Window A/C converted to Mini-Split Success
I know that this has been kicked around a bit on other threads, especially after the Midea-U window A/C unit came out, but I've just completed a successful "science project" to convert the Midea-U 8000BTU window unit into a "mini-split" by separating the indoor and outdoor sections. I have no clearance in my garage for a rooftop unit, not $4000+ for a commercial unit... thus the necessity to attempt a split for less than $500.
Here is the video that gave me the inspiration where it looked like the two pieces could be separated by extending the electrical and refrigerant lines:
I talked with a couple HVAC professionals (I am not one) about the feasibility and they both said: "Yeah... it might work"
Here is a sequence of pictures of the process and end result...
Here is the unit "unboxed":
![157138]()
I removed the "control box" that is part of the outside and extended all electrical wires by 15ft, positioning all connectors at the end that will connect to the outside portion of the unit. The control box itself I decided to remove and join the indoor portion to prevent too much exposure to the adverse undercarriage environment (upper mid-west winters).
A piercing valve was placed on the suction side to evacuate the existing refrigerant (R32).
![157139]()
The outside unit will be positioned between the front and rear wheels on the driver's side. There was a thin support between the frame and side skirt that was removed to allow it to fit. Gutter screen was added to keep out larger debris.
![157140]()
Some brackets were fashioned to support it beneath the van. Super strut on outside and Plus-nuts inserted to the frame on the inside.
![157141]()
Charging the unit with new R410A refrigerant through valves added to the line set. The original refrigerant (R32) is used in Europe and East but is not readily available is the US as it is mildly flammable. R410A is a mix of 50% R32 and 50% R125 which negates the flammability. We hoped it was "close enough" to the OEM spec to work effectively.
![157142]()
Here's the indoor side of the unit mounted near the roof with the control box mounted beneath it. The control box has a heat sink (from the internal inverter?) and this position gives it good airflow to the bottom air inlet. This heat sink would normally get air from the condenser fan.
The line set is looped inside the van to allow enough slack to lower the external unit for service.
![157144]()
The electrical, refrigerant line set, and drain were all routed through a hole into the outside unit.
![157150]()
It hangs about an inch below the skirt but not as low as the passenger side step.
Air baffles were added to force the heated exhaust air downward and keep it from recirculating back into the unit.
![157151]()
What would I do different?
Here is the video that gave me the inspiration where it looked like the two pieces could be separated by extending the electrical and refrigerant lines:
Here is a sequence of pictures of the process and end result...
Here is the unit "unboxed":
I removed the "control box" that is part of the outside and extended all electrical wires by 15ft, positioning all connectors at the end that will connect to the outside portion of the unit. The control box itself I decided to remove and join the indoor portion to prevent too much exposure to the adverse undercarriage environment (upper mid-west winters).
A piercing valve was placed on the suction side to evacuate the existing refrigerant (R32).
The outside unit will be positioned between the front and rear wheels on the driver's side. There was a thin support between the frame and side skirt that was removed to allow it to fit. Gutter screen was added to keep out larger debris.
Some brackets were fashioned to support it beneath the van. Super strut on outside and Plus-nuts inserted to the frame on the inside.
Charging the unit with new R410A refrigerant through valves added to the line set. The original refrigerant (R32) is used in Europe and East but is not readily available is the US as it is mildly flammable. R410A is a mix of 50% R32 and 50% R125 which negates the flammability. We hoped it was "close enough" to the OEM spec to work effectively.
Here's the indoor side of the unit mounted near the roof with the control box mounted beneath it. The control box has a heat sink (from the internal inverter?) and this position gives it good airflow to the bottom air inlet. This heat sink would normally get air from the condenser fan.
The line set is looped inside the van to allow enough slack to lower the external unit for service.
The electrical, refrigerant line set, and drain were all routed through a hole into the outside unit.
It hangs about an inch below the skirt but not as low as the passenger side step.
Air baffles were added to force the heated exhaust air downward and keep it from recirculating back into the unit.
What would I do different?
- maybe not relocate the control box. It may not have been necessary.
- maybe make a different box for the outside unit as the OEM case is a bit cumbersome to work with.
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How would you control it ( turn it on /off ) if you didn't relocate the control box , remote control ?
Btw , nice looking bracket .
Also , it would be nice to see how you evacuated the refrigerant and then how you ran your refrigerant lines and showing how you charged the system .
Do you have to worry about the refridgerant lines becoming contaminated when you first open them ?
Thanks for posting
Btw , nice looking bracket .
Also , it would be nice to see how you evacuated the refrigerant and then how you ran your refrigerant lines and showing how you charged the system .
Do you have to worry about the refridgerant lines becoming contaminated when you first open them ?
Thanks for posting
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The "control box" is just the brains of the unit. All of the operational controls are available on the face of the inside unit (Evaporator) and there is a remote control that came with it, phone app too if you connect it to a network.
My HVAC pro neighbor had the vacuum (remove contaminants), gauges, temp sensors, and refrigerant that helped determine how much refrigerant was needed.
The line set I purchased had flared fittings but I used a R410A optimized ZoomLock fittings to connect the new lines to the stubs of the original unit.
An HVAC Pro definitely needs to be involved in the process as it is not fully DIY. There were a number of pressures and temperature goals that provided feedback that the new configuration was operating correctly.
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Do you run the unit through an inverter or shore or both?
2017, cargo, 130inch, mr, dbl sliders, 3.2 dsl, 3.31 rear end, used 13.5k mi.
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Ah, dah cool air dun cummin frum dah jeenious tinkerer...
Well done! See if you can patent the install design adaptations and monetize all your efforts...
What is the SEER efficiency rating, if I might ask? Small spaces such as the van can be made so much more comfortable with this feature. As a novice tinkerer myself, I installed a minisplit fabricated in Japan with many Korean parts as I found I could avoid totally made Chinese products. I just hate their Nazi-like central communist gov't so much for so many reasons. The home minisplit in a century old cottage is used rarely post thermal envelope upgrades, i.e., proper insulation, thermal multipane windows... Likewise, spouse's ransit minivan was insulated for 4 season use and only really appealing feature missing is a GREAT AC minisplit as you have seen fit to install. Again, great job and keep on thinkin' and tinkerin'!
Well done! See if you can patent the install design adaptations and monetize all your efforts...
What is the SEER efficiency rating, if I might ask? Small spaces such as the van can be made so much more comfortable with this feature. As a novice tinkerer myself, I installed a minisplit fabricated in Japan with many Korean parts as I found I could avoid totally made Chinese products. I just hate their Nazi-like central communist gov't so much for so many reasons. The home minisplit in a century old cottage is used rarely post thermal envelope upgrades, i.e., proper insulation, thermal multipane windows... Likewise, spouse's ransit minivan was insulated for 4 season use and only really appealing feature missing is a GREAT AC minisplit as you have seen fit to install. Again, great job and keep on thinkin' and tinkerin'!
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I’ve observed it pulling from 380W to 480W and 2.5A to 6.5A depending on how hard the condenser is working (120V).
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The Midea U 8000BTU has a 15 CEER rating.
I’m not following what these numbers represent, assuming entire unit is 115/120 VAC. The 2.5A is much less than 380 Watts, and 6.5A is likely more than 480 Watts. Could you elaborate on what you measured and confirm voltages?
I’ve been interested in these inverter driven small window units with +/- 15 CEER since they were announced.
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Why did not try and capture the r32 and then just fill the additional refrigerant using one of the compatible fluids - Freeze+32 for example - i would figure that is cheaper but I am an AC newbie so feel free to correct my thinking
Any concerns with high operating pressure of R410A?
Any performance loss noted with the 410a
I have purchased a 10k BTU unit and will be splitting and was trying to see a way of using the existing R32 -
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Good question!
We actually did capture the R32 before "splitting" the system. However the storage vessel was not new, nor used for only R32 so there was risk of contamination. R32 has not caught on here in the US even though it is widely used in Asia-Pacific regions. R32 is slightly flammable which may be part of the reason adoption is slow. We tried to source new R32 to recharge the unit but were unsuccessful.
It turns out that R410A is a blend of 50% R32 and 50% R125. Given they are part of the same family, we hypothesized the Midea units operating parameters should be broad enough to handle straight R410A, which turned out to be the case in our testing, albeit less efficient than R32.
My help on this "science project" was a lifetime HVAC professional that had the equipment, gauges, and know-how to make the on-the-fly adjustments.
Doing a quick search, I still cannot find R32 available here in the States.
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Coming to this post a bit late with a suggestion inspired by your ingenuity.
You and this lifetime HVAC professional should assemble and sell an AC conversion kit for Camper Van conversions. Aside from the need to pay a professional to manage the refrigerant, I suspect many DIYers would jump at the opportunity to implement something like this in their own build while avoiding the $4000+ cost of commercial AC units.
You and this lifetime HVAC professional should assemble and sell an AC conversion kit for Camper Van conversions. Aside from the need to pay a professional to manage the refrigerant, I suspect many DIYers would jump at the opportunity to implement something like this in their own build while avoiding the $4000+ cost of commercial AC units.
2022 Transit 350 HR Cargo AWD, LWB, all windows, Avalanche Gray, AC and Coolant taps,
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Is their any spike at start up at all? For my apparently virtual van, I already bought a dual inverter LG window unit with a slow start up. Confirmed by watching an ammeter. I may switch to your method. Thanks for posting.
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The Midea U unit is also an "Inverter style" unit. I have not noticed any start-up spike as the startup sequence seems quite well controlled.
Here is the video that inspired me to convert this window unit into a mini-split and it describes some of the efficiency built into the design:
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Could you post the part numbers for the the lineset and zoomlock fittings?
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I picked these up from SupplyHouse.com
It did require a small piece of tube be cut off the Line Set and braised onto one of the Midea unit's lines as there was no compatible ZoomLock size for the Midea (3/16th I think).
I used the "removable" ZoomLock unions close to the condenser unit under the van in case it needed to be vacuumed and disconnected for service.
2022 Transit 350 HR Cargo AWD, LWB, all windows, Avalanche Gray, AC and Coolant taps,
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Thanks for posting this list. Apparently the condensate collecting tray on the inside unit was left intact since you could run a clear plastic tube from the inside tray to the outside unit. If my ordered Transit ever comes, I may use your method. Thanks again.
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Indeed! The condensate collection tray normally uses gravity to route condensate/water that comes off the evaporator coil to the outdoor side of the unit below the fan where the fan slings it onto the condenser coil to enhance cooling efficiency.
I drilled holes in the condensate tray and fitted the tubes to drain the water into the condenser tray. Might be overkill as the condensate could have been drained directly onto the ground.
Also, I did take foam that was included with the unit and placed it to direct the heated air output from the condenser coil down and prevent recirculating the heated air within the cavity where it is mounted under the van.
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Thanks for the help. I'll try to remember to put some pictures up when I get mine done.
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