Help with Mini Split sizing

[Buck Shot]

We built a 24x40 detached addition to our house and are ready to contract the mini split. It has high / vaulted ceilings and spray foam insulation. Addition is on the east side of our house. It has two large windows on each of the north, east, and south elevations with no windows on the west. Also south elevation has two French doors.

I figured we needed about a 3 ton unit based on my research. In addition we have a 25x50 commercial dog kennel with a 3 ton unit in it (sprayfoamed) with very smaller windows and heavy tree coverage. The unit does fine.

I got two quotes for the new mini split.
The first was for a 3 ton unit, but brands I’ve never heard of - either a cooper & hunter or a traiden. His reasoning was that the big unit would help push air all the way across the building and keep up with opening/closing doors.

The second man quoted a 1.5 ton LG. He said that the spray foam greatly reduces the capacity needed for that space.

I’m thinking of getting a third quote, or just asking the first guy to quote a more well-known brand (I’ve had decent success with Gree and York in the past).

What advice would y’all offer? I’m struggling with the discrepancy in sizing.

Thanks in advance!

[7sdad]

I have spray foam and twice the area you're cooling and I have a 3.5 ton standard unit not a mini split. I know all my neighbors have bills from $400 to $800 per month and mine is no more than $250.

[Cookiemonster1]

You don't want to over size the unit for sure when working with foam. I would also ask them about installing mechanical fresh air ventilation.

[bowhntrmatt]

Here is my advice:

1. Don't buy one from anyone that is guessing at sizing. Ask to see the Manual J load calculation that they are basing their sizing off of. This is literally a 20-30min process for someone with the right tools and equipment.

2. Stay away from brands you have never heard of. If they say "hecho en china" on the box, servicing them and finding parts down the road is an absolute nightmare. Same goes for the DIY-type units. Only do this if you plan to DIY the repairs as well.

3. Air mixes itself quite well in a big open space that is well-insulated. The thing about the bigger unit pushing air across better is pretty laughable. The unit is just wider; I doubt there is any more velocity. A ceiling fan in the middle will accomplish much more, if needed.

4. Brand is important on mini splits, and you'll want to stick with names like Daikin, Mitsubishi, LG, Gree, etc. But even more important is a contractor with the knowledge, tools, and training to properly install, maintain, and service the unit.

[glen]

Bowhntrmatt- why is installation so important on these. Helped with two that seem to be doing fine. I agree with getting the right size unit for space but installation is simple on these from my experience and I have zero skills

[warrington]

might go wtih 2 one ton units. they would run off the same compressor. That way the a/c and heat would be spread out and more efficient. Not a huge in crease in price.

[warrington]

Daikin, Mitsubishi, LG, Gree,these are about 40% more in cost. I have had a cheap one it with worked good until a flood happened. had it replaced with a mitsubishi and have been satisified.

[kingranch]

Mini split are simple and easy to install. They even come precharged in some cases.

I've put in several mr cool and Mitsubishi
Daikin probably the best imo-.. use the calculator and a manual J for sure.

Based off what you said I had a similar sf space that did fine w a 18k btu but the ceiling was only 12ft not. vaulted.

My best guess if I'm you I would get a 2ton daikin for 2200$ and a ceiling fan will really help move air.
the installation is something you can handle yourself or even expect to pay no more than 300-500$ to have a contractor do. The other part to consider is how far from the breaker box as you will need a 220/w ac manual disconnect. Likely another 150-200 in wire-breaker and panel

https://www.supplyhouse.com/Daikin-FTX24AXVJU-RX24AXVJU-24000-BTU-SEER-19-Ductless-Single-Zone-Mini-Split-Heat-Pump-Package-Energy-Star-Rated-Wall-Mounted

[Chase4556]

I put a Chigo in my shed at the old house. Acquired it from Afghanistan where it had been in use with limited maintenance for at least 4 years. I installed it myself, and then paid a guy to come pull a vacuum on the lines, check for leaks, and properly charge with R22. It kept that shed like an igloo for 3 years until I sold the house and I bet it still kicking. You can buy a 1 ton Chigo online for around $850 from mini-split warehouse with a 7 year compressor warranty and 5 year parts. I’d have to research parts availability.

I get having a name brand and paying for that name brand so you have a local company that can service it. But I’m also a big fan of saving money. I saw those Chico’s chugging along in 110+ degree heat, and the amount of dust I blew out of mine(I made sure the one on my room got extra love) yet the other ones still kept going. Reliable enough for me.

[Buck Shot]

Here is my advice:

1. Don't buy one from anyone that is guessing at sizing. Ask to see the Manual J load calculation that they are basing their sizing off of. This is literally a 20-30min process for someone with the right tools and equipment.

2. Stay away from brands you have never heard of. If they say "hecho en china" on the box, servicing them and finding parts down the road is an absolute nightmare. Same goes for the DIY-type units. Only do this if you plan to DIY the repairs as well.

3. Air mixes itself quite well in a big open space that is well-insulated. The thing about the bigger unit pushing air across better is pretty laughable. The unit is just wider; I doubt there is any more velocity. A ceiling fan in the middle will accomplish much more, if needed.

4. Brand is important on mini splits, and you'll want to stick with names like Daikin, Mitsubishi, LG, Gree, etc. But even more important is a contractor with the knowledge, tools, and training to properly install, maintain, and service the unit.

Good points. Thanks

[Buck Shot]

Mini split are simple and easy to install. They even come precharged in some cases.

I've put in several mr cool and Mitsubishi
Daikin probably the best imo-.. use the calculator and a manual J for sure.

Based off what you said I had a similar sf space that did fine w a 18k btu but the ceiling was only 12ft not. vaulted.

My best guess if I'm you I would get a 2ton daikin for 2200$ and a ceiling fan will really help move air.
the installation is something you can handle yourself or even expect to pay no more than 300-500$ to have a contractor do. The other part to consider is how far from the breaker box as you will need a 220/w ac manual disconnect. Likely another 150-200 in wire-breaker and panel

https://www.supplyhouse.com/Daikin-F...d-Wall-Mounted

Thanks…we will have two ceiling fans as well to help move air

[Buck Shot]

I put a Chigo in my shed at the old house. Acquired it from Afghanistan where it had been in use with limited maintenance for at least 4 years. I installed it myself, and then paid a guy to come pull a vacuum on the lines, check for leaks, and properly charge with R22. It kept that shed like an igloo for 3 years until I sold the house and I bet it still kicking. You can buy a 1 ton Chigo online for around $850 from mini-split warehouse with a 7 year compressor warranty and 5 year parts. I’d have to research parts availability.

I get having a name brand and paying for that name brand so you have a local company that can service it. But I’m also a big fan of saving money. I saw those Chico’s chugging along in 110+ degree heat, and the amount of dust I blew out of mine(I made sure the one on my room got extra love) yet the other ones still kept going. Reliable enough for me.

Thanks for the input. I’m leaning towards whichever brands have parts readily available at this point

[Buck Shot]

I have spray foam and twice the area you're cooling and I have a 3.5 ton standard unit not a mini split. I know all my neighbors have bills from $400 to $800 per month and mine is no more than $250.

This will be my first experience with spray foam in a living area…hope to see good results on the electric bill

[JTRichardson]

I can't really assist on size of unit, but I had a Daikin installed in my garage last year (800 sq ft) and it will turn it into a freezer in there quickly. That's without me insulating the garage door either.

Having the option for heat is also a plus, I thought I wouldn't need it being in East Texas and all, but during this last freeze I was able to keep my garage at a solid 62 degrees with little to no extra energy costs.

All the above is just letting you know that, from my experience, the Daikin brand lives up to its price point.

[Dejashoot]

I have a 30x40x14 shop that is spray foamed. My installer did a 2400BTU Mitsubish and it works great. It will cool that whole shop down quickly. The Mitsubish has a “sensor eye” that directs the cool to the correct part of the shop that needs the cool. You can also set it manually to blow where you want it (working under the truck I point the unit in that area). Heater is nice in the winter and it has a dehumidifier setting also.