Aqua-Hot on Battery Power?

[Skinner2909]

Originally Posted by sbkahn

Can you determine whether the issue is at the thermostat or the AquaHot? Does this occur when you change the temp down-up, then down-up again? If you can make it fail consistently then you can test whether it's the thermostat or the AquaHot. Check if the Heating Status D1 light is on. What's the year, make, model of your coach? Also, you could call AquaHot in the morning, they are pretty good at diagnosing any control board issues. BTW, it could still be a power issue. FYI, I found this in the 250D manual:

Additionally, the burner switch can be used to reset a
low-voltage condition. This is accomplished by turning the
switch “OFF” for 30 seconds, and then turning it back on. This
is sometimes known as “power cycling.”

Thanks for the recommendation! I'll run through these tests this weekend and try to narrow down the root cause. This 250D is in our '22 HR Nautica 35QZ and is still under warranty until April 2024, so hopefully I'm covered in case the thermostat or control board needs to be replaced.

[WatchMeRV]

From the manual on the AquaHot site, following are the lights on the 250D relay control board:

Relay Control Board
The relay control board at use in your Aqua-Hot 250 Diesel
Series is designed to function in conjunction with the Diesel
Burner Controller to allow the heater to operate. This section
will introduce you to the basic functions of the board.
Indicator lights line the bottom of the relay control board and
are designated D1 through D6. Each of these lights indicates a
function or event that is taking place. The detailed function of
these lights will be explained on the next page.
• D1: Heating Status Light (orange)
• D2: Electric Element Power (green)
• D3: Pump Power (blue)
• D4: Low-Temperature Cutoff Status (yellow)
• D5: Burner Status (green)
• D6: Interior Zone Heating (orange)

[vito.a]

I would disconnect your house batteries from each other and the inverter/charger. Then test them individually. One bad battery can pull the voltage down under load and then the voltage readout will spring back up when the load is no longer there.

[RVFunlovers]

Sounds like you have a battery issue.
If the Aquahot works properly when plugged up then the only difference should be the DC voltage difference.

[Skinner2909]

<< Update >> So I think I've narrowed it down to a faulty control pad. All of these electrical gremlins I've been chasing have led me in so many different directions, but I've now been able to successfully replicate the problem. The issue I was having on battery powered occurred this weekend on shore power as well. 1. Set temp. 2. Aqua-Hot fires up perfect and gets to temp. 3. Aqua-Hot shuts off. 4. Temp drops below set level and "Requesting Heat" messages appears, but burner does not re-fire. What is interesting/strange is that in order to get the burner to re-fire, I don't even have to turn off the Aqua-Hot off and on again (as previously thought), all I have to do is leave the current screen on the UI of the control pad. So, if I'm on the climate control screen and go to the lights screen and back to the climate control....fires right back up! Faulty (and frustrating) control pad is all I can think of. I've got a request out to Precision Circuits Inc about a warranty replacemen, so we'll see how that goes.

[WatchMeRV]

Sounds like your close to a resolution. Precision or Rev Group may be able to assist with some troubleshooting too. Your control panel is new to me, sorry I can't be more help with that. I did look at the Precision Circuits control panel manual and it states the following. Not sure if this is helpful or not.

"Aqua-Hot 250D – There are some status messages exclusive to the 250D heating system. When hot water is being used by other systems in the RV you will see the message “Requesting Heat” instead of “Aqua-Hot On.” Some systems have a “Low Fluid” warning message for when the Aqua-Hot
system does not have enough water to heat properly."

BTW, the 250D fluid level must be a little above the low line when cold in order to operate. This is not your issue, but I would check just in case.

[saddlesore]

Originally Posted by Skinner2909

Yet another weird issue with our Aqua-Hot 250D. It will not re-fire when on battery power. This condition is ONLY present on battery power - works perfectly on the gen or shore power. Has anyone had a similar experience?? Thanks!

OK..A Question..Do You have the Electric element also "on" when running on battery? If so that could cause enough initial electrical draw to cause ignition failure due to low voltage.. Try just using the diesel burner alone.

[Skinner2909]

Originally Posted by saddlesore

OK..A Question..Do You have the Electric element also "on" when running on battery? If so that could cause enough initial electrical draw to cause ignition failure due to low voltage.. Try just using the diesel burner alone.

The electric element was off when on battery power. What you mentioned was something I had thought of also. Those electric elements use a ton of power, around 1500W I believe.

[Skinner2909]

Thanks for the reply. I'm waiting on a response from Rev Group to see how they want to handle the control panel replacement. At this point I'm very confident that's the issue. On shore power last night, woke up cold and found the Aqua-Hot blowing cold air and panel saying "Requesting Heat" (no other heat was being requested via water, washer, etc.,). From the control panel I went back to the home screen then back to the temp menu. I didn't change the temp setting at all, just toggled back and forth to the menu....fired right up in 30 seconds .

[WatchMeRV]

Please let us know what the root cause is once you figure it out. Thanks.

[RichardE]

Sounds like you are on the right track with the control panel.

I make this comment for others following this thread. Using the Aquahot diesel on 12V to heat the coach at night works, BUT it consumes a tremendous amount of amp hours. It takes 12V amps to run the motor in the burner, the motors in the circulation pumps, and the motors in the inside heat exchangers. It works but if this is a regular activity, you should ensure that you have ample battery capacity to support it.

[757driver]

Originally Posted by Skinner2909

The electric element was off when on battery power. What you mentioned was something I had thought of also. Those electric elements use a ton of power, around 1500W I believe.

The electric element on the Aquahot is AC powered. I do not know of any manufacturer that would put that load on an inverted circuit so it will not function on battery power.

[Skinner2909]

<< Update - SOLVED! >>

Defective thermostat was indeed the issue. Email to Precision Circuits Inc was quickly responded to. Technician informed me that a new S/W update was available. Warranty exchange was seamless, and a new 7" touch pad (00-10052-008) makes me a happy (and warm) camper Thanks all for the assistance!