Author Topic: Aqua hot  (Read 1281 times)

Kent Morrison

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Aqua hot
« on: February 13, 2020, 06:30:16 PM »
When running my Aqua hot system I am only getting heat in one zone. The other zone only blows cold air.  I checked the system for faults and there are none.  I only have green lights.  Does anyone have any ideas where I should look?
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David T. Richelderfer

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Re: Aqua hot
« Reply #1 on: February 13, 2020, 07:45:59 PM »
The pump for the cold zone is likely not pumping.  There are numerous threads here on the forum discussing remedies to your symptoms.  Try searching for them.  As I recall, tapping on the pumps, or at least the pump that is not pumping, is a possible fix.
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Lee Welbanks

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Re: Aqua hot
« Reply #2 on: February 13, 2020, 11:58:30 PM »
Seem to me I remember posts in here that talk about tapping the check valve for that cold zone, they get stuck sometimes.
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Gerald Farris

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Re: Aqua hot
« Reply #3 on: February 14, 2020, 03:39:38 PM »
As others have said, the pump check valves on some AquaHot systems are prone to sticking, so locate the check valve just after the pump in each circuit and tap on the check valve using a screw driver handle or something similar with the system running and all zones calling for heat. if the hose does not get hot coming out of each pump after this, you need to determine if there is 12 volts to each pump and determine if the pump is running. Some years of AquaHot production had magnetic drive pump impellers that are very prone to failure, and since you did not say what year coach you have, I do not know if that might be your problem.

The best option is to go to the AquaHot website, and download the maintenance manual for your model unit. The troubleshooting area of the manual will give instruction for everything that you need to do to keep your AquaHot running from yearly services to needed repairs.

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Kent Morrison

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Re: Aqua hot
« Reply #4 on: February 15, 2020, 11:50:33 PM »
Thanks everyone for the ideas. In answer to year of my coach it is a 2005 Monterey. I am totally new to this type of system.  Are the pumps and check valves located inside the gray box in the basement bin next to the water tank.  I see there are two hoses going in the gray box. One is hot the other is cold.  I have not opened the box to see what is inside.
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Steve Huber Co-Admin

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Re: Aqua hot
« Reply #5 on: February 16, 2020, 12:20:34 AM »
The Aqua Hot (or Hydro Hot) is the grey box in one of the basement bays. Most have a couple of screws holding the cover on. Some coaches have access holes for the 2 screws at the bottom of the cover.
Here is the Aqua Hot Manual library.  Download the Service and Owner manuals for your model.
If one hose is hot and the other cold while the thermostats are calling for heat, probably that check valve is stuck, the stir pump (round shiny unit) is not getting 12v or the pump has failed as Gerald noted in his post.
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Bill Sprague

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Re: Aqua hot
« Reply #6 on: February 16, 2020, 04:28:04 PM »

We had a '04 Monterey for a dozen years.  I got to know the HydroHot quite well!  We loved our Monterey in every way but one and it was the HydroHot.  When it worked it was spectacular.  It even kept us toasty in a South Dakota blizzard with below zero temperatures.   When it broke, it was always confusing and sometimes expensive.   

If you are new to Hydro/AquaHots and ever near cold weather, be sure you know how to winterize it.  If it ever freezes, the cost to you will be HUGE.

There are three pumps in there.   Two circulate the heated coolant to the radiators throughout the rig.  One does the front and one does the back.  Both have check valves that point straight up from the pump and go vertically outside the box.   In normal operation, both of the tubes coming out of the box should feel hot.   

The third pump is called the stir pump.  It is on the right.  The HydroHot is a smaller version of the AquaHot and needs the stir pump to circulate the coolant in the tank for consistent hot water.  It has an odd magnetic drive that gradually fails over time.   It is very hard to trouble shoot because the magnetic drive can keep it "stirring" but only marginally.  If hot water is inconsistent, suspect the stir pump. 
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Stan Simpson

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Re: Aqua hot
« Reply #7 on: February 16, 2020, 06:04:20 PM »
We have the same coach. The Hydro Hot is the same thing as an Aqua Hot. Vehicle Systems, the manufacturer, changed the name a few years back to sound fancier. Other than that, and the size of the tank, they are the same components, and system.

If you are not familiar with how it operates, there are some good pictures with flow charts on the website, We have had our Monterey for 8 years, and it has been the single steepest learning curve, among many.

Even if you don't use it like a full timer, it should be serviced once a year by yourself when you become an expert, or a certified aqua hot tech. Especially, change the nozzle, change the diesel fuel filter, and clean the combustion chamber.

To access the inside of the metal box (it has a double hinged lid) get on your hands and knees and look under the bay door. You should see two black rubber plugs. Pry them off, and use a long phillips screw driver to un-screw the screws holding the lid down. Over time, when its time to put them back on, you will learn to use a magnetized screw driver to hold the screws in place while you stick the screw driver back through the holes under the bay door.

Bill Sprague is absolutely right. You must winterize if you are going to store the coach in cold weather. Temporarily in cold weather is okay if the ambient temps rise above freezing during the day. Your coach has a thermostat that will provide heat to your water bay, and the aqua hot components when the temperature gets below a pre-set threshold, usually around 43 degrees F. For it to kick on, the diesel burn switch under the kitchen counter must be on.

Good luck. Its an awesome system once you learn it relatively well.
« Last Edit: February 16, 2020, 06:10:52 PM by Stan Simpson »
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