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Old 07-20-2017, 12:38 PM   #1
Mini-Skoolie
 
Join Date: Jun 2017
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Mini-Split + Engine Mounted Compressor

so the more investigation i do the more questions i have... someone in another thread mentioned using 110v mini splits for cooling and some heating. there are even some 12v systems...

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but there not cheap.

and on Alibaba...

https://www.alibaba.com/showroom/12v...nditioner.html

cheaper.

because i would not want two systems on the bus i.e. to keep complication down is it possible to have the engine mounted compressor in the refrigerant line of the mini-split?

My thought would be to have two 110v mini splits that could run from the inverter or engine.

I have no clue...

or it may just be easier to have a larger house engine mounted alternator and power the inverter while the engine is running

here is a link to what could be a good solution... but risky...

https://www.alibaba.com/product-deta...b8bexFc6sH&s=p

any input or thoughts...? +

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Old 07-20-2017, 12:41 PM   #2
Mini-Skoolie
 
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or am i just being stupid...

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it would be nice to have heat and AC in one unit like the 110v mini-splits though.
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Old 07-20-2017, 12:46 PM   #3
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driving 2 refrigerant circuits with different compressors == fail.

for one, the mini splits use R-410A, vehicle systems use 134A.. the pressures of R410A are roughly double that of 134A so you would likely Nuke a vehicle compressor in short order..

2. minisplits use variable speed compressors and electornicf expansion valves.. you need the computer of the minisplit to be functional to operate the EEV.. once the computer comes up and sees the compressor wont operate it will error out..

-Christopher
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Old 07-20-2017, 03:47 PM   #4
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The 12 or 24 volt mini split is a cool idea but $900-$1200 for an "unknown" 7000 Btu A/C is a hard sell for me.

I think a 12kBtu 110v inverter mini split running from an inverter may be a more cost effective solution and could be assembled from components with good reputation.

just my $0.02
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Old 07-20-2017, 05:20 PM   #5
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Steve / Chris, that's just the reality check I needed thanks.

Ok one last try... Would one of these run in parallel with an engine mounted compressor. There would have to be an interlock that would mean the engine mounted pump had priority. To my knowlege the pumps use reed valves so a check valve would not be needed.

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P.s. I can't help myself I wake up thinking about this stuff...
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Old 07-20-2017, 05:21 PM   #6
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if it will run.. wasnt there someone here who was using a modified sine wave inverter and their mini split wont power up but did just fine on regular shore power?.. so you might have to spring for a pure sine wave..

7-12k btu is going to maybe take the edge off the heat while driving... perhaps better in an RE bus.. but driving into the sun in an FE or conventional bus you need a lot more than 12K
-Christopher
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Old 07-20-2017, 05:49 PM   #7
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Quote:
Originally Posted by Steven UK View Post
Steve / Chris, that's just the reality check I needed thanks.

Ok one last try... Would one of these run in parallel with an engine mounted compressor. There would have to be an interlock that would mean the engine mounted pump had priority. To my knowlege the pumps use reed valves so a check valve would not be needed.

24V Electric Scroll AC Compressor_Auto AC Compressor_Industry Machinery & Auto Part_TUF Marine Equipment Supply factory Company Suppliers Manufacturers in China - TUF Marine

P.s. I can't help myself I wake up thinking about this stuff...

that unit is big.. did it talk about the amperage pulled for various capacity / pressure scneerios? i believe most engine compressors on busses are 10-13 cc ..this one is 25.. id have to look and research it all..

you would have to manage oil return and refrigerant entrapment possibilities to make something like that work.. in theory it should work in an engineered system.. assuming you can get it the 24 volts it needs.. solar / battery?

-Christopher
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Old 07-31-2017, 11:21 PM   #8
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Originally Posted by cadillackid View Post
that unit is big.. did it talk about the amperage pulled for various capacity / pressure scneerios? i believe most engine compressors on busses are 10-13 cc ..this one is 25.. id have to look and research it all..

you would have to manage oil return and refrigerant entrapment possibilities to make something like that work.. in theory it should work in an engineered system.. assuming you can get it the 24 volts it needs.. solar / battery?

-Christopher
Chris
i was clutching at straws trying to find a way to make either existing AC system work in a stationery scenario or a mini split work when mobile. after doing more reading i think the 120v mini split with a decent 24v alternator and inverter may be the best idea. i'm just pre-planning with little knowledge of the subject. but its all part of the learning process.
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Old 08-01-2017, 08:51 AM   #9
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Originally Posted by cadillackid View Post
7-12k btu is going to maybe take the edge off the heat while driving... perhaps better in an RE bus.. but driving into the sun in an FE or conventional bus you need a lot more than 12K
-Christopher
Now that summer is almost over, how many BTUs is a bus going to need sitting stationary?

Coulda/shoulda/woulda put in a window unit that I have sitting in the crawlspace but how long is that going to take to cool off a 40 ft bus sitting in full sun? Without worrying about time (I could run over at lunch and plug it in), my problem will be finding power for it. There's a 15amp service 50 feet away. My extension cord already hates the air compressor. The cord gets hot to the touch as it is. The drop that is closer doesn't have power. It's wired but I don't know where the voltage is. One of these days I should stay late and see if the light at that pole comes on. The next pole, assuming it works, is going to be 75+ feet away.
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Old 08-01-2017, 10:18 AM   #10
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Quote:
Originally Posted by cadillackid View Post
driving 2 refrigerant circuits with different compressors == fail.

for one, the mini splits use R-410A, vehicle systems use 134A.. the pressures of R410A are roughly double that of 134A so you would likely Nuke a vehicle compressor in short order..

2. minisplits use variable speed compressors and electornicf expansion valves.. you need the computer of the minisplit to be functional to operate the EEV.. once the computer comes up and sees the compressor wont operate it will error out..

-Christopher
Question in the same vein as this - my bus uses R22 (yup, that old). I think I've seen a few R22 scroll pumps around. In my case would that work to achieve the "existing system while stopped" scenario?
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Old 08-01-2017, 08:38 PM   #11
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if it will run.. wasnt there someone here who was using a modified sine wave inverter and their mini split wont power up but did just fine on regular shore power?.. so you might have to spring for a pure sine wave..

7-12k btu is going to maybe take the edge off the heat while driving... perhaps better in an RE bus.. but driving into the sun in an FE or conventional bus you need a lot more than 12K
-Christopher
Me! Your mini split will likely not run on modified sine. Mine didn't. Don't bother. I am still getting mine finished up but I had to buy a 2kW pure sine inverter to power the beast. Xantrex has some modestly priced stuff available. Oddly enough, my fridge and all my sensitive electronics run just fine on the modified sine that I have hard wired into my 120v wall outlets. It's just the mini split ... so I use a Xantrex ProWatt for the mini split and a Magnum for everything else.

Also, I fully intend to run mine while moving. As long as it's properly shielded from the wind and the computer isn't throwing codes it should work fine. I wouldn't mess with using an existing compressor or spring for the 12v stuff. There are simpler ways to do it. Mine is literally mounted on my rear bumper. I'm adding a crash bar around it in the event I'm rear ended. Works perfectly.
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Old 08-14-2017, 10:46 AM   #12
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I have considered doing something similar with existing bus AC, my plan was to use the same compressor that the bus AC runs with currently and have a 110v motor that would power the compressor while plugged in. My compressors already have a couple belt pulley at the clutch so in theory the 110 v motor could just free spin when the AC is engaged while driving as long as it is electrically disconnected while driving down the road it shouldn't add to much engine load. This is a rough idea in my mind so things I see that would make it not work are

Amps pulled by a big enough motor to run the compressor.

The controls for this system would be a nightmare but I think I'm up for the challenge.

Since I haven't seen a system like this before I am assuming there is a major flaw in my plan but I'm an instrumentation tech not an AC guy. Is there a reason this wouldn't work?
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Old 08-14-2017, 10:57 AM   #13
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My compressors already have a couple belt pulley at the clutch so in theory the 110 v motor could just free spin when the AC is engaged while driving as long as it is electrically disconnected while driving down the road
Plug that sucker into a wall outlet. Free 110v outlet while driving!!
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Old 08-14-2017, 11:20 AM   #14
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Plug that sucker into a wall outlet. Free 110v outlet while driving!!
the frequency would be constantly changing i think after the pulleys were set up to run the compressor at the right RPM the motor may be putting out about 60 Hz When being driven by the engine. Not sure if about 60 Hz would be useful for anything seems like some battery charging systems can take a range of voltages..... would probably be worth looking into if the AC system could be worked out. Thanks for encouraging my crazy ideas!
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