Heating issue

[Jim Houghton]

It seems that trying to get one more trip in before putting the coach to bed for the winter has raised a new issue. The outside temps (down to low 20's) are a bit much for the Aqua hot system so I have been using it to heat the bedroom and bath area and the front heat pump for the living room area. We went out to see some very nice Christmas lights and came back to find the heat pump off and the front area cold. Noticed that the Aqua hot register was on in the front also. Tried recycling the power it eventually came on and lasted a few minutes and back off. Throught the day if has been cycling through its normal and reversing cycle until now. The thermostat says emergency heat when it shuts off. I'm now running the rear heat pump and the Aqua hot on high fan with the diesel burner on to heat the front. Any ideas where to look on troubleshooting. May cut our trip short by a day and head home tomorrow instead of Sunday.

[Grant Ralston]

Jim, it sounds like it is too cold for your front heat pump to capture any heat in the atmosphere to bring inside and it is shutting down to protect itself.  Without an added heat strip inside the heat pump to help, a air-source heat pump starts dropping efficiency quickly as it gets colder outside.  Perhaps your front unit has seen more use and is more worn than your rear unit due to more use it receives in hot weather?

Here is a item pulled from the web about cold weather operation of heat pumps:
Heat pumps are only efficient by themselves down to about 35-40 degrees. Once it gets into that range they switch to AUX heat. AUX heat refers to an electric "furnace" which is a big heating coil. This is used to help the heat pump out or it may be the sole source of heat below a certain set temp that the manufacturer uses. Emergency heat means that the electric furnace is on full blast and the heat pump is off.

Don't give up, just time for a "hot toddy", a ceramic heater and more blankets!  

Good Luck
Grant

[Bill Sprague]

Jim,

I'm not sure from what you wrote, but I get the idea that you are trying to heat with electricity.  

Heat pumps stop working when it get cold.  The electric function of the Hydrohot can only produce about as much as a single space heater.

When it gets cold, you have to turn on the diesel part of the Hydrohot.  The diesel function produces about 10 times the heat that the electric alone will produce.

We got caught in a blizzard a couple years ago.  It got to 15 below zero and the wind was 50 mph.  The HydroHot kept us toasty warm!

[Jim Houghton]

Ran the hydro hot using the diesel burner and all is now good. Except trying to convince the wife nothing is wrong. Should have read up on it before posting and would have seen that this is all normal operations for these conditions. Darn owners manual it's actually full of useful information. LOL  

[Orman Claxton]

Jim
While running the heat pump, if temps get too low, system will switch to Aqua-Hot operation

[David T. Richelderfer]

Interesting... Orman, are you saying that even with the AquaHot switches in the off positions, both the electric element AND diesel burner switches off, that if it gets cold enough, then the AquaHot will override the off switches to turn on and warm the coach?  I was thinking the roof mounted a/c-heat pumps and AquaHot are independently operated.  Of course, the zone furnaces are operated from the same thermostats as the roof mounted a/c-heat pumps, but the thermostats don't start the electric element and/or diesel burner that I know of.

[Bill Sprague]

The automatic switch over may work well on the larger, more expensive AquaHot units.  They have two thermostats.  One keeps the electric element on.  The other lights the diesel when the electric can't keep up.  

You can run the heat pumps with both AquaHot switches are on.  Since there is little load on the AquaHot, the electric keeps it warm but the diesel burner does not run.  As the temperature drops, somewhere around 40 the heat pumps become too ineffecient and the DuoTherm thermostat controllers will shut off the heat pumps and switch to "Furnace".   As soon as the minimal reserve in the AquaHot provided by the electric element is used up, the diesel will light.

None of this works very well for those of us that got the cheaper units once called HydroHots.  They have only one thermostat that controls both the electric and diesel at the same cut in temperature.  The automatic switching function will still work, but there won't be enough heat inside the HydroHot until the diesel switch is turned on.    

It never made sense to me to run the noisy heat pumps if I had to keep the diesel burner idling for backup.  Instead we bought a silent baseboard heater that usually keeps us warm enough by sitting next to my chair on a low glow.  If not, heat has to come from the HydroHot in cold weather.  

All of this brings up what I think is a problem in how our coaches were designed.  If you are in cold weather by choice or by mistake you are reliant on the diesel burner.   If it is cold and the diesel won't light, you get cold.  As I've written before, I've rewired ours to support a few cheap space heaters I keep deep in the basement for an unplanned HydroHot failure.    I can keep warm with the HydroHot, 50 amp shore power or by running the Onan.    

[Joel Weiss]

We have a Hurricane rather than an Aquahot and a couple of years ago I had Rixen install his ComfortHot in it.  The ComfortHot utilizes the two A/C circuits to provide ~4kW of heating power which is much more than the electric element in an Aquahot.  That's roughly 14,000 BTU/hr which is enough to keep us warm if the temp is ~45 degrees or higher.  When it drops below that we switch on the Hurricane's diesel which gives us a combined output of ~60,000 BTU/hr which keeps us toasty warn.    I don't know if a ComfortHot can be installed with an Aquahot.

[Gerald Farris]

Joel,
A Comfort Hot can be installed into an Aqua Hot system, but there will be a few issues that you will need to resolve. The main one is that the Aqua Hot system has multiple heating loops and pumps, unlike the Hurricane that only has one heating loop and pump. Therefore, on a Hurricane system the Comfort Hot is just installed anywhere in that loop, but with an Aqua Hot you have to decide which loop you want it installed into. It will only supply heat to the system if the loop (pump) with the Comfort Hot installed is functioning. So if you install it into the living room loop, and the bedroom heater is turned on but the living room heater is off, you will not get any circulation at the Comfort Hot, and therefore, no heat from the Comfort Hot.

Gerald