American Coach: Aqua Hot won't heat the water

[Dezignr Gal]

Thank you Cat320, alank, Archer and n2zon for the add'l info and clarification.

That makes sense about the AH system yielding to generate hot water over heating temporarily.

We are also aware that the AH won't work if the diesel gauge is less than 1/4. We try to maintain at least a 1/2 tank of fuel when we stop and were just a tad below 1/2, so we figured that shouldn't have been the culprit.

Since all of this is brand new to me and not necessarily to my husband (who grew up with parents who had motor coaches in their lifetime many years ago), I may not quite have the correct vernacular down pat as to what, what's called. We were 2-1/2 days without hot water and inefficient heat pumping more cold air through the top vents than warm with below freezing temps at night, that we were trying to understand what systems were working so as how to explain the issues we were experiencing to a technician. It was near the undoing of my lack of patience in not being able to keep warm, do dishes or take a nice warm shower. In other words, you don't know what you don't yet know.

Thank you all again for taking the interest and time to weigh in on this issue and help us to resolve!!! So grateful!

Margaret
2022 American Dream 45A

[dano1955]

Margeret, just FYI, heat pumps will not work efficiently when temperatures are at or below about 40 degrees F.

They will continue to blow air, but the air will not get "warm", and you should turn them off and when you should use the gas/LP furnace to heat the interior of your motorhome.

[777 Driver]

For a better understanding of how your AquaHot provides both heat and hot water, perhaps a cutaway view might be helpful:

CLICK IMAGE TO ENLARGE


Both the diesel burner (450D) and the electric element will heat the boiler transfer fluid that's inside the AquaHot tank. The the tank is the area outlined in the red lines. Both the burner and the electric element heat the fluid to about 195F; the diesel burner is way more powerful to heat the boiler fluid.

You can see the 'Water heating loop' that is enclosed and immersed in the boiler fluid. Any time the boiler fluid is heated, the water in the water heating loop will be heated. There are also circulation pumps that will pump heated boiler fluid through tubes to the various heat exchangers. Those heat exchangers have electric fans that push ambient air from inside your coach over the heat exchangers where the air is warmed and pushed out their vents to heat the inside of the coach. Those circulation pumps also push hot boiler fluid thru a loop imbedded in the floor under the tile to provide floor heat.

IF either the diesel burner or the electric element are working, the boiler fluid in the tank will be heated to ~195F. At that point, the electric element and the diesel burner turn off until the boiler fluid cools to ~175F. At that point, the electric element and/or the diesel burner will turn back o to reheat the boiler fluid to ~195F. The water inside the water heating loop will be heated to somewhere between ~195F and ~175F.

Once you turn on a hot water faucet, cold water will be pushed into that water heating loop as the hot water flows to the faucet. As more of that cold water gets pushed into the water heating loop, the boiler fluid will start to cool. Until the electric element or diesel burner starts to reheat the boiler fluid, over a relatively short period of time, the boiler fluid will cool to a point where the electric element and/or the diesel burner will turn back on to reheat the boiler fluid to ~195F. The diesel burner pushes much, much more heat back into the boiler fluid than the electric element.

If you've selected coach heat from the AquaHot through your thermostat, the hot boiler fluid in the tank will be pumped to the heat exchangers and/or the floor heat, further cooling the boiler fluid in the AquaHot tank.

The diesel burner pushes more than 10X the heat into the boiler fluid than the electric element. If it's very cold outside or you want a lot of hot water, you'll have much better luck using the diesel burner.

Also, when the hot water exits the AquaHot, it's about 195F (too hot for safe use), it passes through a tempering valve where cold water is mixed with the too hot water to result in safe hot water being pushed to your faucet. So, a couple of things affect the temperature of the hot water that reaches your faucet; the temperature of the boiler fluid, the temperature of the cold water that's being mixed with it, etc.

Take care,
Stu

[Cat320]

Originally Posted by dano1955

...Margeret, just FYI, heat pumps will not work efficiently when temperatures are at or below about 40 degrees F...

We never use the HP....floor heat and a couple of Lasko towers work much better. If cooler, we add the AH electric heat....if really cooler, the AH burner goes on.

[jbellarmada]

Sounds like you have it solved. One other bit of info. Our AH started having failed ignition this week as we starting prepping to leave MI for Florida. My diesel was last filled in July and thus is a summer blend. I added anti-gelling treatment and the problem was solved. Assuming your fuel was purchased recently and would be a winter blend. Just wanted to share as it could happen if you are snow birding and start with a summer fill!

[fstruys]

With my previous RV, a 1997 Monaco Windsor, we did a fair amount of winter camping; we really like going to Lake Tahoe in February! As many have found, the heat pumps no longer can provide warm air below an outdoor temperature of around 40 degrees. My solution, which provides reasonable heating capacity, was to add the electric element option to the rooftop units.

In my newer 2007 Country Coach Allure, I installed the 5700 btu electric elements to all 3 of my rooftop units. As I said, it won't keep you comfortably warm when the outdoor temps drop below freezing, but will do a pretty good job as an acceptable option when your AquaHot or propane furnace quits and you need heat.

I think I bought all 3 units from Amazon for around $150 total. They are easy to install and the rooftop unit automatically switches to the electric element, turning off the compressors, as needed, JMHO.

Felix & Becky
2007 CC Allure Sunset Bay
Vancouver, WA