Just finished my first mini split install — a few observations

I did an 18k BTU Pioneer unit in my garage last summer and that hole saw through the stucco was definitely the point of no return. I used a stud finder but still held my breath until I saw daylight on the other side. My biggest hurdle wasn't the hole, though; it was getting the flare nuts torqued exactly to spec. I bought a dedicated digital torque wrench for it because I didn't trust my "feel" for it, and I'm glad I did.

One thing I’d suggest for anyone else trying this is to spend the extra thirty bucks on a high-quality flaring tool. The one that came in my cheap manifold kit made some really jagged edges that I had to sand down. I also skipped the rental pump and bought a small vacuum pump and a micron gauge so I could take my time. Seeing that reading stay under 500 microns for an hour gave me the peace of mind I needed to finally crack the valves open.

The electrical part was actually what took me the longest. Running the 220v line from the main panel to the disconnect box meant crawling through a very tight crawlspace. It’s definitely a two-person job like you said, especially when you're trying to bend those line sets without creating a kink that ruins the whole coil.

I acutally went the MRCOOL DIY route specifically becasue I wanted to skip the vacuum pump and flare tool drama. Those pre-charged line sets are a lifesaver if you're working alone, though managing the excess 25-foot coil behind the condenser was a bit of a puzzle. I ended up looping it horizontally behind the unit to keep the oil flowing correctly, wich felt alot safer than trying to shorten the lines and mess with the refrigerant.

The real challenge for me wasn't the hole or the lines, but the electrical sub-panel work. Running the 240v circuit from my main breaker out to the disconnect box required pulling 10/2 wire thru about thirty feet of tight crawlspace. I definitly underestimated how much time I'd spend on my back in the dirt just to get power to the unit. For the base, I skipped the plastic pads and poured a small 24-inch concrete slab. It took an extra afternoon to set, but with the high winds we get here, I didn't want the condenser shifting or vibrating off a lightweight riser. If you’re doing this in a windy area, that extra bit of masonry work is a solid investment for peace of mind.

That sounds like a solid install, but have you ruled out the possibility of a slow vibration leak? Even with Nylog and a good torque, those DIY flares can sometimes micro-leak over a few months of thermal expansion cycles. It’s one thing for it to hold for forty-eight hours, but I'd be curious if you’ve gone over those fittings with a soap bubble test or an electronic sniffer after a few weeks of heavy use. Sometimes that 'whisper quiet' operation masks the sound of a very small refrigerant loss untill the compressor starts struggling next season.

Good on you for getting it done. Back in the day, we didn't have these fancy pre-charged lines or digital gauges; you did it with a manifold and your ears. I still prefer a flare I made myself over those DIY kits, though. One trick from the old school: wrap that exterior line set in some high-quality UV tape or even a slim metal channel. That plastic 'line hide' they sell now gets brittle and cracks after three winters in the sun. If you didn't pull a deep vacuum for at least four hours, keep an eye on the compressor noise next season. Moisture is a slow killer.