AquaHot low temp

[Adam Hicklin]

My AquaHot 431 is acting strange (of course it’s absolutely necessary because all park bathrooms are closed here in Montana).

With the AH on Electric my water temp is at 99 degrees. It will last about 10 minutes then starts to drop.  When water temp reaches 90, the diesel burner will kick on but will only warm water to about 92 degrees, then shut off.  A couple weeks ago it was working flawlessly, at about 120 degrees.

New nozzle and filter about 2 years ago, but probably only 20 hours on AH since service.  Fluid level reads good according to recovery tank. 

Any ideas?

[David T. Richelderfer]

http://beaveramb.org/forum/index.php/topic,7146.msg50685.html#msg50685

My search argument used the two words "aquahot mixing".  There are several threads to look over.

[Steve Huber Co-Admin]

Adam,
Sounds like the mixing (also called tempering valve) may be acting up. Its function is to add sufficient cold water to the output of the boiler to hit the desired temperature. It is located on the back of the unit and has a knob on it. The knob should turn freely. If not, sometimes turning it back and forth will free the valve up and it will start functioning normally. Be sure to mark the position of the knob prior to turning it as its position determines the water temperature. A service manual with pictures of the mixing valve location is available at http://www.aquahot.com/Library.aspx
If you have to replace the valve, be sure to adequately support the connections as it is threaded into copper tubing that will bend if too much torque is applied.
Steve

[Adam Hicklin]

I exercised the mixing valve.  It was all the way hot.  I cycled several times.  It moved relatively freely.  No inference.  It’s working somewhat because I turned it to full cold and water at faucet was cool.  Turned to full hot and water was 90 degrees.  There is a hot water drain valve drain valve right next to the mixing valve which was very hot, so I know it’s heating the water.  Just can’t get it to come out.  Can a mixing valve go completely bad? Not function at all?

[Steve Huber Co-Admin]

Adam,
My understanding is that it can. Mine was intermittent when I replaced it.  Suggest you contact Roger Berke at http://www.rvhydronicheaterrepair.com/Index.htm
He's good about getting back to you. His site will probably have a better price for the valve than AquaHot if that's what  the problem is.
Steve

[Bill Lampkin]

One other consideration is your source water temp, likeley pretty cold in MT this time of year. Colder water in means cooler water out.

[Bill Sprague]

I'm sure you thought of this but.....

Is there any chance you have the outside shower valves on with the shower head off?   I did that a few times.

[Adam Hicklin]

Incoming water temp is about 60 degrees, so not too bad.  No outside shower.  I’m feeling confident it’s the mixing valve.  The interior heat is working fine.  All zones are hot.  Diesel burner is cycling on and off as it should.  I will try to test the tank temp at the thermostats, but I have limited tools to test.  In lieu of ordering a new rebuild kit for the mixing valve (which may take a while to get and my wife is not pleased with no hot water) would there be a downside to taking the mixing valve apart to see if there is some crud in there maybe clogging it up?  I plan on ordering the rebuild kit, but vacation isn’t quite as fun with no hot water. 

[Bill Sprague]

Adam,

If I recall correctly, the valve is made by Honeywell and is not an AquaHot specific part.  I think I remember buying one at Home Depot.   

If you put you finger on the hot inlet of the valve, it should be pretty hot. 

If you can keep from scalding (read burn) yourself you should be able to bypass that valve with some cheap plumbing parts long enough to verify it is the valve, not the AquaHot.

[Steve Huber Co-Admin]

Bill,
Your memory is right on. It is (or mine was) a Honeywell valve.
Steve

[Adam Hicklin]

I’ve been looking for this specific valve on the aftermarket.  Can’t seem to find it.  Aqua-Hot want $230 for the complete valve.  $100 for the rebuild kit.  You gotta do what you gotta do.  Just wish I had realized this before I left home.

[David T. Richelderfer]

https://www.homedepot.com/p/Honeywell-Home-Thermostatic-Mixing-Valve-AM101C-US-1/202264710

I do not know what type of fittings the hot and cold water pipe inlets to the valve are on your coach... but what you want is an "adjustable thermostatic mixing valve," isn't it?  There are many of them to be found with a GOOGLE search.

[Adam Hicklin]

Thanks David.  Mine is different (of course). See attached picture.  But I had a small success.  The top of this valve unscrews and you can get to a spring and internal thermostat.  The thermostat has a pin in the middle that I’m guessing is supposed to be free floating, because I pushed it in and it didn’t come back out. Anyway, I put it back together and now I have 140 degree water.  So, the tempering valve was the culprit.  I think it just got gummed up by being 22 years old.  I ordered a new valve from Roger Berke and I’ll install the new guts of the valve at our next stop.  We have hot water for now.  Hopefully it lasts until the new parts come.  Wife is happy! Thanks for the help.   

[Eric Maclean]

Adam
You tempering valve is the same as the one in my 97 Patriot I just rebuilt the aqua hot last year and I replaced the tempering valve
I believe it was made by a company called Watts and it was available on line.
Eric

[David T. Richelderfer]

This is it?

https://ordering.fwwebb.com/woitem/422631*1?CAWELAID&gclid=CjwKCAjw26H3BRB2EiwAy32zhVyAeo2-tr2byO61hkuUKWt50MVmZf2ACjQypLxMpGZIYvhKMWLgLxoC19UQAvD_BwE