r/DIYminisplit

I live in Minnesota and am converting my detached garage into a workshop. Approximately 575 sqft, 9 foot ceilings, R13 in walls, R49 in ceiling, insulated garage door with green hinges and draft sealing. Basically, about as insulated and sealed as a garage can get without building from scratch.

I don't really care about cooling capacity, but I'd like to keep the garage in the 50-60F range for most of the winter. This includes weeks of single digit temps. I've estimated I need about 24k but of heating for this, but I'm thinking I may pay for a CoolCalc to get a more confident Manual J calculation to verify.

I've been researching mini splits and have determined that the Blue Ridge XS5 24k BTU appears to have the best cold weather performance and HSPF2 Region V rating among the "direct to consumer" mini splits. Their XS6 18k BTU has great cold weather performance and efficiency as well, but I'm worried it won't have the oomph for deep winter and they don't have a 24k BTU option.

I don't need a DIY option, I'm comfortable renting the equipment to vac the line sets. I have received multiple quotes for this between $8-12k which to me is absolutely obscene. They try to really sell me on the warranty but I can replace a unit 2-3 times over for that price. I'm open to any brand or model that sells directly to consumer and has good support. Alpine Home Air has blown me away with their support so far.

We live in Mammoth Lakes, CA and have been finding it difficult to find an HVAC company to quote a minisplit system for us. I think we're ready to throw in the towel and go the DIY route.

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We got one quote for $29k for a 36k btu Mitsubishi hyper heat with 4 indoor units, not including any electrical work or permit. This seems very high.

Another company came over to look at our space and recommended Samsung, but now they've ghosted us.

A third wants at least $300 just to have a look, which fair enough, but haven't pulled the trigger on them yet.

There are a few more options that I'll contact, but being in a small rural area, prepared to not find a pro.

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Our specs:

- Downstairs is 550 sq ft, L shaped, 8' ceilings.
- Three upstairs bedrooms, all about 150 sq ft.
- We live at 8,000' elevation.
- According to the town, our winter design temp is -2F (summer 74F).
- I did an online manual J for our downstairs area (can't remember the site now, but it has been recommended on this sub) and got 15-16.5k btu heating. I do not think this accounted for our elevation, though.

Our setup:

- We primarily use the wood stove downstairs for heating, but want a heat pump to maintain 65-68ish overnight or when we don't light the fire.
- Also have baseboard and wall heaters; these would be removed in rooms where indoor unit added.
- Interested in AC for when we close our windows for wildfire smoke.
- No possibility for ducting. Upstairs we have lofted ceilings with giant beams and no attic.

Our challenges:

- One of the bedrooms would require the indoor unit to both be mounted on an inside wall, and have the lineset run through walls/floors to later become mostly inaccessible (without ripping into finished surfaces). Samsung guy said no to this, Mitsubishi said it would work. We are fine either way, thoughts?
- Our elevation makes sizing a challenge I think?

Other questions:

- I was thinking either 15k or 18k for downstairs, and 6k for each room. Does that sound right?
- Mr Cool for the DIY aspect, so we can have a warranty?
- Any other thoughts or considerations?

Appreciate any guidance you can give me, thank you!

Our central ac and heat unit sounds like it is on its last legs.

Wife wants to replace the current attic unit and outside condenser with a mini split system??

Our single family home is about 1000 square feet, two bedrooms.

I said I don't want a head unit/cassette/wall mounted unit in every room because they are large, our rooms are small and the whole thing would be unsightly.

She said " What you do is put in an "air handler" in the attic and connect that to the current duct work. So no wall head units would be needed inside.

So everything on the inside of the house would look the same, thermostat, vents etc.

And this new system would be more efficient and save us money.

Is this a thing? Anybody know about this or done it?

For background : house with attic, about 1000 sqft, southern California. House built in the 50s