Forum Discussion

Monkeyman_and_L's avatar
Monkeyman_and_L
Explorer
Nov 11, 2017

Too smart a thermostat?

Freeze warning in our area tonight, and they ain't kidding. Hadn't dumped fresh tank and needed to purge lines. So much easier on the class A.

Then I decide to keep coach warm so I can follow up tomorrow with final winterizing stuff. Air purge and pink stuff into drains and tanks.

Set thermostat for both zones to 60, dial to heat pump. Notice the furnace kicked on. Hmmm, not what I wanted, so I remove the furnace fuse.

Come out later to do a couple more quick items, notice coach interior at 37 degrees, both zones. Started troubleshooting. Notice that after I reset the power on the thermostat and set up temperature demand, the unit flashed between heat pump and furnace.

Reinstalled furnace fuse, opened propane tank, cycled twice because of air in the line and timeout. Furnace now heating.

So, is it just smart enough to know it can't jump the temp 23 degrees to insist on the furnace being active?

This heating system has me baffled. Gotta sort it out.

Anyone else?
Class A
  • Mandalay_Parr's avatar
    Mandalay_Parr
    Explorer
    Nov 11, 2017
    Heat pumps don't work below freezing so they automatically turn furnace on.
    Propane is best way to keep everything warm.
  • YC_1's avatar
    YC_1
    Nomad
    Nov 11, 2017
    Yes these things are very smart.

    Some heat pumps don't work below 40. Some go a bit further.
  • Bumpyroad's avatar
    Bumpyroad
    Explorer
    Nov 11, 2017
    YC 1 wrote:
    Yes these things are very smart.

    Some heat pumps don't work below 40. Some go a bit further.


    and they all suck IMHO. I've had a bunch of them and when they are putting out 85 degree air, it feels and is cool on the skin. only time they are comfy is when the electric coils kick on.
    oh to be on a natural gas line again.
    bumpy
  • 3oaks's avatar
    3oaks
    Explorer
    Nov 11, 2017
    YC 1 wrote:
    Yes these things are very smart.

    Some heat pumps don't work below 40. Some go a bit further.
    That's it, plain and simple. Not much more for the O.P. to figure out. Appears the heating system is operating like it should.
  • 3oaks's avatar
    3oaks
    Explorer
    Nov 11, 2017
    Bumpyroad wrote:
    and they all suck IMHO. I've had a bunch of them and when they are putting out 85 degree air, it feels and is cool on the skin. only time they are comfy is when the electric coils kick on.
    oh to be on a natural gas line again.
    bumpy
    Putting out 85 degree air and feels cool on the skin? Sounds like you need a humidifier. :?
  • Monkeyman_and_L's avatar
    Monkeyman_and_L
    Explorer
    Nov 11, 2017
    Checked this morning before going to work. Unit is at expected temperature. 1/6 of my propane to do it.

    I have a heat pump at home. I did my research on that one, and it's effective to about 20 degrees outside before activating emergency heating.

    I know that the Duo-Therm units on my coach are what's offered, and I can't easily spec ones that work in a wider temperature range. I also know that due to the size of the units that the performance will not be as high as my home heat pump. Just figured it would take a bit longer to hit the requested temps.

    Mind you, if I had natural gas service at home, I'd make that the emergency heat source in a heartbeat. When it gets sub zero, I could make heat off the friction from my electric meter.
  • Bumpyroad's avatar
    Bumpyroad
    Explorer
    Nov 11, 2017
    3oaks wrote:
    Bumpyroad wrote:
    and they all suck IMHO. I've had a bunch of them and when they are putting out 85 degree air, it feels and is cool on the skin. only time they are comfy is when the electric coils kick on.
    oh to be on a natural gas line again.
    bumpy
    Putting out 85 degree air and feels cool on the skin? Sounds like you need a humidifier. :?


    85 degree air on 98.6 degree skin. it is cool. sort of like sitting in a draft. when coils kick on it is over 100 degree air.
    just checked, my thermostat shows it is 22 degrees out and it shows that the heat pump is operating. haven't heard/felt the furnace working so it is possible that it just hasn't come on since the temps. dropped.
    bumpy
  • dougrainer's avatar
    dougrainer
    Nomad
    Nov 11, 2017
    1. Dometic HP's will not work below 40 degrees. They have an Ambient temp sensor and once the temps drop below 40 degrees they will lock out and the furnace will kick in
    2. You CANNOT compare residential HP's with RV HP's. TOTALLY different operating parameters and components. HOME HP's will have a 220 Electric Heat COIL back up heat for when outside temps drop below 32 degrees. RV's have to use the Furnace system for back up heat in freezing temps.
    3. When selecting HP in freezing temps, the Furnace system will heat the RV, then once the outside temps rise above 40 degrees the HP heating system will heat the RV. Only when the outside temps then drop below 40 degrees will the Furnace system automatically kick back in.
    4. LAST, IF people would READ the Dometic operating instructions that come with the RV, this would be explained in detail.Doug
  • dougrainer's avatar
    dougrainer
    Nomad
    Nov 11, 2017
    Bumpyroad wrote:
    YC 1 wrote:
    Yes these things are very smart.

    Some heat pumps don't work below 40. Some go a bit further.


    and they all suck IMHO. I've had a bunch of them and when they are putting out 85 degree air, it feels and is cool on the skin. only time they are comfy is when the electric coils kick on.
    oh to be on a natural gas line again.
    bumpy


    If you are talking about Residential HP's the output heat is 120 to 130 degrees on HP.
    If you are talking about RV HP's, YOU DO NOT KNOW WHAT YOU ARE TALKING ABOUT. RV Hp's have NO electric coils and the output heat is above 120 degrees. If you are talking about RV's at 85 degrees you are talking about HEAT STRIPS in the AC units which are NOT heaters, They are designed to take the chill out of the air. Doug
  • georgelesley's avatar
    georgelesley
    Explorer
    Nov 11, 2017
    Our furnace will also come on to help the HP if you select a temp increase of 5 deg or more from ambient. HP shuts off completely at 36 deg and furnace from there.

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