MRcool DIY 18k or 24k to offset opening door

[juicegoose]

So i run a small airbrush business out of my 2 car garage. I'm in Houston and so when the heat turns on it really turns on. I had previously bought a portable 14000 btu AC but it just isn't cutting the mustard. Typically it'll drop the temp from 92-95 down to mid to upper 80's and take a while to do that. If i open the garage door to vent out some overspray or something it's instantly hot again.

I was going to upgrade to a MRCool DIY. Seems to get good reviews, pricing is in line with most other brands but my question is this.

First the specs
Standard attached 2.5 car garage with single insulated door. 1 side is exposed to setting sun and garage door faces NorthEast. I do have a overhang on roof that keeps most of the sun off the garage door. The ceiling above is not insulated although I can and will be doing that this winter.

No windows

I do have an outside fridge and deep freezer that don't help the equation.

I'm really thinkin 24000 is the way to go simply because of my quick recharge needs when i crack the door to vent but I'm not 100% sure.

Any help would be appreciated.

 

[hbus1300]

Oh man. I can here the sizing police sirens now. You'll find a lot of "experts" on here that like to make comments but provide no real value. You're going to get a lot of did you do a load calc? There's your answer.

I'm not an expert but recently went through this sizing dilemma myself. I'm going to guess you're around 500 sq ft based on the 2.5 car size mention. Conventional hvac talk is 1ton per 500sq ft. But thats old thinking and doesn't take in account a lot of variables

Most old school people will say the 24k would be too large, its not going to get the humidity out blah blah blah. But I think with the way inverter systems work on the minisplits that you can do a 24k and be fine. It sounds like your insulation is mediocre at best and you've got some heat sources in there with the fridge and deep freeze.

I vote 24k, but I'm no expert. I'd also encourage you to look at the pioneer systems because its damn near as easy as the mr cool and you don't have the crazy long line set you don't need.

 

[juicegoose]

Thanks Bud Ya i know I'm opening myself up but I realize too it's gunne be 18k or 24k unit.

I have to account for the additional half bay as well. Plus the fact that i crack the garage door often after I've thrown down some clear or used a bigger spraygun for basecoat. The reason i was thinking mrcool is that I like the wifi feature. I like knowing i can kick up the app before i head home and start bringing the garage down to temp although from some review most people just set it and forget it.

I did indeed look at the pioneer systems they are nice too.

 

[juicegoose]

Boom and just like that I notice on the pioneer site that they do indeed offer a wifi connection kit. I also was pricing the pioner 24k 20seer against the mrcool 24k 16seer.
Me thinking the pioneer might be moo betta.

 

[justinjoyal]

Oh man. I can here the sizing police sirens now. You'll find a lot of "experts" on here that like to make comments but provide no real value. You're going to get a lot of did you do a load calc? There's your answer.

I'm not an expert but recently went through this sizing dilemma myself. I'm going to guess you're around 500 sq ft based on the 2.5 car size mention. Conventional hvac talk is 1ton per 500sq ft. But thats old thinking and doesn't take in account a lot of variables

Most old school people will say the 24k would be too large, its not going to get the humidity out blah blah blah. But I think with the way inverter systems work on the minisplits that you can do a 24k and be fine. It sounds like your insulation is mediocre at best and you've got some heat sources in there with the fridge and deep freeze.

I vote 24k, but I'm no expert. I'd also encourage you to look at the pioneer systems because its damn near as easy as the mr cool and you don't have the crazy long line set you don't need.

You can go the professional way, or the hack way. The latest may or may not work properly.

 

[njhoudini]

Just thinking outside of your box, would it help to put up a fence on the outside of the wall exposed to the sun? Another option could be to put in an exhaust fan in the roof or high up in the wall close to the ceiling. I had an exhaust fan with the mushroom top installed with a thermostat in my attic and it only runs when the temps up there exceed 90.

 

[juicegoose]

Thanks for all the responses. So last night I took some measurements and used the online hvaccalc manual J calculator and it's saying probably 18000 will work.
My concern has been that my 14000 portable just doesn't keep up especially if i crack the door quick to evacuate overspray.
I put a document together to outline what my setup looks like. Could anyone backup my data and let me know what they get from their manual J calc?

 

[Fixin'Stuff]

Portable a/c units are not a good reference point to use as a measure of effectiveness. Many of them now use just a single exhaust hose, to send the hot air from the condenser outside. However, that creates negative pressure in the room it's cooling, which then has to pull in outside, hot air to replace the lost volume of air.

A proper a/c system just circulates the air, so it doesn't have to keep working to cool more incoming outside air.

 

[juicegoose]

Ya it was a shortsided mistake to use the portable on my part. I'm thinking the 18k unit will work fine for my needs. I'm also thinking maybe the lower seer model 17seer instead of the 21 seer to offset some cost. The savings dont really outweigh the cost

 

[justinjoyal]

Ya it was a shortsided mistake to use the portable on my part. I'm thinking the 18k unit will work fine for my needs. I'm also thinking maybe the lower seer model 17seer instead of the 21 seer to offset some cost. The savings dont really outweigh the cost

Portable units are awful for the most part..

Only you know how much/how often you open that door to let fresh air in. Makes proper sizing harder.

 

[juicegoose]

Ya it really does. i just think 24k might be to much. Im also thinking the upper seer might not be worth the squeeze.

 

[jp828108]

I would get that ceiling insulated, and see how the current portable unit does. Use that to help gauge your split unit sizing.

 

[softailtom]

Oh man. I can here the sizing police sirens now. You'll find a lot of "experts" on here that like to make comments but provide no real value. You're going to get a lot of did you do a load calc? There's your answer.

I'm not an expert but recently went through this sizing dilemma myself. I'm going to guess you're around 500 sq ft based on the 2.5 car size mention. Conventional hvac talk is 1ton per 500sq ft. But thats old thinking and doesn't take in account a lot of variables

Most old school people will say the 24k would be too large, its not going to get the humidity out blah blah blah. But I think with the way inverter systems work on the minisplits that you can do a 24k and be fine. It sounds like your insulation is mediocre at best and you've got some heat sources in there with the fridge and deep freeze.

I vote 24k, but I'm no expert. I'd also encourage you to look at the pioneer systems because its damn near as easy as the mr cool and you don't have the crazy long line set you don't need.

I would listen to Hbus1300 being oversized on a mini split in Houston is ok if your going to turn it on while driving home or raise the door at all you need a little extra. I’m just north of you with well insulated 550 sqft running 18000 Pioneer and wish I would have went with 24000!


Sent from my iPhone using The Garage Journal mobile app

 

[chrispyny]

Like JP said, you REALLY should finish the ceiling and then see how the 14k does. Honestly even if you did finish the ceiling off, i would STILL suggest the 24k. Inverter minisplits can power down to 25% of max easily. So it can throttle down close to 6k easily. The cost between 18k and 24kbtu is almost NOTHING.
You said yourself, you want fast recovery. I installed both minisplits in my house. One fujitsu and recently a Pioneer. I STRONGLY suggest you get a Pioneer, install everything yourself, and hire an hvac guy to purge draw and release the refrigerant.

LASTLY. i dunno if a minisplit is your best option in a garage which also acts as a paint booth. Minisplits will clog up FAST in those environments. This is the only time i’d say to choose wisely.

 

[juicegoose]

Tom it's funny you say to go 24k. I actually had read your story on your issues and swapped to a 24k.
Chris. I don't run the AC when I'm spraying. I'll drop the garage door cool the space. Cut the ac while I spray and then if needed evac. Most times i'm just airbrushing so overspray isn't an issue but every once in a while I'll spray some clear or something and kinda fog it up.

 

[AA7483]

Why don't you install an exhaust fan to vent overspray?

 

[hbus1300]

So Juicegoose, what did you end up doing? Figure a month later something might have been done.

 

[Rdavis427]

Costco has great deals on the MR. Cool. I just ordered a 24K setup for $1484 with tax and shipping. Plus you get the Costco 2% rebate for exec members and more if you use the CITI card plus they extend the warranty when you use the CITI Costco card. I have 900 sqft well insulated in Michigan. My 17K portable unit does ok but I was looking for something better. I was also looking at going with the 36K but the price jumped $600.

 

[sheltonfilms]

When I did a manual J, using basic variables I found out that just by adding insulation to my ceiling of my 23x22 garage reduces heat load by about 12-15k btus. Something to think about.

 

[sherlocktk]

I put in a 24k mr cool in my garage last year, Typical 3 car garage, insulated on about 1/2 of it (the part touching the house/bedroom above on 1/2, and not on the other 1/2. 600 sq ft total.

The 24k can cool it off when its 105 outside. maintain around 80, it gets hot if you open the door, but does well getting it back to a good temperature. When its "normal hot" during summer, say around 90, after about 30 minutes the garage is a nice temperature. I went slightly oversize as I wanted quick recovery as I only use it the 2 or 3 times a month the kids let me out there.

I like these units being installed toward the ceiling as the air blowing "high" you can point the vents to the area you are working in to help it stay cool. I am thinking of insulating the un-insulated roof as I can just feel the heat pour in from that, and it should be reasonably in-expensive to do so with a staple gun and fiberglass from the HD.