replace Coleman-Mach basement heat pump with mini split heat pump?

[cupe873]

Hi I have 2006 Itasca Ellipse with a basement heat pump and 2 propane furnaces. I am trying to figure out if it would be possible to swap out the Coleman basement heat pump with a mini split heat pump. They do make 110 volt units. You do have limited space where the basement heat pump currently is, but with some modifications you might be able mount the outdoor unit there. I think you might have enough air flow there. Not sure where to mount the indoor unit. Would be great if you could attach the outdoor unit to the old heat pumps indoor coil and blower. Don't really think that could be possible but you never know.
My reasoning for the change is the current heat pump will not work below about 40F degrees. The propane furnace makes a lot of noise and runs for 5 minutes, off for 2 minutes then back on. There are mini splits made for cold weather that will work down to -22F degrees. We don't spend the winter in our motorhome winter, but are in there with temps hovering around 32F degrees in the fall and spring.
I do realize that you need heating for your tanks and wash bay in freezing weather.
Has anyone installed a mini split heat pump in a motorhome?

 

[Mark_K5LXP]

The propane furnace makes a lot of noise and runs for 5 minutes, off for 2 minutes then back on.

Check vent proximity to the thermostat, or move the thermostat. Experiment with the hysteresis setting.

Mark B.
Albuquerque, NM

 

[Brad Buchanan]

Hi I have 2006 Itasca Ellipse with a basement heat pump and 2 propane furnaces. I am trying to figure out if it would be possible to swap out the Coleman basement heat pump with a mini split heat pump. They do make 110 volt units. You do have limited space where the basement heat pump currently is, but with some modifications you might be able mount the outdoor unit there. I think you might have enough air flow there. Not sure where to mount the indoor unit. Would be great if you could attach the outdoor unit to the old heat pumps indoor coil and blower. Don't really think that could be possible but you never know.
My reasoning for the change is the current heat pump will not work below about 40F degrees. The propane furnace makes a lot of noise and runs for 5 minutes, off for 2 minutes then back on. There are mini splits made for cold weather that will work down to -22F degrees. We don't spend the winter in our motorhome winter, but are in there with temps hovering around 32F degrees in the fall and spring.
I do realize that you need heating for your tanks and wash bay in freezing weather.
Has anyone installed a mini split heat pump in a motorhome?

Actually the coleman mach has two complete systems in one package.

That is how they 'load shed' with a lower amperage supply.

I am not a tech but if you could use the existing coils and blower it would be an involved job and basically be fabricating a new unit.

Let us know how you made out.

 

[cupe873]

Check vent proximity to the thermostat, or move the thermostat. Experiment with the .

Mark B.
Albuquerque, NM

Thanks I will try to change the hysteresis setting, I have an older thermostat that I replace 4 years ago, Don't know if i can do it with that model, but will look into it.

 

[John Canfield]

My reasoning for the change is the current heat pump will not work below about 40F degrees.

Long and semi-rambling read:

The outside humidity is a factor for heat pump performance, high humidity and ~40F the coils freeze. With low humidity we've had our Horizon's heat pump function in the low 30s. If Coleman-Mach would have included a defrost function the heat pump could work well in the 20s.

As a bit of a tangent, why did they not include the defrost feature you might be asking. I suspect the packaged Coleman-Mach heat pump was designed and marketed for off-site built homes (factory built in other words) in southern climates. It just dawned on me C-M might have other models with the defrost feature, I don't know. Winnebago might have requested a packaged unit built to a price point which is a common tactic. They did that with the "Sleep Number Bed" and the infamous Dimensions inverter.

Then what is a practical remedy? One time at the Winnebago mother ship I noticed a Horizon (or Vectra) with three roof airs, I thought this was some kind of a Winnebago test mule but no. I talked to the owner and he said "I like it cold." Okay then. I think there are actual heat pump roof airs and not just heat strips, I haven't had a need to know.

The fly in the ointment with using roof heat pumps is of course the basement would not have the benefit of being heated by the propane furnace. In really cold weather we used a little ceramic heater in the plumbing bay. When we were on the road in the Horizon we would run the furnace for an hour or two if we needed the basements warmed up.

Then the mini-split option, I love the idea however I seriously doubt if the outdoor unit could be shoehorned in place of the C-M unit. I also love mini-splits, we have three in our house and one for my shop office. The newer American Standard (Mitsubishi) mini-splits have an Extreme Heat model that will function with 100% efficiency into the single digits (F.) We have two of these models and I'm super impressed with them. Ours are ducted so they basically are the same as a traditional HVAC unit, the evaporator is in the attic and the condenser is the outdoor unit. They are quiet and efficient, I highly recommend them for new construction or replacement.

 

[RayIN]

John the RVP/Coleman-Mach heat pump does have a defrost feature. When the sensor detects ice on the coil it reverses to A/C until the ice melts. I know you meant a 120V feature-nope not that.

 

[John Canfield]

That's interesting Ray, I have never found any reference to a defrost cycle. Can you cite a source? By the way, here's a lousy copy of a typical packaged HVAC unit. I think I have a better copy (or link) on my website.

 

[RayIN]

John, The only place I ever read that is in my Winnebago satchel paperwork.
I'll need to go the RV garage and find that paper.
There is an ice sensor on the outdoor coil, it signals the PC board to switch to A/C mode until the sensor does not detect ice on the coil.
When it happens the unit makes a strange noise, and of course you get no heat. Best I remember the indoor fan motor stops during this "defrost".
I've only heard it happen 2X in the years we've owned the MH, and never since I installed the new RVP 'stat, only with the original one. The OEM 'stat did not switch to lp heat when the 4° differential was sensed, unlike the new version.
The original looked like this, plus has a separate switch on the right for LP heating only.
When this swich was installed I could set the inside temperatur at 65° when outdoor temperature was 40° and only the heat pump would run,no LP, unless the outdoor coil iced up.

EDIT: I'm contemplating removing the new stat and reinstalling the original for that exact purpose.

 

[John Canfield]

The Coleman-Mach thermostat has logic, the freeze switch (a thermistor) will trigger a subroutine that waits for x amount of time, then tries the heat pump cycle, gives up, tries again, etc. It's documented somewhere but I'm too lazy to look it up . I've heard residential heat pumps go into the defrost cycle (the reversing switch is operated) and that makes a very distinctive noise, never heard that in our Horizon's HVAC.

The fact the Coleman-Mach unit will sometimes cease to operate in heat pump mode in the high 30s or low 40s to me is a de facto indictment there either isn't a defrost feature or it's ineffective.

Thanks as always Ray for your participation in the Winnie board

 

[JoelP]

I am interested in hearing any good ideas for replacment. The Coleman Mach has been one of the most troublesome things in my 2010 Itasca Suncruiser. It has had exploding start capacitors that have failed twice, once setting fire to the entire unit. Recently it had another failure that cost me $2800 to repair. When it works it air conditions fine, but it never heats like my gas furnace. I was told that it was not really designed to raise temperatures more than 15 deg F.

 

[SuwanneeDave1]

. I think you might have enough air flow there. Not sure where to mount the indoor unit. Would be great if you could attach the outdoor unit to the old heat pumps indoor coil and blower. Don't really think that could be possible but you never know.

I don't think that would work. A mini split has a control cable connecting the two units that controls the fan and louver opening as well as the thermostat

 

[John Canfield]

I am interested in hearing any good ideas for replacment. The Coleman Mach has been one of the most troublesome things in my 2010 Itasca Suncruiser. It has had exploding start capacitors that have failed twice, once setting fire to the entire unit. Recently it had another failure that cost me $2800 to repair. When it works it air conditions fine, but it never heats like my gas furnace. I was told that it was not really designed to raise temperatures more than 15 deg F.

The only practical alternative that I can think of is install two heat pump roof airs and convert the basement air space to another storage bay. When a roof air croaks, replace with another unit.

The rule of thumb for nominal HVAC operation is a 20F delta between air at the outlet compared to return air. The Coleman-Mach unit in our Horizon was only rated two at tons with both compressors running, one ton short for effective heating and cooling in our three slide 40 footer (and full body paint.)

I added a roof air to the Horizon, I documented that project in my web pages (link in my signature.) It's not all that difficult if you are replacing a standard size vent opening (13"x13" maybe - I forgot the size.) Even adding one in a 'virgin' area of the roof should not be insurmountable.

 

[RayIN]

The Coleman-Mach thermostat has logic, the freeze switch (a thermistor) will trigger a subroutine that waits for x amount of time, then tries the heat pump cycle, gives up, tries again, etc. It's documented somewhere but I'm too lazy to look it up . I've heard residential heat pumps go into the defrost cycle (the reversing switch is operated) and that makes a very distinctive noise, never heard that in our Horizon's HVAC.

The fact the Coleman-Mach unit will sometimes cease to operate in heat pump mode in the high 30s or low 40s to me is a de facto indictment there either isn't a defrost feature or it's ineffective.

Thanks as always Ray for your participation in the Winnie board

I've decided that feature was unique to that old thermostat, and the new RVP 'stat does not support that feature. It did not have that 4° differential, it could be set for a temperature of anything and the LP furnace would not come on unless the slider was manually set to LP heat..
I plan to switch back to the old 'stat this winter, just to regain that feature and the defrost feature..

 

[cupe873]

I've decided that feature was unique to that old thermostat, and the new RVP 'stat does not support that feature. It did not have that 4° differential, it could be set for a temperature of anything and the LP furnace would not come on unless the slider was manually set to LP heat..
I plan to switch back to the old 'stat this winter, just to regain that feature and the defrost feature..

that's good to know, makes no sense that the replacement one didn't have that feature. When we bought our MH it had a newer type thermostat, not like the one you showed in an earlier post.