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Heat Pump vs Furnace vs Aquahot Logic


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2008 Camelot 42PDQ :    Hopefully I can articulate well enough.  Outside tempertature was 50 degress, went to bed with all three AC units set to Heat Pump.   Temperature dropped overnight to the low 20's - Woke up to a cold coach and the AC units silent.   I am thinking that they shut down because it was so cold....'there was no heat to pump'.

The next night, I set zone 1 to heat pump and zones 2 & 3 to furnace - - same thing,  Zone 1 ran and produced heat, I suppose until sometime when the temp dropped really low.  When I awakened, we had a toasty bedroom because the furnace (which relies on aquahot on diesel) did it's thing, and again the heat pump remained silent.

Anybody know what the outside temp needs to be to shut off the heat pump?  Anyway to make it switch from heat pump to furnace on its own?

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I don’t know about a heat pump switching automatically to the aqua hot or furnace. But heat pump is only good down to about 40° after that it cannot produce heat so if you know the temperatures going to drop below that I would suggest just leaving on the aqua hot. The Aqua hot is way more efficient at producing heat over electricity unless of course you’re getting the electricity for free. If that’s the case a little floor heater would probably do the better job.

Tim

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To clarify, Tim and I are both correct… heat pumps on our coaches are very inefficient below 40°F, and they automatically shut off around 30°F. 
 

Newer residential heat pumps are a different story, but that’s not the subject of this post. 🤣. The technology that Dometic (Duo-Therm) used and still uses in RV heat pumps is about 40 years out-of-date.  

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 The heat pump stops around 35. There is a temperature switch on it. We track temperature lows. If they go below 40 then we turn all zones to furnace. We also make sure it is Diesel furnace since my electric is weak (2006 -Older unit). With mine (only 2 zones) both zones have to be furnace for the furnace to work. If one is heat pump it will not kick on. 

Also a brief note. There is a tilt sensor. If the coach tilts too much the furnace will cut off.

Another note. with furnace the air doesn't circulate the same. So the wall sensors read odd numbers. I sleep with one unit set at 71 and the other 68. It evens out to around 70-72 in the whole coach. Just something to note. You should play with the controller a bit to find your number.

 

 

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Heat pumps on the norm stop producing heat below 40 degrees,we have an oasis system that replaced the aqua hot that we keep zone 1 @ 60 degrees,and zone 2 @ 62 degrees on the electric,unless it’s in the 20`s then we switch it to furnace.Now we also use an oil filled radiator type space heater which usually keeps our unit in the 60`s,that’s why we keep our thermostats low 60`s.

FDF8D89E-6A23-4147-A515-F785A4EE3CB8.jpeg

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39 minutes ago, nvrtoofast said:

   With mine (only 2 zones) both zones have to be furnace for the furnace to work. If one is heat pump it will not kick on. 

 

 

 

That seems to be the way mine works as well, thou I have 3 zones (second zone is the center heat pump only), all on the same thermostat.

I was surprised the OP even got the front HP to operate with other zones set to furnace.

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I will throw in my 2 cents...I have a 2006 Camelot with 2 - 15KW A/C-Heat Pumps and two propane furnaces. I have 2 Zones. I have always been able to set up both the front and rear zone to use the heat pumps and, when it get down to around 33-34 degrees the system will automatically switch over to the two furnaces! These are Dometic replacement units, but I have always had the automatic switch-over feature. It may be the configuration I set up on each A/C unit with the DIP switches on the control boards. I have to be sure I keep the furnace degree set-up lower than the heat pumps or it will cook us out of the coach!

Jim G
2006 Camelot
TST Rep

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Agreed, I manually change to furnace around 40-45F .. The heat pump beats itself up icing and deicing (can hear the cracking sounds on defrost), and doesn't seem to do much useful work below that. Also, I notice if we're near border temperature, the cold discharge air from the outside coil will cause the system to flip back and forth ("Oh it's colder now, go to furnace; oh it's not so cold, back to heat pump..")

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36 minutes ago, trailmug said:

Agreed, I manually change to furnace around 40-45F .. The heat pump beats itself up icing and deicing (can hear the cracking sounds on defrost), and doesn't seem to do much useful work below that. Also, I notice if we're near border temperature, the cold discharge air from the outside coil will cause the system to flip back and forth ("Oh it's colder now, go to furnace; oh it's not so cold, back to heat pump..")

I'm guessing your '08 Sig has an Aqua Hot system, so your system would switch to AH heat when it got too cold for the heat pump?

I've tried mine but couldn't get it to switch. I know it's common for propane furnace coaches to work that way.

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