Aqua Hot / Hydro Hot Common Problems


 Common Problems / Posted 4 months ago / 106 views

Hydro/Aqua Hot Problems

Updated 1/11/17

The BAC Forum contains extensive discussions on these and other hydronic heater problems, maintenance and repair. The following are some of the more common questions and solutions listed in the Forum.

Low Coolant Cutoff Alarm Indication (HHE-500-03M):

  1. Coolant level is low. Add more coolant.
  2. Tank is full of coolant. Coolant level switch or float has failed. Drain coolant from tank until level is below where switch screws into tank, replace switch and float.
  3. Switch can be bypassed by jumpering 2 pins on the control board. (15 & 16?? on this model but CHECK YOUR MANUAL to be sure).

Does my Aqua Hydro Hot / Hurricane system have to be on to keep the basement bays from freezing?

Yes. The basement bay heat exchanger is controlled by a separate button style thermostat set at 40°- 45°F. As long as the hydronic system is on in either gas or electric mode, the basement will receive heat as soon as the temperature drops below the thermostat setting. The thermostats in the living areas of the coach need not be on.

Can I adjust the thermostat setting in the basement bays?

No. The thermostat is a button thermostat. To change the temperature setting, you will need to replace the button thermostat with one set to your desired temperature. The factory installed units are set to 40°-45° F and provide the required protection.

The lights in the Gas, Electric, Preheat switches don’t illuminate.

  1. Most common cause is a bad bulb. The bulbs are reportedly replaceable but it is a very delicate operation to keep the switch from coming totally apart. A better solution is replacement of the switch. For older model Beavers, the switches are no longer available from BCS and a panel replacement is required. Another option is to mount small LEDs above the existing switches and wire them to the switch so they illuminate when the switch is on.
  2. Before pursuing the bulb/switch replacement route, check your system documentation. Some switch lamps get their power from the control board. In these cases the problem may be a bad control board or problem with the system the switch controls.

What type of anti-freeze can I use in my system?

Check your system manual. Your overflow tank may also show the correct type for your system. Systems manufactured in 2002 or earlier used Ethylene Glycol antifreeze. This is the green colored antifreeze commonly used in automobile cooling systems. Aqua/Hydro Hot units manufactured after 2002 must use Propylene Glycol (boiler) antifreeze. Per Aqua Hot; Aqua Hot serial #s: 03-725 to 03-733; 03-751; 03-761 and from 03-774 on…
Hydro-Hot Serial #s: 03-586 to 03-590: 03-590; 03-618; 03-619 and from 03-653 on…

It is red in color.  Use Camco -100° Boiler Fluid or the 32 oz concentrate.  Camco Boiler Antifreeze is available at many RV supply sources.

What is the proper mixture of Propylene Glycol and Distilled water?

The following mixtures are recommended; 1 Gallon; MSX-300-270; mix 50/50 with distilled water. The 1 Qt Concentrate; MSX- 300—275; Mix 2 parts distilled water to 1 part Antifreeze. A refractometer can be used to determine the freeze point and proper mixture. AQUA HOT states; “The propylene glycol antifreeze level of the solution in the Aqua-Hot heating system needs to fall between 35% and 50%.  DO NOT exceed 50% Propylene Glycol in an Aqua-Hot System.”

For Ethylene Glycol systems, mix 50/50 with distilled water.

Note: Over time some distilled water can evaporate, increasing the antifreeze percentage in your system. Consider using a refractometer to check the mixture percentage before adding more mixed fluid. You may need to only add distilled water.

Where are Factory Authorized Service Centers for My Aqua / Hydro Hot?


Where can I find Aqua / Hydro Hot Manuals and service information?

(The service manual for each system provides detailed and step by step troubleshooting).

Can The Aqua/Hydro Hot be operated after winterizing the coach?

Yes. The Aqua/Hydro Hot has 2 independent liquid systems; one for heating the coach and one for supplying hot water. The heating liquid (antifreeze) is in a closed system so it can be operated to supply coach heat regardless of the status of the water system. However, if you want to use the water system you will need to evacuate the pink antifreeze and refill it with water.

What can cause intermittent or variable hot water in both Diesel and Electric modes?

  1. Be sure the outside water bay hot and cold water valves that control the shower head are turned off. Turning the water flow off at the shower head will allow hot and cold water to mix through the valves.
  2. A faulty mixing valve. This valve mixes cold water with the heated water from the boiler to arrive at the desired temperature. Check your documentation for location.
  3. A faulty stir pump.
  4. Excessive water flow. For continuous heating, flow must be 1.5 GPM or less. (The coach’s internal water pump meets this requirement).

What can cause intermittent or failure of diesel burner ignition?

  1. A faulty fuel nozzle.
  2. Improperly aligned or failed igniter electrodes.
  3. A clogged fuel filter
  4. Faulty fuel pump.

No heat from 1 or more registers (heat exchangers). Hydro/Aqua Hot is running and hot water is available from faucets.

There are 2 components needed to get heat from the heat exchangers (HEx); hot antifreeze flowing through the HEx and a fan to blow heated air from the HEx into the coach interior. The fan is activated by setting a thermostat to a set point above the coach interior ambient. This causes the electronic controller to apply 12V to the fan motor through the fan speed switch. If the fan does not run, check the following;

  1. Thermostat set on Heat and above interior ambient.
  2. Verify fan speed switch(s) are set to low or high and fan doesn’t run in either position. If fan runs in one position only, the switch is probably faulty.
  3. If none of the fans run in a specific zone, e.g. Living room and Kitchen, check the Heating Zone Status indicators on the Electronic Controller panel. All should be Green if all thermostats are calling for heat. If Red, a short has occurred in that zone’s heating circuit.
  4. Verify the Low Temperature Cutoff status light on the controller is not lit. If it is lit the Low Temperature Cutoff thermostat may be faulty. See your system documentation.
  5. Remove the controller faceplate. Be sure all fan and thermostat connections are tight.
  6. If a Zone Status indicator is Red, a possible cause is a shorted fan motor. Disconnecting the fan should reset the Zone indicator. Replace motor.
  7. If 12V is present at the motor and it does not run, the motor is probably faulty.

Fans run but no heat is produced.

  1. Verify the circulation pumps are running.
  2. Verify system has antifreeze at the proper level.
  3. Check for a kinked antifreeze hose.
  4. Verify that a check valve is not plugged. The valves are located just after the circulation pumps (1 valve per pump). Often a light tap will get the valve unstuck.

Aqua/Hydro Hot maintenance videos are available on the web and in the Private BAC Members Only section of the BAC Forum.

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