Author Topic: Make your own mini split AC's ?  (Read 5127 times)

Offline Kenny

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Make your own mini split AC's ?
« on: July 23, 2008, 06:19:33 AM »
Just an idea. Has anyone every thought of making mini split air conditioning using inexpensive residential window units. It would require disassembling a new unit, mounting the compressor/condenser in one of the bays, remote mounting the evaporator running new lines and recharge. Window units are inexpensive, could buy an extra for spare parts and usualy have better SEER ratings than RV AC units. Several of these could be installed throughout the bus. What do you think?

Kenny
1941 and 1945 Flxible - South Lyon, Michigan

Offline Len Silva

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Re: Make your own mini split AC's ?
« Reply #1 on: July 23, 2008, 06:52:03 AM »
I think it ha been done by folks here.  You will need another blower for the evap section as window units use a single motor for both fans.

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luvrbus

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Re: Make your own mini split Ac's ?
« Reply #2 on: July 23, 2008, 07:04:45 AM »
 The Prevost converters in the late 90's tried using a large split central unit that was designed for residential use and it did not last very long the ones I saw were Sayno units 

Offline rdbishop

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Re: Make your own mini split AC's ?
« Reply #3 on: July 23, 2008, 07:25:35 AM »
Kenny,

That's what I've had in my bus for 15 years. I have 5000 btu for the bedroom, a 7000 btu for the drivers area, and 2 12500 split rooftop units ducted from front to back for the whole bus with the OTR air. Works great.

Richard

Offline rdbishop

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Re: Make your own mini split AC's ?
« Reply #4 on: July 23, 2008, 07:36:50 AM »
Kenny,

I went to  an RV dealer and bought 5 junk rooftop units to make my central unit. Some of them had good compressors and bad fans, and some had bad compressors and good fans. If you split the unit ,you need the same size blower moter on both ends.

Richard

Offline kyle4501

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Re: Make your own mini split AC's ?
« Reply #5 on: July 23, 2008, 07:45:09 AM »
Good idea that allows multiple redundancy & also allows:
the cooling units to be located in otherwise "unusable" space
cold air fans can be selected to your level of quietness & air flow  ;D
the condensers to be located in a way that takes advantage of natural convection to reduce fan loading.  ;D
smaller units to allow constant dehumidification since one is always on
a small enough unit can be used in the bedroom that could be run off the batteries overnight  :o
smaller surge to start
etc
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Offline jjrbus

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Re: Make your own mini split AC's ?
« Reply #6 on: July 23, 2008, 07:54:55 AM »
I took a stab at it. Made in China got me. The copper lines that need to be extended, were odd sizes and unavailable. Maybe they are available, but I could not find them. You may want to try a web search, becuse people haave done it.  Jim
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Offline TomC

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Re: Make your own mini split AC's ?
« Reply #7 on: July 23, 2008, 09:07:52 AM »
There was one bus nut that used two window units to make one, since they are so cheap.  He cut both in half and used the evaporator with fan and motor from one, and the compressor, fan and condensor from the other.  I would think it would be an easy job just to set up an additional condenser fan and motor that could be tied to the compressor operation via a simple 120vac solenoid-or just plainly splice into the compressors power from the thermostat since a condenser fan wouldn't take much power.  Good Luck, TomC
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Offline kyle4501

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Re: Make your own mini split AC's ?
« Reply #8 on: July 23, 2008, 09:22:47 AM »
When they installed the A/C at my house, they used a 3/4 fitting for the 5/8 line. He used silver solder & said while it wasn't his preferred way, it would work. That was 15 years ago & I haven't had to add freon yet! ;D

So, if you can do a good job with silver solder, you may be able to work around the odd line sizes.  ;D
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Offline Nick Badame Refrig/ACC

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Re: Make your own mini split AC's ?
« Reply #9 on: July 23, 2008, 09:39:17 AM »
Hi Kenny,

Yes, it can be done using 2 window units to make 1 split system.

We did this on my dad's 4104 in the late 70's. The only problem with doing this today is that the window

units they sell in the stores are precicely manufactored to only last 5 years!  Most don't last that long...

We have a member "Christy & Larry Hicks" that constructed a simular system in their bus but, they ducted

the air into the bus, leaving the entire unit in the bay.

If you were to ask my advice, I would tell you to stick with the RV systems because of their ruggedness, and

easy to get parts if needed.

Good Luck
Nick-
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makemineatwostroke

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Re: Make your own mini split Ac's ?
« Reply #10 on: July 23, 2008, 10:15:32 AM »
One thing when working with refrigeration copper tubing it is not the same size as standard copper tubing and you won't buy it at a home center or auto parts store
« Last Edit: July 23, 2008, 10:34:50 AM by makemineatwostroke »

Offline Nick Badame Refrig/ACC

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Re: Make your own mini split AC's ?
« Reply #11 on: July 23, 2008, 10:30:48 AM »
One thing when working with refrigeration copper tubing it it not the same size as standard copper tubing and you won't buy it at a home center or auto parts store


Yes, Refrigeration copper is measured by "OD" and plumbing copper is measured by "ID".
For instance, 3/4" plumbing copper is the same as 7/8" refrig. copper.

Nick-

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makemineatwostroke

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Re: Make your own mini split AC's ?
« Reply #12 on: July 23, 2008, 10:42:11 AM »
I saw a bus nut with a mobile home packaged unit in his bay and ducted up into the bus he told me it work good and I guess it did he was in Arizona in Aug

Offline Kenny

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Re: Make your own mini split AC's ?
« Reply #13 on: July 23, 2008, 11:04:32 AM »
Hi Nick,
You mention that a window unit will last for no more than 5 years. Would'nt it last longer in a bus because of less usage. Residential usage is constant many months out of the year. Unless you are full timing it I would think bus usage would be less.

You do bring up a good idea using a residential window unit as-is and duct it into the coach. Seams this would even more benificial relating to cost, installation and replacement. Could be setup in a way that if it goes bad almost any unit at Walmart or Lowes could replace it. What do ya think. Kenny
1941 and 1945 Flxible - South Lyon, Michigan

HighTechRedneck

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Re: Make your own mini split AC's ?
« Reply #14 on: July 23, 2008, 11:22:16 AM »
I have been thinking that when I can afford it, I might do it Larry and Christy's way with my RTS.  The condenser bay is over the engine and already well ventilated and drained.  I know RV systems would be better and in the long run probably cheaper, but they are more money than my budget can stand all at once.  Timed right, the home centers usually do cheap clearances at the end of summer.  Or, used window units can be found real cheap in pawn shops in Oct/Nov around here.

Doing it this way, I could start with one 15K window unit plus the two small temporary ones I use now (out the window).  Then eventually replace one or both small ones with another large one.  It looks like there would ultimately be room for three 15K window units back there.

After one of the smaller units is freed up, I might mount it under the dash, with the condenser vented underneath to serve as driver air and run it from a dedicated inverter when in motion or house AC when docked.  The 6500btu unit is a high efficiency one that is rated at 5amps.  So I would think a 1000W (2KW surge) inverter should be able to handle it smoothly.




Offline edroelle

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Re: Make your own mini split AC's ?
« Reply #15 on: July 23, 2008, 11:41:22 AM »
Kenny,

I built a s3 ystem on my original MCI 8 exactly as you described.  I just lost the 30 minutes of description though.  AUGH !!!

In summary, it worked fine with perfect reliability over 30,000 miles. 

Shortened version -

Bought condenser motors from http://www.surpluscenter.com/aboutUs.asp?UID=2007081819422496&catname=electric

Any 2 of the 3 A/Cs worked on 30 amps and maintained 72 degree interior with 102 degree Missouri exterior.   

Condensers installed in MCI front condenser area and right side of engine.  Evaporators in cabinets and end table.

I silver soldered all joints and attached them, but allowed for movement between pipe and A/c components - similar to wiring. 

I rented a tank of nitrogen to check for leaks and purge humidity.  I then evacuated the systems and called a local A/C shop to fill the units.

Great efficiencies, low power use, excellent performance, BUT, very time consuming.

If you have any questions, let me know.

Ed Roelle
Flint, MI


Offline buddydawg

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Re: Make your own mini split AC's ?
« Reply #16 on: July 23, 2008, 12:03:42 PM »
It may not be worth the extra effort with the some of the inexpensive mini-splits on the market.  I have seen some in the $600 range.
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Offline pvcces

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Re: Make your own mini split AC's ?
« Reply #17 on: July 23, 2008, 11:21:22 PM »
One thing I haven't found out yet is whether the inexpensive mini-split units will run on mod sine wave inverter power. I may get a chance to test this next month.

For what it's worth.

Tom Caffrey
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