Reaching out to the experts today to ask about location of installation of a mini split.  I'm a realtor, not an HVAC contractor.   I'm working on a "flip" that will be more energy efficient than most, think HPwES.  For the separate detached casita we are replacing a window AC unit placed in a sealed off window with a new 3 x 3 window and a mini-split.  An HVAC contractor is proposing the muni-split to be installed on the same south facing wall as the newly installed window.  

The picture belows shows the entire lot and arrow pointing toward the detached casita.  It looks attached, except that the white patio covering does not have walls.  It backs up to the outside laundry room which backs up to the carport and ensuing driveway. 

An HVAC contractor has proposed it best to install the new window and mini-split on the same south facing wall of the casita.  

My idea is to install  the mini-split on the west wall.  Your first thought is why the west wall.  The west wall is in the middle of the casita, across from the front door.  There is a bathroom inside this unit, to the right of the entry door.  The entry door ison the east/right side of the casita.   I also think of air flow and how one affects te other?  We have wonderful winters in Arizona where we can sleep with the windowss open.  We could expand the window size to 4 x 4 if the mini-split was on another wall. 

My question to you all is - which wall would you install a minisplit?  

On the same south wall where the window is located; 

On the west wall to be more centrall located; or 

On the east wall to the left of the entry door?  

Tags: #Airflow, #HVAC, #minisplit, #remodel

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Really hard to advise without knowing the layout. But you're asking good questions. Any chance you can post the floor plan or 'sketch and scan'?

This is a very rough diagram of the detached casita.  There are currently no windows in this casita.  We need to add one to the south end and the current HVAC contractor wants to add the mini-split to the same wall with 7' ceilings  I'm not 100% in agreement.  Thoughts?

Hi Jan, in a room like that with a relatively balanced aspect ratio, flat ceiling and not much glass, the mini-split could probably be located on any wall. With the information provided, the west wall looks good, preferably near the center. 

In general, if a room is much longer than wide (e.g., bonus room), the unit needs to go on an end wall since mini-split throw patterns tend to be longer than wide. That's doesn't appear to the be case here.  Also keep in mind that a wall unit (as opposed to a floor model) needs to be mounted high to avoid 'face washing' and interference from furniture. (Note: Different models can have very different throw patterns.)

Here are some of the things I consider when deciding where to mount a wall unit: room shape, need/opportunity to condition an adjacent nook or room, interference (e.g., soffits or curtain walls), furniture layout and of course, aesthetics.

As an aside... In hot climates, I always try to locate the outdoor unit so it doesn't receive afternoon sun. The benefit is relatively small (on the order of 5%) so it may depend on what that would do to refrigerant line length and routing. For example, you wouldn't want a long run along an exterior wall, especially if it's exposed to direct sunlight.

Thank you, thank you!  I appreciate your insights.  I agree with the idea that installing on the south wall, above the window woudl work.  The room is longer than wider, so instaslling on the farthest wall would be idea.  There's also a huge tree shading the south end of the building.  On the west side, this property is practically ON the property line, so the casita backs to a block wall and might be more difficult to install on the west side.  It would be exposed to a bit more sun on the west side, even though by late afternoon it would be in the shade.  

Did NOT know the flow of air from a mini-split so will keep this in mind for future reference.  Again, I appreciate your insights David!  Will share with my project manager.  

Hi Jan, actually, I said you'd be fine putting it on the west wall since you want a larger window. Keep in mind it's not necessary to set the outdoor unit on the same wall as the indoor unit. Also, according to your drawing, the room (excluding closet and bath) is only slightly longer than wide, not nearly enough to impact placement.

I disagree with Daniel's recommendation to locate unit on south wall since it may have the highest load. There's no logic to that, since the air is directed AWAY from the unit.

Walter noted that some manufacturers recommend 12" spacing between wall unit and ceiling. Since you have limited ceiling height, I would not assume 12" is required. Clearance requires vary by model. Check the installation instructions.

Thank you for that.  I wanted to put it on the west wall since there isn't much chance of a lot of west exposed sun and would look better aesthetically in the room.  The west wall is limited on space between the block wall and the building, so will see if a tech can squeeze in there.

I'm not sure if I'm making myself clear. You don't want to 'squeeze' the outdoor unit between the building and block wall. The installation manual will call out specific clearances for outdoor unit for rear, sides, front and top. Those must be adhered to.

But no worries. If there's not enough clearance you can still install the indoor unit on the west wall and set the outdoor unit at a different wall. Sure, it's easier to mount the two units on the same wall, but mini-splits can be separated by 100 to 150 feet, depending on specific make/model.

When installing units on different walls, ideally the line-set should be routed through the building or attic (as opposed to outdoors subject to sun exposure). Also, there's a slight efficiency advantage for having the units close together. But these should not dictate placement when there are other completing objectives.

First: Mini split are a great option.

Second:vI agree with David that installing on the south wall, above the window woudl work.

I would add where is the power coming from?

how much room for the condenser on the west wall it looks tight over there and I would want 12 inches clear for the condenser 

the south wall proposed might have easier access for the electrical run

I'll check on electrical.  Good point.  

South Wall. It will have the highest load needed for cooling/heating. the shade from the tree could help the outdoor unit operate more efficiently in the summer.

Look into a mini split with a sensor for hot/cool spots. It will direct airflow to where is is needed solving comfort issues.

Being a Flip you must consider the install cost. At least get a bid for a PTAC unit like the ones found in most hotel rooms.

With either choice I would put it on the long wall so it is closer to the center of the room.

If the unit is mostly for cooling mount it higher on the wall. If it is more of a heater get a floor mounted unit.

Most mini split manuals require 12 inches of space above the mini 12 inches of unit unless the ceiling are very tall over the window is not going to look very good.




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