Mini-split installation

BKind2Anmls

Susan
Corporate Member
I have a 10x22 shop. The walls and ceiling are insulated and the inner wall is OSB. I think a mini-split would be a good fit. Is this something I can install myself? I was going to have a contractor install a small concrete pad outside the shop for my mini-split outside unit and my dust collector.
 

rcarmac

Robert
Corporate Member
Most of them you need special tools and such so you need a professional to charge the lines. If you search for DIY ones like by Mr. Cool, they are do it yourself and come precharge. Only down fall is I think it’s a set length of line set that can’t be adjusted between the inside unit and the outside unit. So if your distance exceeds that, this unit will not work. Instead of floor mounting, might look into the wall brackets it it’s close to a wall. Keeps it up off the floor and easy to clear around
 

BKind2Anmls

Susan
Corporate Member
Most of them you need special tools and such so you need a professional to charge the lines. If you search for DIY ones like by Mr. Cool, they are do it yourself and come precharge. Only down fall is I think it’s a set length of line set that can’t be adjusted between the inside unit and the outside unit. So if your distance exceeds that, this unit will not work. Instead of floor mounting, might look into the wall brackets it it’s close to a wall. Keeps it up off the floor and easy to clear around
I have ordered a Mr. Cool from Lowes.
 

tvrgeek

tvrgeek
User
I had a Mitsubishi installed. It works very well except for humidity. The coils are just not cold enough. Tech says they are fine and running @ 65 is normal for a light load. I had to buy a dehumidifier. I think there is something wrong with the expansion valve or control there-of, but tech does not know and the OEM does not return calls. Split pulls out maybe a pint a day and the dehumidifier about 3 gallons. Where that much is coming from is a mystery. 16 x 32 pretty well sealed up. Even with the 90% we have had recently, blowing my mind. I want the shop between 50 and 55%. It had gone over 80 with just the split running.

Depending on your county, there are codes for how it is installed and technically, you need a permit and inspection. Usually an outside dis-connect.

Do NOT mount the outside unit on brackets on the side. They have a low frequency rumble that will drive you crazy. Set it on a platform off the ground unless you have serious isolation mounts. Inside unit goes high on the wall.

Most splits are pre-charged, so if you get the lines on quickly, they wil be fine. The charge is by weight, so you can't test by temp delta like the old days. Fun with variable speed compressors. If it does need to be serviced, only pros can get R410.

Even with my dust collector and air circulator with MERV 13 filters, my evaporator loaded up. So I build a large box around it with MERV 13 filters on it. Coils stay clean.
 

Brian Patterson

Bstrom
User
I had a Mitsubishi installed. It works very well except for humidity. The coils are just not cold enough. Tech says they are fine and running @ 65 is normal for a light load. I had to buy a dehumidifier. I think there is something wrong with the expansion valve or control there-of, but tech does not know and the OEM does not return calls. Split pulls out maybe a pint a day and the dehumidifier about 3 gallons. Where that much is coming from is a mystery. 16 x 32 pretty well sealed up. Even with the 90% we have had recently, blowing my mind. I want the shop between 50 and 55%. It had gone over 80 with just the split running.

Depending on your county, there are codes for how it is installed and technically, you need a permit and inspection. Usually an outside dis-connect.

Do NOT mount the outside unit on brackets on the side. They have a low frequency rumble that will drive you crazy. Set it on a platform off the ground unless you have serious isolation mounts. Inside unit goes high on the wall.

Most splits are pre-charged, so if you get the lines on quickly, they wil be fine. The charge is by weight, so you can't test by temp delta like the old days. Fun with variable speed compressors. If it does need to be serviced, only pros can get R410.

Even with my dust collector and air circulator with MERV 13 filters, my evaporator loaded up. So I build a large box around it with MERV 13 filters on it. Coils stay clean.
Your experience is good to know - these splits are meant for smaller spaces but should perform as a ducted system - if they cant handle the humidity that’s an issue.

One DIY installer used a vacuum gauge to test and clean the lines before releasing the charge. Doable by most but only with a solid understanding of the dynamics involved.

You also have wall/window mounted heat pump AC Units to consider that are truly plug and play Without a 220 power line needed, etc.
 

junquecol

Bruce
User
Unless the lines attach with piercing valves, and are precharged, then you need to sweep them with nitrogen, then pull a vacuum. Prior to Jan 1, 2020, anybody could buy a cylinder of 410-A
 

BKind2Anmls

Susan
Corporate Member
Your experience is good to know - these splits are meant for smaller spaces but should perform as a ducted system - if they cant handle the humidity that’s an issue.

One DIY installer used a vacuum gauge to test and clean the lines before releasing the charge. Doable by most but only with a solid understanding of the dynamics involved.

You also have wall/window mounted heat pump AC Units to consider that are truly plug and play Without a 220 power line needed, etc.
Has anyone used one of those window unit that heats and cools? Sure would be easier and less expensive. I've already had a 220 line pulled to the shop.
 

Oka

Oka
Corporate Member
Mitsubishi does offer a split system that does not require brazing the lines, something to consider. Splits are fairly easy to install
 

gmakra

George
Senior User
All units come precharged.
Yes you can install the system [rough in]and have a tech come out and evacuate the lines and commission the system.

I used to be a hvac contractor and can tell you you may save a couple hundred. But honestly just have a pro install it. They have access to all the specalty tools and knowledge.

AC is expensive but screwed up HVAC is extremely expensive.
 

chris_goris

Chris
Senior User
Im almost certain the Mr Cool brand is complete DIY. Unless you're afraid to hookup the 220V line (maybe they sell 110 versions , I dont know). They are touted as all DIY. Precharged and ready to go, simply attach the lines and open the valve.
 

jlimey

Jeff
Senior User
All units come precharged.
Yes you can install the system [rough in]and have a tech come out and evacuate the lines and commission the system.

I used to be a hvac contractor and can tell you you may save a couple hundred. But honestly just have a pro install it. They have access to all the specalty tools and knowledge.

AC is expensive but screwed up HVAC is extremely expensive.
George, I got a quote from a HVAC company that was > $4000 for a unit that costs about $2200. A friend got a similar quote from someone else. So there is a lot of expense in the labor that I don't quite understand. The company I used to install a furnace charged me the same labor cost for a two 1/2 day job that they want for what I assume to be a morning activity. I keep thinking that the costs of mini-splits will fall as they become more commonplace, but it hasn't happened yet.
 

Chris C

Chris
Senior User
My parents put one in their 12x12 California room about twenty years ago. It's still running like a champ. It's mounted low to the floor in the wall. It does an excellent job... No complaints.


Has anyone used one of those window unit that heats and cools? Sure would be easier and less expensive. I've already had a 220 line pulled to the shop.
 

mdbuntyn

Matt
Corporate Member
Has anyone used one of those window unit that heats and cools? Sure would be easier and less expensive. I've already had a 220 line pulled to the shop.
A friend of mine has used two (one 220v, the other 110V), to cool the place that he rents, for close to 10 years, if not more. I can't tell you the BTU rating of either, but they keep the 750-800 sqft house at 72-73F, without appearing to be overworked.

He had to replace the big one a year ago (maybe two). The other still cools, but the electronics have gone "wonky", for lack of a better word, and he'll need to replace it any day now.
 

junquecol

Bruce
User
Has anyone used one of those window unit that heats and cools? Sure would be easier and less expensive. I've already had a 220 line pulled to the shop.
Used to build metal buildings, and we used GE sleeve units like you see in motels. Never a problem.
 

Ken_NC

Ken
User
I had a 24K BTU Fujitsu mini-split installed in my workshop seven years ago. I have not had a single issue with it. It heats & cools my shop in a hurry. I saved a little money by running the electric line myself. Also, the wife & I made sure the walls & ceiling were as well insulated as we could make them. Had a guy insulate the floor, too. I'm convinced that all that insulation is why the mini-split works so well.
 

drw

Donn
Corporate Member
I had an 18,000 BTU Mitsubishi mini-split installed in my basement shop (about 900 sq ft) and it does a beautiful job of both heating and cooling. I also purchased a small dehumidifier which I have draining directly into a sump pump...between the mini-split and dehumidifier the shop is very comfortable.
 

tvrgeek

tvrgeek
User
So, yours does not do a sufficient job dehumidifying either? I have tried to contact Mitsu support and ask the spec on the evaporator coil but they do not return my call nor to the installer. Nice machine, unfortunately seems not a good company. Mine is running around 65 degrees. No where near cold enough to dehumidify. My small dehumidifier is running at 55. Kind of defeats the efficiency if a high efficient AC has to have the entire power wasted for an auxiliary dehumidifier. The aux unit pumps about 3 gallons a day. Can't imagine where that much is coming from.
 

drw

Donn
Corporate Member
Given the fact that my shop is a basement shop, with a concrete floor, a significant amount of the water vapor comes up from the floor. While the AC does aid in dehumidification, when the set temperature has been satisfied and the unit cuts off, water vapor continues to diffuse into the shop, so the dehumidifier helps.
 

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