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Help me size a mini split for my shop

reklund5

Member
Joined
Aug 15, 2005
Messages
15
Location
Northern Nevada
Looking for some feedback from all that have done this before, so lets have it!

My shop layout is a bit unique- the photos will hopefully help explain it better than I can. I have 3 areas in the shop I'd like to have heat/AC in as follows:

My office is a 12x16 with 7.5' ceilings. I work from home and spend the majority of my weekdays in there. Currently I have a portable heat pump that vents through the wall with a 5" duct. It does a fine job of regulating the temperature, however it is LOUD, making it difficult to have a phone conversation or web meeting. 196 sq/ft. Call it 200 sq/ft for rough numbers

The "storage" side of the shop is 2 bays, 26x38 with 11' ceilings. My office is in the back corner of this space, so you can subtract the area of the office from that space. 796 sq/ft. Call it 800 sq/ft with 11' ceilings for rough numbers

The "work" side of the shop is one bay, 16x45, with 16' ceilings. 720 sq ft. I have a 2 post lift and my tools, etc in there. Currently I have a pellet stove in there that will cook you out in the winter, but eats up real estate on the floor I'd like to use for storage. In the summer I use a small swamp cooler in a window, and it keeps it below 80ºF, but it keeps the humidity between 40-55% despite my efforts to ventilate the building.

The "work" side is walled off from the "storage" side with only a 7x4 opening to walk through. No door, just a framed in opening to pass from one side to the other. I'm thinking a 36k/9/12/18 3 zone unit will handle it. Hoping to put the 9k unit in the office, 12k in the storage side and 18k in the work side. Thoughts? Building is well insulated, with blown in insulation in the ceilings and the walls are stuffed with insulation, although I don't know what kind. All 3 garage doors are insulated with foam and seal pretty well for big garage doors.


I live in Northern Nevada, so we see 0-5ºF as a max low in the winter (but not usually that cold) and 105ºF as a max high in the summer. Today it's gonna be every bit of 95ºF. Ideally, I could keep the office at 70-73 in the summer and 68-70 or so in the winter, just like a house. The storage and work areas need to not freeze in the winter (there is water in the building, and I've never seen it get below 40º inside, even if not running the pellet stove. I would like the ability to warm up the work areas to 60 or so in the winter. My big concern is the tall ceilings in the work side- will an 18k unit keep up?
 

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jack stand

Well-known member
Joined
Feb 29, 2012
Messages
3,314
Location
Lakes Region Maine
From what I understand they're not at all like sizing a conventional system where short cycling is really not a concern with a m/s system. As long as the numbers work....
My system (m/s) seems like it's almost always "on" but just at an idle from listening to both the inside units and the outside compressor. It's a very stable temperature both heating and cooling.
 
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reklund5

Member
Joined
Aug 15, 2005
Messages
15
Location
Northern Nevada
From what I understand they're not at all like sizing a conventional system where short cycling is really not a concern with a m/s system. As long as the numbers work....
My system (m/s) seems like it's almost always "on" but just at an idle from listening to both the inside units and the outside compressor. It's a very stable temperature both heating and cooling.
How does yours keep up in the winter?
 

jack stand

Well-known member
Joined
Feb 29, 2012
Messages
3,314
Location
Lakes Region Maine
How does yours keep up in the winter?
It's a little hard to say. We use it until December when we fire up the wood boiler that's primarily for heating my shop. The house and shop have in floor radiant. Then I've super insulated with 3" of foam with 3 1/2" of fg on the inside.
I see no reason that it wouldn't heat the house all winter here in Maine.
Overall I couldn't be happier with the mini splits for heating, cooling and dehumidification.
 
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jack stand

Well-known member
Joined
Feb 29, 2012
Messages
3,314
Location
Lakes Region Maine
I'm surprised that a real HVAC guy hasn't responded to your question yet.
I asked a similar question during my "negotiation" to the company rep knowing that a/c run time is critical for removing moisture, a/c was our primary motive. He was proven correct.
 

theoldwizard1

Well-known member
Joined
Feb 22, 2011
Messages
43,109
Location
SE MI
My office is a 12x16 with 7.5' ceilings. I work from home and spend the majority of my weekdays in there.
I know this is not a big area, but I recommend installing a separate mini-split for this area. It should be quiet and comfortable !

If you want reasonable air distribution (temperature) you are going to need at least 2 air handlers, maybe more. If possible, install interior walls to separate the other areas.
 
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reklund5

Member
Joined
Aug 15, 2005
Messages
15
Location
Northern Nevada
I know this is not a big area, but I recommend installing a separate mini-split for this area. It should be quiet and comfortable !

If you want reasonable air distribution (temperature) you are going to need at least 2 air handlers, maybe more. If possible, install interior walls to separate the other areas.
That is why I was considering a 3 zone unit.
 
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