Airxcel Aqua-Hot 100 Series User manual

Service Manual
100Series
AHE-125-GN1

IntroductionIntroduction
©Aqua-Hot® 125-GN1 Service Manual REV 220427
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Contents
Caution Notes...............................................................................2
Introduction ..................................................................................3
Maintenance Schedule................................................................6
System Features ..........................................................................7
Component Cut-Aways .................................................................9
Operational Flowchart................................................................11
Operating the Aqua-Hot & LCD................................................. 12
Aqua-Hot Controller................................................................... 14
Controller Replacement Procedure...........................................18
Fluid Level Sensor......................................................................21
High-Limit Thermostats............................................................. 23
Low-Temperature Cutoff Thermostat........................................25
Three-Way Valve ........................................................................ 26
Tempering Valve ........................................................................ 28
Fluid Circulation Pump.............................................................. 30
AC Electric System..................................................................... 32
AC Relay ..................................................................................... 34
ETS Module ............................................................................... 35
Fuel System Replacement.........................................................37
Fuel System Purge Procedure .................................................. 39
Burner Troubleshooting ............................................................ 40
Burner Operation after Service ................................................ 43
General Troubleshooting........................................................... 44
Winterization.............................................................................. 45
Appendix A: System Schematics.............................................. 46
Appendix B: Parts...................................................................... 50
Appendix C: Measuring Antifreeze ........................................... 55
System Overview
The Aqua-Hot 125GN Series is a Hydronic Heating System
that can provide heat and hot water on demand using a built-in
electric heating element and an external gas burner.
The Aqua-Hot Heating is a 2-in-1 System
1. Interior heating system: provides quiet, comfortable interior
heat and even temperatures.
2. Tank-less hot water system: provides a ow of comfortable
hot water.
The Aqua-Hot heating system heats an ethylene glycol-
based antifreeze (50%) and distilled water solution (50%) that
is stored in the Aqua-Hot’s boiler tank. This uid solution must
be up to operating temperature before the Aqua-Hot will provide
interior heat or hot water. The tank-less hot water system
produces approximately 0.8 GPM of hot water. This system is
also hot water priority, so it will shut off the heat any time hot
water is called for.
Once the uid is to temperature (180°F), a uid circulation
pump transports the heated glycol/water mixture through the
heating loop and to heat exchangers to evenly warm the RV.
Water is heated on-demand by going into a heat exchanger
Gas Burner
Cozy #1
Living Space
Aqua-Hot
Heating System Cozy #2
Kitchen Cozy #3
Bedroom
located in the Aqua-Hot. The water is heated by transfer from
the heated antifreeze and distilled water solution. The heated
domestic water then ows through the tempering valve to be
mixed with cool water from the fresh water tank to achieve an
appropriate temperature before it ows to the faucet.
To get the Aqua-Hot to temperature, turn the electric heating
element and/or the external gas burner to the “ON” position
on the Aqua-Hot LCD screen, or on the RV control panel. It may
take up to 20 minutes to get to operating temperature before
heat or hot water are available.
For continuous hot water or heat in colder conditions, it is
recommended to utilize the external gas burner. The electric
heating element will provide heat only in mild conditions and
provide light duty hot water needs.
Should additional assistance be needed, please contact the
Technical Support at 574-AIR-XCEL (574-247-9235), Monday
through Friday, between 7:00am and 4:00pm MST.
Figure 1
NOTE: The image below is just a sample for mounting locations
of the Cozy heat exchangers, burner, and Aqua-Hot. Actual
placement and quantity may vary on the individual design of the
RV. For questions or assistance, contact Aqua-Hot at 574-AIR-
XCEL (574-247-9235).
Caution Notes
As you read this information, take particular note of the NOTICE,
CAUTION, WARNING, and DANGER symbols when they appear.
This information is important for safe and efcient use of the
Aqua-Hot system.
NOTICE signals a situation where potential damage to the
Aqua-Hot could occur.
CAUTION signals a situation where potential harm or risk
of minor or moderate injury could occur if you do not follow
instructions.
WARNING signals a hazardous situation where potential harm,
risk of serious injury, or death could result if instructions are
not followed.
DANGER signals a situation where immediate risk of serious
injury or death will result if instructions are not followed.
NOTE: This manual will also use notes sections similar to
this one to draw attention to features and practices which
must be observed.

IntroductionIntroduction
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WARNING!
Read and understand all instructions before servicing the
Aqua-Hot unit and the external gas burner. Aqua-Hot Heating
Systems is not liable for damage resulting from failing to
follow instructions contained in this, and any other Aqua-Hot
documentation relevant to this unit.
Improper installation, adjustments, service, and maintenance
can cause personal injury or loss of life. Reference the service
and user manuals before maintenance or service.
• The product identity label contains specications of the
unit, to what standards it has been tested, and important
safety notices.
• Disconnect electric wiring to the Aqua-Hot System before
welding or plasma cutting the RV to avoid damage to
equipment.
• The Aqua-Hot tank and heating loop operate at 0 PSI (zero
pressure system). Air pressure to the tank must not exceed
18 PSI. Exceeding this rating will cause internal damage to
the Aqua-Hot.
• Use caution when working on or near any gas systems.
• DO NOT connect the 12-volt DC power to the Aqua-Hot if the
vehicle requires welding.
• At maximum operating temperature, the coolant and vapor
will be very hot and scalding that may result in serious
burns or injury. Be aware of hot surfaces.
• Use special caution when children are present. Children
must not be allowed to play with the heater or perform
cleaning and/or maintenance.
• Installation and repairs may only be carried out by an
authorized, factory-trained Aqua-Hot technician. The
heating system must be serviced in accordance with local
codes, or, in the absence of local codes, follow NFPA 1192.
National safety regulations must be adhered to.
Introduction to this Document
Welcome to the Aqua-Hot 125GN Service Manual. This
manual will serve as a guide for diagnosing and repairing the
Aqua-Hot, how to perform standard maintenance, and guide
you through troubleshooting procedures to repair the Aqua-Hot.
This service manual is designed to aid trained and qualied
technicians to properly service and troubleshoot the Aqua-Hot
125GN.
Each section in this manual is dedicated to the diagnosis
of specic components within the Aqua-Hot which may be
inhibiting the operation of the heater.
Troubleshooting and diagnosis of the Aqua-Hot is most
efciently and effectively accomplished with the Aqua-Hot LCD
display, which will relay in plain-language, diagnosis of many
Aqua-Hot related issues.
If additional assistance is needed in diagnosing and
repairing the Aqua-Hot, please contact our Technical Service
Department at 574-AIR-XCEL (574-247-9235) from 7:00am to
4:00pm MST Monday through Friday.
As with any appliance, allow the Aqua-Hot to
completely shut down BEFORE disengaging the
RV 12V power disconnect.
Figure 5
Aqua-Hot 3.5in LCD
Heat Priority Option:
The Aqua-Hot comes equipped with the three-way valve
(sometimes known as the summer/winter valve). This controls
the ow of the antifreeze and water heating solution within
the Aqua-Hot to deliver either hot water or interior as priority.
Tapping on this element will change the valve’s orientation.
When this element displays “INT. HEAT”, this valve is oriented
to provide interior heat by circulating the heating solution
throughout the interior heating zone. When the element says
“HOT WATER”, the valve is oriented so that the heating solution
is routed to prioritize hot water.
Figure 2
External Gas Burner:
The gas burner is the Aqua-Hot’s primary and most powerful
heat source, and provides all of the heating and hot water
needs when cold temperatures exist, and/or when there is a
high demand for hot water. It can be activated by turning the
burner on by tapping BURNER to ON on the LCD screen shown
below.
The burner has 2 modes: ON and OFF. When the burner is ON,
the burner will keep the tank temperature between 160°F and
180°F. The burner will toggle between ON and OFF as needed,
using temperature readings from the RV interior thermistors. In
OFF mode, the burner is off and will not provide any heat to the
Aqua-Hot tank.
Electric Element:
The electric element is the Aqua-Hot’s secondary heat source
and can be used when plugged into shore power. The electric
element will work to maintain tank temperature at 5°F below
the heater activation threshold. It can be activated by tapping
on the ELECTRIC button of the LCD screen interface.
The electric element has 2 modes: ON and OFF. When the
electric element is ON, the electric element will keep the tank
temperature between 165°F and 180°F. The electric element
will toggle between ON and OFF as needed, using temperature
readings from the RV interior thermistors. In OFF mode, the
electric element is off and will not provide any heat to the Aqua-
Hot tank.
NOTE: Aqua-Hot recommends regular exercise of the Aqua-
Hot heating system to avoid issues with starting after a
several-month idle period.
NOTE: The Fuel System requires that the gasoline used
(in the vehicle for the burner supply) must be 87 octane or
greater (87, 89, 91, or 93 octane).
NOTE: Contact your Authorized Service Center or Aqua-
Hot Heating Systems if you have any questions before
starting any service or maintenance. Information can
be found online at www.aquahot.com.
If the information in this manual is not followed
exactly, a re or explosion may result, causing
property damage, personal injury, or death.
Figure 4
Figure 3
GAS

System FeaturesIntroduction
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Maintenance Schedule
Monthly Maintenance
Check the Aqua-Hot’s antifreeze and distilled water heating
solution to ensure that it is at the proper level. This can be
accomplished by visually checking the coolant level in the Aqua-
Hot’s expansion bottle; reference Figure 87 on page 44.
Please note that the coolant level should ONLY be checked
when the Aqua-Hot is at maximum operating temperature.
This should be done immediately after the electric element
disengages, or after the gas burner has completed a cycle.
At maximum operating temperature, the antifreeze and distilled
water heating solution should be at the level marked “HOT” on
the expansion bottle.
Annual Maintenance
To maintain the Aqua-Hot at its full potential, it is highly
recommended to have the gas burner tuned up annually.
This involves cleaning the burner, inspecting the exhaust and
combustion air lines for damage and ensure they are clear,
checking the fuel lines for any leaks, and checking the hoses
and wiring to make sure there is no damage or cracks.
Replenishing the Heating Solution
If the antifreeze and water heating solution needs replenishing,
remove the expansion bottle cap and ll it to the “HOT” mark.
Replace the expansion bottle cap when this is complete. DO
NOT operate the unit without rst replacing the cap of the
bottle. Reference Figure 87 for additional information. Excess
air will escape through this bottle as the stir pump of the unit
operates. While bleeding this system of air, it will be necessary
to continue to ll the bottle until this process is complete.
The Aqua-Hot does not need regular replacement of the
antifreeze and water heating solution, but in the event that more
antifreeze is required, contact Aqua-Hot Heating Systems to
purchase antifreeze, or for guidance in selecting an appropriate
antifreeze product for use with this unit.
Overheat Protection
Every Aqua-Hot is equipped with at least two overheat
protection devices. These are commonly known as the high-
limit thermostats. These thermostats operate by maintaining a
circuit while the unit is below 218°F.
In the event of an overheat condition, the high limit thermostats
will cut the operating signal to the gas burner, and/or the electric
element. When this signal is interrupted, the electric element
and gas burner will immediately disengage. Contact Aqua-Hot
Heating Systems LLC for assistance in locating a qualied
person to service this heater after an overheat situation.
In order to provide the best freeze protection, boil-over protection,
anti-corrosion, and rust protection, a mixture of 50/50 ethylene
glycol antifreeze and distilled water is recommended. The Aqua-
Hot 125GN boiler tank holds approximately 1.8 gallons.
The mixture may be modied to provide the most adequate
freezing, boiling, and rust/anti-corrosive protection. A 50/50
mixture of ethylene glycol and distilled water has a freeze point
of approximately -35°F and a boiling point of approximately
223°F. Refer to the table below to determine the best protection
mixture ratio and also reference page 55 for the proper tool
and instructions for use in measuring the system’s antifreeze
mixture ratio.
Maintenance Schedule
NOTE: This product label is attached to the side of the Aqua-
Hot, and provides a ready reference to specications, test
standards, and important safety notices.
Figure 6
System Specications
Electric Element
Power Consumption......................................1500 W (maximum)
Voltage ..............................................................................110V AC
DC Power
Power Consumption.......................................... 57 W (maximum)
Zone Heat Circulation
Pumps...........................................................................................1
Power Consumption (max)............................................20W/1.7A
Voltage ............................................................................... 12V DC
Interior Heating
Maximum Heating Zones.............................................................3
Cozy........................................................6W/0.5A - 8,000 BTU/hr
Whisper............................................4.5W/0.37A - 4,000 BTU/hr
H.E. II...................................................3W/0.25A - 4,000 BTU/hr
Domestic Water Heating
Maximum......................................................................... 0.8 GPM
Physical Specications
Dimensions (US)..............................17.66”L x 7.50”W x 11.50”H
Dry Weight ............................................................................45lbs.
Wet Weight............................................................................59lbs.
NOTE: Control Panel “Quiet Mode” reduces heat exchanger
power consumption by 20%
All vehicle installations must comply with the requirements
listed in the Recreational Vehicle Industry Association’s
(RVIA) ANSI/NFPA 1192 Handbook for Recreational Vehicle
Standards.
DO NOT attempt to reset the high-limit thermostats after
an overheat condition until the unit has been serviced by a
qualied technician. Failure to do so could result in damage
to the unit, personal injury, or death.
DO NOT operate the gas burner and/or electric heating
element without antifreeze and distilled water heating
solution present in the Aqua-Hot’s boiler tank. Doing so will
cause serious damage to the heater.
Freeze
Point (°F)
Concentra-
tion (%)
32 25 20 15 10 5 0 -10 -20 -30 -40 -50
010 16 21 25 29 33 39 44 48 52 56
Ethylene Glycol to Distilled Water Ratio
NOTE: It is also recommended to run the gas burner at least
once a month for a full cycle (at least 20 minutes) to ensure
optimum heater condition.
When the Aqua-Hot is at maximum operating temperature,
the coolant is very hot. If the Aqua-Hot heating system is
accessed, scalding by hot vapor or coolant may occur. Before
cleaning or servicing, disconnect all power supplies.

Basic ComponentsSystem Features
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Component Cut-Aways
Aqua-Hot 125GN
1. Fluid Circulation Pump
2. Tempering Valve
3. Aqua-Hot Controller
4. Antifreeze and Water Heating Solution Tank
5. AC Electric Element
6. AC Activation Relay
7. Plate-to-plate Heat Exchanger
8. Three-Way Valve
9. Zone Air-Bleed Valve
10. Fluid Expansion Port (to overow bottle)
11. Zone Return
12. Fluid Fill Port
13. Zone Supply
14. Service Panel
15. External Gas Burner Supply
16. External Gas Burner Return
17. Domestic Cold-Water Inlet
18. Domestic Hot-Water Outlet
19. Domestic Low Point Drain
20. Cabinet Drain
Figure 10
Figure 9
11
13
14
15
17
18
10
9
19
20
12
16
12345
6 7 8 9
Figure 8
Figure 11
NOTE: The side panel in the view above has been made
transparent to aid in the explanation of the heater. DO NOT
remove this side panel. Doing so risks irreparable damage
to the Aqua-Hot. Only remove the service panel for service.
3
Figure 7
System Specications
Gasoline Burner
Heat Flow...............................................5,188 to 17,060 BTU/hr
Diesel Fuel Consumption...............................0.05 to 0.17 gal/hr
Coolant Pump................................................................20W/1.7A
Operating Pressure (med heat)....................................36.25 PSI
Flow Rate (minimum).....................................................36.25 PSI
Working Altitude .............................................................. 16,000ft
*Fuel
Fuel Type................................................GASOLINE ≥87 Octane
Fuel Consumption (Low Output)...................................... 0.05g/h
Fuel Consumption (High Output)......................................0.17g/h
DC Power
Consumption .................................................................10 to 37W
Operating Amp Range............................................... 0.83 to 3.8A
Operating Temperatures
Burner Operation ..................................................... -40 to 176°F
Burner Storage................................ .........................-40 to 248°F
Fuel Pump Operation ................................................. -40 to 86°F
Fuel Pump Storage...................................................-40 to 194°F
Physical Specications
Dimensions................................................ 8.8”L x 3.4”W x 6.9”H
Weight ..................................................................................6.3 lbs
TECHNICAL SPECIFICATIONS
Heating Medium Ethylene Glycol/Distilled Water
Thermal Power (W)
High Power Operation: 5000W
Low Power Operation: 1500W
Fuel GASOLINE (87 Octane or higher)
Fuel Consumption
(gallons per hour)
Low power operation: 0.05 g/h
High power operation: 0.17 g/h
Power supply (battery
for the engine) DC12V
Power Consumption (W)
At start <100 W
High power operation: 37 W
Low power operation: 10 W
Working pressure (MPa) 0.25
Lowest working
temperature -40°F
Net Weight (heater
only) 10.6lbs
Working height
(above sea level) 16,405 ft
Weight of Main Heater 6.3lbs
Temperature of Coolant
when blower is started 113°F
NOTE: This product label is attached to the top of the
burner and provides a ready reference to specications,
test standards, and important safety notices.
All vehicle installations must comply with the requirements
listed in the Recreational Vehicle Industry Association’s
(RVIA) ANSI/NFPA 1192 Handbook for Recreational Vehicle
Standards.
*NOTE: The Fuel System requires that the gasoline used
(in the vehicle for the burner supply) must be 87 octane or
greater (87, 89, 91, or 93 octane).

Operational FlowchartBasic Components
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Component Cut-Aways
Operational Flow Chart
A heat source is selected from
Interior Control Panel
Electric Element External Gas Burner
Electric Heating Element
will activate, providing
heat to the antifreeze and
water heating solution
within the boiler tank
The gas burner will begin
providing heat to the
antifreeze and water heating
solution present within the
boiler tank
The antifreeze and water
heating solution in the boiler
tank heats between 165°F
and 180°F
An Interior Zone
Thermostat Calls
for Heat
A hot water faucet opens,
signaling a need for heat to the
boiler tank
The uid circulation pump
activates and begins circulating
the heated antifreeze and water
solution throughout the interior
heating zone
The heating zone
fans activate
Heat is transferred to the
vehicle interior via the heat
exchangers
The cooled antifreeze
is returned to the boiler
tank to be reheated
Hot water ows from the water
faucet
Heat is transferred to the
domestic hot water system
Figure 12
6
14
12
15
1
9
18
20
19
10
4
11
7
17
3
8
2
Figure 13
Figure 14
Figure 15
16
5
13
Belief Gas Burner
1. Combustion Air Fan
2. Burner Outer Casing
3. Burner Inner Casing
4. Combustion Chamber
5. Glow Plug
6. Flame Sensor
7. Temperature sensor
8. Over-Heat Sensor
9. Burner Controller
10. Air Inlet Pipe
11. Mufer
12. Fuel Pipe
13. Coolant Pump
14. Fuse
15. Main Wire Harness
Connector
16. Fuel Pump
17. Exhaust Pipe
18. Coolant outlet Pipe
19. Coolant Inlet Pipe
20. Burner

Operating the LCDOperating the LCD
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Operating the Aqua-Hot & LCD
Introduction:
This document will outline the basic operating instructions
for the Aqua-Hot LCD Screen.
Climate Pages:
The climate pages are for all intents and purposes the
“Home” of the LCD screen. From here, the end-user will select
their interior temperature set-points, activate or deactivate the
gas burner and/or the electric element.
Zone Control (1):
Precise zone control display will differ depending on the type
of zone thermostats used within the RV.
Section 1A demonstrates the appearance of the zone control
section when ON/OFF thermostats are used within the RV. In
this use-case, these buttons serve only as ON/OFF toggle
switches.
Tapping on one of the zones shown above will display a new
screen where the interior temperature can be set.
Section A:
This section shows the current zone
temperature (shown as 71°F in the example
above) as well as a button to turn the zone
on or off. (Setting specic temperatures can
1A
3
4
5
2
1
B
C
A
only be done if thermistors are installed.
Thermostats would only show ON/OFF.)
If the zone temperature is set, but this item
is not set to ON, the zone heat exchanger will
not activate.
Section B:
These arrows are used to increase or decrease
the desired set-point temperature of the zone
thermistor.
Section C:
After the desired temperature set-point has
been selected tap “SET” on the LCD to set
that temperature. The Aqua-Hot will now work
to maintain this interior temperature, and the
screen will return home.
External Gas Burner Activation (2):
The external gas burner of the Aqua-Hot can be activated by
tapping on the “burner” item on-screen. The gas burner has two
modes: ON and OFF.
ON:
While set to ON, the Aqua-Hot gas burner will
work to maintain a tank temperature of 180°
F, with a minimum tank temperature of 160° F.
OFF:
While off, the gas burner will not serve to
provide any heat to the boiler of the Aqua-Hot
whatsoever.
Electrical Element Activation (3):
Similar to the external gas burner, tapping the electric item
will signal to the controller to activate the AC electric relay,
energizing the 1500W electric element within the Aqua-Hot.
The electric element also has two modes: ON and OFF.
ON:
While set to ON, the electric element will work
to maintain a tank temperature of 180° F,
with a minimum tank temperature of 165° F.
OFF:
While off, the element will not serve to
provide any heat to the boiler of the Aqua-Hot
whatsoever.
System Status (4):
This item will indicate the current operational status of the
Aqua-Hot. If any faults have triggered, those will be displayed
here.
During normal operation, this should display either INTERIOR
HEAT or HOT WATER relating to the priority and position of the
3-way valve.
While in INTERIOR HEAT mode, the 3-way valve is oriented so
as to circulate heated antifreeze and water solution through the
heating zones of the RV.
While in HOT WATER mode, the 3-way valve is oriented so
that the heated antifreeze and water solution is circulated
immediately back into the boiler tank. This is known as “stirring”
the tank, and it is done to provide as much heat as possible to
the domestic water line while water is owing.
Module Options (5):
Tapping on the module options screen (the 3 lines on the
bottom right of the home screen) will display the screen shown
above. This is known as the Module Options screen. From here,
it is possible to access unit diagnostics, activate Quiet Mode,
change the temperature units, adjust screen brightness, and
unit timeout.
Screen Timeout (A):
The screen timeout item sets the amount of
time required to allow the screen to shut-off
when idle.
Screen Brightness (B):
This setting changes the screen brightness.
Unit of Measurement (C):
This setting will change the display units of the
Aqua-Hot. Either Fahrenheit or Celsius can be
selected.
Diagnostics (D):
Tapping on this element will direct you to the
Aqua-Hot’s built-in diagnostic, testing, and
troubleshooting tools.
Quiet Mode (E):
This option toggles the Aqua-Hot’s quiet mode.
Quiet mode is a setting where the speed and
output of the heat exchanger fans is reduced
to 80%. This is done to reduce noise of the
heat exchangers.
Please note that this feature must be activated
and deactivated as needed.
A
B
C
E
D

ControllerController
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The Aqua-Hot Controller
Introduction:
The Aqua-Hot 125GN operates on a controller platform
which has been modernized and updated from the previously
used Electronic Controllers and Relay Control Boards of older
Aqua-Hot units.
This controller is best utilized with the Aqua-Hot 3.5in
display. Using the Aqua-Hot with this new display will ensure
that you can take advantage of all of the tools and features of
this controller.
Features:
This new controller brings with it new features to it which
effect functionality from every stage of operation. Fail safe
functionality, climate control, and troubleshooting and
diagnostics have all been overhauled on this new control
architecture. These features will be explained in detail below.
Troubleshooting:
The new troubleshooting functionality is perhaps the largest
and most substantial change to come about from the new
controller architecture. Many faults and failures within the
Aqua-Hot can now be relayed in plain language to the technician
servicing the Aqua-Hot. There are ve system faults which will
Figure 16
Figure 17
be utilized; System Voltage, Low-Level Cutoff, Over-Current,
Overheat, and Burner Failed to Ignite. These will be explained
below.
System Voltage:
System voltage faults indicate that there is a
problem with the RV-side power supply which
powers the Aqua-Hot.
The Aqua-Hot can only operate within a
voltage range of 11V DC to 16V DC. If voltage
drops below 11V, or exceeds 16V DC, the
controller will shut down the Aqua-Hot as a
safety mechanism.
Low-Level Cutoff:
The Low-Level Cutoff fault will only trigger if
the minimum uid level within the Aqua-Hot
is below an acceptable operational threshold.
If the controller is showing a low-level cutoff
fault, begin by diagnosing the oat sensor.
Over-Current:
Over-current faults are triggered by an output
channel (pump, fan, etc) that is attempting
to draw too much current through the
controller. This fault will be accompanied by
the component which triggered the fault,
for example “PUMP 2 OVER-CURRENT” will
display if Pump 2 is not operating correctly.
If over-current faults are appearing on the
display, troubleshoot the offending component
listed as being over-current.
Overheat:
Overheat faults indicate that the unit has
exceeded its overheat threshold of 210°F.
If an overheat condition has occurred,
diagnose the cause of the overheat by
investigating the heating sub-systems of the
Aqua-Hot (electric and/or gas burner).
Under-Current
Under-current faults indicate that the unit
does not have enough voltage to properly
operate. If voltage drops below 11V, the
controller will shut down the Aqua-Hot as a
safety mechanism.
If an under-current fault is displayed on the
screen, troubleshoot the offending component
listed and also check power into the Aqua-Hot.
The fault codes shown above will cover the most common
Aqua-Hot related issues. For more complex issues, it may be
necessary to utilize the DIAG screens, which will be explained
next.
Diagnostic Screens (DIAG)
The diagnostic screens will show the current operational status
of different elements within the Aqua-Hot. By comparing these
operational statuses against the expected results it is possible
to discern operational issues.
Shown below are the diagnostic screens. From these screens it
is possible to see the current status of elements within both the
Aqua-Hot and the status of certain elements within the RV such
as zone thermostats and on/off signals. Each element on the
screens listed below will be explained in detail.
Operating Mode (A):
The operating mode contains six items which relay at-a-glance
information about the function of the Aqua-Hot.
System Voltage:
This section of the Operating Mode page
indicates the status of the supply voltage to the
Aqua-Hot. This will display “OK” if the supply
voltage is between 11V DC and 16V DC.
If this element displays anything except “OK”
begin troubleshooting the RV-side voltage.
Burner:
This indicates the current burner status as
either ON, OFF or FAULT. ON indicates that the
burner is active, and able to re to provide heat.
OFF indicates that heat is either not required or
not requested by the controller.
FAULT indicates that there is an issue with the
burner.
Electric:
The Electric section indicates the controller’s
current handling status of the AC electric relay.
This status indicates that the controller is
attempting to activate the element relay only.
This does NOT indicate whether the electric
element is in working order or not.
Heat Zone #:
The next three elements indicate the current
status of the heating zones (maximum 3).
This element (ON or OFF) only indicates that
the zone thermostat is requesting heat, AND
that the controller is providing power to the
zone fans.
Inputs from RV (B):
The Inputs from RV section will display the signals received
from within the RV as pertaining to the RVC network and the
heating zone thermostats.
With respect to the zones, there will be three different items
displayed next to the Zone # items depending on the type of
RV-side thermostat in use.
• ON: This indicates that the zone is active, and the zone
thermostat is calling for heat
• OFF: This indicates that heat is either not needed, or not
requested by the zone thermostat
• 71°: This indicates the set-point of the RV thermostats.
The example in Figure 18 is showing the RV thermostat
is requesting it be 71°F in Zone 1. This is only available
with certain RV thermostats.
Outputs to RV (C):
The Outputs to RV indicates that the controller is sending power
to components within the RV. This section may also show faults
with components in each zone.
In the example in Figure 18, the controller is not sending power
to the boost pump, so the boost pump is shown as OFF.
Zone 1 is ON, meaning that the controller is sending power to
the Zone 1 fans.
Zone 2 is Over Current, indicating that there may be a problem
with the fans in this zone.
Zone 3 is not active. The controller is not receiving a request for
heat from the RV, and it is not powering the zone fans.
Figure 18
A
B
C

ControllerController
©Aqua-Hot® 125-GN1 Service Manual REV 220427
©Aqua-Hot® 125-GN1 Service Manual REV 220427
p. 17p. 16
Burner Status:
The Burner Status element on this page
indicates the status of the external gas burner.
LTCO Status:
The LTCO status indicates the sensor reading
from the Low-Temperature Cutoff Thermostat,
which is the device that governs whether to
provide heat or hot water.
LLCO Status:
LLCO status relays the current sensor reading
of the Low-Level Cutoff sensor within the
overow bottle.
The LLCO is implemented to measure the uid
level within the overow bottle to ensure that
it does not drop below a safe threshold.
Tank Temperature:
The Tank Temperature status will display the
current temperature of the antifreeze and
water heating solution within the Aqua-Hot.
The ETS Thermistor (short for engine
temperature sensor) provides this temperature
information to the controller, which then
governs when the external gas burner and/or
electric element shut off.
Outputs to Aqua-Hot (D):
The Outputs to Aqua-Hot section describes the current status
of the controllable elements within the Aqua-Hot which are the
Burner Status, Fluid Circulation Pump, and the Electric Element.
This indicates only that the controller is attempting to operate
these elements, not their current functional status.
Inputs from Aqua-Hot (E):
The Inputs to Aqua-Hot will contain the current readings from
sensors within the Aqua-Hot. Four elements will be shown on
this page; Burner Status, LTCO Status, LLCO Status, and Tank
Temperature.
Figure 20
Figure 19
D
E
Electric (C):
Activating the Electric heating sub-system will energize
the relay which controls the AC electric element.
After tapping this button on the screen, there should be
an audible click from within the Aqua-Hot cabinet. If there
is no such click, verify the functionality of the AC electric
relay.
This test CANNOT directly energize the AC electric
element. It is used only to verify the functionality of the
command and control system.
Burner (D):
This element will energize the Gas Burner signal wire,
which will then trigger the heat source to activate.
Three-Way Valve (E):
The nal element on this screen is not directly related to
the heating subsystems of the Aqua-Hot.
The three-way valve (sometimes known as the summer/
winter valve) controls the ow of the antifreeze and water
heating solution within the Aqua-Hot to deliver either hot
water, or interior heat as requested.
Tapping on this element will change the valve’s
orientation. When this element displays “INT. HEAT” this
valve is oriented to provide interior heat by circulating
heating solution throughout the interior heating zone.
When this element displays “HOT WATER” the valve is
oriented such that heating solution is routed so that hot
water can be provided.
Testing Functionality:
One of the new features of this control system is the ability to
independently activate specic elements within the Aqua-Hot
for testing purposes.
This will allow a technician to activate specic elements within
the Aqua-Hot as needed without jumping wires or utilizing
external power supplies in most troubleshooting cases. Any
elements activated via the testing screen will remain active for
a maximum of ve minutes.
Pumps (A):
Both the zone circulation
pump and the boost pump (if
applicable) can be activated by
tapping the corresponding pump
on the test screen.
Fans (B):
All three zone fans can be
activated as needed to test
communication between the
zone fans and the controller.
Please note that this will only
work if the zones have been
directly wired to the Aqua-Hot
as described in the installation
manual.
Heating sub-systems can be activated independent of their
control circuits and other control sensors as a means of testing
functionality. These systems will activate for a maximum of ve
minutes before shutting down.
Activating heating sub-systems in this manner will disregard
all sensor inputs while attempting to activate these heating
systems. As such, if the unit is near operating temperature,
activating these systems may trigger an overheat condition.
Heating sub-system testing is NOT a substitute for
normal operation, and attempting to use it as such
may result in catastrophic damage to the Aqua-Hot.
Figure 21
Figure 23
D
C
E
DO NOT attempt to activate these sub-systems
while the unit is near operating temperature
Figure 22
A
B
RV-Side
Connections &
Components Inputs from RV
Outputs to RV Aqua-Hot
Connections &
Components
Inputs from Aqua-Hot
Outputs to Aqua-Hot
Aqua-Hot 3.5in
LCD Screen
Aqua-Hot
Controller

ControllerController
©Aqua-Hot® 125-GN1 Service Manual REV 220427
©Aqua-Hot® 125-GN1 Service Manual REV 220427
p. 19p. 18
13. Using the previously removed hex nut, fasten the
mounting plate to the wall of the Aqua-Hot.
14. Carefully reinstall all of the plugs from the DC harness.
• Ensure that both tabs for all Molex connectors click
into place indicating a properly seated connection.
• Ensure that the single tab for the RVC cable clicks
into place indicating a properly seated connection.
• Suggested order:
• 8-Pin Molex (bottom of the controller)
• 15-Pin Molex (middle left of the controller)
• RVC (middle right of the controller)
• 9-Pin Molex (top left of the controller)
• 12-Pin Molex (top right of the controller)
• 3-Pin Molex power connector
• Continue to the next section to set up the controller after
installation is complete.
NOTE: All plugs have only ONE correct orientation. Do NOT
force the plug into place.
9-Pin
Molex 12-Pin
Molex
RVC
8-Pin
Molex
15-Pin
Molex
Figure 32
Controller Replacement Procedure:
1. If possible, tap the three lines icon at the bottom right
corner of the LCD screen.
• Tap the DIAGNOSTICS icon. Record all the
information in the “Aqua-Hot Information Section”.
• Tap and hold (for 3 seconds) within the information
section.
• Tap OPTIONS, CLIMATE ZONES, and take a picture
of this screen.
2. Disconnect all power to the Aqua-Hot.
3. Remove the four Philips screws attaching the top cover of
the Aqua-Hot, and remove the top cover to gain access to
the interior components.
Tap and hold 3
seconds anywhere
in this section
Take a picture
of this screen
Figure 26
4. Using a ⅜” (10mm) socket, remove the hex nut from the
top of the mounting plate (SAVE THE NUT TO USE AGAIN)
5. Gently lift up on the controller bracket and remove the
plugs as they become accessible. The high-limit
thermostat may need to be disconnected to provide
clearance (a pair of needle-hose pliers is recommended
to remove the connections).
6. Disconnect the DC harness from the controller.
• Suggested disconnect order (see Figure 29):
• 3-Pin Molex power connector
• 12-Pin Molex (top right of the controller)
• 9-Pin Molex (top left of the controller)
• RVC (middle right of the controller)
• 15-Pin Molex (middle left of the controller)
• 8-Pin Molex (bottom of the controller)
Figure 27
Figure 28
High-Limit
Thermostat
NOTE: DO NOT DISCONNECT THE DC HARNESS FROM ANY
OTHER ELECTRICAL CONNECTION IN THE UNIT.
9-Pin
Molex 12-Pin
Molex
RVC
8-Pin
Molex
15-Pin
Molex
Figure 29
7. Lean the top of the mounting bracket out from the unit
wall, and then slide the controller and mounting plate
upwards and out of the unit.
• The bottom of the mounting plate has two key-ways
holding it in place (no nuts or other fasteners)
8. With the controller and mounting plate out of the unit,
use a ¼” socket or nut driver to remove the four nuts
attaching the controller to the bracket. The controller is
supported by four small bushings - ensure that all four
bushings remain on the bracket screws. Remove and
discard the defective controller.
9. Plate new controller onto the mounting plate.
• Ensure the controller is properly oriented - reference
Figure 32.
10. Using the 4 nuts previously removed, fasten the controller
to the mounting plate.
11. Insert the controller and mounting plate into the Aqua-
Hot. As you insert the controller and mounting plate
into the Aqua-Hot, the bottom of the mounting plate
should slide along the wall with the top of the mounting
plate leaned away from the wall to ensure the bottom
catches the key-ways (Figure 30) while the top clears the
mounting stud.
12. Lean the top of the controller and mounting plate back
against the wall and ensure that the bottom of the
mounting plate is seated on the key-ways.
Figure 30
Figure 31
Figure 24
Figure 25

Fluid Level SensorController
©Aqua-Hot® 125-GN1 Service Manual REV 220427
©Aqua-Hot® 125-GN1 Service Manual REV 220427
p. 21p. 20
Instructions for Controller Setup after Installation:
After replacement and installation of the controller, the system will need to be updated via the LCD Screen or RV Control panel.
Please follow the following steps to set up the heating system.
1. Provide power to the main harness of the Aqua-Hot. After the screen lights up, tap the three lines icon on the bottom right
corner. Complete the following steps in order:
• Tap the DIAGNOSTICS ICON
• Tap and hold (for 3 seconds) within the “Aqua-Hot Information” section
• Tap SERIAL NUMBER and follow the prompts on the screen
2. After completing Step 1, go back to the “Diagnostics” page, tap and hold (for 3 seconds) in the “Aqua-Hot Information”
section.
• Tap OPTIONS, CLIMATE ZONES, and then select the number of climate zones (A).
• Choose a label and temperature input type for each zone (B).
• Tap BACK until you’ve reached the “Home Screen”.
3. Test for normal operation.
Fluid Level Sensor
Introduction:
The uid level sensor monitors the current uid level within
the Aqua-Hot. This device is intended as a fail-safe measure
which will disengage the Aqua-Hot if the uid ever drops below a
set threshold. The uid level sensor is located on the expansion
bottle, which is either mounted to the side of the unit (see
Figure 37), or within the RV.
If the uid level sensor is malfunctioning, the Aqua-Hot
will show no signs of operation whatsoever. Troubleshoot this
sensor if there is an adequate amount of uid present within
the Aqua-Hot, and the unit does not operate.
Troubleshooting Guidelines:
Before troubleshooting the uid level sensor, ensure that the
following requirements have been met.
• The uid expansion bottle is lled to at least the “COLD”
mark.
• Verify that all RV-side in-line fuses are functional.
• Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the Aqua-
Hot’s electric element.
• Ensure that the uid level sensor is oriented correctly (see
below).
If any of the requirements above are not fullled, correct
them before continuing to diagnose the uid level sensor.
Reference the troubleshooting guide to the right.
Locate the uid level
sensor (Figure 35)
Using a multi-meter, test
for continuity across the
uid level sensor
Does the uid level sensor
have continuity?
Yes
No
Yes No
Fill uid
expansion
bottle. Re-
test Aqua-
Hot.
Replace the
uid level
sensor
Is the uid expansion
bottle lled to at least the
COLD position?
Locate the 3.5in LCD
screen
Navigate to the INPUTS
FROM AQUA-HOT section.
HOME-->Aqua-Hot
Diagnostics --> DIAG
Locate “LLCO.”
Does LLCO display TANK
FULL?
Yes No
This uid
level
sensor is
functioning
as intended
Replace the
controller.
Troubleshooting Procedure:
Figure 35
Figure 36
Fluid Level
Sensor
Figure 34
Figure 33
Tap and hold 3
seconds anywhere
in this section
A
B
Tap and hold 3
seconds anywhere
in this section

High-Limit ThermostatsFluid Level Sensor
©Aqua-Hot® 125-GN1 Service Manual REV 220427
©Aqua-Hot® 125-GN1 Service Manual REV 220427
p. 23p. 22
Replacement Procedure:
In order to replace the uid level sensor, the overow bottle
must also be replaced. Please visit www.aquahot.com or call
574-AIR-XCEL (574-247-9235) to order the expansion bottle
kit. Once you have the replacement part in hand, follow the
procedure below.
1. Locate the uid expansion bottle.
2. Clamp the overow hose as close to the bottom tting as
possible.
3. Grab a bucket or drain receptacle and place it directly
under the lower tting of the expansion bottle.
4. Remove the clamp from the lower tting of the expansion
bottle.
5. Remove the hose and allow the excess uid to drain into
the bucket.
6. Remove the overow hose from the upper tting of the
expansion bottle.
7. Remove the old expansion bottle, disconnect the Faston
connectors, and discard the old bottle.
8. Secure the new bottle in position.
9. Crimp the new faston connectors to the new uid level
sensor.
10. Connect these wires to their receptacles on the Aqua-Hot
harness.
11. Reconnect the overow hose to the upper tting.
12. Reconnect the expansion hose to the lower tting.
13. Fill the bottle with the previously drained uid.
14. Remove the hose clamps.
15. Test the Aqua-Hot for normal functionality.
If additional assistance is required please contact the Aqua-
Hot Heating Systems Technical support department at 574-AIR-
XCEL (574-247-9235) from 7:00am to 4:00pm MST Monday
through Friday.
Lower Fitting
Upper Fitting
Figure 38
Before continuing to the replacement procedure,
ensure that the unit has cooled to ambient temperature,
all power sources have been disconnected, and the
unit is completely shut off.
Figure 37
Expansion Bottle can either
be found mounted to the
side of the Aqua-Hot unit or
within the RV.
High-Limit Thermostats
Introduction:
The Aqua-Hot is equipped with three resettable High-Limit
Thermostats. These thermostats are in place to prevent the
heater from operating beyond its safe operational threshold.
These thermostats are resettable and easily replaceable.
Begin troubleshooting the High-Limit Thermostats if the
controller issues an overheat fault, or the electric and/or gas
burner fail to operate correctly.
Troubleshooting Guidelines:
The following conditions must be met before the High-Limit
Thermostats can be diagnosed, and if necessary, repaired.
• The uid expansion bottle is lled to at least the “COLD”
mark.
• Verify that all in-line fuses are functional.
• Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the Aqua-
Hot’s electric element.
If any of the above conditions are not met, correct them before
continuing with troubleshooting. Results of the troubleshooting
procedure cannot be veried if the conditions listed above are
not fullled.
AC High
Limit
Left High
Limit
Right High
Limit
Figure 39
Troubleshooting Procedure:
Locate the high-limit
thermostat which is
suspected of failure
Using a multi-meter, test
for continuity across this
thermostat
Is continuity present
across this thermostat?
Yes
No
Depress the red button in
the center of the high limit
thermostat (Figure 40)
Re-test for continuity
Does the thermostat now
have continuity?
Yes No
This thermostat is
functioning as intended.
This
thermostat is
functioning as
intended.
Replace this
thermostat
Figure 40

Low-Temp Cutoff ThermostatHigh-Limit Thermostats
©Aqua-Hot® 125-GN1 Service Manual REV 220427
©Aqua-Hot® 125-GN1 Service Manual REV 220427
p. 25p. 24
Replacement Procedure:
If it has been determined that one, or multiple high-limit
thermostats need to be replaced, they can be easily replaced
by following the directions below.
1. Disconnect all sources of AC and DC power from the Aqua-
Hot (if the AC high-limit thermostat is the issue, the AC
access cover will need to be removed - see Figure 41).
2. Disconnect the wires which connect to the non-functional
high-limit thermostat.
3. Using a ⅝” (16mm) wrench, remove the thermostat from
its location on the uid tank.
4. Locate the new thermostat and secure it in place of the old
thermostat.
5. Reconnect the disconnected wires as described by the
table below.
High Limit Thermostat Wires
Left J6-3 and BOT1
Right BOT1 and J6-3-HL
AC AOT1 and AOT2
6. Test the Aqua-Hot for normal operation.
If issues persist, please contact Aqua-Hot Heating Systems for
additional assistance.
Figure 42
Figure 41
Figure 43
AC Cover Removal
AC High-Limit Thermostat Removal
Low-Temperature Cutoff Thermostat
Introduction:
The Low-Temperature Cutoff Thermostat (LTCO) is installed
to measure the incoming domestic water temperature. Using
that reading, the Aqua-Hot controller is able to determine
whether a demand for hot water exists or not.
This thermostat should be diagnosed if there is a lack
of interior heat or hot water and the tank is up to operating
temperature. Follow the directions below to diagnose, and if
necessary, replace the Low-Temperature Cutoff Thermostat.
Troubleshooting Procedure:
Use the following troubleshooting tree to diagnose the Low-
Temperature Cutoff Thermostat.
Locate the Aqua-Hot
LCD screen. Navigate to
INPUTS FROM AQUA-HOT.
Turn on a hot water faucet
within the RV. Monitor the
Aqua-Hot LCD.
Does the LTCO element
display “HOT WATER”?
Yes
No
The LTCO is functioning as
intended.
Locate the LTCO at the
unit, and using a multi-
meter, test for continuity
across the thermostat.
Does the LTCO have
continuity while water is
owing?
Yes No
Replace the
controller
Replace the
LTCO
Figure 47
Replacing the Low-Temperature Cutoff Thermostat:
1. Disconnect all sources of AC and DC power from the Aqua-
Hot
2. Disconnect the wires from the LTCO.
3. Remove and discard the defunct LTCO thermostat using a
⅝” wrench.
4. Position and secure the new LTCO thermostat into place.
5. Connect wires J4-1 and J4-2 to the new LTCO thermostat.
Low-Temperature Cutoff
Figure 45
Figure 44
Low-Temperature Cutoff
Figure 46
NOTE: The side panel has been made transparent in the
view above to aid in the explanation of the repair. DO NOT
remove this side panel. Doing so risks irreparable damage
to the Aqua-Hot.
DC High-Limit Thermostat Removal (Right)

Three-Way ValveThree-Way Valve
©Aqua-Hot® 125-GN1 Service Manual REV 220427
©Aqua-Hot® 125-GN1 Service Manual REV 220427
p. 27p. 26
Three-Way Valve
Introduction:
The three-way valve (aka the summer/winter valve) is
responsible for changing the ow of coolant either through the
interior heating zone (int heat) or circulating coolant within the
boiler tank (stir mode) to produce hot water.
If the three-way valve has failed, it can lead to a loss of interior
heat and/or hot water. Follow the steps below to troubleshoot
the three-way valve.
Troubleshooting Procedure:
Continue trouble-
shooting here
Grab the hoses
highlighted green below.
While hot water is
running they should be
hot to the touch.
Grab the other hoses
highlighted green below.
While hot water is
running, these should
be cool.
Are the hoses warm and
cool during the conditions
described above?
Yes No
Replace the
three-way
valve
Set the unit to call for
interior heat and perform
the test again.
The hoses which were
previously cold should
now be warm. Are these
hoses now warm? Replace the
three-way valve
Please contact
Aqua-Hot for
additional
assistance
Yes
No
Go back to the Aqua-Hot
LCD screen. Navigate to
the TEST page and tap
NEXT.
Tap THREE-WAY VALVE
to actuate the three way
valve.
Leave the probes of the
multi-meter in place.
Check the multi-meter.
Does the voltage polarity
measured by the meter
invert?
Yes No
Replace the
three-way
valve
Replace the
controller
Locate the Aqua-Hot LCD
screen. Navigate to the
TESTING page (Figure 48).
Tap NEXT
The 3-way valve should
begin to actuate. This
can be heard outside the
cabinet.
Yes
No
Activate the electric or
gas burner and allow
the heater to heat to
temperature
Locate the J6 plug and
test for voltage between
pins J6-10 and J6-11
Is voltage present
between these pins?
Yes No
Continue
trouble-
shooting to
the right.
Replace the
controller.
Tap THREE-WAY VALVE
Does the three-way valve
actuate?
Continue troubleshoot-
ing to the right.
Open a hot water faucet
within the RV.
1.
1.
2.
2.
Figure 48
Continue trouble-
shooting here
• There may be residual uid that exits the ttings -
use towels or other clean up items as necessary.
9. Carefully remove the Three-Way Valve from the last ¾”
heater hose on the right of the valve.
• There may be residual uid that exits the ttings -
use towels or other clean up items as necessary.
10. Remove constant tension clamp from the brass of the
Three-Way Valve on the right, and place it on the new Three-
Way Valve in the same position on the brass.
11. Discard the old valve and ttings.
12. Using a nylon wire brush, clean the threads of the PEX
tting so that it is free of leftover thread sealant.
13. Carefully insert the single barb back into the heater hose
that the old valve was attached to.
14. Add thread sealant (454 Loctite or better) to the threads of
the PEX tting.
15. Using a wrench, thread the PEX tting into the three-way
valve.
• 3-6 rotations
• DO NOT BRACE ON THE BLUE PLASTIC WHEN
TIGHTENING. This may damage the mechanism or
electrical components.
16. Install the hoses on the tee on the top of the valve.
17. Move the constant tension hose clamps to just behind the
barb of each tting.
• Left side of the tee on the top of the 3-way valve.
• Right side of the tee on the top of the 3-way valve.
• Right side of the 3-way valve, off the brass onto the
hose.
18. Connect the electrical wire from the valve to the DC harness.
19. Reinstall the side panel and lid using the saved screws and
washers from Step 2.
20. Rell the unit with the coolant saved from Step 1.
• Add more coolant is needed.
• Monitor the newly installed parts and ttings for
leaks.
Replacement Procedure:
1. Drain coolant from system.
• Pour into a bucket to be reused later.
2. Remove top and side panels from the Aqua-Hot.
• Save screws and washers to reuse later
3. Locate the Three-Way Valve in the Aqua-Hot.
4. Disconnect the electrical connection from the Three-Way
Valve to the DC harness.
5. On the right side of the Three-Way Valve, move the constant
tension clamp onto the brass of the Three-Way Valve to
ensure it is out of the way.
6. On the top of the Three-Way Valve, move the two (2)
constant tension clamps AWAY from the tee tting so that
they are as far from the barb as possible.
7. On the left of the Three-Way Valve, unscrew the brass PEX
tting from the Three-Way Valve using a wrench.
• There may be residual uid that exits the ttings -
use towels or other clean up items as necessary.
8. Remove ¾” heater hose from the tee on the top of the
Three-Way Valve.
DO NOT remove the rivets securing the side panel into place.
Attempting to do so risks irreparable damage to the boiler
tank of the Aqua-Hot
Before replacing the 3-way valve, you must purchase the repair
kit. The Repair Kit should include:
• Three-Way Valve
• Black Nylon tee adapter
• Black Nylon barb adapter
• 2-Pin electrical connector
Three-Way Valve
Figure 49
Figure 50

Tempering ValveTempering Valve
©Aqua-Hot® 125-GN1 Service Manual REV 220427
©Aqua-Hot® 125-GN1 Service Manual REV 220427
p. 29p. 28
Tempering Valve
Introduction:
The tempering valve of the Aqua-Hot mixes the hot domestic
water from the interior of the Aqua-Hot with cold incoming
domestic water to temper it to a threshold where scalding will
not occur.
NOTE: The side panel has been made transparent in the
view above to aid in the explanation of the repair. DO NOT
remove the side panel - only remove the service panels.
Doing so risks irreparable damage to the Aqua-Hot.
NOTE: Adjusting the mixing valve beyond 120°F (49°C)
will result in a lack of hot water and may result in scalding.
Do NOT attempt to adjust the tempering valve without
assistance from Aqua-Hot Technical Support or a qualied
Aqua-Hot technician.
Activate the Aqua-Hot’s gas burner
to provide as much heat as possible
to the boiler tank. This test cannot
be completed with only the electric
element.
Open the shower head valve within
the RV to its hottest setting.
Place one hand on the red PEX
tubing, and before the tempering
valve and outside the Aqua-Hot.
Are both the red PEX and just before
the tempering valve warm while hot
water is running?
This tempering valve is
functioning as intended.
Replace the
tempering valve.
Yes No
Figure 51
Testing Procedure:
Follow the testing procedure to the right in order to diagnose
the tempering valve. Troubleshoot the tempering valve if the
following conditions have occurred:
• A lack of hot water.
• Hot water supply is uneven.
• Hot water is too hot.
NOTE: The Aqua-Hot Domestic Water System is rated for a
water ow of 0.8 GPM. It is not recommended to modify the
water ow. This can cause an over-pressurized system or
lack of consistent hot water.
Replacement Procedure:
1. Shut off the external domestic water connection, and open
a hot water faucet valve within the RV to relieve the water
pressure.
2. Open the domestic water drain valve on the Aqua-Hot and
release water in the system.
• Attach hose to the ½” PEX barb to release uid without
spilling throughout the RV
• Ensure that the hose does not rise from the drain valve
otherwise proper drainage will not happen.
3. Disconnect the RV side domestic water connections
4. Remove the top cover and side covers of the Aqua-Hot to
gain access to the interior components.
• Save the screws and washers to be reused later.
5. Using a ⅜” (10mm) socket, remove the nut which secures
the domestic water valve assembly to the side of the Aqua-
Hot cabinet (shown below).
6. Disconnect the swivel ttings attached to the brass tees on
the tempering valve.
• One swivel tting is attached to the red PEX and the
other is attached to the blue PEX.
• There may be residual uid in the lines. Use clean-up
items and tools as needed.
7. Remove the P-clamp from the stud on the wall of the Aqua-
Hot. Save the P-clamp for reuse later.
8. Slide the tempering valve assembly gently backwards
towards the coolant tank until the PEX tubes of the
assembly are no longer protruding from the Aqua-Hot.
• Ensure you do not collide with the controller or damage
any other components in the Aqua-Hot.
9. Remove the assembly from the Aqua-Hot.
10. Remove all three ttings from the tempering valve as shown
below.
11. Discard the defunct mixing valve.
12. Using Teon tape and domestic water safe thread sealant,
reinstall all ttings to previous orientations.
13. Place previous P-clamp onto the assembly before inserting
into the Aqua-Hot.
14. Insert repaired assembly into the Aqua-Hot and slide the
red and blue PEX through their ports in the front face of the
Aqua-Hot.
• Use soapy water as necessary to lubricate the PEX
going through the rubber grommets in the ports.
• DO NOT SPRAY ELECTRICAL COMPONENTS AND WIRES
WITH SOAPY WATER.
15. Connect the swivel ttings back to their respective places
on the assembly.
• Do NOT over-tighten the swivel ttings.
16. Using the nut from Step 5, tighten down the P-clamp on the
assembly.
17. Reattach the domestic water lines and check for leaks
before replacing the side and top panels of the Aqua-Hot.
18. After checking for leaks, replace the side and top panels of
the Aqua-Hot using the screws from Step 4.
Figure 52
Figure 53
Figure 54
NOTE: The side panel has been made transparent in the
view above to aid in the explanation of the repair. DO NOT
remove the side panels. Doing so risks irreparable damage
to the Aqua-Hot.

Fluid Circulation PumpFluid Circulation Pump
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Fluid Circulation Pump
Introduction:
The uid circulation pump operates to provide uid circulation
to either the interior heating zone or the antifreeze boiler tank
depending on the heating and hot water needs at the time.
Troubleshooting Procedure:
If the uid circulation pump has failed, it will typically indicate
an over-current fault on the controller fault log. If this is the case,
the fault must be veried before replacing the circulation pump.
Follow the procedure to diagnose the uid circulation pump.
Power cycle the Aqua-Hot to
clear any current faults.
Locate the Aqua-Hot LCD
screen. Navigate to the
TESTING page (Figure 57a).
Activate the internal
circulation pump, and if
necessary the boost pump
Does the suspect pump
activate?
Navigate to the faults page
(Figure 57b).
Using a multi-meter, test
for voltage between pins
J6-7 and J6-8.
No
Yes
Is voltage present between
these pins?
Navigate to the TEST tab
and activate the internal
circulation pump
NoYes
Replace the
circulation
pump
Replace the
Aqua-Hot
controller
Yes
Are any pump over-current
faults displayed?
Replace the
circulation
pump
This pump is
operating as
intended.
No
Figure 55
NOTE: The side panel has been made transparent in the
view above to aid in the explanation of the repair. DO NOT
remove the side panels. Doing so risks irreparable damage
to the Aqua-Hot.
Figure 57a
Figure 57b
Figure 56
Replacement Procedure:
1. Drain coolant from system. Pour into a bucket to be reused
later.
2. Remove the top and side panels from the Aqua-Hot. Save
the screws and washers to be reused later.
3. Place a paper towel into the Aqua-Hot unit on the bottom of
the cabinet. (This is to help absorb any residual coolant left
in the lines upon pump removal.)
4. Remove electrical plug to the circulation pump and move
up and out of the way.
5. Remove both hose clamps from the barbs of the pump.
• Leave the clamps on the 90° hose and hose from the
tank - to be reused later - see Figure 58.
6. Carefully remove the 90° hose from the pump.
7. Carefully remove the ump from the hose attached to the
tank.
8. Remove the pump from the Aqua-Hot and discard it.
9. Insert the new circulation pump into the Aqua-Hot and
attach it to the hose coming from the tank.
10. Attach the 90° hose to the circulation pump barb.
11. Move both hose clamps onto the barbs of the new
circulation pump.
12. Plug the connection from Step 4 into the circulation pump.
13. Reinstall the side and top panels using the saved screws
and washers from Step 2.
14. Rell the unit with the coolant saved in Step 1.
• Add more coolant if needed.
• Monitor the newly installed parts and ttings for leaks.
Figure 59
Circulation Pump
NOTE: The side panel has been made transparent in the
view above and below to aid in the explanation of the repair.
DO NOT remove the side panels. Doing so risks irreparable
damage to the Aqua-Hot.
Figure 58

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AC Electric System
Introduction:
The AC Electric system of the Aqua-Hot 125GN unit functions to
provide heat to the Aqua-Hot boiler tank. This is done with an
electric element and an electric relay.
Troubleshooting Procedure:
Troubleshoot the AC Electric system if the electric element is
not functioning properly.
The following conditions must be met before the AC Electric
system can be diagnosed, and if necessary, repaired.
• The expansion bottle is lled to at least the “COLD” mark.
• Verify that all in-line fuses are functional.
• Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the element.
• Verify the thermostats are in working order.
• Verify there are no faults on the Aqua-Hot LCD.
If any of the above conditions are not met, correct them before
continuing with troubleshooting. Results of the troubleshooting
procedure cannot be veried if the conditions listed above are
not fullled.
Locate the Aqua-Hot LCD
screen. Navigate to the
TESTING page (Figure 60)
The AC electric relay
should let out an audible
click from within the Aqua-
Hot cabinet
Yes, click sound
Leave ELECTRIC on. Tap
PREVIOUS and activate
pump. Allow the Aqua-
Hot to get to 170°F
(approximately 20 minutes)
Tap ELECTRIC
Open a hot water faucet
within the RV.
No click
sound
Verify the AC electric
relay has functionality
Verify the tank
temperature on the LCD
screen on the DIAG page
(180°F). See Figure 61.
If no functionality, replace
the AC electric relay
If tank temperature
is not 180°F, check
element for 11.2-13
amps
Replace
the Electric
element
This AC Electric system is
operating as intended.
Hot water? No
Yes Replace
Controller
No
Figure 60
AC Electric System
Figure 61
Replacement Procedure:
1. Ensure that the Aqua-Hot has been completely shut down
and all power sources have been disconnected. Be sure the
boiler tank is completely cooled.
2. Using hose pinch-off pliers, clamp off the heating zone inlet
and outlet ports.
3. Drain the antifreeze and water solution from the Aqua-Hot’s
boiler tank from the TO HEAT SOURCE and FROM HEAT
SOURCE hoses, turning the unit so that the front is down.
Drain the coolant into an external container to be reused.
4. Remove the AC access panel on the Aqua-Hot (Figure 63 &
Figure 64).
5. Remove the two wires secured to the defective electric
heating element by releasing the screw terminals (Figure
65).
6. Using a 1-½” (38mm) socket, remove the defective heating
element from the Aqua-Hot’s boiler tank.
7. Use a healthy amount of Loctite 454 on the threads of the
new electric element to ensure that it forms an adequate
seal.
8. Install the replacement 1500W electric element into the
boiler tank and secure it with the 1-½” (38mm) socket.
9. Reconnect the wires previously disconnected from the
electric heating element and tighten the screw terminals,
then put the AC cover back on.
10. Rell the Aqua-Hot boiler tank with the previously drained
uid, add more 50/50 mix of ethylene glycol and distilled
water to the tank if needed.
11. If necessary, purge the heat exchanger lines to remove any
and all air from the system by running the uid circulation
pump for 20 minutes.
Failure to disconnect all power supplies and/or allow
the unit to cool before servicing could cause serious
damage and/or personal injury.
Figure 63
Figure 64
Figure 62
AC High
Limit
Left High
Limit
Right High
Limit
AC Relay
Electric Element
AC Electric System
Electric Element
Figure 65

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AC Relay
Introduction:
The AC Relay is an electrical device where the DC circuit from
the controller determines whether the AC power is permitted to
ow to the electric heating element. This allows the controller
to switch the electric heating element on and off in conjunction
with the interior switch panel and ETS module even though the
electric element is on a separate circuit.
Troubleshoot the AC Relay if the electric element fails to operate.
This can be veried with a simple test outlined below.
The following conditions must be met before the AC Relay can
be diagnosed, and if necessary, repaired.
• The expansion bottle is lled to at least the “COLD” mark.
• Verify that all in-line fuses are functional.
• Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the Aqua-
Hot’s electric element.
• Verify the thermostats are in working order.
If any of the above conditions are not met, correct them before
continuing with troubleshooting. Results of the troubleshooting
procedure cannot be veried if the conditions listed above are
not fullled.
Troubleshooting Procedure:
1. Locate the AC wires connected to the AC Relay and remove
the wires from the relay.
2. Using an ohmmeter, check the AC relay pins for continuity.
3. If no continuity exists, follow the procedure to replace the
AC Relay.
AC Relay
Figure 66
Figure 67
AC Relay
AC Relay Rivets
ETS Module
Introduction:
The ETS (Engine Temperature Sensor) Module is a brass
thermistor that continually measures the temperature of the
uid within the Aqua-Hot boiler tank. This module then relays
the information to the Aqua-Hot controller, thereby allowing the
controller to activate and deactivate the unit as heating and hot
water needs change.
Troubleshooting Procedure:
Troubleshooting the ETS module is a relatively straight
forward process. Follow the instructions below to diagnose
the ETS module. Troubleshoot the ETS module if the following
conditions have occurred:
• A lack of hot water.
• A lack of interior heat.
• The Aqua-Hot is not operating.
Verify the following before proceeding with the troubleshooting:
• The overow bottle is adequately lled.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the Aqua-
Hot’s electric element.
• The high-limit thermostats are not tripped.
• All fuses are in working order.
If any of the above conditions are not
met, correct them before continuing with
troubleshooting. Results of the troubleshooting
procedure cannot be veried if the conditions
listed above are not fullled.
Using a meat thermometer,
measure the temperature
of the tank face. Record
this temperature on a
piece of paper.
Locate the Aqua-Hot LCD
screen. Navigate to the
DIAG page
Find INPUTS FROM AQUA-HOT,
and record the temperature
listed by TANK TEMPERATURE
(Figure 69). Record this
number on the sheet.
Are the recorded
temperatures
approximately the same?
Yes
This ETS
module is
functioning
as intended.
Disconnect the ETS
module from its leads on
the wire harness
Navigate back to the
INPUTS FROM AQUA-HOT
section of the LCD screen.
No
Yes No
Does the Aqua-Hot display
any temperature?
Replace the
controller.
Replace the
ETS module
Figure 68
Figure 70
Figure 69
ETS Module
Replacement Procedure:
1. Ensure that the Aqua-Hot has been completely shut down
and all power sources have been disconnected. Be sure the
boiler tank is completely cooled.
2. Ensure that the RV is not connected to shore power and
that a generator is not connected during this procedure.
3. Remove all wires from the relay.
4. Remove the defective relay by drilling the rivets that hold
the relay in place (reference Figure 67) and discard the
defective relay.
5. Rivet the replacement AC relay to the previous position.
6. Using the wiring diagram on page 49, connect the wires
previously removed to the replacement AC relay.

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Replacement Procedure:
If the ETS Module has been diagnosed and a replacement
must be made, follow the instructions below.
1. Drain the unit by clamping the “TO HEAT SOURCE” hose
(shown below) located outside the Aqua-Hot, and removing
it.
2. Allow the uid to drain into an external bucket or container
to be reused later. If necessary, activate the pump to aid in
draining the Aqua-Hot.
3. After approximately half a gallon has been drained from the
unit, clamp the hose to stop the ow of coolant.
4. Disconnect wires from the ETS Module.
5. Using a 14mm wrench or deep socket, remove the defunct
ETS module from the tank face and discard it.
6. Place the replacement ETS module in its position on the
tank face, and nger tighten it into place.
7. Using the 14mm wrench, tighten the module until it is snug
in place.
8. Reconnect the disconnected wires from the harness.
9. Reconnect the “TO HEAT SOURCE” hose to the Aqua-Hot
and remove the hose clamp.
10. Pour the previously removed uid back into the uid
expansion bottle and allow it to ll the Aqua-Hot tank.
11. Once this has been completed, locate the Aqua-Hot LCD
screen, navigate to the test section, and run the uid
circulation pump (and if applicable the boost pump) for at
least twenty minutes to purge the heating loop of air.
12. Continually ll the uid expansion bottle as the uid level
drops.
13. Test the Aqua-Hot for normal operation.
Figure 71
Figure 73
Figure 72
Clamp across
this hose
Hose is highlighted in yellow
to properly show the process.
Fuel System Replacement
Fuel Lines Requirements
• Use the provided Ø4mm x 1mm (to heater - transparent)
fuel hose and Ø2mm x 5mm (to fuel tank - blue) fuel line
with the included couplers and clamps. (See Figure 75)
• The fuel hose should not be descending from the fuel pump
to the burner - see Figure 75.
• The fuel line should be properly secured to avoid sagging.
• The fuel line must be installed in a manner that won’t cause
damage to the fuel line (i.e. close to exhaust).
• The fuel line must be secured to the connections and
couplers by hose clamps. See Figure 76.
• Damper installation should be according to the practical
situation.
Fuel Hose to Burner Fuel Line to Tank
Fuel Pump
• The fuel pump is a combined pumping, metering, and shut-
off system. It pumps fuel from the vehicle supply to the
burner via the fuel lines.
• The outlet of the fuel pump is required to be installed
upwards. The angle should be between 15°-35°. See
Figure 77 for fuel pump orientation.
Fuel System Replacement:
1. Remove fuel line from the burner before performing the
Fuel Purge Procedure (Page 39).
2. Remove any defective part.
3. Check fuel lines and connections for damage.
4. Replace as necessary. See the diagram above and Pages
38-39 for further instructions.
Figure 75
Figure 74
NOTE: The diagram above is not drawn to scale. It is simply a reference
for proper installation of the fuel system for the Belief Gas Burner.

ETS ModuleETS Module
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Fuel System Replacement
Figure 76
NOTE: The fuel lines must be secured and supported properly to avoid air
traps or bubbles. Avoid unnecessary dips or bends, the line should not run
downward from the fuel pump.
Fuel Line to Coupler Hose
AClamp CFuel HoseBCoupler
B CA
Bubble
WRONG
BC A
CORRECT CORRECT
B
C
A
WRONG
Bubble B
C
A
Please follow instructions to ensure safe
operation. Always check for any fuel leaks
before operating the burner.
NOTE: The Fuel System requires that the gasoline used
(in the vehicle for the burner supply) must be 87 octane
or greater (87, 89, 91, or 93 octane).
Figure 78
Figure 77
Fuel Pump Orientation
35°
1
2
min. 15°
0°
1. Allowable Installation Angle
2. Optimum Installation Angle
2
1
GAS
Fuel System Purge
Fuel Line Connection
Fuel Purge Procedure
The fuel lines should be automatically primed with the rst
operation of the burner. It may take 5-6 starts for the burner
to ignite for the rst start-up after installation, because the
fuel pump needs to ll the fuel lines leading to the burner for
ignition. An ignition failure may occur within the rst 5-6 starts.
Perform this procedure once the burner and Aqua-Hot are
completely installed and the Aqua-Hot is adequately lled and
purged.
1. Connect a 12V power source to the fuel pump to pulse
the pump. The power source must be able to be pulsed
(turned on and off) rapidly for this process.
• The pump can be powered with wire and gator
clips. The Pin numbers are labeled below:
Do NOT exceed 12V when powering the fuel pump.
This can cause irreparable damage to the fuel pump.
Fuel Pump Pins
Figure 79
1 2
• Ground goes to Pin #1
• Power goes to Pin #2
• If you would rather use a plug instead of the wire
and gator clips, the mating part numbers needed
for the connector are:
○ Housing: 1-967644-1
○ Terminal; 0965906-1
○ Seal: 0-967067-1
2. Pulse the fuel pump at a steady 1-2 pulses per second
until fuel begins to come out of the fuel line where it
will connect to the burner.
3. Connect the fuel line to the burner.
4. Ensure all hose clamps and fuel ttings are tight and
properly secured.
5. Ensure that the exhaust is well ventilated.
6. Turn the burner on at the screen (see Figure 81). The
burner should cycle on because of the primed fuel
lines.
• There may be smoke from the exhaust on initial
start-up, this is normal.
7. If the burner does not cycle on with the rst start up, it
will try a second time.
• If the second start-up fails, there will be a fault
message on the LCD screen (Figures 82-83). Tap
the burner OFF at the screen.
• Repeat Step 6.
• If fault occurs again, repeat Steps 4-6.
8. After a successful start up, run the burner for 5
minutes.
After a complete, successful rst operation, the fuel lines should
be purged of any air and ready for normal operation and use.
Figure 81 Figure 82
Figure 80 Figure 83
Fuel Pump Connection
Fuel Pump PlugFuel Pump
NOTE: Once the fuel lines are primed, the fault should clear,
but the fault may need to be reset in the process. Just press
the RESET button (Figure 83) to clear all the faults.
LCD Screen Burner Status on Fault Codes
NOTE: The fuel lines can be fully primed by turning the
burner ON/OFF via the LCD screen (Figure 81) without having
to direct power and pulse the fuel pump. Once the burner
starts and cycles, and any Ignition Failures/Faults are clear,
the burner is ready for operation.
NOTE: DO NOT run the gas burner without the coolant lled
and purged as it will cause serious damage to the burner.