Mini Split Units

ZihuatanejoMan

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12:02p, 3/7/25

I am wanting to do a DIY unit in my 40' insulated container. My research shows about 20btu per sq ft. I have about 272 sq ft insulated. I should be fine with 6000-8000 btu. I have been looking on Amazon and prices are everywhere. Couple of questions:

Will it hurt to go with a higher btu unit?

Does anyone here have experience with DIY and recommendations on a brand?

Thanks.

UmustBKidding

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7:03p, 3/7/25

Mr cool is the only one i know of that are really designed for novice installer. The sell you pre charged line sets so you dont need a vacuum pump to evacuate your system. You pay a significant premium and others indicate that repair parts are not readily available. I have installed several in multiple buildings on the farm. Typically buy from ac suppliers like ac wholesale, hvac direct, pioneer rather than Amazon. Went ahead and invested in the necessary equipment. Oversized is in general not great since you need runtime to lower the humidity. But minisplts are typically have variable speed compressor so its not as critical. I recommend using one of the online manual j calculator to size the system based on your zone, insulation, windows and doors and any shade.
I have talked with my son who does hvac for tdcj about doing guided system startups using quality equipment for people.
We typically spend 2500-3000 on name brand systems (lg Mitsubishi etc) that vendors quote between 5000-7500$. I understand they have overhead, but if you are skilled and careful saving can be significant.
Email in profile or pm if have questions

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wunderbrad01

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4:16p, 3/10/25

AG

I have all my bedrooms on a 6k btu and haven't had any problems. Biggest bedroom is 244 ft2 iirc. Full disclosure, we havent had a summer in this house.

I bought my units from alpinehomeair.com. Prices were well in line, great customer service. I had a few questions and issues during install since it was my first time. The tech support was incredibly helpful to me. You do have to have AC gauges and a vacuum pump to self install, which I have from working on auto AC units.

ZihuatanejoMan

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5:01p, 3/10/25

So, one of my biggest question is if they come self charged you still need the gauges and vacuum pump to get running? I'm sure we can figure out it since we have the equipment but was curious how the self charge units worked. I'm sure it will all confuse me in the instructions. LOL.

Hope Is A Good Thing

RoyVal

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In reply to ZihuatanejoMan • 7:45a, 3/14/25

AG

ZihuatanejoMan said:
So, one of my biggest question is if they come self charged you still need the gauges and vacuum pump to get running? I'm sure we can figure out it since we have the equipment but was curious how the self charge units worked. I'm sure it will all confuse me in the instructions. LOL.

no you don't need any gauges or vacuum. I don't know the first thing about HVAC, but I installed a Mr. Cool in my garage a couple of summers ago and it works like a CHAMP. My buddy saw my garage and made me come install one in his garage as well LOL.

The lines come pre-filled, so once you get everything installed, you just turn a screw on the lines that opens them all the way to the compressor. Very easy!

Absolute

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8:08a, 3/14/25

AG

I installed a Mr Cool in my garage. I believe it is the 12000 btu one. It runs on 115 single pole circuit which made the electric install easier. The precharged stuff worked great. Installed was very simple. No specialized hvac equipment or knowledge needed.

Has been going strong now for 4.5 years

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yayaggies

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In reply to ZihuatanejoMan • 8:56a, 3/14/25

There is a big difference between pre charged and DIY friendly. The Mr Cool DIY units have special hoses and connectors and do not require vacuum or special tools. There may be other manufacturers with similar provisions.

Most, if not all split units are precharged where once you install and connect the lines properly and pull a vacuum you can turn a screw and release the refrigerant stored in the outdoor unit into the system. No external refrigerant is required.

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Whitetail

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12:41p, 3/14/25

AG

I've installed 2:

1st one was a Mr cool 12k DIY. It started leaking after a year. I think I paid $1700. I've read if you don't do the fittings just right, it can leak. I couldn't figure out how to fix it and I found going the AC repairman route wasn't economical.

2nd one was a Senville 12k, not DIY. I installed everything (mounted everything, plus electrical) up until the coolant lineset. Paid an AC guy $400 cash to install the lines. Paid $750 for the system I bought off Amazon. The thing has been running solid for 8 months.

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UmustBKidding

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11:22a, 3/16/25

If line set is not pre charged you need vacuum pump (you can rent at most auto parts store) and should have access to gauge set, equipment to nitrogen purge line set and a micron gauge to measure the vacuum. I have this equipment, or you can pay a hvac tech to do your startup.

AgLA06

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In reply to ZihuatanejoMan • 11:59a, 3/17/25

AG

ZihuatanejoMan said:
I am wanting to do a DIY unit in my 40' insulated container. My research shows about 20btu per sq ft. I have about 272 sq ft insulated. I should be fine with 6000-8000 btu. I have been looking on Amazon and prices are everywhere. Couple of questions:

Will it hurt to go with a higher btu unit?

Does anyone here have experience with DIY and recommendations on a brand?

Thanks.

Your calcs are probably correct, but I imagine that is for normal code meeting insulated space. I imagine that container soaks up the heat. Something to consider.

Ryan the Temp

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In reply to ZihuatanejoMan • 12:09p, 3/17/25

AG

ZihuatanejoMan said:
I am wanting to do a DIY unit in my 40' insulated container. My research shows about 20btu per sq ft. I have about 272 sq ft insulated. I should be fine with 6000-8000 btu. I have been looking on Amazon and prices are everywhere. Couple of questions:

Will it hurt to go with a higher btu unit?

Does anyone here have experience with DIY and recommendations on a brand?

Thanks.

I've installed 3 Mr. Cool units (2 single zone, 1 dual zone). They were very easy. The one problem I had with the smallest unit (9,000 BTU) in a small space was it cooled the space too quickly and did not run long enough to remove the humidity from the air. It created condensation all over EVERYTHING. The solution was to run a separate dehumidifier non-stop.