Runnig out of hot shower water

[Dennis Belfils]

Our Hydro-Hot is not keeping up with even a short shower on diesel.  Looked around at the posts of Hydro-Hot woes & it is quite extensive. Don't know where the mixing valve or stir pump are. Any suggestions?

[Steve Huber Co-Admin]

Dennis,
At this web site you can download your model number service manual which has a parts locater for each model. http://www.aquahot.com/Library.aspx

This site is good for service help and parts:  http://www.parts.rvhydronicheaterrepair.com/
Steve

[George Harwell]

Dennis, is the diesel burner running when you run out of hot water? There are several people in the club that are highly experinced on the hydro hot so I am confident they will chime in. The stir pump is on the lower right side of the burner assembly. About the size of a d cell flashlight around 4 to 5 inches long. The temp regulator can be seen with a mirror at the rear center portion of the unit. It has a round plastic knob but I don't recommend adjusting it until you are assured everything else is OK. You can also go to Aqua hots web site and search for the archived manuals for your model. It will help if you give us the model of your unit. Good luck.

[Dennis Belfils]

Yes, am running out of HW while using diesel. Model is HHE-200 50K BTU

[Darrell Terry]

Dennis,
I had a similiar issue. Water would start Hot, but cool down during shower to warm.
My issue turned out to be a bad Control Thermostat which I replaced and problem was solved.
Go to Hydronic Heating website. Lots of good information there on Forum.
Other possible causes are as someone already mentioned, Stir Pump and Mixing Valve.

http://www.rvhydronicheaterrepair.com/

Darrell Terry
2004 Monterey

[Dennis Belfils]

That's what we are experiencing. Where is the Stat located?

[Bill Sprague]

That's what we are experiencing. Where is the Stat located?

Every model is different.  Get the books from the links Steve posted. 

If my experience of 12 years in a Monterey means anything, you will spend more effort and time keeping your HydroHot running than anything else.  You need the books and need to understand how it works.  It is the most complex heating system in anything we'll ever live in.

We had shower problems twice for extended periods.  The last time, two well known factory certified techs missed the diagnosis.  The third, John Carrillo, found it.  First, he explained the trouble shooting was difficult and time consuming.  Every component, including the thermostats, had to be checked first.  If everything else was working, the last component would be the "stir pump" which could only be "tested" by replacing it.   He did, and the shower returned to normal.  The original stir pumps in '04 were too small and had a short life.  It was replaced once at about year 5.  The third was bigger and beefier, but I think the new owner has replaced that one too!

[Darrell Terry]

Dennis,
 I have an HHE-500-07M. The Control Thermostat is located just above the Burner Head on mine. It looks like a brass nut with two wires coming out.
This was the simplest, cheapest, and easiest of the 3 common causes for fluctuating hot water so I chose to replace this first.
You will need to drain about 6 gallons of antifreeze from the tank before removing the thermostat.
I used a drill with a small circular pump to siphon out and filled empty plastic jugs so I could replace the antifreeze after I  R&R'd the thermostat.
I purchased my Control thermostat from Roger Berke at Hydronics Heating.I believe the thermostat was about $68. I also borrowed a modified socket from him to facilitate removal and replacement.
He will credit you when you return the part or you can purchase if you like.
If you purchase from Roger he will also send you instructions.
Hope this helps.
Darrell Terry

[Steve Huber Co-Admin]

Dennis,
The mixing valve can cause the problem you are describing. While another responder noted you should not adjust it (I agree) if it is intermittant, turning the adjustment "knob" back and forth will sometime free up the crud inside and get it  working again. Just be sure to set the knob back to it's original position.
Steve

[Michael Hannan]

I run out of hot water in electric mode.  When I first feel it cooling off I give the tap a slight nudge towards hotter and it gets hot again but this cools down after 30 seconds or so.  I just figured it was because the supply tank was small.  I don't take long leisurely showers either.  It's been like that since I bought it December 2014 and the last thing the dealer worked on before I took delivery was getting the diesel hot water to work so I figure the system was up to spec.  Maybe not?

MJ

[Joel Ashley]

Electric won't keep up with uses as demanding as a shower.  Yours is acting normal, Michael.  Only the diesel side will keep up adequately.  Before hitting the shower, be sure to flip on the diesel side.  The electric side is okay for low demands, and is useful to help defer using more diesel than you have to when you've already paid for electric-included RV sites anyway. 

You should also notice, especially on cooler days, that your furnace outlets shut down after a few seconds of hot water use, because hot water has priority over space heating, and the system makes sure with the diesel side that hot water is as plentiful as possible.

-Joel

[Michael Hannan]

Is switching to the diesel side more complicated than turning the burner is switch on?

MJ

[David T. Richelderfer]

The two will operate concurrently.  You can have on neither, one or the other, or both.  They have different thermostat settings so that they will not fight each other.  If both are turned to their ON setting, then the thermostat settings force them to cooperate with each other to heat water.

Our coach has a breaker in the main 110v breaker panel located in the bedroom to turn ON/OFF the hydronic (electric water) heater in the Aquahot.  The Hydronic heater will only operate while plugged into shore power or with the generator running.  In our coach the Diesel Burner switch for the Aquahot is located on the wall facing forward above the kitchen sink's countertop and over the end of the couch.  Next to it curbside is located the Engine Preheat switch which circulates heated coolant to the engine for those cold morning startups.  They both have green lights to show they are in the ON position.  Next to the Diesel Burner switch street side is another Aladdin joystick and the living room thermostat control box.  The Diesel Burner operates through the inverter, so it will operate from shore power, generator power and battery/inverter power.  It will also operate while traveling down the highway on engine alternator power, but that should never be necessary because the engine will heat water in the Aquahot through the same coolant hoses that deliver heat to the dash heater and engine preheat.

[Michael Hannan]

I have the diesel burner switch on all the time and still not enough hot water to take a full shower.  Is there something down in the Aqua Hot I need to check or change?

MJ

[David T. Richelderfer]

The first thing I would check is to make sure the diesel burner is actually running.  Turn off the electric water heater, turn on the diesel burner and now turn on the hot water at the outside water bay.  In a few minutes the diesel burner should start up and you will have hot exhaust coming out its exhaust pipe located just aft or under the outside water bay door.

If you don't get hot exhaust, then the diesel burner is not burning.