how well does a mini split AC/heat hold up in garage ?

[rfuerst911sc]

Another year has gone by with me procrastinating about adding AC/heat to the man cave. I have a three car detached garage, a single bay sectioned off from the other two it measures 12 ' x 26 ' with a slanted 2/12 pitch roof. The roof is only 2 x 4 construction but I plan on scabbing in another 2 " of wood to give me the ability to add R19 insulation to it. The walls are R13 with wood siding outside and wood sheet inside. The two bay is 24 ' x 26 ' with a more conventional pitched roof. The walls are also R13 with wood siding and wood sheet inside. Ceiling is not finished but I plan to finish it and add about R40-R50 in the ceiling. So that is the baseline for adding heat/AC. Being in Georgia taking the edge off with heat is all I'm looking for as it doesn't get that cold here, generally the coldest we see is 30 degrees. But the summer can be quite warm and humid so that is the bigger concern. So I have about 940 s.f. between the bays in total . My electric box in the garage has four open slots so I think I'm OK for expansion.
For security reasons I don't like the idea of window AC units. And for stand alone heat I could have the home natural gas line extended out to the garage and run two ceiling mounted heaters. But the more research I do I'm thinking one mini-split with capability to run two zones is the way to go. Would a 18,000 BTU unit do both sides ? In the winter I would set the unit as low as it would go maybe 45 and in the summer leave it at 80. Then adjust when I want to work in the garage. I am not doing woodworking so no sawdust just general car maint. and working on the boat. So will a mini-split live in this environment ? I am finally going to pull the trigger this year and I have started email chat with a local HVAC company but Pelicans tend to be smart and honest Sorry for the long post.

[LakeCleElum]

I asked a local heating company that question last year for my garage. It's 48 x 32 with 10 ft ceilings....Insulation and sheet rock.......It's often right at 32 F in the winter w/o heat.....

Very happy with a 80,000 BTU ceiling mounted Propane heater.....I don't leave the heat on. I can walk out when it's 32 and be working in a sweat shirt in 10 minutes.......

If you have a natural gas line, that is the way to go. With your size and climate, you'd be fine with a lot less than 80,000.......

[ShakinJoe]

go with a 24 k or a dual zone 24k. The Fujitsu unit offers low ambient operation and is great quality. Sold by Johnstone in Atlanta.

[fred cook]

My shop is about 24' x 24' (enclosed) plus a 12' wide carport on one end. The building is completely open on the inside with a 6/12 pitch roof. To heat and cool this large volume (length x with x height), I had a 4 ton Trane heat pump installed as a split unit. The compressor is outside under the carport while the blower unit is mounted in the storage area over the carport. It will easily keep the shop area either cool or warm and under normal use only costs about $20 - $30 per month for power. I also have two large ceiling fans that hang from 6 foot rods. During much of the year, just using the ceiling fans will move enough air to keep things comfortable. Before installing the heat pump, I tried heating the shop with a couple of space heaters. That kept things bearable but not comfortable. The walls and ceiling are insulated, but the main overhead door is not.

[356racing]

Originally Posted by ShakinJoe

go with a 24 k or a dual zone 24k. The Fujitsu unit offers low ambient operation and is great quality. Sold by Johnstone in Atlanta.

ShakinJoe speaks the truth. I run a 18k in my 2 car garage in Phoenix and it works great. For a 3 car garage I would definitely do a dual zone 24K. The dual zone will help circulate the air.

[GH85Carrera]

I looked into having a central unit put out in my garage. It was going to be very spendy. My garage is a 3 car garage and it is oversize with a small workshop area on one end. I only really care about heating or cooling one bay and the workshop area. I did not want an open flame propane or something I had to vent so I went electric.



It is 220 and will heat up the area in 10 minutes to be totally comfortable to work while wearing a t-shirt and jeans. It just cycles on or of as needed. Plug and play installation.

For A/C I put in a window unit in a frame I built for the human size door that goes outside.

I can put the frame in the doorway and slide the AC unit in place and still close the steel door when the AC is not in use for full security. I put it up in the spring and take it down in the fall. It will keep me comfortable on days that are 100 degrees. Many times I have gone into the house and it noticed the garage was cooler than the house on a very hot day. I have calculated that a full day of AC cost me about 8 bucks. To be able to work all day and not be covered in sweat and exhausted from heat is worth every penny.

This is my AC project.

My Garage upgrade project

[red-beard]

rfuerst911sc

Gree makes some very efficient units. Since the garage will not be insulated the same way as a house, I would go a size up. 12000 BTU/hr should do it. The installation is a lot less than anything other than a window unit. And the more efficient units are VFD (variable frequency drive). They cycle by reducing output instead of shutting off.

I design Solar applications and one part of the overall design is more efficient air conditioning.

[ShakinJoe]

Originally Posted by red-beard

rfuerst911sc

Gree makes some very efficient units. Since the garage will not be insulated the same way as a house, I would go a size up. 12000 BTU/hr should do it. The installation is a lot less than anything other than a window unit. And the more efficient units are VFD (variable frequency drive). They cycle by reducing output instead of shutting off.

I design Solar applications and one part of the overall design is more efficient air conditioning.

Gree is China made designed vs Fujitsu/Mitsubishi which are Japanese. the Japs make much better quality product at much higher efficiency levels and much better support on parts and service.

[rfuerst911sc]

I was talking with a guy at work this morning that used to be in the HVAC business. He said another option is a " packaged " heat pump. He made it sound like a larger version of a mini split with the unit on the outside of the building but ducts running into the building. Just another option I suppose. I have a local HVAC company in email conversation and I'll have them come out after Christmas to give me my options. I am leaning towards the mini split but have one concern and that is the two wall mounted units would mount on the 24 ' wide wall. So that means the heat/air would have to travel the 26 ' depth and I'm not sure how efficient that would be ? But I assume a large ceiling fan could help with that. Thanks for all the feedback I'll end up with something.

[GH85Carrera]

Try hard to convince the AC folks to not look at your garage on a standard living area. When I was looking for central AC one guy would not budge from looking at it just like a standard living area. As soon as you open the garage door to go in or out a ton of cold air goes away.

My setup work fine if all the cars are already at room temperature. If my wife leaves and return with a car with a hot engine and a car that has been in the sun my AC just can't keep up with the heat load. I usually ask her to leave her car in the driveway if she is going to run an errand.

[URY914]

Look into an exterior wall hung unit like those used on mobile office trailers. They are cheap and easy to install and self contained. They are not high tech but for this application it may work.

[rfuerst911sc]

I just got off the phone with a local HVAC guy he's coming out Wed. morning to look it over and discuss options.
Paul the mobile office wall hung units are they electric or gas ? Do they need ductwork or are they ducted as part of the unit ?

[grendiers]

We bought two Frederich units from these guys. I did the major installation, setting up both the indoor and outdoor units. Ran the wiring to the box, the condensation line, and the refrigerant lines. Called out our handy dandy A/C guy, who also is an electrician, and he did the rest. Cheap option. They work great in our pizza restaurant kitchen. Lots of flour dust as well for fun.

Wall Mount Mini Split Air Conditioners

[red-beard]

Originally Posted by rfuerst911sc

I was talking with a guy at work this morning that used to be in the HVAC business. He said another option is a " packaged " heat pump. He made it sound like a larger version of a mini split with the unit on the outside of the building but ducts running into the building. Just another option I suppose. I have a local HVAC company in email conversation and I'll have them come out after Christmas to give me my options. I am leaning towards the mini split but have one concern and that is the two wall mounted units would mount on the 24 ' wide wall. So that means the heat/air would have to travel the 26 ' depth and I'm not sure how efficient that would be ? But I assume a large ceiling fan could help with that. Thanks for all the feedback I'll end up with something.

A package unit is a fully complete unit, evap condenser and circulation in one unit. You run the duct from the unit into the garage and then connect a return back to the unit. ANYONE can install one of these, since it is just duct work, except for the electrical hook up.

Efficiency should be OK, but generally you will only get a single stage unit, SEER usually around 14 with a max of 15-16. Minimum size will be 2 tons.

https://www.theacoutlet.com/product_list.php?cat_id=41

Mini split systems

https://www.theacoutlet.com/product_list.php?cat_id=100

[VincentVega]

Good thread

I'm looking at the same thing, but in my case I'm thinking a 2 unit mini split with 1 in the house and 1 in the garage. I too am struggling with the proper calcs to determine btu requirements for the garage. It's colder here in MD but like you my primary concern is keeping the tools from being ice cold, no issue wearing a jacket in the winter.

My last garage had a wall mount 220v AC, great for cooling, cheap and easy to install. If you have alternate heat it's a great option.

[fireant911]

rfuerst911sc,
We purchased an 18K condenser and two 9K wall mounted Fujitsu's earlier this year. Before your HVAC guy arrives, take a look at the EComfort website and see the cost of their 24K packages (Heat Pump Wall Mounted - Dual Zone - eComfort.com). Ask the HVAC guy for a breakdown (materials and labor). Compare the cost is if he supplies the system and if you supply the system - I bet you will see a significant difference in cost. You will have to get the linesets (which are not cheap) but the cost of materials from EComfort versus purchasing from an authorized dealer was vastly different... I mean vastly!

Be aware that most mini-split manufacturers will not warranty their products if NOT purchased from an authorized distributor but EComfort has a nice and attractive warranty (Warranty Claims - eComfort.com). We had a very pleasant experience with EComfort. Take a look at GarageJournal ('heating and A/C' section) as there has been several discussions regarding mini-splits, DIY installations (which I would not attempt), brands, and where to purchase the mini-split systems.

VincentVega - I found that sizing units was maddening. Each calculator I used arrived at much different numbers. This one (Interactive Mini Split Sizing Calculator - eComfort.com) made the most logical sense to me but my calculations deviated from what the HVAC engineer at EComfort calculated.

[URY914]

Originally Posted by rfuerst911sc

I just got off the phone with a local HVAC guy he's coming out Wed. morning to look it over and discuss options.
Paul the mobile office wall hung units are they electric or gas ? Do they need ductwork or are they ducted as part of the unit ?

Electric and no ductwork needed. Supply from the top and return at the bottom.

[David]

I have a 24K btu Mitsubishi mini-split heat pump in my 22' x 43' insulated garage and it works great. I've had it for a few years and it still works great. I had a 24k btu window unit before that and it just couldn't cool unless I let it run a long time.

There's a built in filter but I don't know how well it would keep sawdust out. The wall unit is pretty easy to open so perhaps a periodic coil cleaning would keep it working well.

For your size, in a climate similar to mine in Houston, I'd go with a 24k btu mini-split heat pump like mine but with 2 wall units for the 2 garage areas.

I installed it myself and it was pretty easy. A plain flair tool is all you need for the copper lines and a vacuum pump to evacuate the lines before you open the refrigerant valve to charge the system. My local HVAC supply had a mini-split installation kit in stock for about $100 that had the copper lines and I bought the system online.

[JJ 911SC]

That is the way I'm going. The new version are working in -15 F temperature.

[rfuerst911sc]

Originally Posted by URY914

Electric and no ductwork needed. Supply from the top and return at the bottom.

Paul any idea what that type of heater/AC is called ? Not sure what to search for ?