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Aqua Hot Expansion Tank


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I've had my coach now for a few years and noticed that the expansion tank level is always between cold and hot markings, never changes. This week, I replaced the expansion tank return hose which had been separated from the filler neck and replaced the 13# pressure cap then filled the expansion tank to the full mark. After a couple hours running and a cool down period there was no change is the expansion tank level. So now what?

As far as hot showers and other running water goes, my vintage Aqua Hot AHE-100 series works great although I can't say much about the floor vents. The rear seem weak, the mid-ship works great and the front are hardly noticeable. Thanks, Jim E.

 

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I’ll guess that after 21 years a fair amount of dust, hair, and dog fur has collected on the fans and heater cores.  Would have been nice if you could just undo a couple of screws and slid the assembly out for cleaning.  

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You did not mention whether the AH tank (not the expansion tank) is full of anti- freeze when cold. Also whether the AH has had a normal service of the diesel heater. If the tank is full when cold, it pretty well has to go to the expansion tank if the unit is heating up to the proper temp. Also you did not mention whether the tubes going to all three of the heating sections are hot when the unit is up to temp. If they are really hot and the fans or operating, then it may be the radiator units. My guess it is the AH itself.

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The burner unit was serviced a little over a year ago and all check valves are hot when running. The one thing I’m not sure about is the amount of fluid in the AQ itself or how to check it.

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If any of the zones / domestic water are hot, then the burner is doing it's job.

Inspect and clean the radiators.  Ensure the fans are all working when that zone is calling for heat.

Feel the zone water hoses to see if they get hot when that zone is calling for heat.

It's a possibility that the pump for the colder zones isn't working up to snuff, but typically they either work or don't work.

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Thanks David. Burner is running good, exhaust is clean and water is HOT. Only zone A heating seems to have a problem (living room supply) and its check valve is not as hot as B & C. Now to determine how much fluid is in the tank. As mentioned before, the expansion tank return line was not and has not been connected to the over flow on the tank neck for a long period of time so a lot of fluid may have been lost there. Jim

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Not sure why the fluid level has to do with one Zone.

The fluid services all zones.  So that's not the issue.

Look for issues with Zone A only:  Zone A pump, thermostat, radiator, fans.

You could swap parts from Zone to Zone to isolate:  ie: take Zone B pump and put that to Zone A hoses.  If Zone B thermostat calls for heat, then Zone A radiator should get hot.  But before doing that, check the easy:  Fans working and radiator clean on Zone A.  Zone A thermostat calling for heat (you can see the lights on the Aquahot control unit to see which zone is calling for heat).

Then check voltage at Zone B pump while Zone B is running to get a baseline of what the voltage should be.  Check zone A while Zone A is calling for heat.  Should be similar voltage.  check ground is good ground to the pumps.

After that, swap or replace the Zone A pump...

Edited by DavidL
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3 hours ago, engine103 said:

 

I've had my coach now for a few years and noticed that the expansion tank level is always between cold and hot markings, never changes. This week, I replaced the expansion tank return hose which had been separated from the filler neck and replaced the 13# pressure cap then filled the expansion tank to the full mark. After a couple hours running and a cool down period there was no change is the expansion tank level. So now what?

As far as hot showers and other running water goes, my vintage Aqua Hot AHE-100 series works great although I can't say much about the floor vents. The rear seem weak, the mid-ship works great and the front are hardly noticeable. Thanks, Jim E.

 

I replaced my pressure cap with a 7# one on the A H and the ISX 525 i had on a 07 Executive. I also choose to join rogerberke.com forum. Expert on A H, and parts available at a good price point.

 

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With ANY fluid problem you FIRST check to make sure that the boiler tank is full by removing the radiator cap and stick you finger down into the hole. If you can't feel any fluid then it is too LOW. Once the boiler tank has been filled and you know that the hose between the radiator cap neck and overflow tank is tight without any leaks then you can observe the level in the overflow tank rise when the Webasto burner is running. Once the burner turns off, check the fluid level to make sure it is close to the FULL mark on the overflow tank. Now you can monitor the level changes as the boiler heats up and cools down. That will be your operating levels.

If you notice ANY drastic changes between those levels then you need to start searching as to why.

Edited by Dr4Film
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Thanks Richard, you said it all in your first line. My Aqua Hot is of the 431 series and does not have zone lights or low fluid level cut off switch. Roger Berke replied to check fluid level and the good part (not known to me) is that the early 431 series uses everyday anti freeze like prestone. Big money saver there. Jim

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On 4/10/2021 at 7:42 AM, engine103 said:

 

I've had my coach now for a few years and noticed that the expansion tank level is always between cold and hot markings, never changes. This week, I replaced the expansion tank return hose which had been separated from the filler neck and replaced the 13# pressure cap then filled the expansion tank to the full mark. After a couple hours running and a cool down period there was no change is the expansion tank level. So now what?. Thanks, Jim E.

 

When the antifreeze heats up it expands, pressurizes the tank, pushes past the radiator cap and flows into the expansion tank. Then when the system cools down, it pulls the antifreeze back in. In mine, the difference between hot and cold is about 2-1/2 qt.
If your level is not changing in the expansion tank it could mean there’s a leak where the pressure cap is soldered to the tube coming up out of the tank. This is a common failure point. 
If the tank is really low, it might explain yours not pulling in antifreeze when it cooled down, but if everything was sealed up it would likely expel some vapor when heating and then draw a significant amount of liquid back in as it cools. 
Cheers

Walter

Edited by wamcneil
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Thanks Walter, for the time I’ve owned the coach I never noticed that the tubing had separated from the fill neck because it was still held in place by a small remnant of itself. Also checking the pressure cap nearly all rubber inside the cap was missing so I doubt that it was possible to have built any pressure. It will be interesting to see how much anti-freeze I will need to fill the AQ tank. 

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Something to check. On my coach the heater blower units that are under cabinets were set back from the front vent covers a couple of inches. The air blowing out was going back under the cabinets not into the room. Typical Monaco Mickey Mouse half way done crap. I took the outside vent cover off and built a duct from the front of the heating unit to the back of the cabinet. Now all the air coming through is blowing into the room. Noticeable difference. I had four registers done this way. Under front center console, under refrigerator, under sink in bathroom and under bed. Try one and see if it helps.

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On 4/10/2021 at 8:21 AM, engine103 said:

Thanks David. Burner is running good, exhaust is clean and water is HOT. Only zone A heating seems to have a problem (living room supply) and its check valve is not as hot as B & C. Now to determine how much fluid is in the tank. As mentioned before, the expansion tank return line was not and has not been connected to the over flow on the tank neck for a long period of time so a lot of fluid may have been lost there. Jim

I can't see why your overflow tank didn't just drain out completely :classic_blink:

They have an overflow / air vent hose at the top of the tank.

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3 hours ago, engine103 said:

It will be interesting to see how much anti-freeze I will need to fill the AQ tank. 

After you fill it, watch it for several cycles. If the neck is cracked the level can go up/down a few times, sucking in air each cycle till the level eventually settles.

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Jim,

BTW, I also have the AH-431/12 model in my coach. Originally it came with a 100-01 model but two years after purchasing the coach the fresh hot water loop sprang a leak. I had a rebuilt unit installed back in December-January 05/06. That's what Aqua-Hot in Colorado had sent for a replacement. Basically the same units.

If this one ever craps out I will be done with Aqua-Hot. It will be replaced with an ESPAR diesel unit.

I recently received a complete used AH-100-01 unit from a friend who had it removed and replaced with the ESPAR diesel unit. I sent the Webasto burner off to John Carrillo in Colorado for refurbishing. So I now have a spare Webasto ready to be installed if needed.

I also have all of the spare pumps, relays, combustion chamber, overflow tank, control box, etc. I stripped it down except for the mixing valve and the 120 VAC electric element. The carcass went to a metal scrap collector.

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Speaking of the 431/12.. where do we get parts for these aqua hot units? I need a new tip or nozzel..

Thanks

Ryan

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Ryan,

There are two online sources, one managed by Roger Berke and one managed by John Carrillo. There are also other lesser known sources available on the Internet. You just have to do some searches for them.

Roger Berke Aqua-Hot Parts - https://www.parts.rvhydronicheaterrepair.com/main.sc

John Carrillo Aqua-Hot Parts - https://heatmyrv.com/

For other sources just do a search for the part number of the nozzle. Make sure it is the correct one as there are many nozzle choices, part # WPX-886-41A.

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Can vouch for Rudy Leggit out of Dayton Texas. He was a tremendus help after I rebuilt the freash water coil on my old 100 series Aqua hot. If you have some loops colder that others it is most likely air mixed into those lines. The system will not self purge. Must pressurize the Aqua hot tank and follow specific steps to purge the air. I down loaded the service manual and was able to walk through the air bleed steps which resulted in hot air at all registers.

Edited by Jonbrooks
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