mini split air conditioners

[Oonrahnjay]

Not meaning to revive an older post but this does have a ton of information especially when determining what A/C to install in your bus. My question is, how are your units running 220 from a 110 transformer with no phase separation?

     In my opinion, it is better to revive an older thread (esp. one that's relevant) than to clutter the board with fractures of info on the same subject.  And you're right, lots of info on this one.  Re: the transformer, you can't run 240V without the phase separation so it always seemed to me that if a transformer works properly, it has to --  1) "transform" from 120V to 240V, and 2) provide the properly spaced phase separation.  I hope I'm not wrong on that.  I've looked at the websites for a number of these transformers and I am not sure (I was wondering about this myself).  Unfortunately, the Chinglish (or Indglish) on these websites makes it hard to know if they really mean what they seem to be saying; in fact, most of the "technical data" isn't very technical and doesn't contain much data.   I wrote this exact question to the Contact Us on some of these websites and got back answers that are either undecipherable or vague.

Originally I was just going to go with a single A/C split system mounted in the rear over the engine compartment and drop the ac lines right down to the outdoor unit sitting in the engine bay. Ill have to do some sheet metal work to create air flow but I'm hoping I wont be using my units for OTR. The OTR A/C did work when I bought the bus but I think my Freon has all leaked out. But by the replies in this post, I think one in the rear and one in the front will suit me well. I kept the old fiberglass shell that came out of the front with intentions of reinstalling it. I may mount the indoor unit over the driver seat where the storage racks used to be. Time will tell though

       I've been researching mini-split systems for a while.  Everyone's layout and needs vary slightly, but if you read posts from people who live in or frequent really hot climates (like everywhere south of Whitehorse), you come away with the impression that the 45K - 48K BTU capacity is about the minimum for genuinely full comfort throughout a bus -- that's for traveling (which has it's issues of air leakage and solar heat loading, esp. through our big windshields) and also stationary (plugged in or running off a generator). 
       That implies either 3 15K or 4 12K BTU rooftop units or a similar output from mini-splits.  And since most of us have varying floor plans, with mini-splits, there is the issue of number of indoor-units and placement.  One way that's worked for some people is to keep their OTR running a dash air con unit (engine driven) for the purpose of providing a lot of cool for driving and two mini-splits running 120V off of separate 120V circuits, one in the front of the bus and one in the rear.  This is doable, but it requires the expense of two systems and maintenance of OTR air and it's a fairly large load on a 120V system in a bus.  (Some people solve their air conditioning electrical load issues by running their generator as they're driving.   This does not appeal to me on a purely aesthetic level but it may be the best option in many situations.)
       As I think you've concluded, if you're going to be running a mini-split system and you'll need 2-3 indoor units to give you the capacity and distribution you need, it's likely the best solution will be a 240V system with a large single compressor (outdoor) unit and the multiple indoor units.  That implies either a full 240V shore-power layout, or a capable transformer with sufficient 120V supply to support it, or a generator that's set up to supply 240V.
       In my opinion, it appears that the issue of the large startup surge draw of air conditioners is solved by the characteristics of inverter-type mini-split systems.  Some people that tried them a few years ago had troubles caused by the vibration, air flow, heat loads, and other difficulties of use in a bus.  It appears that the use of newer units with installation to meet the needs of the mobile environment are adequate but it's clear that care must be taken -- and you're entirely on your own for product support because a manufacturer will not recommend their use or warranty them in mobile applications.

       It seems to me that you're on the right track but you're running up against the same hard questions that others have found.

[richard5933]

Instead of a residential style mini-split which is not designed for bus/mobile use, what about using a split system in the style of what's used in the marine world? There are a number of split units available similar like the Cruisair units, many with higher BTU ratings at 120v. These setups have an indoor unit with the blower and evaporator that is usually set up for running ducts. The indoor unit's placement is much easier when it can be stuck in an upper cabinet with ducting run to distribute the cool air. Our bus has two similar systems installed - no idea who manufactured ours as they don't look like Cruisair - but they work well and cool nicely. Seems like it would be possible to get lots of BTU shoved in a bus using two of these systems. The big downside is the cost and possibly the need for a licensed HVAC guy for the install.

Here is just one site with the units: https://citimarinestore.com/en/189-split-ac-systems

[Oonrahnjay]

Instead of a residential style mini-split which is not designed for bus/mobile use, what about using a split system in the style of what's used in the marine world? ...

Here is just one site with the units: https://citimarinestore.com/en/189-split-ac-systems 

      Thanks, Richard.  Good info, but all the units I can find must use a sea-water connection for cooling condensers.  Any idea for purely air-cooled units?   Thanks,  BH

[Oonrahnjay]

Instead of a residential style mini-split which is not designed for bus/mobile use, what about using a split system in the style of what's used in the marine world? ...

Here is just one site with the units: https://citimarinestore.com/en/189-split-ac-systems 

      Thanks, Richard.  Good info, but all the units I can find must use a sea-water connection for cooling condensers.  Any idea for purely air-cooled units?   I like the Dometic Compact Unit ( https://citimarinestore.com/en/dometic-self-contained/4692-dcu18k-115v-205600818.html ) but, again, sea water.   Thanks,  BH

[richard5933]

Scroll down towards the bottom of this page - look for the air cooled units.

https://www.dometic.com/en-us/us/products/climate/air-conditioners/air-conditioners-for-marine

[luvrbus]

Scroll down towards the bottom of this page - look for the air cooled units.

https://www.dometic.com/en-us/us/products/climate/air-conditioners/air-conditioners-for-marine

In their former life before Dometic  those were Cruisair I install 3 in my Eagle in 1998 bet AC units I ever owned 20 years later they are still going

[ArtGill]

Bruce,  The mini splits only draw what current they need for the conditions.  ie. outside temperature vs inside temperature and how many heads you have on at a time.  A transformer is made up of 2:1 ratio.  The 120 vac side has two wires, one to hot and the other to neutral and on the 240 vac side one wire goes to Hot 1 and the other to Hot 2.  The other plus of the inverter units that they are not too sensitive to voltage sags. 

[chessie4905]

Those early AC units were much more durable. Now they have cut down on the thickness of the copper tubing or switched to aluminum, which is also thinner to lower costs. Now they list a heavy duty Coleman rooftop for harsh enviornments. Probably uses the older heaver tubing  and components.

[luvrbus]

I think the mini splits will work fine no more miles than people drive a RV,I know this group that has 3 in their Eagle.
I am trying to get him signed up here to comment on what goes wrong with the splits when you rack up 70 to 100,000 miles per year in a bus.I want him to do it so it will be first hand information 

[Jim Blackwood]

One thing you can do to decrease the surge current is use a delay relay to turn on the fans. That way the compressor comes on and then a few seconds later the fan does.

Jim

[Oonrahnjay]

Scroll down towards the bottom of this page - look for the air cooled units. ... 

      I did.  $$$ Ouch $$$. 

[Oonrahnjay]

Bruce,  The mini splits only draw what current they need for the conditions.  ie. outside temperature vs inside temperature and how many heads you have on at a time.  A transformer is made up of 2:1 ratio.  The 120 vac side has two wires, one to hot and the other to neutral and on the 240 vac side one wire goes to Hot 1 and the other to Hot 2.  The other plus of the inverter units that they are not too sensitive to voltage sags.

      Thanks, Art.  The low current draw is BIG for me; also, the idea that they will start without a surge is also a big plus.   I have been looking at Daikin - did you install it yourself or have a "certified" installer do it (Daikin's website if big about certified installers).
      My bus is currently wired for 120V but I have been thinking that it would be easy to re-configure to a full 50A/240 setup.  I'd use a 240V/50 Amp shore cord when it was available; when only 120V/30 Amp (or even 15Amp) is available, use the transformer so that the only shore power is 240V.  My big Onan generator is easy to reset for 240V.   Then, wire for 240V to the mini-split unit, run 240V to anything else that needs it, and then split legs for 120V circuits (like house wiring).
       I need a new inverter anyway -- might as well buy a large-capacity 24VDC // 240V/60Hz unit and be done with it.

       My wife and I were down at her place at Emerald Isle a couple of weekends ago; we went over to Beaufort to show her parents around.  We will be back in September (rented out until then), I'd sure love to meet up then if you're available. 
       Best wishes,  BH

[Oonrahnjay]

Those early AC units were much more durable. Now they have cut down on the thickness of the copper tubing or switched to aluminum, which is also thinner to lower costs. Now they list a heavy duty Coleman rooftop for harsh enviornments. Probably uses the older heaver tubing  and components. 

     Yeah, the "march of progress".   They make more money when the customer gets less.  Are any of the "usual suspects -- Coleman, Dometic, Atwood, etc. (and I'm guessing they're all owned by the same Chinese company now anyway) -- making a quality inverter-type rooftop unit with the harsh-environment rating?

[chessie4905]

Eventually someone will offer all the benefits of mini splits except for the roof protrusion in rooftop units.

[brmax]

In concept only, Im on to an idea with a flat solar panel above with fans blowing through chilled mesh.
Estimating a 3? height. I may have to work on this 



Have a good day

Floyd