What to do with my HydroHot

[Jtcochran]

I know what you’re saying, HydroHot? Who has that anymore? I have a 2002 MADP with the original HydroHot. The coach has been continuously lived in for 17 years and I service it every year. The Hydronic system has been nearly trouble free this whole time with the exception of two stir pump failures. I currently run a marine coolant pump in place of the original. Every year I pick a system to upgrade. I’m thinking the hydronic system should be next as it must be ready to give out after all these years. Any recommendations would be appreciated.

[azSkier]

I am a fan of preemptive replacement myself. An new Aquahot 450D (I think) is a drop in replacement and costs about $10K installed.

There are specialists like John Carrillo who travel around the country and repair/replace this system.
https://heatmyrv.com/

The primary failure that warrants a new system is when the coils fail. They cannot be repaired.

My Hydrohot system had problems and I purchased just the Webasto burner and the control box.

I think I would continue replacing parts as needed and replace the whole system when a leak develops that cannot be repaired.

You have an old coach. I suspect there is something else that needs attention this year

[SteveR161]

We too have a 2002 MADP. We recently had an inner coil failure preceded by a small leak at the domestic hot water outlet in the rear of the hydro-hot unit.
I contacted Aqua Hot, and as the previous poster commented, direct ordered an AHE 450 DE4 Aqua Hot unit. The cost delivered was $8200.00. I installed it myself saving the $2000 install cost and aggravation of not having the coach as we live in ours as well.
The new unit came with a flash drive that had all the installation instructions.
The hardest part was removing the exhaust fittings from the boiler itself. Cut it off with a 4 inch grinder.
Used a motorcycle ramp to slide out the old and slide up the new unit.
The control switches in the passenger overhead compartment had to be replaced. I did not have the engine pre heat feature. There were no wires from the Aqua Hot controller wiring originally run on our coach. I opted not to wire up this feature on our new furnace.
Although expensive, the new unit is more efficient, quieter, cleaner burning and I expect, with maintenance, another 18 year lifespan unit.
Good luck,
Steve

[Jtcochran]

I don’t have the preheat switches, but my engine is always warm to the touch. When I changed the air cleaner a few months ago the engine was warm as was two coolant lines entering on the driver’s side. Assumed it was just plumbed through the glycol. The engine does, after all, supply heat to the HydroHot during operation because we have taken a few scalding hot showers while parked in rest areas after long runs.

[azSkier]

>> Assumed it was just plumbed through the glycol.

FYI, the engine is not plumbed with glycol. The pre-heat option allows engine coolant to exchange heat inside the Aquahot.

This adds complexity when changing out a hyrdohot unit. You have to drain both the glycol fluid and the engine coolant.

[HJLowell]

This is in our 99 coach.
Talking to the aquahot people keeping the correct fluid clean and updated prevents, and prolongs rusting out.
They said it was like maintaining a radiator.
They told us, in our unit to use the green only antifreeze.

Every 6 or 7 years we pump, flush and replace with fresh antifreeze.
We have never pumped sludge crud, rust off the bottom of the tank. Like some refure to. Thankfully.

Id like to get another 4 to 6 years out of ours.

Good luck
Its a big decision.

The new updated units are very nice.

[azSkier]

>> They told us, in our unit to use the green only antifreeze.

You should verify this. Antifreeze is toxic. The coolant inside the hydrohot circulates through coils which are in contact with fresh water. If a small leak were to occur, then the antifreeze could contaminate the fresh water making the fresh water toxic.

You are suppose to use a GRAS (generally regarded as safe) substance like propylene glycol. I believe propylene glycol is the recommended boiler fluid for Aquahot systems.

You definitely do not want to run engine anti-freeze in a Aquahot system.

Aqua-Hot - Frequently Asked Questions

Interesting that the boiler fluids changed in 2002. So what worked for your 99 coach is no longer recommended.

[HJLowell]

( I will call them to verify .)
Over the past twelve years we have visited with the factory people several times.
Up untill that point , 12 years ago we were adding the aqua hot boiler fluid.
The aqua hot boiler fluid turned brown and got thicker over time plugging the zone valves. Till tapping didnt open them.
We called aquahot tech and they told us to change out all valves. Flush the system and use only the green Antifreeze. The new zone valves havent stuck. The fluid isnt getting thicker.

Yes
I will call to verify.

Thank you.

Regardless, flushing the system and replacing the fluid every ??? 6 or 10 or whatever years is good.
Some even back flush to clean the heat exchangers. I have not felt that I needed to do that.

Like I stated, I would like to get another 5 years before I spend $10,000. To update.

[azSkier]

I thought you had installed a new aquahot in your coach. Putting anti freeze in a new system is not recommended.

[HJLowell]

No
The picture shows my unit.
Original in 99

I thought I had a leak last fall ?
An aqua hot service center fully inspected the unit also, in November
But could never verify it.
Its never been reoccurring

Originally Posted by azSkier

I thought you had installed a new aquahot in your coach. Putting anti freeze in a new system is not recommended.

["007"]

Aqua Hot maintenance can be found in this link.

[HJLowell]

Welll, I haven't received the $10,000. Check from you yet [emoji848][emoji6]

Originally Posted by azSkier

I thought you had installed a new aquahot in your coach. Putting anti freeze in a new system is not recommended.

Well azSkier
Your so correct on new units.

Im convinced now that the previous owner, back 15 years or so added Aquahot Boiler fluid. To the antifreeze used for this model in the 90s.
There was a quart of aquahot Boiler fluid in the bay with the unit.
The factory technician that I referred to said that turned the mixture brown and thick. Clogging the zone valve's.
So we had to drain and flush twice to get it cleared up.
Then added fresh antifreeze as described in the manual pictured.
Recommended by the aquahot technicians three times as the only fluid to use. Back when we were dealing with a stuck zone valve and troubleshooting.
The set up instructions are very clear as to the peramiter of antifreeze to use as you can read.

So no, no new unit for me. Like I stated.
Id like to get another 4 to 8 years ? Or more out of this unit.
As it works beautifully.

[HJLowell]

I have all the booklets.

[HJLowell]

Engine coolant return clearly shown.
Engine Coolant Supply.
Engine preheat pump