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Old 01-20-2021, 09:05 PM   #1
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Brand: Thor Motor Coach
Model: Chateau 31L
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THOR #20195
Mini Split Upgrade?

Has anyone upgraded their class c? I have a 2014 31L Chateau with 30 amp single 18k Roof top ducted AC. Was thinking about a Mr Cool mini split to add to the rear and run off separate electrical to breaker and run to 50 amp and converted plug. Last Summer in southern Ca temps where 126 degrees during the day and RV never got below 100 degrees inside! Please let me know what youíve done and what size I need to get to make sure this doesnít happen again!
Thanks!

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Old 01-20-2021, 10:01 PM   #2
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Where are you going to put the outside compressor/condenser unit, the other half of the "split"? The only place I can see is to hang it off of your bumper, but will be pretty exposed there.

David
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Old 01-20-2021, 10:10 PM   #3
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A good idea,
we use a portable unit vented out the front driver window with power from a cord I drilled thru the slid floor under the couch, thru the floor and storage bin floor to the 20a on the power pedestal (no extra breaker added).

Take a look at this thread for several things you can do to make the roof unit much more efficient. Sounds like with 2 units and 120* you'll need to do a lot of these cheap and easy day's
A long and very worthwhile read
https://www.thorforums.com/forums/f2...ice-12980.html
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Old 01-20-2021, 11:49 PM   #4
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We used a portable for a number of years before just deciding to bite the bullet and add a second rooftop unit. In our case we didnít have an existing vent so had to cut and frame a new opening. We hard wired it to a new 20A inlet with a breaker in our electrical compartment. Instead of rewiring to a 50A plug we either just use a 20A outlet on the power pole or use a 50 to 30/20A ďYĒ adapter. Itís easier and more versatile than rewiring. Iím glad we did it.
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Old 01-21-2021, 03:35 AM   #5
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THOR #20195
Thanks, good read and I will check insulation , leaks and proper location or relocate probe if needed! I think Iím still leaning for a mini split heat pump maybe 18k or 12K in back bedroom slide heat pump! If I go 12K it will be 120 volt 18k would be 240 volt. Just not sure if a 18k would be too much. Has anyone done this before on a Class C? As far as mounting it I would think Iíd install above the left tail light and run lines through protected covers below for drain and above for refrigerant lines up to a 4Ē hole for the evaporator inside above the rear window! I would support from roof and back wall with aluminum angle and seal. Thoughts?
Thanks!
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Old 01-21-2021, 04:20 AM   #6
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Originally Posted by Boomer56 View Post
Thanks, good read and I will check insulation , leaks and proper location or relocate probe if needed! I think Iím still leaning for a mini split heat pump maybe 18k or 12K in back bedroom slide heat pump! If I go 12K it will be 120 volt 18k would be 240 volt. Just not sure if a 18k would be too much. Has anyone done this before on a Class C? As far as mounting it I would think Iíd install above the left tail light and run lines through protected covers below for drain and above for refrigerant lines up to a 4Ē hole for the evaporator inside above the rear window! I would support from roof and back wall with aluminum angle and seal. Thoughts?
Thanks!

If you install a 18K that requires 240 Volt electricity, how will you power it? If your motorhome came from factory with only one A/C, then it has 4,000-Watt generator. For that matter, even larger motorhomes with 5,500-Watt generators can only produce 120-Volt power. Just saying that if the generator canít work for your ďupgradeĒ, and you have to be connected to shore power anyway, then whatís the advantage of mini-split versus standard RV rooftop air conditioner? Granted it would be quieter, but mini-splits are popular for their energy efficiency, and if youíre not paying for electricity at a campground, does a mini-split make sense?

Iím not following why you want a mini-split for an RV versus normal rooftop A/C or heat pump.


P.S. ó Iím aware of a few owners who installed mini-splits so they could power it with limited energy from batteries and/or solar, but that doesnít seem to be your goal.
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Old 01-21-2021, 08:51 AM   #7
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Most all campgrounds we go to have 50-30-20 amp connections! My goal is when the weather gets ready hot or cold Iíll have multiple options for staying comfortable! Last years trip we really suffered in 120+ days! To solve the power problem this would only be done when at campgrounds where there is plenty of power knowing my generator will not power both! I have totally gave up on replacing a heat pump to the existing bedroom power vent! Still weighing it out! I also can do some creative wiring to plug 50 amp with two separate panels!
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Old 01-21-2021, 08:53 AM   #8
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Have not gave up on a heat pump is what that was supposed to say!
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Old 01-21-2021, 11:45 AM   #9
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Quote:
Originally Posted by Pete'sMH View Post
We used a portable for a number of years before just deciding to bite the bullet and add a second rooftop unit. In our case we didnít have an existing vent so had to cut and frame a new opening. We hard wired it to a new 20A inlet with a breaker in our electrical compartment. Instead of rewiring to a 50A plug we either just use a 20A outlet on the power pole or use a 50 to 30/20A ďYĒ adapter. Itís easier and more versatile than rewiring. Iím glad we did it.
Iím in the process of doing this as we speak.
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Old 01-21-2021, 12:50 PM   #10
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You can waste time and energy on portables, quick fixes, duct blocking etc. Eventually you will add a second a/c with it's own circuit. That's the answer for the climate you described. How do I know this. I went through all the above and finally gave up and installed the second a/c (13,500 non ducted with it's own 20 amp circuit. At the beach in full sun and high humidity I can cool it to whatever temp I want, typically 72 deg.
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Old 01-21-2021, 01:40 PM   #11
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The beauty of mini-split (actually, most inverter air conditioners) is that they become more energy efficient at partial capacity because they run slower to match reduced cooling requirements.

However, at 120 F outside, the A/C is going to run 100% capacity and the energy efficiency may not be as great as one expects. If designing for 120 F, which is considered desert conditions, you practically canít add too much cooling capacity.

Note that at desert conditions, air conditioners require significantly more power and ďmayĒ deliver significantly less cooling depending on inside temperature. To achieve 80 F inside the motorhome while itís 120 F outside takes a lot of rated capacity.
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Old 01-21-2021, 05:42 PM   #12
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Originally Posted by Chance View Post
The beauty of mini-split (actually, most inverter air conditioners) is that they become more energy efficient at partial capacity because they run slower to match reduced cooling requirements.



However, at 120 F outside, the A/C is going to run 100% capacity and the energy efficiency may not be as great as one expects. If designing for 120 F, which is considered desert conditions, you practically canít add too much cooling capacity.



Note that at desert conditions, air conditioners require significantly more power and ďmayĒ deliver significantly less cooling depending on inside temperature. To achieve 80 F inside the motorhome while itís 120 F outside takes a lot of rated capacity.


But the ugly is youíve got to find a place for the outside unit to live.
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Old 01-21-2021, 08:42 PM   #13
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My point was that there is nothing magical about mini split systems. The same technology can be, and is being applied to window air conditioners with similar results; and has been used on central air conditioners for a long time, albeit at much higher cost.

Iíve seen reports that inverter technology may be used on RV rooftop air conditioners. The biggest issue is that RV A/Cs are used so few hours annually that energy savings donít justify the added investment. You would need/want the inverter technology for reasons other than energy savings.
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Old 01-21-2021, 09:23 PM   #14
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Minisplits are available in 120 volt models
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Old 01-21-2021, 09:40 PM   #15
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Originally Posted by Pete'sMH View Post
But the ugly is youíve got to find a place for the outside unit to live.
Yes I would like to see a pic of a mini-split installation on a MH. I doubt if it would be pretty, both for the outside unit as well as the inside.

David
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Old 01-21-2021, 10:21 PM   #16
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The inside unit on the back wall of the bedroom would look fine. Now if the mini-split outside unit had a horizontal fan/compressor unit that you could put on the roof of an RV they might find they have a market. Vertical condensers/fans just look "Jethro'd" on the back of an RV (Yes, that's a Beverly Hillbillys reference).
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Old 01-21-2021, 11:02 PM   #17
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The inside unit on the back wall of the bedroom would look fine. Now if the mini-split outside unit had a horizontal fan/compressor unit that you could put on the roof of an RV they might find they have a market. Vertical condensers/fans just look "Jethro'd" on the back of an RV (Yes, that's a Beverly Hillbillys reference).


Certainly not a Gibbs reference!
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Old 01-22-2021, 12:58 AM   #18
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It doesn't matter how many A/C units you have when the summertime temps in the southwest are triple digits. From Texas to the west during the summertime, if you are not in the mountains or in a campsite with plenty of trees the inside of your RV will be hot. Sure, I can go to the Gulf Coast and park in a 50 amp site and the two A/Cs will keep my coach comfortable. But if I go to Abilene the same weekend, 20 A/C units are not gonna keep out the west Texas heat.
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Old 01-22-2021, 01:23 AM   #19
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Anyone know of a 12k mini split that can be mounted flat on the roof??
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Old 01-28-2021, 07:58 AM   #20
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Many thanks

Just a follow up! I decided to put an additional 15k heat pump in the place of the powered vent is. I ran separate 10-3 so cord where 12 volt was already ran through the ceiling down and out thru closet to the electrical cord box and braced with 2-20 amp breakers (one is extra). Measurement is 14.5x14.5 and factory braced aluminum tubing. When the unit I bought comes in from RecPro Iíll remove the power vent and install it there! Still would have love a mini split but all the manufacturers couldnít or wouldnít come up with a low profile condenser to lay on top of the roof and we decided not to look like the Clampits through our retirement journeys! Iíll update after weíve put some miles to it! Love this forum, glad to be able to bounce ideas!
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