Can we have a 13,500 btuh coach air conditioning system that uses less than 900 watts and will start on a 1000 watt invertor. You bet. You could run it while traveling, off of the Engine alternator, or a hybrid inverter. You could run it off of 15 amp circuit and plug-in cord. You may be able to boondock all night after you shut down the genset. You Could you downsize your genset because the starting in rush current or locked rotor amps are within 1 amp of full load current.
This technology has been around for almost ten years and it keeps improving. You can walk into home Depot, and buy this oriental hvac unit.
Newest technology in propeller fans (which we are running horrific efficiency stamped steel fans) has vastly
Improved, the already very efficient composite plastic fans have been improved by adding turbicles, and by preventing end vortex shedding. LG were able to achieve a 10% increase in flow, and a 20% decrease in hp. R&D in America is stuck.
We as coach owners are stuck with crap, until [alternatives] enter the market.
[updated topic title to be more descriptive - minor edit on one phrase based on member complaints - Michelle]
Like to have a link to a 13500 btu ac that would run off a 1000 watt inverter.
My shoulder just popped back in the socket after going fer the Big Dictionario to look up: Turbicles
You learn something new every 24 to 46 hours, doncha? I'm ok.
Unfortunately RV air conditioners, are not available this way. Tried to attempt/convience the builders of Coleman RV a/c units to explore this option. I got no response. I have cornered their "engineers" at a restaurant close by me. They seemed very interested but no follow up call.
If they are so easy to build profitably, go build them.
Old Phart is obviously talking about ductless mini splits, and having installed several I agree, they are awesome. Head and shoulders above any other form of residential ac for efficiency, low cost, high quality, quietness but with their limitations of placement. AC contractors are often detractors as the equipment lends itself to self installation.
Like many others I have pondered installing one in the coach. I believe a company that wanted to develop retrofits could do well.
Here's a good article on "tubercles":
Whale of an Idea - Design Engineering (http://www.design-engineering.com/features/whale-of-an-idea/)
7 year old article. I have never heard of these.
Names can be funny: "...Dr. Frank E. Fish, now WhalePower's president." What are the chances??
I intend to attempt to build one this winter, to fit the standard roof opening. Profitable I doubt, at this point since I will be buying a completed unit and disassemble it to gain access to the inverter compressor, complex control boards, ecm fan motors, and electronic expansion valve. Airxcel is just mile down the road from me, maybe then they may wake up if I showed it to them.
America has forgotten about R&D and wonders what happened as their market share shrinks or disappears entirely.
Are you going to use ceiling cassette style evaps?
Modified mini-split systems [basement air] have been installed in coaches for 40 years or so [Prevost, Newell etc].
The compressor/condenser takes up a lot of room under the coach and because of the fan it needs, produces noise at ground level.
A motor home would require several zones or several units or an elaborate ducting system. The mini splits big enough to cool a motor home all require 220 volt service available on bus conversions and high end coaches, but not on most cheaper coaches.
The industry likes the roof top because they are cheap, easy to replace [they are throwaway] and do not take up any basement room.
A lot of the recent Newell's and bus conversions are being ordered from the factory with 3 or 4 or even 5 roof units because of the problems with basement air.
Thanks for the explanation, I'd wondered why I'd seen so many high liners lately with lotsa roof units! ^.^d
I was looking into ceiling cassette units to retrofit my ACs but a couple of problems exist.
1. The dimensions of the ceiling cassettes are much larger than the standard 14x14 rooftop air opening. They are designed to fit into a standard 24x24 opening in a drop ceiling typical in a commercial building.
2. Ceiling cassettes are a minimum of 7" tall which would mean it would need some sort of weatherproof cover built over it on the roof.
I have pretty much given up on the ceiling cassette units and am looking at floor console units (http://www.mitsubishicomfort.com/products/indoor-units/floor-mounted/gallery) which mount low enough on the wall that it would fit underneath our windows.
I would get roof airs instead of basement air in a prevost and I would never get 4 slides so I could get over the road air as well.
1996 U270 Dual Central Air Conditioning (http://www.foreforums.com/index.php?topic=16993.0)
I am going to try the existing 14x14 holes, I believe it will take 2 evaporator coils and 2 condenser coils per unit to get the efficiency, so the roof unit shroud will grow longer and have to be fabricated. So two dead or used donor roof units per system. Or slice up the mini's coil and reconfigure it and resolder.
I would consider a multizone mini but where would you mount the condensing unit, and they require 220 power which would require a boost transformer. 220 power units are however available in higher EER. SEER ratings are horse poo generated by the marketing department, and adding majic factors, or omitting essential filters etc.
Where will you put the compressor/condenser units?
I initially considered a transformer but have since decided to use a 240 volt inverter. You can use a cheaper option like this 4000 watt AIMS unit (https://www.amazon.com/Power-PICOGLF40W12V240VS-4000W-Inverter-Charger/dp/B00JJ8UDG0/ref=sr_1_3?ie=UTF8&qid=1502559178&sr=8-3&keywords=aims+240+v+inverter) or you can go the more expensive route by using two5000 watt 12v Victron Quattro units (https://www.victronenergy.com/inverters-chargers/quattro) to create split phase 240v to power the mini split (probably could get by with the cheaper 3000 watt Victron Multi units also since inverter mini splits don't have the large start up current that non-inverter units have).
I would mount the condensing unit behind the driver's side rear tire that is currently occupied by my engine's air filter which would be moved to the rear engine bay opening like some Foretravels originally were set up. The small space requirements will limit the choices available in a multi-zone condensing unit though.
In the extended fabricated roof shroud, coils in a vee arrangement top discharge.
The Aussies (AirCommand available in the US) Atwood looks like it has some of the features you require, mainly improved 3 stage air flow 330 CFM @ 66dB. It only requires 11.3 Amps / 1270 Watts ,BUT states needs 2000 watts starting (maybe less?). They also have many different technologies to choose.
Maybe MR B2 can chime in 'bout how much better he has it living "Down Under"
Dan
Coleman power saver 13.5 runs on 11.2amps and will start on most 2kw invertor generators
Removing the big muffler and replacing with a resonator will give you a lot of room behind the drivers side rear wheel.
So basically a more efficient rooftop unit?
Yes, but after reading how much Jerry spent I may rethink. But then again it sounds like a fun project, and I can hide out in the garage all winter:)
The Dometic brochure I attached lists two split systems available for RV's. Would need a 240V/50 hz dedicated invertor.
Dometic aircommand heron 2.2 | Dometic - Mobile living made easy. (https://www.dometic.com/en-au/au/products/climate/air-conditioners/air-conditioners-for-rvs/dometic-aircommand-heron-22-_-136297)
They ran around $1200. Can't guarantee they will ship to US.
Amazing that the inverter compressor takes AC single phase power, converts to DC power, and then converts back to achieve ac multiphase power to run the motor. Samsung's new compressor operates on six phase power IRC
That's looking like a pretty complex installation. I think you could quite simply install one of the ceiling mount evaporator units (the ones that are made to retrofit to a ducted conventional split system ac) in the cabinet above bed. Extend duct as per Foretravel on into the living room. Leave condensing unit in case, remove useless dash air condenser, build insulated enclosure in space, add grille, slide in standard condensing unit. Still not trivial but would allow you to easily replace any part of system without having to make custom mods. The output of a 24K btu unit will vastly exceed two roofmount 15K units and provide real heat if desired.
You would still need 240 volts for the 24K unit. How does a 24k unit outperform two 15k btu rooftop units? In air conditioning, BTU's are the amount of heat removed. Does not matter how the unit operates, removing one btu is removing one btu. Foretravels are well insulated but pushing cold air through a duct down 40 ft of coach 2 inches under a hot roof would not be very efficient, to say nothing about the size and noise of the blower required.
Not trying to throw cold water on your idea's, but the 2 million dollar coach makers, where money is no object, have tried every method and are now going back to good old roof airs.
While I agree our dash air is weak compared to the later units we came through Nevada this week then through the baker grade to so cal.
Outside on the world tallest thermometer it was 104 and with the dash air on high and the front roof air on at 75 and auto fan on the front was comfortable. Small fan clipped to the passenger side window frame helped the sun side.
Like I said. Comfortable.
I am very happy with my present dash air. Have never had a diesel pusher that had a good engine driven compressor dash air, almost always had to supplement with a roof air and run generator. Present coach dash air will actually keep front area of coach cool in 95 f. ambient temps. Am seeing about about a 38 degree drop through the evaporator with blower on high. I think Mel at MOT told me once that if he had $5 for every coach he sold with a non working dash ac, he would be a rich man. Of course, I have no idea how many thousands of dollars the PO spent on getting it working right.
It happens when the 24k BTU unit actually removes 24K BTU, and the two so called 15K BTU units actually remove around 9K each.
Inverter compressors can and do go into overdrive at 80hz vs 60 hz for a limited amount of time, or till they max out the rated amperage. Control boards are very smart. A 12k btuh unit may actually have an 18k btuh compressor that the control board that allows to work as hard as needed, and modulate evaporator fan & condenser fans to provide the biggest bang for the buck
Now that the cooling question has entered the conversation, I have wondered why my 2 13k units which would be over 2 tons cooling on a residential rating don't cool the coach as good as my one 1 1/2 ton (18k) that I have in a room with more cu. ft. than the coach. I have guessed that the distribution was the cause. But are these coach units being over rated? The room has west facing 8' window and does have air space in the attic which I figured cancelled each other out..
https://www.energydepot.com/RPUcom/library/BUILD001.asp
Even dual pane windows do not have very much insulating quality especially when compared to sheetrock, plywood, fiberglass insulation etc. and your coach has a lot of windows. Your house ceiling may have up to r-32 insulation valve, The foam in the roof of a Foretravel may be as low as r-10. I have closed cell blinds on every window on my coach, If I Ieave them open, I will need both roof airs, if I close them all, one ac will keep the coach cool.
Simple experiment, cool coach to 75 f. shut off ac and leave. Come back in 2 hours and take temps inside. Do the same thing in your room in your house and compare results.
No, observation and comparison only. It's a reasonable guess that rooftop units are not producing the optimistic 15K BTU they were rated at. In lab conditions. Possibly with voltage tuned to optimum. New.
These splits, or at least the ones I've had experience are hitting way above their numbers. I've replaced a two ton older conventional with a 12K and the performance is far superior, cooling wise. Using a fraction of the power.
Split units are used all over Asia and in many places in Europe and in many cases are far more efficient and cool better than window or central units in many applications.
The problem is the application. With a 12 by 12 room with few windows and no heat sources and fairly good insulation. a small split unit evaporator unit near the ceiling will do a great job.
Now take a 40 by 10 box moving over a 120 degree surface with a 100000 btu heat source on one end a 20000 btu heat source on the other, with lots of big windows and direct sun on at least on the roof and probably on one side as well. Add in many small barely noticeable air leaks, and maybe r-6 insulation overall, and only be able to use ac compressors that run on only 120 volts, and you will see why motorhome ac's seem so inefficient.
I would agree that the current RV rooftops are not delivering into the coach what they claim. My Coleman units has an unsealed shaft leaking air on the evaporator side. Furthermore I think the motors may be running in reverse on both units.
Certain 120 v single phase motors can and do operate backwards. My units draw air through the condenser coil on the vacuum void side (rear facing) of a moving vehicle and discharge the 140 degree air only to be sucked back thru the condenser coil.
Oriental splits can post some extremley high efficiency numbers since ARI has not been able how to test them apples to apples.