HVAC Mini-Split Installation in Garage?

[Bassman]

Looking for those familiar with HVAC to help me decide on whether a mini split / ductless system makes sense to cool / dehumidify a garage? I live in the Southeast (hot and humid year round) and my two car garage (~600-625 sq ft) is consistently an oven and very humid which makes projects uncomfortable. I’m looking to reduce the humidity and temperature by installing a mini split. A few questions I have for the pros but input is always appreciated!

• Are mini splits good dehumidifiers? Expectation is that this would run fairly consistently given the heat / humidity in our area. I’d probably keep around 78-80 degrees, again I’m more focused on humidity than making the space an ice chest.
• Given the above, how often will refrigerant need to be added?
• Pros / cons of a 110v vs. 220v system given the same BTU?
• How many BTUs should I target? Seems like 12k seems to be what I need.
• Any particular brand that I should look at or avoid? Options seem to be all over the place, ranging from <$900 units on Amazon to $2,000
• Is this a DIY project I can take on? I’m pretty handy and have a friend who is an electrician so seems within our capability. Are we off base/overconfident?
• Am I crazy for considering such an idea?

 

[signing off]

Garage journal.com has lots of conversation about this. Might want to go there.

 

[GSPHUNTER]

The refrigerant should never need to be replaced unless there was a leak or compressor had a burnout. I would go with 220 volt system. If you have any mech ability at all, it's a do it yourself job. Just be sure to follow institution. Given your ambient condition I think I would go with 1.5 ton system. Be sure to insulate garage if not already done. Drywall would also help.

 

[IAm_Not_Lost]

I built my own home and self installed two outdoor and six indoor Mr.Cool DIY units.

They dehumidify very well.

A 12k unit would be very marginal for a 600sq ft space that is drafty and less insulated than other areas (a garage with garage door).

It would still work, but would likely struggle to reach that temp in the summer, based off my experience in Arizona. It would likely run almost continuously.

Personally I’d get an 18k unit. If you are reasonably handy you could install it yourself if you used Mr. Cool or a similar DIY brand with pre-vacuumed lines. Takes about half a day including the prep for the outdoor unit. 220v units are the better option. Electrical install isn’t hard, but you need to know how to look up how to properly run an 8ga or 10ga (depends on unit size) 220v line from your panel to the outdoor mini split panel with the cut off, and from there the flexible whip extension that goes to the unit. Not difficult, but you just need to be able to do some research.

You shouldn’t ever have to add coolant, or at least not in any normal use period. Maybe 10 or 15 years down the road you might loose a little.

 

[Nine Banger]

• Are mini splits good dehumidifiers?

No

• Given the above, how often will refrigerant need to be added?

Never. Only if there's a hole in the lines somewhere...usually an indicator of end of life.

• Pros / cons of a 110v vs. 220v system given the same BTU?

110V will be odd/abnormal, get 220v

• How many BTUs should I target? Seems like 12k seems to be what I need.

I'm thinking 15,000

• Any particular brand that I should look at or avoid? Options seem to be all over the place, ranging from <$900 units on Amazon to $2,000

Go with Mitsubishi. Avoid all others.

• Is this a DIY project I can take on? I’m pretty handy and have a friend who is an electrician so seems within our capability. Are we off base/overconfident?

Overconfident. You can open the walls for the HVAC guy and run the wire. Let them install the unit and the line sets and drains. You can close it back up and do the drywall work, etc.

• Am I crazy for considering such an idea?

No.

You need a dehumdifier too. Like this:

https://www.amazon.com/gp/product/B0BS41L689/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[H'n'F]

I'm a mechanical engineer and I design HVAC systems for a living. In a previous life I was a service tech and installed and serviced these as well as other HVAC systems. Nobody can tell you what size this needs to be without knowing the size of your garage, number of doors, insulation type and thickness, whether it's shaded or indirect Sun, etc. you will get dehumidification with air conditioning in the conditions you are discussing but we would need the range you are looking for in order to assess if the mini split can manage that level of dehumidification. At 80°F, you'll probably want to be somewhere in the 50% to 60% range for comfort. Whether your particular mini split can accomplish this will depend on a lot of factors, the largest likely being infiltration. If your garage is buttoned up well, I don't see you needing an additional dehumidifier... It's just another space like any other in your home and the mini split should handle it well and make it comfortable as long as proper load calcs are done and it is sized for the appropriate runtime. If you just throw one in that's oversized, it will be cold and humid in the space as you won't have the appropriate dwell time on the coil for the dehumidification to take place.
Do not try and install it yourself. You can't legally open a system without an EPA 608 certification... At least that's how it used to be.
Have a qualified and reputable installation company come take a look and I'm sure you will get it squared away properly. Good luck!

Sent from my Pixel 9 Pro using Tapatalk

 

[displacedtexan]

I'm a mechanical engineer and I design HVAC systems for a living. In a previous life I was a service tech and installed and serviced these as well as other HVAC systems. Nobody can tell you what size this needs to be without knowing the size of your garage, number of doors, insulation type and thickness, whether it's shaded or indirect Sun, etc. you will get dehumidification with air conditioning in the conditions you are discussing but we would need the range you are looking for in order to assess if the mini split can manage that level of dehumidification. At 80°F, you'll probably want to be somewhere in the 50% to 60% range for comfort. Whether your particular mini split can accomplish this will depend on a lot of factors, the largest likely being infiltration. If your garage is buttoned up well, I don't see you needing an additional dehumidifier... It's just another space like any other in your home and the mini split should handle it well and make it comfortable as long as proper load calcs are done and it is sized for the appropriate runtime. If you just throw one in that's oversized, it will be cold and humid in the space as you won't have the appropriate dwell time on the coil for the dehumidification to take place.
Do not try and install it yourself. You can't legally open a system without an EPA 608 certification... At least that's how it used to be.
Have a qualified and reputable installation company come take a look and I'm sure you will get it squared away properly. Good luck!

Sent from my Pixel 9 Pro using Tapatalk

I agree with most of your post.

But you can easily buy pre charged systems. Easy to get up and running without opening them.

 

[H'n'F]

I agree with most of your post.

But you can easily buy pre charged systems. Easy to get up and running without opening them.

The EPA would disagree with you. I am still 608 Certified and so I went to the EPA website and found this.
As I thought, it is not legal to connect precharged lines or add/remove refrigerant without federal certification.

It's also just a bad idea.

Can I install an R-410A mini-split window unit?

No. Section 608 Technician Certification is required for activities that could reasonably be expected to violate the integrity of the refrigeration circuit. Adding or removing refrigerant from a mini-split as part of installation, and/or connecting or disconnecting hoses or pre-charged lines requires a Section 608 technician certification. Activities reasonably expected to violate the integrity of the refrigerant circuit include but are not limited to: attaching or detaching hoses and gauges to and from the appliance; adding or removing refrigerant; adding or removing components; and cutting the refrigerant line.

 

[SneakyThunderCat]

I installed one in my garage this spring due to keeping all of my taxidermy in the garage. For reference I’m in Iowa and my garage is 1500 sf and I used a 2 ton unit. I bought a commercial dehumidifier to help it out and it runs quite often to keep humidity at 55-60. I believe it’s roughly 108 pts a day. No way a mini split could keep it at that humidity level by its self.


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[displacedtexan]

The EPA would disagree with you. I am still 608 Certified and so I went to the EPA website and found this.
As I thought, it is not legal to connect precharged lines or add/remove refrigerant without federal certification.

It's also just a bad idea.

Can I install an R-410A mini-split window unit?

No. Section 608 Technician Certification is required for activities that could reasonably be expected to violate the integrity of the refrigeration circuit. Adding or removing refrigerant from a mini-split as part of installation, and/or connecting or disconnecting hoses or pre-charged lines requires a Section 608 technician certification. Activities reasonably expected to violate the integrity of the refrigerant circuit include but are not limited to: attaching or detaching hoses and gauges to and from the appliance; adding or removing refrigerant; adding or removing components; and cutting the refrigerant line.

Fair.

Stupid, but that's about the norm for regulation.

 

[Bassman]

I'm a mechanical engineer and I design HVAC systems for a living. In a previous life I was a service tech and installed and serviced these as well as other HVAC systems. Nobody can tell you what size this needs to be without knowing the size of your garage, number of doors, insulation type and thickness, whether it's shaded or indirect Sun, etc. you will get dehumidification with air conditioning in the conditions you are discussing but we would need the range you are looking for in order to assess if the mini split can manage that level of dehumidification. At 80°F, you'll probably want to be somewhere in the 50% to 60% range for comfort. Whether your particular mini split can accomplish this will depend on a lot of factors, the largest likely being infiltration. If your garage is buttoned up well, I don't see you needing an additional dehumidifier... It's just another space like any other in your home and the mini split should handle it well and make it comfortable as long as proper load calcs are done and it is sized for the appropriate runtime. If you just throw one in that's oversized, it will be cold and humid in the space as you won't have the appropriate dwell time on the coil for the dehumidification to take place.
Do not try and install it yourself. You can't legally open a system without an EPA 608 certification... At least that's how it used to be.
Have a qualified and reputable installation company come take a look and I'm sure you will get it squared away properly. Good luck!

Sent from my Pixel 9 Pro using Tapatalk

Very helpful feedback. A dedicated dehumidifier sounds like it will be necessary in my situation

 

[Bassman]

Thanks for all the feedback. Sounds like a Mitsubishi 15k unit is what is needed in addition to a dehumidifier.

 

[IAm_Not_Lost]

The EPA would disagree with you. I am still 608 Certified and so I went to the EPA website and found this.
As I thought, it is not legal to connect precharged lines or add/remove refrigerant without federal certification.

It's also just a bad idea.

With your DIY specific mini split brands, the refrigerant is already in the unit, and the lines have refrigerant that won’t come out until the line is connected as they have a push valve in the line.

You are doing nothing with the refrigerant until you open the valves once everything is hooked up.

Edited, I incorrectly misspoke about the pre-charged line.