Minisplit for 480 sq ft garage

[k1rodeoboater]

My wife pitched the idea of getting the garage air conditioned to me the other day while we were discussing future projects for the house. This came up because the bedroom above the garage (garage is attached to the house) is always noticeably warmer than the rest of the house. What would be an appropriate sized mini split for this application? The garage is finished, and from what I've been told about the construction here they insulated the garages...but I'll check with a borescope to be sure. I don't know what R-value they may have used. The garage door is currently un-insulated, which I plan to remedy with some rigid foam, and the seals look to be good and tight.

I'm not expecting performance like our indoor unit, but keeping the garage at about 80 degrees in the summer and 60 degrees in the winter. Summers here can be around 100 with high humidity (80-90%) and winters are in the mid 20's at the lowest, but it's usually above freezing. I imagine regulating the temperature in the garage will make the bedroom above it more even keel with the rest of the house.

 

[shade]

Make sure there is insulation above the bedroom. This is not always the case that it is. Mine wasnt. I put in insulation and it made the situation better.
Also make sure the exterior wall is also insulated. This generally isnt either.
Then we AC/d the garage.
Youll get different answer on the tonnage. Do you have appliances out there, anything that generates heat. That will have to be accounted for.

 

[dshop]

Miami? Seattle? Phoenix? your location might factor into suggesting a fix.
It doesn't cost any more to add your location to your listing info.

 

[k1rodeoboater]

Oops. Yeah I'll have to update that. Finally settled now after retiring from the military earlier this year. I'm in Central NC.

As far as insulation goes. The bedroom is fully insulated as is the floor. The ceiling is done as best they could given if follows the trusses for part of it.

As far as heat producing appliances. I have 2 water heaters in the garage planning to build a "closet" around them to enclose them both. Aside from that vehicles, a welder that gets used occasionally (not enough to factor for) and I may put an oven out there to bake on finishes (not a certainty, also probably not used enough to account for).

Sent from my Pixel XL using The Garage Journal mobile app

 

[justinjoyal]

We need to know at least the dimensions of the garage, number of windows/doors and their size and the R-value of your insulation. Otherwise the sizing will be a simple guess.

 

[Marctrees]

I may be retarded in my thinking, but what is wrong w a through wall ( "Window") AC of about 12k for around $400 ??

Marc

 

[Ilikeike]

I may be retarded in my thinking, but what is wrong w a through wall ( "Window") AC of about 12k for around $400 ??

Marc

He wants heat also.

 

[pbon]

Some have heat. I have a Friedrich 18k cool 12k heat window/wall unit that is mounted through the wall about 7.5’ up. Cools my 750SF 9.5’ ceiling (13’ above the lift) insulated shop. I have since installed a 50k NG shop heater, which was always the plan, but the 12k heater unit in the AC kept the 60F that I asked even when it was 15F outside until I got the hanging shop heater installed. I doubt it would have handled opening the garage doors a lot or the -15-20 that we see in NH. I paid $629 or $679 about a year ago, but it looks like it is $899 now. Someone just posted a link to a pioneer mini split that is 18k for $900. Looks interesting, but heat is effective only above 5F ambient so I could not use one. Plus it is more complicated to install. Maybe the payoff is in efficiency, through reduced bills.

 

[Notgrownup]

Eastern NC here 600 sq ft shop, I got a Blueridge 18000 btu 18 seer mini split and it barely breaks a sweat... I think 12000 btu would work good for you.

 

[k1rodeoboater]

I may be retarded in my thinking, but what is wrong w a through wall ( "Window") AC of about 12k for around $400 ??

Marc

HOA says it's a no-go. Would love to have an easy solution like that but it is what it is.

Sent from my Pixel XL using The Garage Journal mobile app

 

[k1rodeoboater]

We need to know at least the dimensions of the garage, number of windows/doors and their size and the R-value of your insulation. Otherwise the sizing will be a simple guess.

24x20x12
Garage door is uninsulated currently, normal 2 car size.
No windows
Single steel door into the house.

Per code here
Walls are Batts of R20
Ceilings are R38

Sent from my Pixel XL using The Garage Journal mobile app

 

[Marctrees]

HOA says it's a no-go. Would love to have an easy solution like that but it is what it is.

Sent from my Pixel XL using The Garage Journal mobile app

You are not allowed to even put it on the back wall where no one but you can see it ?

Marc

 

[k1rodeoboater]

You are not allowed to even put it on the back wall where no one but you can see it ?

Marc

Putting it in the back wall would have it exiting above the toilet, or in the vanity mirror, in the downstairs bath. One of the side walls is my front walk, the other faces a neighbor's house with clear LOS from the street. So sadly, nope. It's either mini split or my 14000BTU portable unit that we brought from Colorado in case we bought a house with a shed that I could turn into a backyard workspace. And even that would necessitate two dryer vents cut into the wall facing my neighbor, or install a window, at which point the mini split very well may be the same cost and/or less of a pain to install.

Sent from my Pixel XL using The Garage Journal mobile app

 

[Marctrees]

So put it above the toilet and duct tape a headrest pillow to it !!!!!!!!!

Sorry, just joking.... and sorry you live in an HOA community.

Marc

 

[Marctrees]

So, what about on the "Walkway" side ?

Slow downnnn ... and read the below -

Disregarding knee jerk thinking... is there not room for approx a 15" projection above walking head height?

And out of sight of the cruising crime patrol HOA Nazi ?

Heat when needed can come from one or two $20 "space heaters"

****... we use two of them for 6 yrs now to heat our 1100 ft sq 2 br house in winter NO problem after deciding to not replace furnace/ AC system for 8k.

Marc

 

[k1rodeoboater]

So put it above the toilet and duct tape a headrest pillow to it !!!!!!!!!

Sorry, just joking.... and sorry you live in an HOA community.

Marc

Hahaha now that's funny.

Yeah it wasn't ideal but it's 1.3mi from work, 3mi from a boat launch for a huge lake, and I will have it paid off in 7-10years. At that point a nice rural property with acreage will be more feasible once my boys are teenagers

Walkway side is even more exposed. And there an 8" deep planting "bed" between the edge of the walkway and the exterior of the garage. The designer was an idiot.

Sent from my Pixel XL using The Garage Journal mobile app

 

[Marctrees]

OK... Remember the Kids grow up VERY fast.

I guarantee that... WAY faster than you think the time goes by.



I, myself, did the mistake of building rural dreaming of the Kids continuing the Fam self employed biz and living and contributing to a gorgeous place 7 acres 3 br Barndominium ON 250' TX Gulf Saltwater w west facing views.

Once they "Saw the lights of the Big City", they were gone.

NY Brooklyn and Phoenix for years now.

The best to you and your Family.


Marc

 

[Notgrownup]

Do a mini split and be done with it.

 

[k1rodeoboater]

Do a mini split and be done with it.

That's what I'm leaning towards. Still don't know what size or even how to figure that out.

I'm guessing 12k or 14k, especially because the door won't be as insulated as the walls.

Sent from my Pixel XL using The Garage Journal mobile app

 

[Notgrownup]

If you go with 18000 btu you will be safe. It won’t struggle... if You are able to install, wire and set it up, do you know Anybody who would flare lines, pull vacuum for you? If so, you could do like me and buy a nic3 unit with everything you need from like Alpinehomeair.com ...I have $1500 in mine including everything.

 

[k1rodeoboater]

If you go with 18000 btu you will be safe. It won’t struggle... if You are able to install, wire and set it up, do you know Anybody who would flare lines, pull vacuum for you? If so, you could do like me and buy a nic3 unit with everything you need from like Alpinehomeair.com ...I have $1500 in mine including everything.

Probably call in a HVAC guy to do the flaring and vacuum. The flaring part is the only thing that gives me pause. Is it like flaring brake lines?

Sent from my Pixel XL using The Garage Journal mobile app

 

[Notgrownup]

I am sure it is somewhat similar but I didn’t take any chances...Some things I don’t have the tools and knowledge and for $180 I thought it was fair...This was a guy that has a light business but they are only 2 guys, not a big outfit.
I am really satisfied with my results.

 

[SALIV8]

Brake lines are double flared while ac is single flared. However I also used a pro that was able to get me local utility rebates and the manufacturers warranty.

Well worth the added cost.

 

[dcg9381]

I agree that 18k BTU would probably be good in that "moderate" for cooling based on internet arm-chair not-math.

It's "more OK" to oversize inverter mini splits than traditional ducted AC.
You need a real calculation (which people here can do for you) if you want a better answer. Your biggest problem is probably a 2-car uninstalled garage door.

Line sets can be bought pre-flared (I've had success with 2 out of 3). Under $1200 for Daikin if you can do most of the work....

 

[k1rodeoboater]

OK so after doing more research I feel confident in installing everything. I am trying to find a local HVAC tech will test, vac, and "charge" the system if only for the ability to maintain the warranty. The power company's requirements for rebates, and what they pay out, are laughable at best. Probably doesn't help that I pay $0.08 per kWH so there's not a whole lot of wiggle room.

Some of the non-DIY units are attractively priced at under $1K with shorter line sets. I only need about 12-16'. 25' would be pretty ridiculous and there's no good place for me to coil up the excess without it looking really out of place.

 

[SALIV8]

Do not use pre flared Linesets. Well, you can use them for everything but their flares and flare nuts.

Cut off the flares, throw out the flare nuts and use the factory flare nuts that come with your system and reflare the copper.

I got $400 back per system for a total of $800 from ComEd and the seer/hspf ratings were reasonable to get that also.

Good luck! You'll love your minispit(s)

 

[Git]

I bought and installed a Mitsubihi Mr Slim about 5 years ago now, and bought everything through eComfort. I just checked, and they still have a worksheet you can download and fill out with all your specs, and one of their 'in house' engineers will recommend a package for you. It looks like they now charge a $25 fee for it, but they will give you credit for it if you buy a system from them

https://www.ecomfort.com/stories/1439-What-Size-Mini-Split-Should-You-Buy.html

I think you will probably end up with a 18k btu system. Before I actually ordered the system from them, I found a local, licensed Mitsubishi dealer that agreed to do the 'start up' for $300. That included looking over the system, checking for leaks, pumping it down and releasing the charge. I had already flared the lines, pretty easy actually, but I am sure they would do it also. (having the dealer 'commission it' was for warranty purposes)

If I had to do it again, I would either buy another Mr Slim from eComfort or one of the Mr Cool DIY units from Costco

edit - flaring was very easy with the proper tool, the one I bought cost $120, so you my just want to pay for someone to do it

https://www.amazon.com/gp/product/B002SB5RMA/?tag=atomicindus08-20

 

[QwikKotaTx]

What is wrong with $0.08/kw-hr? I have to sign up for short term contracts to get mine that low. Its closer to $0.12 in Houston for 12 month contracts.

Sent from my VS987 using Tapatalk

 

[Git]

$.08 kWh is almost like having free electricity!

Here is what we are paying in S Cal during the summer rates. Yes, $.49 kWh during peak times (5 pm to 8 pm) on weekdays. This is why we went solar and the prices are only going to go one way - UP

 

[k1rodeoboater]

What is wrong with $0.08/kw-hr? I have to sign up for short term contracts to get mine that low. Its closer to $0.12 in Houston for 12 month contracts.

Sent from my VS987 using Tapatalk

The rebates for any energy savings appliances are laughable and must be installed by one of their preferred contractors. Don't get me wrong labor rate in NC is cheap but the quotes you get from those folks vs buying it yourself and doing a DIY install is insane.

I've been trying to get a hold of local HVAC contractors and have been having trouble just getting ahold of someone. There's a lot of new construction in my area so it's not like they're hurting for jobs.

Sent from my Pixel XL using The Garage Journal mobile app

 

[k1rodeoboater]

$.08 kWh is almost like having free electricity!

Here is what we are paying in S Cal during the summer rates. Yes, $.49 kWh during peak times (5 pm to 8 pm) on weekdays. This is why we went solar and the prices are only going to go one way - UP

Funny thing is I have a 2.3kWH array on my roof from the previous owners. Saves me a whopping $10 a month on my bill [emoji38]

Sent from my Pixel XL using The Garage Journal mobile app

 

[QwikKotaTx]

That is insane. I don't see how anyone can afford to live in CA. Don't get me wrong, Texas is full!

I negotiated a good deal on a Lennox 20 SEER variable speed install thinking I was getting the rebates posted online only to find out my vendor does not participate in that program as it costs him money which translates to the customer, or so he said. Most other companies had a good bit higher price but it took him 3 days to install and he was a bit stumped on the new fancy touch screen thermostat but he eventually figured it out. Bottom line is to clarify all available rebates up front. I've been burned on that twice, even with a well known vendor. Some bait and switch with low end and high end units of course.