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Comment by djanogo | Hacker News Reader

Where are the refrigerant lines, how did they run them from compressor to evaporator?, I thought the biggest issue with AC self install is filling the refrigerant and sealing those lines.

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> Where are the refrigerant lines, how did they run them from compressor to evaporator?

Look at this image from the blog post showing the post install view:

https://www.techprowd.com/content/images/2020/09/image-24.pn...

Notice on the left edge there is a large white "pipe" running from the evaporator unit down to a hole in the wall (the hole was already present and visible in other photos). The refrigerant lines are running inside that white cover and through that hole to the outside unit.

> I thought the biggest issue with AC self install is filling the refrigerant and sealing those lines.

As for the refrigerant fill, yes, that is the part of the work that most DIY folks will not have the equipment to perform. The evaporator and compressor units for most of these mini-split units come prefilled with refrigerant plus enough extra for X length of tubing (I forget the length X at this time). The install basically involves installing the lines, evacuating them (refrigeration grade vacuum pump needed here) and then opening the shutoff valves in the two units to release the already present refrigerant.

Since most DIY's will not have a refrigeration grade vacuum pump, and are unlikely to be able to justify the several hundred dollars for one for a one-off install, this is the point where the DIY'er would need to call a professional for the final completion of the install.

In japan there is also way to rent tools, next time I am doing it by myself it costed almost third AC to get 2 installed... When materials and rent didn't even cost more than 1 install cost

> refrigeration grade vacuum pump needed here

My understanding is that some of the DIY units had a built-in vacuum pump for this step.

Edit: never mind, I think I’m making stuff up in my head. But I could see it being a feature in the future.

What makes a vacuum unit “refrigeration grade”? Other than recovering what you’re vacuuming if you’re doing maintenance instead of a first install?

Generally what makes it 'refrigeration grade' is the level of vacuum down to which it can pull.

Here are some examples of refrigeration vacuum pumps:

https://www.grainger.com/search/hvac-and-refrigeration/air-c...

Rated to pull high vacuum, <500 micron at the most. You can get such pumps very cheaply, the issue is usually the volume on them - when I tried using a very cheap ($60) one it took a very long time and kept going into thermal protect on the way down, and that was with a small system. Refrigeration techs use vacuum pumps that both move a large volume and can do very high vacuum and that's pretty expensive, although not insanely so - I see one from a popular HVAC brand for $500.

Some mini-splits (MrCool DIY series) also come with the lines precharged using quick-connects. These require no professional tools or equipment, with the drawback that installation is limited to the exact length of line provided.

Units come pre-charged now. My new central air unit was pre-charged at the compressor for 50ft of line. You need to still seal the lines to the unit which requires something hotter than a propane torch(acetylene), then you should purge the lines with nitrogen, have HVAC gauges to verify the pressure holds, then evac with a pump watching the gauges again. Those are some pricey one-time use tools. Some mini-splits now have DIY connectors and precharged lines to work around those issues.

When it comes to pricey one-time use tools, I’ve found that I can come ahead by buying online (used or from Asia) and reselling it locally once I’m done.

It’s the tools I keep that end up costing me. I might need that 2nd jack, 3rd ladder, always nice to have a bucket of 10mms, bike rack for changing tire 1x/yr.

Like are those wall color piping on the left side. The mini split ACs in japan come with precharged outdoor unit which has valves closed so the installers route lines from indoor to outdoor unit (using already packed with insulation lines). The connections are made using flare connectors. After all connected they use vacuum pump to evacuate air from lines and then opened up lines that's basically all in the installation.

There are some mini-splits that have a "quick connect" type of tether that don't require a professional to install. Here is one: https://www.forestair.ca/en/serie-mini-anglais

I looked at that model (I can't install a traditional mini-split at my apartment) as a way of reducing the noise in my bedroom b/c of the AC, but the reviews are mostly bad, and many related to issues with the refrigerant after trying to disconnect and reconnect it over time...

There are units that come with compressors pre-charged with an amount of refrigerant for the units and a lineset length of between X and Y. You can also buy linesets of different lengths that have all the ends pre-fabricated.

After installing everything, you open two valves on the compressor unit to flood the lineset and evaporator with the refrigerant. It's not perfect [the lines are likely to have some water vapor in them], but it works. (The manufacturers also charge a premium for these "DIY" versions, so if you can find a way to do the traditional charging, you can save some money [or apply that towards an HVAC tech to come out, do a quick vac the lines/leak test/charge].

I recently installed a mini-split in my garage, Mr. Cool DIY 24k. The lines come precharged, as long as you don't need to alter the length, you can completely DIY it. Most people just coil up the extra line behind the unit if needed, the length of my run meant I had no extra.

It's clearly not the same quality as the non-DIY Mitsubishi and other units, but US installers barely know what mini-splits are anyway. Installing mine cost under 2k total IIRC, and the nearest quote from a pro was 5k+. Highly recommended.

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