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Last fall mine started overflowing and it water pump pressure related.  The internal coil wore thru due to age and vibration. I just bypassed the hot water coil and added a 4 gallon Bosch hot water electric tank until I could get back to my summer home/shop,  I pulled the unit this weekend and disassembled it. Thanks to it being in the middle of the coach the easiest way was to remove the cargo tray and rail then slide it out that way. took about 6 hrs to do. Mine has propane and the gas pipe running from drivers to passenger side had to be removed to clear the neck of the tank. 2 foot pipe wrench and 8 foot pipe to get the exhaust nipple out of the bottom of the tank while under the coach was the pits.

I have a 10" set of ramps that I use to get the coach up so that made a big difference, even with the air out I can still move around under pretty well.

I contacted John Carrillo  www.HeatMyRV.com , and he is rebuilding just the tank with new coils, switches and elements. I ship mine out this week if all goes well and it's about a week turn time for him once it arrives.  He can send one out and then wait for your core but I am in no hurry. His shop is right across from the Aqua hot facility in CO and he has done 100's of these tanks, even built his own coil winder to make the coils. This will end up costing about half of one from the factory if you have the means to do it. 

The engine preheat hose are hard and should be replaced, Mike(zmotorsports), over on the other site did his awhile back and it was a real pain. even thou the unit is out I still can't move the hoses in the bay due to cable ties galore so I am thinking about just routing them over the black/gray tanks and then out thru the the back wall and continue on the the back of the motor. 

Some pictures of the carnage 🙂

 

 

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Yeah, tons of fun pulling it out. Good job! I feel your back pain. Luckily, our fresh water loop is external so no need to cut the tank. My problem ended up being a coolant leak by the exhaust pipe, a pin hole. Later, the brass filler neck cracked and separated from the tank. It is just a brass piece soldered to steel pipe... I converted it to non-pressurized system with a nice test plug in place of the cap, used for radiator testing. It overflows into the overflow tank just like it always has, no difference. Since the thermostats will not let it actually reach boiling temperature, it works great ever since. There are ways to repair/replace the neck but it's just much easier this way and functions exactly the same.

Pics for comparison:

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I am sure the internal coil provides better heat transfer but ours is plenty hot the way it is also. No complaints.

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I hope I don't get scolded again but I had a 35,000 Suburban furnace loud and obnoxious and the fan motor stopped so I replaced it with a 25,000 unit thinking it may be quieter which it isn't. After seeing the complexity of your heating units it seems extreme to replace these for a twenty year old coach. I had always heard they are the best heating system but repairs seem to be intense. What is your overall opinion of them? My unit cost me $450 to replace. Is the Aqua-hot worth the price? Thanks for posting the pictures.

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I think the AH is awesome. Hot water on demand, house heat through registers in 3 separate zones, engine preheat if needed and free hot water after a drive from engine heat. Like anything, parts break and wear out. Maintenance is simple, just like household oil burners. Repairs seem expensive and everyone has different financial pain threshold. I have never taken the coach to any shop  for anything, other than my own and my labor is free, so yeah, I like it.

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I have stated this previously in some other thread but after spending $6K back in 2005/6 for a rebuilt Aqua-Hot due to a fresh water leak in the external coils, if my current unit fails it will be replaced with an Espar Diesel System. Gene Howe had done that to his 2003 Diplomat when he removed his two propane furnaces. I happen to stop at his sod farm to stay one night and got to see the Espar in action. What prompted this conversion was he wanted to install a Samsung Residential fridge in place of his NotSoCold but he had a furnace under the fridge which prevented him from doing that easily so he removed both of the furnaces.

The Espar system comes with heat ex-changers and hot water on demand. The diesel fired burner is also much easier to work on and more accessible.

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Just wondering, was it $6k to repair the external coil or an exchange for a different unit?

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I don't remember the exact price but it was between $6K & $7K for the complete job.

The shop bought a rebuilt unit from the AH Colorado plant then shipped my failed one back for the core charge.

A lot cheaper back then versus today. it would most likely be over $10K now and that's probably just for the rebuilt unit with no labor.

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Any chance you have seen where on the coil the leak was? I suspect the steel hold down at the last twist of the coil might cause future problem but that would be an easy fix once the unit is out... certainly much cheaper than the mentioned 10k cost. In hindsight, I should have isolated it when it was out, oh well, time will tell.

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12 hours ago, Tim503 said:

I hope I don't get scolded again but I had a 35,000 Suburban furnace loud and obnoxious and the fan motor stopped so I replaced it with a 25,000 unit thinking it may be quieter which it isn't. After seeing the complexity of your heating units it seems extreme to replace these for a twenty year old coach. I had always heard they are the best heating system but repairs seem to be intense. What is your overall opinion of them? My unit cost me $450 to replace. Is the Aqua-hot worth the price? Thanks for posting the pictures.

Tim, I'm kind of like you about AquaHot. I have ordered 3 new Dynasties, and one HR Scepter; all without AH.  I don't spend any time in cold weather, so am not interested in engine preheat.  We are almost always are in a full hookup campground, so we have power to heat water.  I agree that the furnaces are  noisy, but in the environment we are normally in, we just use space heaters with thermostats built in.  We let them run all night if necessary.  I know that there is a lot of support for AH, but it has not been of interest to me.

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23 minutes ago, Ivan K said:

Any chance you have seen where on the coil the leak was? I suspect the steel hold down at the last twist of the coil might cause future problem but that would be an easy fix once the unit is out... certainly much cheaper than the mentioned 10k cost. In hindsight, I should have isolated it when it was out, oh well, time will tell.

The unit was never disassembled before it was shipped back to the factory.

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The job looks familiar.  I had mine rupture.   I talked to a tech at Aqua hot before I cut the tank open and he said that he had heard that people had cut the bell open and fixed the break with a splice coupling and then he added that this is unofficial of course.   I cut the tank open and found that it was an engineering design issue of the two coils rubbing.  I have an 05 coach and at some later time Aquahot changed the diameter of the hot water coil too 3/8" from 1/2".    I found that the two coils, engine preheater and hot water, rubbed together  till the hot water one wore thru.  I moved the engine coil about a 1/2" then I took it to a weld shop and had them put a  splice coupling on, weld and pressure test the tank and walked out the door for $210.    That was 5 years ago.  The shop said it was not much different then a carpet cleaning unit that they repair all the time since the carpet cleaners don't think about winterization.

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This is what John Carrillo does but he replaces the coils with better material and design so they should never rub again. He even reskins the tanks if they are to rusted.

The boiler bulkhead is about 1/2 steel so that almost never goes bad, same with the combustion chamber.

I used to have a radiator shop locally that I would have trusted but they not of this world anymore...

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Tank is in CO, will be about 2 weeks until done due to busy season... meanwhile in dirty jobs

I will be replacing the aqua hot and coach heat heater hoses from front to rear.

Ordered 50 foot of Gates green stripe 5/8 for the aqua hot to engine loop, the engine to front is part hose part tube so I need to determine how much I need but I suspect another 50 feet.

I had done all the other hoses 2 years ago but as long as I am in this deep these really should be done now, no easier time.  

 

 

 

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That's quite an undertaking how hard was it to pull the old hoses?    Did you attach the new and pull them along?

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Whatever the distance is from engine to front wouldn't you need to double that?

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I will not have the hoses until this week, Mike over on the other board did his a while back and said around 100 feet.

He could not pull the hoses, too many damn wire ties and the section between the rear bulkhead and AH is bad to get to with the AH out can't imagine doing it with it in there. 

The front "metal"  tubes end back by the motor so those lines are not that long but 100's of zip ties. 

The front  half is going to be a joy as well

 

 

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I wonder if you wound an external coil for the hot water how well it would work? Sure would be cheap fix. Use a thermal mastic to conduct heat from tank to coil. 

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Isn't the engine loop inside the boiler tank whereas in the older models like my 431/12 the fresh water loop is wrapped around the outside of the boiler tank allowing me to use just plain green ethylene glycol coolant?

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You got it!

I think Bill G is talking about rebuilding a leaking newer unit, by running the coil around the outside, like yours.

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I have heard great things about the quality of work and workmanship from John Carrillo. I have yet to hook up with him. In the  past he is always more out west than here in the east.

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