Air conditioner idea - will it work??

[Chaz]

Hey Guys,
  I have an idea for air conditioning. I think it will work but not for sure. I need the advice of you electrical gurus.
  I am running a 105 amp alternator on the engine. I am thinking about running a 2000 watt AC invertor to run a 800 watt, 8 amp room air conditioner that sits on the floor. I am figuring double that for start up.  I will plumb out the hot air and drain but I'm wondering if this electrical set up would work while driving down the road?? If it does, I will be killing two birds as I can plug in to a pole or run a small gen when camping. Thoughts??
  Thanks a bunch!!
  Chaz

[TomC]

Chaz-How'ya doin? While that sounds good on paper, and the 8,000btu A/C would run on the inverter-8,000btu just isn't much cooling. I have 3-13,500btu roof mounted Colemans. I usually run the front two with front most aimed at me while I drive (I don't have dash air).
Considering most dash airs are around 25-35,000btu, personally I wouldn't even fool with that 8,000btu-I think you'd be disappointed with it's performance. Good Luck, TomC

[TomC]

One more point-while that 8,000btu may keep the front of the bus cool while sitting, remember running down the road presents a lot air pressure on the front forcing in lots of hot air that has to be cooled. Multiply that if you're running into the sun.

[DoubleEagle]

One more point-while that 8,000btu may keep the front of the bus cool while sitting, remember running down the road presents a lot air pressure on the front forcing in lots of hot air that has to be cooled. Multiply that if you're running into the sun.

And, that cool air will gravitate towards the rear while going down the road. The front needs a lot to keep the driver cool. Entertainer coaches will have five rooftops, or 3-4 ton basement airs with a separate A/C for the driver. 8000 btu's won't cut it going down the road, and might not be enough while parked, unless in the shade, and the heat has baked off the engine.

[lvmci]

Front windows radiate heat,  you will have to overcome that first, I did this by putting a 9000btu window AC below drivers seat in tool compartment,  short distance to vents at front seats,  only worked during the spring, lvmci...

[Tony LEE]

Close to 4kW coming in the front windows, plus large air infiltration as you drive so it is a losing battle.

[bevans6]

I think that electrically this will be marginal long term.  A 105 amp 12V automotive alternator might be able to produce 105 amps for a short time at peak RPM, but probably will produce half that at idle and probably will over heat if asked to put out full power full time.  I read once that the rule of thumb is 60% of full output continuously, unless the alternator is designed for full load all the time.  If you could get 105 amps full time, that's around 1300 watts from your inverter.  You'll probably be drawing close to 1,000 watts to run the AC unit (8 amps at 120 volts is 960 watts nominal), so it might work, but if your bus uses any electricity at all you'll be drawing down the batteries, and the alternator will probably have a short life.  Add a second alternator and it would probably work OK.

[Oonrahnjay]

Front windows radiate heat,  you will have to overcome that first, I did this by putting a 9000btu window AC below drivers seat in tool compartment,  short distance to vents at front seats,  only worked during the spring, lvmci... 

     Yeah, not even close when that's all you got, but let's say that you have a pretty good system (maybe 2-3 rooftops) that just needs a little help at the most extreme heat times -- wouldn't that be good as "extra cooling"?  Of course, the best thing to do would be to have a system that makes enough cool that you wouldn't have to have extra or buffer additions around but sometimes it doesn't work out that way.
     It would also seem likely to me that if you had a large capacity blower to move that cool air around you'd be doing yourself a favor.  But the big principle is "if you don't have enough BTUs of cooling, you're going to be hot".

[Nel]

I can tell you the 10k btu portable unit we used last summer just barely kept up in the spring parked, summer, wife not happy at all, may look  into the 15k split 110v this year. I'm trying my best to avoid the roof airs because of the way they look.

[Oonrahnjay]

I think that electrically this will be marginal long term.  ...  Add a second alternator and it would probably work OK.

     Brian, every point you make is technically correct but wouldn't the whole thing be a lot of work and expense for very little real-world gain?  You're talking about component and installation costs, load on the engine, battery purchase and maintenance costs, etc. for 8K BTU.  If it tips the scales between being too hot and comfortable, yeah, I see that, but in most situations, it would seem to be too much cost for the benefit.

[Oonrahnjay]

I can tell you the 10k btu portable unit we used last summer just barely kept up in the spring parked, summer, wife not happy at all, may look  into the 15k split 110v this year. I'm trying my best to avoid the roof airs because of the way they look.  

      I've been using a portable to keep some semblance of cool inside my bus while I've been working through my engine change.  The things are just not very good.  Once they really start working, they pull air that they've already cooled down into the unit to cool the condenser and then exhaust it out the little hose at the back.  So they're cooling air that they then pump out of your living space.  If there was some way to rig up two hoses -- one to bring in outside air to cool the condenser, and one to exhaust the air after it had been heated by that function of going through the condenser/heat exchanger -- it should improve things a lot.  Even better would be mod that would make it work like "recirculation" on your car; draw in already cooled air to go over the evaporator and cool that air even more before it's blown into your living space so you're not losing so much of your cooled air to air leaks, etc.  
      Of course, much of this would be solved by a split system.  I just have found that portable systems are pretty doggone inefficient.

(Edit:)   I just went back to the original post and re-read.  It appears to me that's asking about a portable (I was thinking Gary Throneberry's principle of a "redneck" installation of a window air conditioner in the side of the bus).  He says "plumb out hot air and drain" but still, a portable has a lot of built in inefficiencies.

[dtcerrato]

We'd like to throw something in here, we have one 13,500 btu roof top on the 4104. When we run it on the genny going down the hwy it keeps us a lot more comfortable than not - no matter what the temps are OS. It also lowers the humidity which is a great help. If the sun coming in the windshield makes it feel uncomfortably warm we throw a drivers fan on - solves that. We'd like to think a 160 amp engine generator (original equipment) would run an inverter to keep from having to run the genny for that A/C. So we feel where Chaz would like to go with the 8000 btu unit (but don't think it has enough cooling) - to keep us on thread. 

[bevans6]

     Brian, every point you make is technically correct but wouldn't the whole thing be a lot of work and expense for very little real-world gain?  You're talking about component and installation costs, load on the engine, battery purchase and maintenance costs, etc. for 8K BTU.  If it tips the scales between being too hot and comfortable, yeah, I see that, but in most situations, it would seem to be too much cost for the benefit.

He asked if it would work electrically, so that's the question I answered.  He didn't ask if it would work thermally, and everyone else had answered that already, but no one had said if it would work electrically.

[TomC]

Electrically was answered.
As to the look of the roof top A/C's-you'll notice that the majority of sticks and staples are using roof tops. On the high end coaches, 3-5 are used. What they do is create a side extension of the wall to effectively hide the A/C's and the awnings. You could do that also with the bus. Believe me when I say, roof top A/C's work the best, are easiest to work on. BUT-they are also the noisiest and look bad. Good Luck, TomC

[lvmci]

hi Bruce, my window AC install under the drivers seat idea, was to help while driving, with the roof front AC, that was 13 or14' back, it was a front kitchen floor plan, nothing like external ducting, fans, etc, worked in the hot desert. originally tried a wheeled upright portable, with 9000btu, I thought it was to dangerous in an accident, and thought I would get more effecient with the exhaust heat out of the room, lvmci...