Aqua-Hot 450D Service Manual
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Aqua-Hot 450D Service Manual

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AHE-450-DE5 Service Manual
Introduction:
This service and parts manual is designed to aid trained and qualified service technicians with the process of
troubleshooting and servicing the Aqua-Hot 450D Hydronic heating system.
About the Aqua-Hot:
The Aqua-Hot 450D heating system features a 12V DC powered diesel-burner and a 120VAC 1650 Watt electric heating
element. These two heating sources are used in conjunction with an FDA-approved "GRAS" (Generally Recognized as
Safe) propylene glycol based boiler antifreeze and water heating solution in order to provide a continuous supply of
domestic hot water, interior/fresh water tank heating, independent interior zone heating, and engine preheating. Be sure
to reference Figures 5 through 8 for a complete component overview.
Understanding the Aqua-Hot 450's Major Systems:
The basis for the Aqua-Hot heating system's functionality is the antifreeze and water heating solution, which is
comprised of water that is distilled, deionized, or soft, as well as FDAapproved "GRAS" propylene glycol based boiler
antifreeze. Through this solution's ability to maintain and transfer heat, the Aqua-Hot's three major systems: the
domestic water system, engine preheat system, and interior heating system, are able to function effectively. This
antifreeze and water heating solution is contained within the Aqua-Hot's boiler tank and is heated by the diesel-burner
when its operating criteria are met and/ or by the electric heating element when its operating criteria are met. In order for
the diesel-burner to be considered as a heating source by the Aqua-Hot, it must have an adequate fuel supply, receive
power from the Reporter, and be selected as a heating source from the interior switch panel. In order for the electric
heating element to be considered as a heating source by the Aqua-Hot, it must receive power from either a generator or
from shore power and be selected as a heating source from the interior switch panel. Once the antifreeze and water
heating solution achieves operating temperature (as determined by the Aqua-Hot's control thermostat/ETS Module), the
domestic water system, the engine preheat system, and the interior heating system are permitted to operate as needed.
Domestic Hot Water Priority System:
The Aqua-Hot 450D is a Hot Water Priority System. Meaning that the Aqua-Hot 450D cannot heat the interior of the
motor home, and produce continuous hot water simultaneously. When Domestic Hot Water is being used, the interior
heating system will shut down, until no more Domestic Hot Water is called for. The domestic hot water priority system is
responsible for providing hot water whenever a hot water faucet is opened, such as with a shower or sink. When hot
water is requested, domestic water from the motor home's fresh water tank is transported through a copper coil in the
https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu...
Updated: Fri, 21 Jun 2024 03:21:17 GMT
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Summary of Contents for Aqua-Hot 450D

  • Page 1 Reporter, and be selected as a heating source from the interior switch panel. In order for the electric heating element to be considered as a heating source by the Aqua-Hot, it must receive power from either a generator or from shore power and be selected as a heating source from the interior switch panel.
  • Page 2 Aqua-Hot 450D includes a motor-aide feature, which uses the circulation of the motor home’s engine to transport the engine’s coolant from the Aqua-Hot’s boiler tank to the motor home’s warm engine and back to the boiler tank. Through this process, the boiler tank is kept heated, which reduces the time required to bring the tank to operating temperature for interior heat and continuous domestic hot water.

  • Page 3: 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 tank; reference Figure 140 on page 83.

  • Page 4: System Features

    System Features https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 5 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...

  • Page 6: System Specifications

    System Specifications Diesel Burner Heat Input (Firing Rate) ........56,000 BTU/hr Fuel Consumption ............0.40 gal/hr Electric Element Power Consumption ........1650 W (maximum) Voltage ................120V AC DC Power Consumption ............174 W (maximum) Zone Heat Circulation Pumps ...................2 Power Consumption (max) .........21 W (each) Voltage ................
  • Page 7 8. Interlock Switch 14. Wiring Harness Port Pump Pump 3. Zone 2 Circulation 9. VAC Access Panel 15. Aqua-Hot Reporter 21. Engine Preheat Inlet Pump 4. Diesel Burner 16. Domestic Water 10. AC Terminal Block 22. Domestic Cold Water Inlet...
  • Page 8 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 9 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...

  • Page 10: Operational Flow Chart

    Antifreeze and Water Heating Solution Introduction: As the antifreeze type and mixture ratio is essential to the Aqua-Hot’s performance and ability to comply with regulations, the following information is being supplied to understand various types of antifreeze, the quality of water necessary, and the mixture ratio.
  • Page 11 Although RV & Marine antifreeze is often “Generally Recognized as Safe” by the FDA, it should never be used in the Aqua-Hot’s Hydronic Heating System. This type of anti-freeze is not formulated to transfer heat, which is essential to the heating system’s functionality and does not contain rust inhibitors.
  • Page 12 Boiling Point: The Aqua-Hot utilizes the antifreeze and water heating solution as a transportation means for the heat produced from the internal processes. The antifreeze absorbs the heat created until its boiling point is reached; it is at this point that the liquid turns to a gas and is expelled to prevent the heating system from overheating.

  • Page 13: Using A Refractometer

    Using a Refractometer Properly Apply Antifreeze to the Prism Assembly Use the guide below to properly apply the propylene 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 “Propylene Glycol”...

  • Page 14: Interior Switch Panel

    Introduction: The interior switch panel is used to control the two potential heating sources for the Aqua-Hot’s boiler tank, as well as to control the engine preheat feature. When a switch is activated, the indicator light on the switch will illuminate.
  • Page 15 • Total exhaust length must NOT exceed 20 feet, and shall contain no more than two 90° bends • The 3-in and 4-in black pipe nipples and the exhaust elbow - originally supplied with the Aqua-Hot must be present https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu…...

  • Page 16: Interlock Switch

    The interlock switch is a safety device designed to ensure that the Aqua-Hot’s access cover is securely installed before allowing the diesel-burner to operate. If the Aqua-Hot fails to operate, and shows no illuminated lights or displays, it is possible that the interlock switch is faulty. Follow the directions below to troubleshoot, and if necessary, replace the interlock switch.
  • Page 17 1. Disconnect the Aqua-Hot from all power sources. 2. Disconnect the interlock switch’s wires by pulling the quick connectors from the switch’s spade terminals. 3. Release the interlock switch from the Aqua-Hot cabinet by pushing in on the locking tabs and pulling the interlock switch.

  • Page 18: Fluid-Level Sensor

    Troubleshoot the fluid-level sensor if the Reporter has issued a low fluid level fault and the Aqua-Hot is adequately filled. The fluid-level sensor operates by relaying a continuity signal to the Reporter while it is wet. If this signal does not exist, then there may be an issue with the Reporter, OR the fluid level sensor may be physically damaged.
  • Page 19 Coolant Temperature Sensor (ETS) Introduction: The ETS module precisely measures the temperature of the coolant inside of the Aqua-Hot boiler tank. This allows for very granular control of the unit to deliver precise heating and hot water as needed. The ETS module went live on the Aqua-Hot 450-DE5 series. Older units utilized the control thermostat.
  • Page 20 3. Check the J8-6 and J8-3 pins on the Reporter to check for cut, corroded, or otherwise damaged wiring. 4. Using a meat thermometer, measure the temperature of the tank face of the Aqua-Hot. 5. Record this temperature on a notepad.
  • Page 21 6. Using a 10mm deep-well socket, tighten the ETS module until it is snug. DO NOT OVER-TIGHTEN THE ETS MODULE. 7. Reconnect the wires of the ETS module. 8. Test the Aqua-Hot for normal operation. AC High-Limit Thermostat Introduction: The AC High-Limit thermostat serves as a safety measure in the event that the electric heating element continues to operate after the maximum operating temperature is reached.
  • Page 22 • 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 verified if the conditions listed above are not fulfilled.
  • Page 23 5. Using a ⅝” wrench or socket, remove the defective high limit thermostat from the Aqua-Hot’s boiler tank. 6. Install the replacement high-limit thermostat into the port on the Aqua-Hot’s boiler tank and finger tighten only (15 in-lbs).
  • Page 24 • 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. If any of the above conditions are not met, correct them before continuing with troubleshooting. Results of the troubleshooting procedure cannot be verified if the conditions listed above are not fulfilled.

  • Page 25: Low-Temperature Cutoff Thermostat

    2. Remove the two wires from the defective high-limit thermostat by pulling firmly on the wires. 3. Using a ⅝” wrench or socket, remove the defective high-limit thermostat from the Aqua-Hot’s boiler tank. 4. Install the replacement high-limit thermostat into the port on the Aqua-Hot’s boiler tank and finger tighten only (15 in-lbs).
  • Page 26 • There is a lack of hot water Troubleshooting Procedure: 1. Locate the Reporter and navigate to “INPUTS FROM AQUA-HOT” 2. Turn on a hot water faucet within the coach. Monitor the Reporter screen. 3. Confirm the Low Temp Sensor element displays “HOT WATER”. If it displays “INTERIOR HEAT”, locate the LTCO in the Aqua-Hot cabinet.

  • Page 27: Check Valves

    Replacing the Low-Temperature Cutoff Thermostat: 1. Disconnect the wires from the LTCO by separating the quick-disconnect terminals. 2. Remove and discard the defunct LTCO thermostat using a ⅝” wrench. 3. Position and secure the new LTCO thermostat into place. Hand tighten only to 15 in-lbs. Do NOT over-tighten. 4.
  • Page 28 • If interior heat is present after tapping the check valve, the check valve was stuck closed and no further action is needed. 3. Check the Aqua-Hot’s antifreeze and water heating solution’s ratio of water to propylene glycol. The mixture ratio should be approximately 50/50. If the solution is comprised fully of antifreeze (100%), the check valves will continue to stick.
  • Page 29 Replacing the Check Valve: 1. Ensure that the Aqua-Hot has been completely shut down and that all power sources have been disconnected. Be sure the boiler tank has adequately cooled. 2. Drain the antifreeze and water heating solution from the boiler tank using the drain valve.
  • Page 30 Tempering Valve Introduction: The tempering valve for the Aqua-Hot mixes the heated domestic water from the boiler tank with cold domestic water from the coach’s fresh water tank to reduce the risk of scalding. 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: •...
  • Page 31 5. Remove the pressure relief valve assembly from the tempering valve assembly as the tempering valve cannot be removed from the Aqua-Hot with the pressure relief valve still attached. 6. Using a back-up wrench, unscrew the tempering valve from the Aqua-Hot. 7. Remove the brass fittings from the defective tempering valve.

  • Page 32: Circulation Pumps

    10. Install the replacement tempering valve onto the Aqua-Hot using a back-up wrench to tighten. 11. Install the pressure relief valve onto the replacement tempering valve. 12. Reconnect the PEX tube and fittings to the tempering valve and the Aqua-Hot. Be sure to inspect the rubber seals and replace if necessary.
  • Page 33 Troubleshooting Procedure: 1. Verify the Low Temp Cutoff (LTCO) is showing on the Reporter, as it will be whenever the boiler tank is at operating temperature and domestic hot water is not being used. 2. Turn on the interior room thermostat corresponding to the circulation pump not operating (heating zones 1 & 5 operate with pump #1, and heating zones 2, 3, &...
  • Page 34 4. If the pump does not operate after testing, use a voltmeter to check for 12V DC power at the Reporter on J2 (pin # will depend on which pump is faulty - refer to the schematic on page 98). https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu…...
  • Page 35 Replacement Procedure 1. Ensure that the Aqua-Hot has been completely shut down and that all power sources have been disconnected. Be sure the boiler tank has adequately cooled down. 2. Drain the antifreeze and water heating solution from the boiler tank using the drain valve.
  • Page 36 Introduction: The stir pump circulates the antifreeze and water heating solution within the Aqua-Hot’s boiler tank in order to ensure even heating of the solution. To accomplish this, the stir pump draws the solution from the bottom of the tank and immediately deposits it back into the top of the tank.
  • Page 37 • If there is voltage, follow the steps to replace the stir pump. Replacement Procedure 1. Ensure that the Aqua-Hot has been completely shut down and that all power sources have been disconnected. Be sure the boiler tank has adequately cooled down.

  • Page 38: Engine Preheat Pump

    10. Refill the boiler tank with the antifreeze and water heating solution previously drained. Engine Preheat Pump Introduction: The Engine Preheat circulation pump draws the cold antifreeze and water heating solution from the motor home’s engine and then transports it through the Engine Preheat heat exchanger that is located inside the boiler tank. Troubleshoot the Engine Preheat pump if the pump is not operating, the Engine Preheat switch is on, Pump 4 is showing ON on the Reporter, and the “Low Temp Cutoff”...
  • Page 39 Replacement Procedure 1. Ensure that the Aqua-Hot has been completely shut down and all power sources have been disconnected. Make sure the heater is adequately cooled. 2. Using hose pinch off pliers, clamp both hoses attached to the engine preheat pump closed.
  • Page 40 AC Electric Element Introduction: The electric heating element uses AC power as an alternate power source for heating the Aqua-Hot’s boiler tank. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 41 • 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 verified if the conditions listed above are not fulfilled.
  • Page 42 4. Verify the Reporter is sending 12V DC to the AC relay by going to the TESTING page and see if the AC relay makes a “click” sound. The AC electric relay should let out an audible click from within the Aqua-Hot cabinet •...
  • Page 43 9.5 ohms. If not, follow the replacement procedure to replace the element. Replacement Procedure: 1. Ensure that the Aqua-Hot has been completely shut down and that all power sources have been disconnected. Make sure the boiler tank is adequately cooled.
  • Page 44 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 45 • 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 verified if the conditions listed above are not fulfilled.
  • Page 46 Replacement Procedure: 1. Ensure that the Aqua-Hot has been completely shut down and all power sources have been disconnected. 2. Make sure the motor home is not connected to shore power and the generator is not connected during this procedure.
  • Page 47 Introduction: The Aqua-Hot Reporter is a new generation of command and control module which manages all functions of the Aqua- Hot from start-up to shutdown. The previously used electronic control board has been retired on new units in favor of the Reporter.
  • Page 48 Minimum Voltage........11.0V DC Maximum Voltage........15.0 V DC Minimum Current........75mA Maximum Current........15A Please note that the minimum current rating is the minimum requirement for what will operate the Reporter. Operating at this current rating will not provide sufficient power to any components dependent upon the Reporter. Input Load currents •...
  • Page 49 Replacement Procedure: 1. Ensure that the Aqua-Hot has been completely shut down and that all power sources have been disconnected. 2. Remove the four screws that are securing the Reporter. 3. Disconnect the positive and ground wires from the back of the Reporter.
  • Page 50 8. Reinstall the replacement Reporter and secure with the four screws previously removed. 9. Ensure that all electrical connections are made with the Aqua-Hot and the onboard RV-C system (if applicable) and that power is supplied to the new Reporter.
  • Page 51 The RESET button shown above on the Reporter fault screen can be used to reset the Reporter after a component has been changed or modified. Some components will require a full power-cycle in order to fully reset the Aqua-Hot system.
  • Page 52 Low-Level Cut Off Aqua-Hot units require a minimum amount of antifreeze in order to function correctly. Keep in mind that the exact fluid volume may differ depending on the layout of your coach. If the heater drops below the minimum fill level as indicated on the expansion bottle, the Reporter will shut down all fans, pumps, and heat sources until the unit has been refilled and the Reporter has been reset.
  • Page 53 During this time, inputs from the control thermostat are ignored to allow the test to take place. Do NOT activate the burner heat test without allowing the unit to cool. Not doing so could complicate further diagnosis and may cause irreparable damage to the Aqua-Hot. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu…...

  • Page 54: Manual Mode

    The “DIAG” tab of the Reporter allows the user or technician to access input and output information to record communication information within the Aqua-Hot heater, and between the heater and the coach. This tab is read-only and will not allow the manipulation of the elements listed. There are four screens maintained under this tab: Inputs from Coach, Outputs to Coach, Inputs from Aqua-Hot, and Outputs to Aqua-Hot.
  • Page 55 Introduction: The Aqua-Hot’s diesel burner is a device that ignites a mixture of diesel fuel and air within a controlled setting to serve as a heat source. The flame is established in a combustion chamber within the Aqua-Hot’s boiler tank, and the heat from the flame is transferred to the antifreeze and water heating solution where it can be used for each system of the Aqua- Hot - domestic hot water, interior heat, and engine preheat.
  • Page 56 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 57 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 58 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 59 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 60 Diesel Burner Operation https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 61 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 62 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 63 Detaching the Burner Instructions for Detaching the Diesel Burner Step 1: Turn off the diesel switch Light on the interior switch panel should turn OFF when switch is turned to OFF. Or the burner status should show OFF on the coach interior control panel. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu…...
  • Page 64 Step 4: Remove the fuel lines from the Aqua-Hot • Locate where the fuel lines on the diesel burner connect to the Aqua-Hot bulkhead fittings. • Using a 7/16” wrench, loosen the nuts securing each fuel line to the Aqua-Hot.
  • Page 65 Step 5: Remove the Diesel Burner from the Aqua-Hot The diesel burner is secured to the Aqua-Hot with two nuts that can be loosened, and swung out of the way by using a 10mm socket wrench with a 10” long extension.
  • Page 66 Reattaching the Diesel Burner to the Aqua-Hot Step 1: Reattach the Diesel Burner to the Aqua-Hot The diesel burner is secured to the Aqua-Hot with two eye-bolt nuts that can be swung into place, after the diesel burner has been properly aligned and set in place.
  • Page 67 Align the fuel lines on the diesel burner with the fittings on the Aqua-Hot, and using a 7/16” wrench, tighten down both the supply and return fuel fittings. Step 3: Reconnect the Controller and Mount Locate the diesel burner’s Controller and connect both plugs that were previously disconnected.

  • Page 68: Burner Components

    Burner Components Diesel Burner Motor The diesel burner motor drives the combustion air blower and the fuel pump. In order to perform the following procedures, it may necessary to detach the diesel burner head. Troubleshooting Procedure: https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 69 1. Locate the diesel burner controller’s C-plug and insert the probes of a DC voltmeter into the C-2 (+) and the C-5 (-) locations. • Turn the burner switch ON and verify the burner status and heating status are showing ON, on the Reporter. •...
  • Page 70 • Using a voltmeter, check for 12V DC on the back of the Reporter (wire #20). If no power is present, verify the Reporter is receiving power and there are no faults showing. • If the Reporter does not have 12V DC power at the Board Power pin, the Reporter will have to be replaced. RPM Test: 1.
  • Page 71 5. Place a few wraps of black electrical tape around the clutch halves, and then place a small piece of reflective tape over the black tape. 6. Disconnect the motor’s black (+) and brown (-) wires from the C-plug harness’ black (+) and brown (-) wires. 7.
  • Page 72 Motor Replacement Procedure: 1. Follow the directions for detaching the diesel burner. 2. Remove the four ignition coil screws that secure the ignition coil to the protection cap. Lift the ignition coil to disconnect its wires from the C-plug harness prior to removing. Remove the protection cap from the diesel burner so that the motor clutch halves are exposed.

  • Page 73: Flame Sensor

    Flame Sensor The flame sensor is a photo resistive device which supplies the diesel burner’s controller with a DC voltage signal when it detects a flame. When the flame sensor senses the light of the flame, it will shut the ignition coil off, and send a signal to the Controller indicating that everything is working properly.
  • Page 74 3. Connect the flame sensor’s green and blue wires to an ohmmeter. 4. Check resistance by placing a shop rag over the flame sensor’s glass surface, to simulate a no-flame condition. Remove the rag and expose to a light source to simulate a flame condition. 5.

  • Page 75: Ignition Electrodes

    3. Slide the tab of the new flame sensor into the provided slot in the photo disc and secure in place with the screw. 4. Connect the flame sensor’s green wire to the green C-plug harness wire (pin 6), and connect the blue wire to the C-plug harness’...
  • Page 76 Ignition Electrode Adjustment Procedure: 1. Follow the directions for detaching/reattaching the diesel burner. 2. Using a 10mm socket, lightly loosen the retaining clamp bolt. 3. Place the electrode adjustment gauge on the fuel nozzle manifold hex making sure the gauge is pushed all the way down until it rests on the tip of the nozzle.

  • Page 77: Ignition Coil

    Ignition Coil The diesel burner’s ignition coil produces a high voltage ignition spark (approximately 8000 volts), which is released across the metal tips on the ignition electrodes during the initial diesel burner start up. Use extreme care when testing the ignition coil, as a High Voltage Shock may result. Component Test: 1.

  • Page 78: Fuel Nozzle

    Replacement Procedure: 1. Disconnect the ignition cables from the ignition electrodes. Remove the four ignition coil screws that secure the ignition coil to the protection cap. Lift the ignition coil and disconnect its wires from the C-plug harness wires, prior to removing.
  • Page 79 • Install rubber fuel lines on both the supply and return fuel pipes, and install the other end of the rubber fuel lines into an adequate supply of diesel fuel. 3. Remove both the ignition cables from the ignition electrodes, or connect a jumper wire (with alligator clips) across the metal tips of the electrodes.

  • Page 80: Fuel Solenoid

    recommended annually. Fuel Nozzle Replacement Procedure: 1. Use a ¾” wrench to hold the fuel nozzle stand hex while loosing the fuel nozzle with a ⅝” wrench and remove as shown in Figure 110. 2. When replacing the fuel nozzle, be sure to tighten the nozzle, loosen it a ¼ turn, and then firmly re-tighten. This will establish a seated fit and avoid any leaks.

  • Page 81: Fuel Pump

    Fuel Solenoid Replacement Procedure: 1. Disconnect the C-plug harness’ violet (+) and brown (-) wires from the fuel solenoid. 2. Using a 8mm wrench, remove the lock nut and flat washer from the end of the fuel solenoid shaft and then pull the fuel solenoid away from the nozzle stand approximately ½”.
  • Page 82 7. If fuel does flow through the fuel pump when ran off an external source, inspect the following in the coach: • Check the motor home fuel tank for diesel fuel. If the fuel level is below ¼, the Aqua-Hot diesel burner will not operate.
  • Page 83 teeth of the nylon drive gear with white lithium grease (IsoFlex LDS-18 is recommended). 7. Fit the nozzle stand plate inside the cast-aluminum blower casing and secure in place with the four nozzle stand plate screws. Install the grommets on the fuel return and supply banjo pipes and secure the pipes to the fuel pump with the new banjo bolts and gasket rings.
  • Page 84 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 85 Bearings The bearings support the combustion air blower’s shaft and allows the blower to turn smoothly. Bearings Test: 1. In order to perform the following procedure, it is necessary to detach and reattach the diesel burner head. Be sure to review the detaching and reattaching section for detaching and reattaching instructions. 2.
  • Page 86 disconnect its black (+) and brown (-) wires from the C-plug harness wires, prior to removing. Remove the protection cap from the diesel burner so that the motor and clutch halves are exposed. 5. Remove the three hex head screws that secure the motor and motor flange to the blower housing. Remove the motor and flange assembly along with the clutch halves.
  • Page 87 16. Reinstall the protection cap. Reconnect the black (+) and brown (-) wires of the ignition coil to the C-plug harness’ yellow (+) and brown (-) wires. Reinstall the ignition coil and secure to the protection cap with the four ignition coil screws.

  • Page 88: Diesel Burner Controller

    plate screws. Reattach the fuel supply and return lines to the diesel-burner head. 18. Follow the instructions for reattaching the diesel burner, in the detaching/reattaching section in this manual. Diesel Burner Controller The diesel burner controller operates all the components of the diesel burner head and safely shuts the heater OFF in the event of an overheat, flame-out, and low voltage condition.
  • Page 89 Component Test: The following conditions must exist prior to performing the following diesel burner controller circuit tests. If one of the conditions below does not exist, please contact Technical Support at 574-247-9235, Option 1, for assistance. Condition 1: A battery voltage level between 11.6-14 Volts DC must be present at the diesel burner controller during all testing. It may be necessary to perform a voltage check to ensure that this condition exists.
  • Page 90 Locate the diesel-burner controller’s B-plug and C-plug. Insert the probes of a DC voltmeter into the C-1 (+) and B-2 (-) locations and turn the diesel switch ON. If a voltage reading does not register on the voltmeter, the diesel-burner controller must be replaced.

  • Page 91: Troubleshooting

    18-25 seconds after the initial start-up, the diesel-burner controller must be replaced. Replacement Procedure: 1. Disconnect the Aqua-Hot from any and all power sources. 2. Remove the B-plug and C-plug from the controller. Gently slide out the controller from the side of the diesel burner.
  • Page 92 • Impeller Fan Not Gapped Properly – The impeller needs to be gapped at .018-.020, or tighten fan down until it rubs, back it off ¼ turn. If the Aqua-Hot is Producing Blue/White Smoke: 1. If the Heater smokes on start up or shut down: •...
  • Page 93 If one of the Aqua-Hot Heating Zones will not get hot: 1. General Issues: • Diesel/Electric not operating (coolant is cold) • Heater is not up to operating temperature • Interior Zone Thermostat is not calling for heat • Zone Circulation Pump Not operating •...
  • Page 94 ◦ Hold onto both upper and lower hose to make sure both get hot. If the Antifreeze is Leaking: Inspect the following components on the Aqua-Hot system for leaks: On the Front Side of the Aqua-Hot: 1. Fluid Level Sensor •...

  • Page 95: Wire Gauge Information

    • For example, the 450D heater with six Cozy heat exchangers with the Reporter placed 15 feet from the vehicle’s battery would require an 8-gauge wire.

  • Page 96: Fuel Pressure

    Fuel Pressure Instructions for Checking Fuel Pressure: Step 1: Remove the diesel burner Refer to the section on detaching the diesel burner. Step 2: Install the fuel line bypass fittings onto the diesel burner. 1. Locate the ¼” fuel tube unions on the bottom side of the diesel burner. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu…...
  • Page 97 2. Using a 13mm and a 9/16” wrench, remove the steel fuel lines from the diesel burner. 3. Using a 13mm and a 9/16” wrench, install the fuel bypass fittings onto the diesel burner. Step 3: Install the fuel pressure gauge 1.
  • Page 98 2. Using a ⅝” and ¾” wrench, install the fuel pressure gauge. Step 4: Running burner off an external fuel source 1. Using an external fuel source and rubber fuel lines, hook the burner supply and return fuel lines up to run off the external fuel source.
  • Page 99 2. Turn the diesel burner ON, either on the switch panel or the coach control panel. A pressure will register on the fuel pressure gauge once the fuel solenoid opens (after approximately 10-20 seconds). Instructions for Adjusting Fuel Pressure: Step 1: Follow the directions for Adjusting the Fuel Pressure 1.
  • Page 100 2. Turn the diesel burner ON, either on the switch panel or the coach control panel. A pressure will register on the fuel pressure gauge once the fuel solenoid opens (after approximately 10-20 seconds). Step 2: Adjust the Fuel Pressure to 145 PSI 1.

  • Page 101: Extreme Cold Weather Operation

    Extreme Cold Weather Operation 120V AC Electric Element Please note that the 120V AC Electric Heating Element is the Aqua-Hot’s secondary heat source for heating both the interior and/or the domestic hot water during low heating demand situations (such as when moderate ambient temperatures exist and/or when there is a low demand for domestic hot water).
  • Page 102 2. Diesel burner operating properly 3. Antifreeze concentration in the boiler tank must be between 30-50% 4. Heating system must be properly installed according to the 450D Installation manual • At least 5 heat exchangers installed in the interior of the coach •...
  • Page 103 The level of the antifreeze and water heating solution within the expansion tank should only be checked when the Aqua-Hot is at maximum operating temperature. If additional antifreeze and water heating solution is required, fill the expansion tank to the “HOT” level mark. Reference Figure 140. Be sure to reference page 8 for the type of antifreeze and heating solution.
  • Page 104 Annual Maintenance: To keep the Aqua-Hot running smoothly, it is recommended to have the diesel burner tuned up annually or after the coach has been stored unused for a long period of time. A tune-up should consist of a new fuel nozzle and fuel filter, along with a thorough cleaning of the combustion chamber.
  • Page 105 Aqua-Hot Maintenance Procedure Step 1: Test Run the Diesel Burner 1. Turn the diesel burner ON, either on the interior switch panel or coach control panel. 2. After the diesel burner has ignited, inspect the exhaust for smoke. 3. Shut the diesel burner off and wait for unit to completely shut down. Figure 143 Step 2: Replace the Fuel Filter https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu…...
  • Page 106 2. Using a 7/16” wrench, loosen the nuts securing each fuel line to the Aqua-Hot. 3. The diesel burner is secured to the Aqua-Hot with two nuts that can be loosened and swung out of the way by using a 10mm socket wrench with a 10 inch long extension.
  • Page 107 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 108 4. Carefully pull the diesel burner away from the Aqua-Hot 4 - 5 inches before rotating the burner, then remove completely as shown in Figure 150. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 109 2. Once the combustion chamber has been removed, use a long handled wire brush, and brush the heat transfer tabs to loosen soot deposits. Failure to do so will reduce the Aqua-Hot’s heat transfer capabilities. 3. Inspect the Combustion Chamber assembly and Air Swirler for damage or signs of warping.
  • Page 110 Inspect the following: 1. Electrodes • Damaged • Improperly adjusted 2. Fuel Pump • Leaks 3. Photo Disc • Warped • Bent 4. Harness & Ignition Coil Wires • Cracked or bare wires • Hard or brittle wires 5. Flame Sensor •...
  • Page 111 • Rubber has been cut out • Right & left properly positioned 7. Broken or cracked “Ears” • Due to over-tightening of eye-bolts Step 8: Clean Ignition Electrodes and Flame Sensor 1. Ignition Electrodes • Polish away any carbon deposits that may have baked onto the metal tips of the ignition electrodes with a coarse sponge.
  • Page 112 Step 10: Adjust Ignition Electrodes 1. Using a 10mm socket, slightly loosen the retaining clamp bolt. 2. Place the electrode adjustment gauge on the nozzle manifold hex and insert the metal tips of the ignition electrodes into the appropriate notches of the electrode adjustment gauge. 3.
  • Page 113 Step 13: Reconnect the Fuel Lines 1. Align the fuel lines on the diesel burner with the fittings on the Aqua-Hot. Using a 7/16” wrench, tighten down both the supply and return fuel fittings. Step 14: Plug in the Diesel Burner’s Controller and Mount 1.
  • Page 114 Step 15: Reinstall the Aqua-Hot’s Access Cover 1. Reinstall the Aqua-Hot’s access cover. 2. Securely tighten the three bolts securing the access cover in place. Step 16: Test for Normal Operation 1. Turn the diesel burner ON and allow the diesel burner to run for a complete cycle, until it shuts off on its own.

  • Page 115: Filling The Aqua-Hot

    Aqua-Hot system by creating leaks that cannot be repaired. This damage is not covered by the Aqua-Hot warranty. If disinfecting the hot water system, be sure to follow NFPA 1192 Standard on Recreational Vehicles “Instructions for Disinfection of Potable Water Systems” or any other applicable local standards for Potable Water Systems.
  • Page 116 -A bucket or pale 2. Fill the bucket with the heating solution. Ensure the fluid expansion tank is connected to its port on the Aqua-Hot. 3. Open the Aqua-Hot’s drain valve located at the front of the heater. Reference Figure 173.
  • Page 117 Purge Procedure: 1. Locate the fluid expansion tank of the Aqua-Hot. As any air is purged, it will exit through to this expansion tank. 2. Locate a gallon of glycol antifreeze. This will be used to top-off the fluid expansion bottle as air is purged from the system.
  • Page 118 1. Connect a piece of ½” PEX-type tubing or rubber hose to the drain valve. This piece should be long enough to transport the antifreeze and water heating solution from the Aqua-Hot to a bucket. 2. Open the Aqua-Hot’s drain valve located at the front of the heater. See Figure 173. https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu…...

  • Page 119: System Schematics

    System Schematics https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 120 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...
  • Page 121 https://tiffin-motor-homes-prod.mindtouch.us/Technical_Support/Class_A/2024/Allegro_Bus/35_CP/Component_Manuals/Aqu… Updated: Fri, 21 Jun 2024 03:21:17 GMT Powered by...

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