My 1995 Dina has three 15K BTU rooftop A/C units. I have one in the rear bunk area, and two in the front living/kitchen area. The two up front can barely keep up on a 90+ degree day. One of the front A/C units appears to have lost its refrigerant. We were struggling to keep the front area at 85 degrees with only one working A/C unit.
The 1999 I want to use a mini-split. How many BTUs would I realistically need? 36K BTU seems like a lot, but 36K BTU is less than the 45K BTU in my 1995. Now, I understand that rooftop A/C units can be very inefficient so a mini-split can be smaller. My 1,300 square foot house only has a 30K BTU central A/C system. I saw a video tour of a Van Hool double decker conversion recently. They said they have an 18,000 BTU mini-split. That seems quite small to me.
It depends on the location, glass and insulation in a bus ,they shouldn't be that hard to cool when parked in the shade, here in AZ with the heat mini splits struggle I know a owners that has 3 -9000 btu mini splits he went with 9000 btu because they are 110v he put one roof top back on for faster cool downs once it cools down he does ok with 2 running in a 40 ft bus parked, Ac units cannot keep up when driving a bus down the road ,just stop and think the dash air on a automobile is around 27k btu on high fan.My friend Kenny went with 3 of the new inverter type (like a mini) 13,500 roof tops on his Prevost they do a good job here in AZ.He went that way to get away with losing bay space bay for the condenser and fan plus the lines routing for the mini's he loves his new units they are quite too, He is like me he doesn't like the looks of the cassette hanging on a wall inside the bus, I don't like those in a house either my daughter has 2 in her house lol they look like something in motel room to me
I am always in the sun. No shade where I go. My 1995 only has the three rooftops for road air. It works okay most of the time.
The 1999 has working road air. The issue is all the space it takes up, plus the ductwork is in the overhead luggage racks. I also read it can cost a ton of money to keep it working.
This summer we put a Furrion chill 18K on the roof in the LR Kit area and with the 13.5 in the Bedroom Houghton rec pro the Bus stays very nice even in 109 degree that it was this year. I don't care about the looks of the roof tops and I too don't care for the ones inside hanging off the wall. The ones we have are very quit. About 45 to 50 at full speed and lower at low speed. The Furrion even has a Turbo cool the really cranks it up fast if needed. :^
Quote from: Dave5Cs on October 03, 2025, 07:27:13 AM
This summer we put a Furrion chill 18K on the roof in the LR Kit area and with the 13.5 in the Bedroom Houghton rec pro the Bus stays very nice even in 109 degree that it was this year. I don't care about the looks of the roof tops and I too don't care for the ones inside hanging off the wall. The ones we have are very quit. About 45 to 50 at full speed and lower at low speed. The Furrion even has a Turbo cool the really cranks it up fast if needed. :^
The Chill Cubes are nice units, but I really want heat pumps. I have an Atwood rooftop unit that makes all kinds of wind noise when driving regardless if running, or not.
The debate on mini-split vs rooftops could go on forever. The folks who have mini splits in their RVs really like them.
Attwood AC units are just a downgraded Dometic AC I had one that didn't last 2 years,your AC is choice no one can make that call for you.You can duct 3 roof tops and they are quite I had 3 Colemans 15,000 btu with heat pumps on my Country Coach you barley hear those run , what I didn't like was the heat pumps were worthless below 30 degree but I had floor heat along with the Aqua Hot so I seldom used the heat pump
The coldest were in was -5 and the floor heat was my choice when plug to power ,it never made a sound and kept you very warm. If I buy another RV it will have floor heat.In our Eagle we had 3 Cruise/Air they were quite with vibrable speed fans only thing I didn't like was the price of those units
I have two 18k heads in the bus. One on the back wall and one over the windshield.
I'm in the direct sun and it gets very uncomfortable at times. The windows are the issue.
Also, the head in the back is oversized. I probably should have done 24 and 12. It causes the humidity to climb as a result if the small space.
3 heads would be great but didn't have a place for it.
If I had it to do over I would double the btus
Quote from: epretot on October 05, 2025, 03:09:28 AM
I have two 18k heads in the bus. One on the back wall and one over the windshield.
I'm in the direct sun and it gets very uncomfortable at times. The windows are the issue.
Also, the head in the back is oversized. I probably should have done 24 and 12. It causes the humidity to climb as a result if the small space.
3 heads would be great but didn't have a place for it.
If I had it to do over I would double the btus
That is some good information for Belfert ,I have always said when you see the mini splits offered from the big boy converters and motor home somebody has figured it out and that won't happen till the mini splits are manufactured for RV and mobile use.I know Taylor tried it on a few if her entrainer buses a few years ago but running a 100,000 mile a year they didn't hold up and she went back to 5 roof mounts on her buses ,the tubing on those are paper thin, where do get service for 1 in bus here no AC Co. will work on a mini in bus we tried for a friend calling a dozen places
I've discovered I have a very close friend who spent his career in the HVAC industry, often designing custom systems with multiple units and his son went into the business as well and is still active. He has volunteered to take a look at my sketches and specs for the system I want to build and then pass it along to his son for evaluation and recommendations. If both of them need more expertise they know where to find it.
I talked with Ed about the system I want. The key is finding 3 high efficiency soft start compressors with about a 18k btu capacity that run on 110v. The next step is designing a suction side manifold that will guarantee correct oiling for each compressor and not starve any of the three for oil. Ed is familiar with such manifold designs.
So now I need to sit my butt down and write up the specs as completely as I can manage to do, and once I pull this one off I will have a system that makes use of all the original OTR parts with a few more bits for stationary operation. Should end up being an absolute killer system if it all works out as intended, and not terribly expensive to install. Not putting warts on the roof will be a plus I think.
Jim
Air conditioning is all the same you circulate the freon and it absorbs the heat inside and dumps it outside ,you just figure out the most effective way to do it that works for you
My bus has sort of a shelf above the engine in the back. Could I place a mini split in there and bring air in from the side and exhaust air out the side? Would this work while in motion?
Quote from: belfert on October 06, 2025, 08:36:17 AM
My bus has sort of a shelf above the engine in the back. Could I place a mini split in there and bring air in from the side and exhaust air out the side? Would this work while in motion?
Are saying install the condenser inside the bus and pipe fresh air to it % they need all the fresh air they can get to keep from building up high head pressure and shutting off
Systems can be simple or complex. For example the OTR 102 system has one condenser, one compressor, and four evaporators. It can run any of the 3 smaller evaporators while powering the main one, or none of them except the main one. Simple solenoid valves control the flow and the compressor cranks out enough freon for about 13 tons of cooling in total as I understand it. The use of smaller compressors and valving to direct the freon to the smaller evaporators should allow satisfactory cooling for stationary use. That's my plan anyway, we will see how well I am able to implement it.
Jim
Quote from: luvrbus on October 06, 2025, 10:03:30 AM
Are saying install the condenser inside the bus and pipe fresh air to it % they need all the fresh air they can get to keep from building up high head pressure and shutting off
Yes, not really any different than placing it in a luggage bay like some do. Also not much different than drawing air through for for generator in a luggage bay. The Dina has limited luggage bay space due to being 43 feet versus 45 feet, plus the short wheelbase. I would prefer not to take up a luggage bay. I would build a box for it with some sort of gasketed doors to work on it. The side and back wall of the bus would have large vents for airflow.
I realized the one reason not to do this is how hot it gets back there. I chose not to put my LifePo4 batteries back there due to the heat. I built an insulated wall with gasketed door to try to keep that heat out of the rest of the coach.
Three an a half years ago I installed a Pioneer 9000 BTU 120V in our bedroom. Our GM-4106 is fully sprayed foam with double bubble wrap inserts for all windows covers. Since this is in the bedroom I knew we wouldn't be running it on the road. I installed the condenser in the bay on a turntable (best air flow a @ triple digits). First surprise was how much we enjoyed the heat pump, that is used more than the AC. Being so quiet we can have it on when we sleep. There is not high amp start up, pulls 6-7 amps, w
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Re: Mini split(s) - How many BTUs for a bus?
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e can run it on a 20 amp circuit. We enjoyed it so much, the rattle box will be replace soon (new unit in garage patiently waiting).
I looked at a 2026 Prevost yesterday a friend was transporting to FL from Oregon ,4 roof airs and 1 basement unit , you couldn't hear the 4 roof air running,the basement unit was loud outside . I have no idea where people get the money to buy a 3 million dollar RV ,the sticker price was over 3 million for something with laminate covered cabinets
We live in Florida.
We have both a Pioneer 12K Mini Split in the front and a Coleman 15K rooftop in the rear.
We love the Mini Split, works fantastic, very quiet sips electricity, we are able to run it off our Solar System for a lot of the day. Keeps the entire bus cool, using a box fan in the middle of the bus blowing into the back, the problem arises when it gets into the mid 90's then the mini split can't keep up.
That's why we bought the Coleman Mach 15 Roof top unit, this AC Kicks A$$, will cool the bus off in minutes, holds it's own into the upper 90's and beyond, But there is nothing efficient about this unit, it's loud and consumes lots of electricity, it will never run off the solar system, Generator or shore power only.
Between the two we are very happy with them, usually run them both to cool the bus off then shut down the Coleman and maintain with the Mini Split.
These units only keep the bus cool when stationary, once we are rolling down the interstate all the cool goes out the window (literally).
Not sure why, I know there are plenty of air leaks, or possibly the hot air moving by the bus?
I have kept the Original OTR AC, it does not currently work, it's on the list of things to fix.
Peter
We are trying a mini split with our basement air and a single roof air for quick cool downs. The "trying" refers to the mini split being a 24DC, so as to not require the generator to run, as it runs directly off of our LiON house batteries. And being a DC mini split, it doesn't need to run through the inverters so hopefully more efficient. In addition, it is a ducted mini split so no cassette is required on the inside wall. The cool air is pumped through in wall ducting.
Still testing as there is quirk or two to work out re: load draw.
I'll follow up as progress is made.
Take care, Phil
We have a Pioneer 12,000 btu mini split that keeps the bus "tolerable" in 95 degree weather. The head is above the windshield, so it is a long way from the bedroom. We recently installed a 24v 8000 btu mini split in the rear bedroom but we haven't had a chance to use it yet, as the weather turned cold. The 8000 btu one runs off the bus alternator so we'll run it while driving. I plan to hook it up to my 24v lithium house battery (with 4000 watt solar) soon. That way we can switch it over when parked. We figure it will use less power at night when we're sleeping. I recently ordered a 2000 watt inverter that will connect the Pioneer unit to the bus system while driving so that we don't deplete the house batteries. When all we had was the Pioneer unit, we ran out of power one time, due to running the AC all night, then in cloudy but hot and humid weather while driving all the next day.
We believe we will be in a pretty good place with the two units this coming season. Just to clarify, we mostly boondock, so our plan is to run only one mini split at a time, depending on which part of the bus we're occupying. If we were to be connected to shore power, I imagine running both units will turn the bus into a refrigerator.
In our GM 4106, walls & ceiling is spray foam. All widows (Peninsula) we added double bubble reflective insulation ( two layers). Three years ago we changed out the rear roof AC with a 9000 BTU mini split to the bedroom. First we can sleep with it on, second the heat pump is used more the AC, third is sips energy (compared to roof). In triple digits the unit will keep the room at 70 degrees. I have already purchased a second 9000 BTU mini split to replace the front roof AC. We made a thermal drape to hang behind the front AC so going down the road we are only cooling the front 8 feet of the coach. Grant the the windshield it the biggest heat generator heading into the sun. That scenario we run around 80 degrees, fans help. The front AC does run on the inverter and engine generator.