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Alert To All AquaHot And Hydronic Heating System Users

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This is an alert to all Aqua Hot users.

Our AquaHot's boiler cap was stuck and allowed the boiler to boil out 11 gallons out of 16 gal of coolant over a period of I don't know how long! The cap was so deteriorated (brittle) that the rubber seals came apart in pieces when I removed the cap, which I had to use Channel locks to remove. The missing 11 gallons of coolant was causing the temp of the hot water to fluctuate, which I thought originally was the mixing valve; but after circumstances led me to check the coolant level I found out differently!

After cleaning the Boiler cap neck, which was very difficult on our 04 Monaco Exec, because of where it is located and the size of the AquaHot and filling it with coolant, the Electric Heating Element burned out and I had to replace it. The Heating Element Replacement requires that you drain the boiler. Well there went the 11 gallons of Coolant I just put in by pumping it in with a new Weed sprayer, which was a real chore, because of where my boiler's cap and inlet were located!
I did have an unused 40 gal blue tank, that I was able to use to recycle the 16 plus gallons of 50/50 coolant mixture.

Note: Use Distilled water along with the coolant to achieve the 50/50 solution. This will keep the corrosion down in the room heat exchangers and save you money and
trouble in the long run.

The AquaHot Owner's Manual & the AquaHot Repair Manual says to check the coolant level in the reservoir tank and neither manual mentions checking the level of the fluid in the Boiler tank OR what type of Coolant to use!. The tank has a radiator cap on top of it like a car's radiator. Do not trust just checking the reservoir's fluid level!!!



I would advise everyone with an AquaHot to check the boiler's coolant level. Wait until the boiler is cool. If you can feel that the radiator cap on top of the boiler (Just like a car's radiator cap) is cool to the touch, along with the area around it remove the cap slowly and if the level is correct and full, the coolant will be right up to the cap and may even
overflow as you remove the cap.


If you cannot see or feel the coolant level go to: http://rvhydronicheaterrepair.com/RVHYDModelInfo.htm and see what type of coolant your AquaHot uses and fill it up. Note: you should find out what type of coolant your AquaHot uses anyway!
In any case you should check the boiler cap once a year and replace it every 2 years! You will save yourself a lot of headaches & heartaches, along with a lot of
money in repairs!

:) God Bless and have a supper day, :)
Larry the Tweety Coach Guy

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Hi Larry. Excellent post !!

This issue has come up at times and you have done a good job of explaining the cause and effect.

Thank You for your time posting this information.

Rich.

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Larry,

Welcome to the Forum.

When you drained the coolant did you have it tested? When I drained my unit I had it tested and found it in need of replacing. I do keep a pump up sprayer, with 50/50 in it to top off the tank. When I had to replace the 16 Gallons I got a bucket (5 gallon) and put a connection in the bottom, connected a hose long enough to reach the tank while the bucket was mounted on a raised platform to gravity feed the coolant into the tank.

Worked like a dream.

Herman

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I have the AH 450-D, the manual says to use Propylene Glycol, which is a boiler type antifreeze.

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Does anyone have a part number or source for the Hydo Hot Radiator cap other than Hydro Hot. Mine needs replacement and is it available by some part number in an auto or truck parts store?

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Remember this is applicable only to older AH systems.

After 07 they did not have the rad cap system. They have a small bleed valve only plus the standard overflow system.

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Does anyone have a part number or source for the Hydo Hot Radiator cap other than Hydro Hot. Mine needs replacement and is it available by some part number in an auto or truck parts store? This 4" diameter cap is NOT a std radiator cap. where do you get one?

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Does anyone have a part number or source for the Hydo Hot Radiator cap other than Hydro Hot. Mine needs replacement and is it available by some part number in an auto or truck parts store? This 4" diameter cap is NOT a std radiator cap. where do you get one?

You have a old oddball one and yes they are expensive. $105.00 the one I looked at most others just use a 13 lb automotive cap.

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