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Can Aquahot be run without water in the hot water coils?


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You need to ask aqua hot whether it is OK to have the coils empty. An aqua hot rep and my service person says water lines should be filled with RV antifreeze to prevent condensation causing freezing and then busting coils. With lines full, he said there is no problem turning it on for the heat. I learned this the hard way. Other models may be different.

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I’ve run mine while winterized with antifreeze since I bought the coach in 2017.  I figure the Aquahot won’t know the difference between antifreeze and water being in the loop.  
   
I thought the Aquahot could not be run with empty water loop.  I’d like to know if it can be done, so I wouldn’t have to go through 8 gallons of antifreeze.  I could just blow the lines out with air.

Dan D.         
2012 Diplomat 43DFT

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Blowing out the lines and not adding antifreeze is not recommended because there is the possibility of some water remaining in the loops and settling at the bottom. This could get real expense real quick. 

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I have been told that the coil when blown out with air still has water sitting in the low spots which can freeze. I understand replacing a damaged coil gets into 5 figured repair bills so the antifreeze is the way to go. I don't know why you need 8 gallons through. I do my entire coach with 3-4 gallons.

Edited by erperry_44
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We have run ours with the fresh water loop "evacuated".  We have been about 50/50 on whether we use antifreeze to winterize our '06 Dynasty, with one exception.  We ALWAYS run the RV anti-freeze thru the AquaHot part of the system at the end of the process.  AquaHot and Monaco essentially say that just doing the AquaHot with air is not an option.  Once completed, enough water will flow back down to the bottom of the loops and will freeze and will cause failure and will eat up at least a hundred $100 bills!!

At least by using AntiFreeze on that portion of the plumbing only, we minimize the amount of time in the spring to get the AntiFreeze taste out of the coach's plumbing system. Also, as one of the last steps, I blow that AntiFreeze out of the low point drain, as well.  That further minimizes the concentration to deal with in the spring, and the only "liquid" remaining in the AquaHot in the spring will be the little bit of puddled AntiFreeze in the bottom of the loops instead of several feet of tubing full of the stuff.

Finally, I am relatively sure we have run our AquaHot in years past after winterizing as above.  When the boiler is heating, the zone 2 pump runs and acts as a "stir pump" to keep the boiler fluid circulating in the containment.  This keeps from having excessively hot spots near the boiler interface wall.  Personally, I would not be uncomfortable running the AquaHot for heat with the fresh water loop essentially free of liquid.

I will offer a thought and let you digest it, as I will.  If the burner is operated and at the same time zero domestic hot water is being used, the fresh water loops should reach essentially the same temperatures whether liquid is inside the loops, or not, as there would be zero cooling effect to the tubing walls from the liquid within them versus air being in them.  So my belief is that the only requirement is that as long as any traces of liquid in the bottoms of the loops be unable to freeze at the temperatures they will be exposed to, i.e. AntiFreeze, operating the unit with it "evacuated" should be fine.  As Collin Raye would say, "That's my story and I'm stickin' to it."

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