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Old 10-17-2013, 09:42 AM   #1
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Join Date: Oct 2013
Location: KS
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Hydro-Hot/Aqua-Hot Question

I have read all coach manuals and searched the internet and within forums but have not discovered answers for the following:
We will not take our new-to-us 2004 CC Intrigue from cold climate to warmer South until mid-winter so have winterized the coach. This brings a question of the Hydro-Hot system for when we leave, with empty water tanks.
In my documentation it states that Hydro-Hot's primary purpose is domestic hot water and coach heat is secondary. I do not understand that statement, and have further concern of detrimental effect of running the system to heat the coach when departing, since there will be no water in the domestic water lines.

I understand the system has 3 pumps, for the two heating zones plus engine preheat, and zone thermostat will not start the pumps and exchanger fans until the boiler antifreeze reaches a certain temperature.

Now, help me understand how the domestic heated water works. Assumption is the domestic water has an exchanger within the Hydro-Hot and hot tap water flows from this exchanger.

If domestic hot water is "primary", is the thermostat that allows coach heat to operate within the domestic water exchanger or does it monitor the boiler antifreeze, or both?

If thermostat is just within the boiler, how does this determine hot water is primary and coach heat secondary?

If the thermostat is within domestic water exchanger, with no water, will it allow coach heat to work?

Will the domestic exchanger overheat and be damaged due to it not containing water?

Thanks for all input.

Bob & Rosalee
2004 CC Intrique 36'
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Old 10-17-2013, 10:32 AM   #2
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hydra hot

It's my understanding that the hydra hot that is diesel fired unit that heats a volume of water and antifreeze. This heated liquid is circulated by the pumps controlled by the thermostats in the various areas of the mh. according to temp set point. All these pumps are behind a panel that comes off for service, and you will also find a small burner (that looks like the larger ones you find on a home furnace), various relays and the wires coming from your thermostats, basically all the control apparatus.

So in my unit for heat this heated fluid is circulated to all areas of the mh for heat--it's not ordinary water- it-s a mixture 50/50 (should be good way down below zero) --no need to drain this unless you're planning to change it out. The need for that is not to often if at all.

Now for domestic hot water your hydra hot unit has a loop of heat exchange tubing in this reservoir (the big stainless steel box ) in one of your bay's. Sinnce the hydra hot only heats up to about 140 degrees, if you happen to empty your hot water line, it will not harm your aqua hot if you were the turn in on to warm up your coach with out any water in your domestic system. To repeat, the hot water isn't directly heated by the flame from the burner, the antifreeze mixture is and is not drained when you drain you domestic water system.

Some day when You will when get into it a bit more, you will find that there is a way to check the level of this heated mixture and probably should check it once at least a year---however they rarely will need anything added and you might own and operate a system for years with out knowing to do anything to it until one day it might not work for some reason.

Hope this helps


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Old 10-18-2013, 10:12 AM   #3
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I think Loren covered it quite well.
Here is a link to a web site specifically relating to HydroHot/AquaHot systems...
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Old 10-18-2013, 11:33 AM   #4
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While I understand how the AH system works, I did wonder if it was OK to operate the system for heating the coach even after the domestic hot water system was drained and winterized. However, my AH manual says the domestic hot water portion must be winterized with the pink RV antifreeze (and not merely blown out with air) to ensure it will not freeze. So, if the domestic water system has RV antifreeze in it, I would think it would be OK to use the AH for heating the interior of the coach if needed.

That said, if you live in the north and are heading south, why would you not just add some water to your holding tank, use the pump to fill your water lines and just hit the road south? If you are living in the coach while traveling you will be using the AH for heat, mostly likely, so nothing is going to freeze while you travel.
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Old 10-18-2013, 03:25 PM   #5
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That is exactly what we are doing as well. Our winterizing amounts to traveling further south ahead of the really cold weather. We will settle in central Fl. for the winter.

While traveling you will be using the heating system. Why would you bother winterizing the water system. It will not get cold enough to freeze.

The other consideration is these coaches do funnel some of the heat to the basement areas where there is water when the basement gets cold enough.
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Old 10-18-2013, 03:50 PM   #6
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We put our A/H to the maximum test last Jan. When we left northern Illinois with half a tank of water, it was 5 below zero, stayed around single digits most of the day. The coach was warm, wet bay did not freeze. I was skeptical to say the least, but I'm sold on Aqua Hot
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Old 10-18-2013, 08:15 PM   #7
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Thanks for all your replies.
I was not familiar with the Hydro-Hot forum site, thanks John.
Roger Berke on that forum replied to my inquiry and advises that yes, the coach heat is locked out (zone pumps will not operate) until boiler temp reaches setpoint, and then will lock out any time you demand heavy use of domestic hot water (thermostat in unit on cold water input drops to a setpoint). This answers my question on coach heat being secondary, and how that works.
Seems all Hydro-Hot documentation I came across makes the statement about primary/secondary while diagrams show everything in parallel without explaining the domestic water thermostat and its control over coach heating. Roger did confirm what others have stated, that the unit will work just fine while winterized, the thermostat will eventually allow coach heat to kick in, even with no water in system.
I don't believe I want to go thru de-winterizing in sub-zero weather, maybe down the road at our first stop when temps reach a balmy mid-teens or so.
Thanks again for everyone's input.

Bob & Rosalee
2004 CC Intrique 36'
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