Will a single mini split work well in a 33 foot motorhome?

[kd7vea]

We are trying to wrap up our remodel on our 33 foot 1987 Champion Eurocoach Check it out on Instagram. I think I can get around 2KW of solar power on the roof, and a pretty good bank of batteries for storage, so I am ow looking into the option of adding a minisplit AC/heat pump. A lot of our trips will be in southern Utah where 110+ degrees during the day can be fairly common, so I my thought is it we are in the sun throughout the days, we should get more than enough solar to run the AC during the day and still get a good charge on the batteries for the night. My question is for anyone that has installed a minisplit AC in an RV, is a single minisplit enough for a 33 foot class a motorhome? most Mini splits claim to cover around a 400 square foot room. A 33 foot motorhome, 8 feet wide comes out to 264 square feet, but it would actually be closer to 240 square feet or less because of the floor plan. would a single minisplit in the back be enough to cool the entire RV? Would it take a long time to get the front end cool? if I mount the indoor unit facing forward in the middle of the motorhome, will it be hard to get the back end cool? Any info would be very helpfull.

 

[uchu]

I don't really think it would be enough to cool down the entire motorhome, especially with the temperatures you mentioned. It'd definitely help to cool down a small section of the MH. As for the solar setup, pros and cons, etc., this article may give you more info:

Can You Put a Mini Split AC in an RV?

Do you feel like the air conditioner in your RV isn’t getting the job done? Consider installing an efficient mini split AC for your RV.

www.mortonsonthemove.com

 

[Rene T]

I think it would depend on what size the wall unit is and how big a condenser you can get which runs off 110 volt AC.
One of our members from the UK should be able to answer you question if he reads this. He was a former installer of mini splits. He is TonyL.

 

[kd7vea]

I could set up a dual mini split if that may work, so one In the bedroom in the back, and one against the wall in the middle. With solar, the idea was that I can get it fired up the day before we leave, get it cooled down then just let it run non stop, I just don’t know how realistic this is. I know tons of people are using the minisplit systems in motor homes on RVs, but I haven’t seen anything that really answers my questions.

 

[Mark_K5LXP]

RV's and homes are way different, as an RV is much more poorly insulated. I can almost guarantee you won't be happy with a single mini split in a 33 foot RV in 100+ temp days. In mine the best one A/C unit can do is about 20-22 degree reduction in temp vs outside. So if it's 100 out, it's 80 inside. If you're looking for a 30+ degree difference you're going to need a lot more Btu.

Mark B.
Albuquerque, NM

 

[Gary RV_Wizard]

The chilled air doesn't circulate well in an RV, which is essentially a long hallway. Even RVs with ducted a/c don't cool uniformly. I think you will need multiple outlets for the chilled air.

 

[TonyL]

Mark is correct in that RV's are poorly insulated, hence the need for correct sizing of AC units to match the load.
What you call mini- split systems can go up to around 11 kilowatts of output, but airflow from a single unit might be the issue. Multi-split units will have 1 outdoor unit and 2 or three indoor units which will solve the air distribution problem. Nearly all quality heat pump systems have inverter driven compressors which don't have such high starting currents as the old direct on line compressors, but you would need to research actual units to see if you can run one.
Also take in to consideration, domestic type units are not designed to be bounced down the highway. The resulting vibrations could cause pipe fractures.

 

[TonyL]

Consider also, that larger capacity units might be 220 volts, not 120.

 

[kd7vea]

Well, I would rather learn this now before I spend a couple thousand dollars getting everything put in. Right now, I am running the 2 original roof top units, and when we were working on the motorhome last summer, with 90+ degree temps outside, we just couldn't get it cooled down very well, there are no curtains right now, so a lot of heat was probably coming in from the windows (And this has a lot of BIG windows). What options are out there to help with cooling? Its sounding like there wont be a lot of options to help retain the cold air. We are planning on a lot of boondocking, so I don't want to let the generator run all day while we are out but if we don't, I'm afraid it will not cool back down again for hours. Are there any tips from the experienced RVers on keeping it cool or rapidly cooling a 33 foot motor home down when its close to 100 degrees outside? I haven't started working on the generator yet to see if its going to fire up or not. The generator is only a 4KW generator, so that wont even run both of the AC units at the same time, so maybe I need to focus on getting a 6KW or better generator installed.

 

[Gary RV_Wizard]

If the rig is in full sun and the ambient is 95+, you won't be able to keep it much below 80. With some shade, it gets somewhat better. People's notion of cool varies a lot, though. Some say 70 or 72, while others are perfectly happy at 78 or more.

There isn't a whole lot you can do to improve heat gain/loss. You can add insulation in some key places, like front (above the windshield) and rear cap areas, and use insulating pillows in skylights. And if you have stripped down the interior for remodeling, you might be able to add a surface layer of insulation in some places. A 1980's vintage rig probably doesn't have a lot of insulation anywhere.

Your existing roof a/c units aren't short of btus - they probably total 27,000-30,000 btu capacity. That amount of btus is about 2.5 tons of cooling capacity, which would cool a modest sized (1200 sq ft) site built home quite nicely. Just converting to the mini-split design doesn't necessarily increase cooling at all - you need to increase the cooling btus, improve air distribution, and cut down on heat gain wherever possible.

 

[Mark_K5LXP]

any tips from the experienced RVers on keeping it cool or rapidly cooling a 33 foot motor home down when its close to 100 degrees outside?

Drive somewhere cooler. Not a useful answer but you're dealing with basic thermal transfer. Much like folks will insulate their campers for cold weather the same would apply to the inverse - cold inside, warm outside. Insulated window coverings, filling cavities behind cabinets, covering skylights, etc etc. Anything facing the sun will be conducting heat into the living space so any surface you can shade, insulate or reflect will help - but doing that to most surfaces isn't usually practical or possible. From there it becomes a race of Btu in and Btu out. If you have an expectation of 35 degree temperature delta plus solar loading you have your work cut out for you. If this is boondocking the only real option you have is lots of A/C and lots of genset.

Mark B.
Albuquerque, NM

 

[kd7vea]

Luckily, the motorhome does have spray foam insulation everywhere. The roof, walls, and even between the floor and the storage underneath, so hopefully that helps a little. I do t know what the average pricing was back in 1987, but the motorhome sold new for $77,000. This makes me hopeful that maybe the build is a little better than most from that time frame. $77,000 in todays money is still a pretty nice motorhome, so 1987, I’m assuming this was one of the nicer ones. A lot of good info here, so I’m on the hunt now looking for generators that will give me the power I need at the efficiency I would like. If a 9kw generator will run for 11 hours at half load and has a 7 gallon tank, at todays fuel prices, I’d be better off paying for a camp site with full hookups.

 

[Ex-Calif]

Last summer my single roof unit would barely keep up with Florida heat (up to about 95*) in a shaded spot. I had internal temps of about 75 degrees which for me was tolerable.

The better news was that after the sun went down I could actually lower the thermostat a little.

I could not imagine trying to keep the RV cool with a generator. Occasional boondocking yes but all the time the generator would probably never be shut down.

You really have two issues - One is whether you install one unit or two to solve the basic cooling problem and the second is where you get the power from.

 

[Pud]

Which brand mini solit did you use ?
Pud