Page 1 Aqua-Hot: 125-D02 Service Manual This manual contains information related to diagnosis, repair, and maintenance of the Aqua-Hot AHM-125D series of RV water heating systems. Download the complete PDF here: AHM-125-D02-Service-Manual Caution Notes As you read this information, take particular note of the NOTICE, CAUTION, WARNING, and DANGER symbols when they appear.
Page 2: System Overview
System Overview The Aqua-Hot AHM-125D 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 diesel burner. The Aqua-Hot is a 2-in-1 System https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A…...
Page 3 1. Interior heating system: provides quiet, comfortable interior heat and even temperatures. 2. Tank-less hot water system: provides a flow 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.
Page 4 Heat Priority Option The Aqua-Hot comes equipped with a three-way valve (some- times known as the summer/winter valve). This controls the flow of the antifreeze and water heating solution within the Aqua-Hot to deliver either hot water or interior heat as priority. Tapping on this element will change the valve’s orientation.
Page 5: Electric Element
External Diesel Burner The diesel 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.
Page 6 Introduction to this Document Welcome to the Aqua-Hot AHM-125D 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 qualified technicians to properly service and troubleshoot the Aqua-Hot AHM-125D.
Page 7 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. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A…...
Page 8 If the information in this manual is not followed exactly, a fire or explosion may result, causing property damage, personal injury, or death. WARNING! Read and understand all instructions before servicing the Aqua-Hot unit and the external diesel 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.
Page 9: Maintenance Schedule
1192. National safety regulations must be adhered to. Maintenance Schedule Monthly Maintenance Check the Aqua-Hot’s antifreeze and water heating solution to ensure that it is at the proper level about once a year. Please note that the coolant level should ONLY be checked when the Aqua-Hot is completely cold.
Page 10: Overheat Protection
Replenishing the Heating Solution If the antifreeze and water heating solution needs replenishing, remove the boiler tank cap and fill it. Replace the cap when this is complete. DO NOT operate the unit without first replacing the cap of the tank. Place a bucket under the overflow hose and turn the burner on.
Page 11 In the event of an overheat condition, the high limit thermostat will cut the operating signal to the external diesel burner, and/or the electric element. When this signal is interrupted, the electric element and diesel burner will immediately disengage. Contact Aqua-Hot Heating Systems for assistance in locating a qualified person to service this heater.
Page 12: System Features
System Features NOTE: This product label is attached to the side of the Aqua-Hot, and provides a ready reference to specifications, test standards, and important safety notices. Boiler Tank System Specifications https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 13 Electric Element Power Consumption....................................W (maximum) Voltage......................................DC Power Power Consumption ........................................W (maximum) https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 14 Zone Heat Circulation Pumps ........................................Power Consumption (max)..................................1.7A Voltage......................................Interior Heating Maximum Heating Zones......................................Cozy......................................0.5A - 8,000 BTU/hr Whisper....................................... 0.37A - 4,000 BTU/hr H.E. II........................................0.25A - 4,000 BTU/hr NOTE: Control Panel “Quiet Mode” reduces heat exchanger power consumption by 20% Domestic Water Heating Maximum.....................................
Page 15: Physical Specifications
Physical Specifications Dimensions (US)......................................x 7.90”W x 9.66”H Weight......................................Weight......................................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. Parking Heater System Specifications Diesel Burner Heat Flow......................................
Page 16: Operating Temperatures
Diesel Fuel Consumption....................................to 0.16 gal/hr Coolant Pump ........................................1.7A Operating Pressure (medheat)....................................Flow Rate (minimum)....................................Working Altitude......................................Fuel Fuel Type ........................................Fuel Consumption (Low Output) ........................................0.07g/h Fuel Consumption (High Output) ........................................0.16g/h DC Power Consumption ........................................to 37W Operating Range ........................................
Page 17 Burner Operation....................................-40 to 176°F Burner Storage......................................to 248°F Fuel Pump Operation....................................-40 to 86°F Fuel Pump Storage......................................to 194°F Physical Specifications Dimensions....................................8.8”L x 3.4”W x 6.9”H Weight ........................................Technical Specifications Heating Medium Ethylene Glycol/Distilled Water High Power Operation: 5000W Thermal Power (W) Low Power Operation: 2400W Fuel...
Page 18: Technical Specifications
Technical Specifications High Power Operation: 0.16 g/h At Start: <100W Power Consumption (W) High Power Operation: 37W Low Power Operation: 10W Working Pressure (MPa) 0.25 Lowest Working Temperature -40° F / 4.4° C Net Weight (Heater Only) 10.6lbs / 4.8kg Working Height (above Sea Level) 16,405 ft / 5,000 m Weight of Main Heater...
Page 19 M125 Heating System Diagram Index Pump 3. Tempering Valve 9. Coolant Out 19. Domestic Cold-Water 15. AC Aviation Relay 4. Three-Way Valve Inlet 10. Coolant In 16. Fluid Fill Port w/ Radiator 5. Cozy Heat Exchanger 20. Domestic Hot-Water Aqua-Hot Outlet Controller 6.
Page 20 Belief Diesel Burner Diagram Index Combustion Temperature 13. Coolant Pump Sensor Burner Outer 18. Coolant Outlet Casing Pipe 14. Fuse 8. Over-Heat Sensor Burner Inner Coolant Inlet Main Harness 9. Burner Controller Casing Pipe Connector 10. Air Inlet Pipe Combustion 20.
Page 21: Operational Flow Chart
Operational Flow Chart Operating the Aqua-Hot & LCD This section will outline the basic operating instructions for the Aqua-Hot LCD Screen. Climate Pages: https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 22: Zone Control
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 diesel burner and/or the electric element. Zone Control 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.
Page 23 Section 1 demonstrates the appearance of the zone control section when thermistors are used. Tapping on one of the zones shown above will display a new screen where the interior temperature can be set. Section 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.
Page 24 External Diesel Burner Activation The external diesel burner of the Aqua-Hot can be activated by tapping on the “burner” item on-screen. The diesel burner has two modes: ON and OFF. While set to ON, the Aqua-Hot diesel burner will work to maintain a tank temperature of 180° F. OFF: While off, the diesel burner will not serve to provide any heat to the boiler of the Aqua-Hot...
Page 25: System Status
Electrical Element Activation Similar to the external diesel 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. While set to ON, the electric element will work to maintain a tank temperature of 180°...
Page 26: Module Options
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.
Page 27 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 The screen timeout item sets the amount of time required to allow the screen to shut-off when idle. Screen Brightness This setting changes the screen brightness.
Page 28 Controller The Aqua-Hot AHM-125D 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.
Page 29: System Voltage
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.
Page 30: Over-Current
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 fluid level within the Aqua-Hot is below an acceptable operational threshold.
Page 31: Operating Mode
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. Diagnostics 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.
Page 32 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. Burner: This indicates the current burner status as either ON or OFF.
Page 33 Inputs from RV 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.
Page 34 Outputs to Aqua-Hot 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 The Inputs to Aqua-Hot will contain the current readings from sensors within the Aqua-Hot.
Page 35: Tank Temperature
The Burner Status element on this page indicates the status of the external diesel 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 present sensor reading of the Low-Level Cutoff sensor located on the boiler tank.
Page 36 One of the new features of this control system is the ability to independently activate specific elements within the Aqua- Hot for testing purposes. This will allow a technician to activate specific elements within the Aqua-Hot as needed without jumping wires or utilizing external power supplies in most troubleshooting cases.
Page 37 Pumps Both the zone circulation pump and the boost pump (if applicable) can be activated by tapping the corresponding pump on the test screen. Fans 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.
Page 38 functionality. These systems will activate for a maximum of five 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. DO NOT attempt to activate these sub-systems while the unit is near operating temperature.
Page 39 Three-Way Valve The final 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 flow 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.
Page 40 • Tap OPTIONS, CLIMATE ZONES, and take a picture of the following screen. 2. Disconnect all power to the Aqua-Hot. 3. Remove the plugs from the controller and disconnect the DC harness from the controller. 4. Unscrew the four screws attaching the sheet metal cover/housing to the wall, and remove the defective controller. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A…...
Page 41 5. Install the replacement controller using the 4 screws previously removed. 6. 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. NOTE: All plugs have only ONE correct orientation.
Page 42 Continue to the next section to set up the controller after installation is complete. 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. 1.
Page 43: Float Switch
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). •...
Page 44: Troubleshooting Procedure
Troubleshooting Before troubleshooting the float switch, ensure that the following requirements have been met: • Ensure that the unit is completely cool. • The tank is filled with heating solution. • Verify that all RV-side in-line fuses are functional. • Ensure that DC electrical power is supplied to the Aqua-Hot. •...
Page 45 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 46 Replacement Procedure 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. In order to replace the float switch, a float switch kit with the switch and the quick disconnect terminal must be ordered. Please visit www.aquahot.com or call 574-AIR-XCEL (574 247-9235) to order the kit (part number ELX-135-M01).
Page 47 2. Grab a bucket or drain receptacle and place it directly under the lower fitting of the boiler tank. 3. Remove the clamp from the lower fitting of the tank. 4. Remove the hose and allow the excess fluid to drain into the bucket. 5.
Page 48: High Limit Thermostat
10. Fill the tank with the previously drained fluid. 11. Remove the hose clamps. 11. Test the Aqua-Hot for normal functionality. If additional assistance is required please contact the Aqua-Hot Heating Systems Technical support department at 574-AIRXCEL (574-247-9235) from 7:00am to 4:00pm MST Monday through Friday. High-Limit Thermostat The Aqua-Hot is equipped with a resettable High-Limit Thermostat.
Page 49 Troubleshooting Befor continuing the diagnosis, AC power MUST be disconnected. Any time the AC cover is removed, the AC power supply must be disconnected to avoid serious injury or damage to the RV or system. To verify that the element is working, the AC power does not need to be connected.
Page 50: Replacement Procedure
Replacement Procedure If it has been determined that the high-limit thermostat needs to be replaced, it can be easily replaced by following the https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 51 directions below. 1. Disconnect all sources of AC and DC power from the Aqua-Hot (the AC access cover will need to be removed - see Figure 36). 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 boiler tank. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A…...
Page 52: Low-Temperature Cutoff Thermostat
4. Locate the new thermostat and secure it in place of the old thermostat. 5. Reconnect the disconnected wires. 6. Test the Aqua-Hot for normal operation. If issues persist, please contact Aqua-Hot Heating Systems for additional assistance. Low-Temperature Cutoff Thermostat The Low-Temperature Cutoff Thermostat (LTCO) is installed to measure the incoming domestic water temperature.
Page 53 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 54 Replacing the Low-Temperature Cutoff Thermostat 1. Disconnect all sources of AC and DC power from the Aqua- 2. Disconnect the wires from the LTCO. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 55 3. Remove and discard the defunct LTCO thermostat using a 3/16” socket. 4. Position and secure the new LTCO thermostat into place. 5. Connect wires J4-1 and J4-2 to the new LTCO thermostat. Three-Way Valve The three-way valve (aka the summer/winter valve) is responsible for changing the flow of coolant either through the interior heating zone (int heat) or circulating coolant within the boiler tank (hot water mode) to prioritize hot water.
Page 56 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 57 Before replacing the 3-way valve, you must purchase the repair kit. The Repair Kit should include: • Three-Way Valve • Black Nylon elbow adapter • Black Nylon barb adapter • 2-pin electrical connector https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 58 Replacement Procedure 1. Drain coolant from system. • Pour into a bucket to be reused later 2. Locate the Three-Way Valve. Clamp off the hoses at the three-way valve: 3. Disconnect the electrical connection from the Three-Way Valve to the DC harness. 4.
Page 59 6. Install the new three-way valve and then reinstall the hoses on the new valve. Ensure that the orientation of the valve remains the same. 7. Tighten the hose clamps and reconnect the wire harness to the valve. 8. Refill the unit with the coolant saved from Step 1. •...
Page 60: Tempering Valve
Tempering Valve Introduction The tempering valve of the Aqua-Hot mixes the hot domestic water from the Aqua-Hot with cold incoming domestic water to mix it to a threshold where scalding will not occur. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 61 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 62 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 qualified Aqua- Hot technician. NOTE: The Aqua-Hot Domestic Water System is rated for a water flow of 0.8 GPM.
Page 63: Testing Procedure
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. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A…...
Page 64 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 RV domestic water drain valve and release water https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 65 from the system. 3. Disconnect the RV side domestic water connections 4. Locate the tempering valve assembly within the RV. 5. Remove the fasteners that secure the tempering valve assembly. 6. Disconnect the water lines from the brass fittings on the tempering valve assembly. •...
Page 66 7. Remove all fittings from the tempering valve as shown below. 8. Discard the defunct tempering valve. 9. Using Teflon tape and domestic water safe thread sealant, reinstall all fittings on the new valve to previous orientations. 10. Place previous P-clamp onto the assembly before inserting into the Aqua-Hot. 11.
Page 67 12. Reusing the fasteners and P-clamps, reattach the tempering valve assembly to the vehicle. Tank Fluid Circulation Pump Introduction The fluid circulation pump operates to provide fluid 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 fluid circulation pump has failed, it will typically indicate an over-current fault on the controller fault log.
Page 68 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
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Page 70 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 71 Replacement Procedure 1. Place a paper towel on the bottom of the cabinet. (This is to help absorb any residual coolant left in the lines upon pump removal.) 2. Drain coolant from the lower tank fitting (see Figure 53). Pour into a bucket to be reused later. 3.
Page 72 6. Carefully remove the hose (leading to the burner pump) from the pump. 7. Carefully remove the pump from the hose attached to the tank and discard it. 8. Insert the new circulation pump and attach it to the hose coming from the tank. Make sure the pump orientation is the same as it was before removing.
Page 73 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 boiler tank is adequately filled. •...
Page 74 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 75 Replacement Procedure Failure to disconnect all power supplies and/or allow the unit to cool before servicing could cause serious damage and/or personal injury. 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.
Page 76 5. Using a 1-½” (38mm) socket, remove the defective heating element from the Aqua-Hot’s boiler tank. 6. Use a healthy amount of Loctite 454 on the threads of the new electric element to ensure that it forms an adequate seal. 7.
Page 77 • The boiler tank is adequately filled. • 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.
Page 78 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.
Page 79 6. Rivet the replacement AC relay to the previous position. 7. Reconnect the wires previously removed to the replacement AC relay. 8. Reinstall the AC cover panel and test for proper operation. ETS Module The ETS (Engine Temperature Sensor) Module is a brass thermistor that continually measures the temperature of the fluid within the Aqua-Hot boiler tank.
Page 80 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. •...
Page 81 Replacement Procedure https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 82 If the ETS Module has been diagnosed and a replacement must be made, follow the instructions below. 1. Drain the unit by pinching off the lower tank fitting hose (shown below) with pinch off pliers, and removing the hose. 2. Allow the fluid to drain into an external bucket or container to be reused later. 3.
Page 83: Fuel System
12. Continually fill the tank as the fluid level drops. 13. Test the Aqua-Hot for normal operation. Fuel System NOTE: The diagram above is not drawn to scale. It is simply a reference for proper installation of the fuel system for the Belief Diesel Burner.
Page 84: Fuel Filter
Fuel System Plumbing • Ensure the fuel system meets the requirements detailed in Figure 65. • Ensure no connections leak. Any leaking connections will lead to burner problems. • Where possible, the fuel line should have a gentle incline from the fuel tank to the burner. Fuel line should be installed as flatly as possible, avoiding sharp rises and falls.
Page 85 Please follow instructions to ensure safe operation. Always check for any fuel leaks before operating the burner. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
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Page 87 Fuel System Fill Procedure Perform this procedure after any fuel components have been serviced and/or replaced. • Ensure all fuel system connections have been made. • Ensure all fuel line clamps are tight. • The fuel level in the vehicle’s tank must be above the fuel pickup level. •...
Page 88 • If a different fault is displayed, follow the trouble shooting guide on page 40 and address the cause of the fault. External Diesel Burner Troubleshooting The troubleshooting procedures listed below are arranged in order of repair complexity. Do not replace parts without correctly determining the failure.
Page 89: Heater Lock-Out Reset Procedure
turned ON, the LCD screen will show STATUS as “FAULT”. Tapping on FAULT will take you to the FAULTS screen which will display “Burner: Failed to Ignite”. After about a minute, the fault screen will show the specific fault code. Refer to the Burner Faults and Remedies section for the fault codes and their remedies.
Page 90 The burner lockout reset must be done manually as shown below. Troubleshooting Procedure • Turn on the burner, on the interior control panel. • Remove the main power connection to the burner or pull the fuse for a minimum of 20 seconds. •...
Page 91 Fault Fault Cause Remedy Code Burner: Heat Plug Failure Poor/Reduced Performance • Replace glow plug • Replace controller Burner: Heat Plug Failure Heat Plug Voltage not detected Burner: Fan Speed too high • Replace burner controller Burner: Fan absent/broke circuit •...
Page 92 Fault Fault Cause Remedy Code Burner: Temperature sensor absent/broken circuit • Check temperature sensor (normal Burner: Temperature sensor short-circuit temperature resistance about 10 Ω) • Replaced temperature sensor Burner: Coolant temperature is too high prior to ignition Burner: Flame sensor absent/broken circuit •...
Page 93: Servicing The Burner
This section covers the typical failures of the diesel burner. Refer to the following table for additional failures and their remedies. Failure Symptom Possible Cause Remedy No combustion after start or Switch off burner and switch back on automatic repeat start •...
Page 94 • Check fuel lines for any leaks, kinks, cracks, or damage. • Check plumbing lines and circulation pump to make sure they are properly secured and free of any damage. • Check the fuel pump and circulation pump for any damage. •...
Page 95 3. Listen for burner ignition, it can take around 1 minute to ignite. 4. Tap the three lines icon -> Diagnostics -> Diagnostics -> Next 5. Locate the "Tank Thermistor" field https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 96: General Troubleshooting
6. Watch for the "Tank Thermistor" temperature to increase 2 to 3 degrees. • If no temperature increase is seen diagnose the burner following the service manual. 7. Allow the burner to heat the tank to full temperature (180°F). 8. Tap the Home icon -> Back -> Burner to OFF. Note: It is recommended to run the burner for at least 20 minutes every month to ensure optimum heater condition Note: Both the electric heating element and the external diesel burner are thermostatically controlled.
Page 97 A lack of interior heat or hot water when provided with adequate heat from either the electric element and/or the diesel burner can be attributed to an overheat thermostat, the Aqua-Hot controller, the three-way valve, or the fluid circulation pump. Follow the directions below in order to troubleshoot the Aqua-Hot.
Page 98 9. Locate and test the fluid circulation pump. Replace if necessary. 10. Locate the three-way valve and test it for functionality. Replace if necessary. 11. Make sure there are no faults displayed on the LCD screen as shown to the right. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A…...
Page 99 NOTE: The float switch is located on the Aqua-Hot's boiler tank, as shown in figure 79. If the antifreeze solution in the tank drops below the level of the float switch, the Aqua-Hot will not operate. Winterizing the Aqua-Hot Not winterizing the Aqua-Hot when freezing temperatures are present will https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A…...
Page 100 result in serious damage to the Aqua-Hot domestic water heating system. Ensure that only non-toxic RV antifreeze (FDA approved "GRAS" antifreeze) rated for winterization is used when winterizing this unit. The warranty does not cover freeze damage. The Aqua-Hot’s domestic water heating system must be completely drained of domestic water at any time the heater is stored where freezing temperatures may be experienced.
Page 101 The Aqua-Hot Heating components are not compatible to prolonged exposure to sodium hypochlorite (bleach or liquid bleach). Using products containing bleach, including water refreshers, may cause corrosion of the domestic water lines, resulting in a catastrophic failure of the Aqua-Hot system by creating leaks that cannot be repaired. This damage is not covered by the Aqua-Hot warranty.
Page 102 Zone Heat Exchangers & Zone Thermostats https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 103 External Diesel Burner https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 104 Sensors, Thermostats, & Electric Element Parts NOTE: For more parts & information, please reference the AHM-125-DO2 Parts manual found online at https://www.aquahot.com/library/aspx. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 105 Thermistor, Tank Temperature Sensor Thermistor, 10K NTC, Room Temperature Sensor Purchase at Tiffin Motorhomes Here RV-Side Wire Harness (optional) Aqua-Hot LCD, Screen, RVC 3.5in Aqua-Hot Series 125 Mainframe Harness https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 106 Low-Temperature Cutoff Thermostat with Spade VAC High Limit Thermostat 215°F with Leads Terminals 1500W, 120 VAC Electric Element, 1" NPSM Controller, 12VDC, 100-200 Series, Kit Purchase at Tiffin Motorhomes Here https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 107 Float Switch Kit, 1/2" NPT with Quick Disconnect Heat Exchanger, Cozy III Terminal Purchase at Tiffin Motorhomes Here Purchase at Tiffin Motorhomes Here Fluid Circulation Pump Small Heat Exchanger, (2) 1/2" FNPT, (2) 2" MNPT Purchase at Tiffin Motorhomes Here https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A…...
Page 108 Pressure Relief Valve, 125 PSI Harness, Buehler C20 Pump Purhase at Tiffin Motorhome Here Tempering Valve Kit, Three-Way Motorized Valve, 1/2" NPT Purchase at Tiffin Motorhomes Here Purchase at Tiffin Motorhomes Here https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT...
Page 109 AC Relay, 30A 277VAC Cover, AC Element Cover for 125 Series Hose, 3/4" Safety Stripe, Rubber Assembled Fuel Pump Refractometer Belief 5kW Diesel Burner Circulation Pump https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 110 Fuel Hose to Burner Fuel Hose to Fuel Tank (Blue) Clamp, (10.5mm), Soft Hose and Tube Clamp, 3/8 to 7/16 (11.3mm), Soft Hose and Tube Burner K_Line Converter Burner Wiring Harness https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...
Page 111 Measuring Antifreeze Using a Refractometer Properly Apply Antifreeze to the Prism Assembly Use the guide below to properly apply the ethylene glycol mixture to the prism assembly of the refractometer. Once that is complete, peer through the eyeglass of the refractometer to continue to the next step. Adjust the Boundary Line Once the glycol solution has been properly applied, adjust the calibration screw until the boundary line labeled “Ethylene Glycol”...
Page 112 ©2022 Aqua-Hot Heating Systems, LLC. Printed in the USA https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_B/2023/GH1/19_AV/Component_Manuals/AquaHot/A… Updated: Mon, 15 Jul 2024 23:59:07 GMT Powered by...

Tiffin Motorhomes Aqua-Hot AHM-125D Series Service Manual

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