the resistance is out of range,
replace the gas valve.
6. Check the voltage across the main
gas valve wires (blue - light blue
#3) during operation. The voltage
reading should be 93-120 VDC. If
the voltage is not within normal
range, replace the computer board.
Code 521: Air Damper Failure
1. Verify the DIP switches are set for
the proper installation altitude.
If adjustment is needed, turn off
power to the heater and adjust.
Then go to step 4 for the error
code reset and test heater. If this
doesn’t fix it, go to steps 2-4.
2. Visual inspection of the air damper
for blockage and/or loose fit.
Remove any debris or blockage
that would keep the damper from
rotating.
3. Normal: 3 to 11 VDC between
COM (white) & brown (during
operation) Visual inspection of PCB:
connection/breakage of wires and/
or burn marks on the computer
board.
4. To reset this error code, go to Reset
Procedure, step 10 of 991 error
code on page 24.
Code 551: Abnormal Solenoid
Gas Valve (SV1, SV2, and/or
SV3)
This code indicates a driving circuit
fault for one or more of the solenoid
gas valves (SV1, SV2, or SV3).
1. Check the wire connections to the
gas solenoid valves for burns or
cuts.
2. If the unit was serviced recently

TROUBLESHOOTING
20 • On-Demand Water Heater Service Handbook for X3P Models
and the gas valve had to be
removed, make sure that each
gas valve wire is plugged into the
proper place. (For each connector,
the number stamped on the metal
must match the number that is
printed on the wire’s label.
3. Verify that the supply gas pressure
is within the specified limits. Too
high of an inlet gas pressure may
cause the main gas valve to jam or
could be damaged.
4. With the power off, check the
resistance of each valve. Normal
resistance reading for SV1 is 1.35-
1.65 kΩ. Normal resistance reading
for SV2 and SV3 is 2.07-2.53 kΩ.
If the resistance is out of range,
replace the gas valve.
5. Check the voltage across these
solenoid gas valve wires during
operation. (The dark blue wire is
common.)
• SV1: Green (#9) & Blue
• SV2: Orange (#53) & Blue
• SV3: Red (#73) & Blue
In each case, the voltage reading
should be 93-120 VDC. If the
voltage is not within normal range,
replace the computer board.
Code 611: Abnormal Fan Motor
This code indicates a fan motor fault.
1. Disconnect power to the water
heater by unplugging it from the
wall outlet or turning it off at the
circuit breaker.
2. Check venting for blockages or for
the presence of contaminants in
the water heater area (e.g., lint,
dust). Make sure that there are
no contaminants inside the water
heater cabinet. Correct any issues
that are found.
3. Visually check for breakages in the
fan motor wiring or burn marks on
the computer board (PCB). Repair/
replace as needed.
4. Check for leaks at the heat
exchanger.
5. Check the fan housing for water.
6. Turn on power to the water heater,
then test the heater.
7. Complete this step only if the previous
steps did not solve the issue.
During operation, check the voltage
between the fan motor wires listed
below. The blue wire is common. (See
“FM” in the wiring diagram, page
28.)
• Red & Blue
Normal: 132 to 192 VDC
(during operation)
• Yellow & Blue
Normal: 13 to 17 VDC
(during operation)
• Orange & Blue
Normal: 2 to 6.5 VDC
(during operation)
If the voltage readings fall within the
normal range, replace the fan motor.
If the voltage readings are not within
normal range, replace the computer
board.
Code 631: Pump Fault
1. Verify the check valve is operating
properly. This code appears when
water moves backwards through the
pump.
2. Check the filter on the return
connection and clean as necessary.
3. Inspect the pump for buildup or debris
in the connections that can reduce the
speed of the pump impeller. Clean out
the debris. Once re-installed make sure
the pump is not air locked.
4. Inspect the wires to the pump for any
cuts or breakage. Replace the wires if
they are compromised.
5. Complete this step only if the previous
steps did not solve the issue.
During operation, check the voltage
between the pump wires listed below.
The blue wire is common. (See
“PUMP” in the wiring diagram, page
28.)
• Red & Blue
Normal: 132 to 192 VDC
(during operation)
• Yellow & Blue
Normal: 13 to 17 VDC
(during operation)
• Orange & Blue
Normal: 1.0 to 6.5 VDC
(during operation)
If the voltage readings fall within the
normal range, replace the pump. If the
voltage readings are not within normal
range, replace the computer board.
Code 651: Flow Adjustment Valve
Fault
This code indicates a flow adjustment
valve fault.
1. Inspect the flow adjustment valve
(item number 402, p. 73) for the
following:
• Broken or disconnected wires
• Debris or scale buildup inside the
valve assembly that would prevent
the valve from opening or closing
• Water leakage at the flow
adjustment valve (Replace the
seals/component.)