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I am about to have a Mitsubishi minisplit installed. In case it matters, the installation will be on an interior wall; on the other side of that wall is a closet with a sump pump which we will use for drainage.

The unit (#MSZFS12NAU1) is 12.6 inches tall and 9.2 inches deep. It will be installed above a 9" deep bookshelf. The distance from the top of the bookshelf to the ceiling is 19.25".

The contractor says that distance should be at least 22", so the bookshelf has to go and be replaced by something shorter. I am inclined to try the experiement of keeping the existing bookshelf, living for a while with the minisplit, and then replacing the bookshelf if (and only if) I am unhappy with the performance.

Question 1: How likely is it that the difference between 19.25" and 22" will significantly affect performance?

Question 2: If performance is in fact affected, can I compensate by changing the temperature setting? For example, if I would normally set the temperature to 70 degrees, but the performance is hampered by the proximity of the bookshelf, would I be able to set the temperature to, say, 65 degrees and get the result I want?

Question 3: Given that I want to at least try the experiment of keeping the existing bookshelf (unless responders here talk me out of it), does this have any implications for exactly how far from the ceiling the unit should be installed? (In case it matters, it's a drop ceiling with lots of room above it.)

WillO
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  • The required vertical space may not be entirely about performance. Read the installation instructions thoroughly to determine if there are other reasons you need that space. Does the drainage hose exit the unit from the bottom, and if so is its required space included in the 12.6" ? How do you remove the air filter to clean it? Does that require access from above or below the unit? Are there any other access ports for maintenance on the top or bottom of the unit? What about the IR receiver, if there is one. Where is that, and will it be blocked from view by the bookshelf? – jay613 May 28 '21 at 12:10
  • Your Question 2 is difficult to answer. If the unit "performs" poorly, ie is literally unable to cool the room for some reason, then setting the thermostat lower will not help. If the thermostat performs poorly, ie, is unable to detect the actual temperature of the room, then maybe you can experimentally determine the relationship between room temperature and detected temperature at the thermostat and modify your settings to fool the device. Seems like a odd installation strategy. – jay613 May 28 '21 at 12:14
  • You could apparently (from what you have stated) raise a section of the drop ceiling to make more room above the bookshelf. – Ecnerwal May 28 '21 at 17:19

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If you do not have the space to mount the unit with the required space above you void the warranty! You are purchasing a premium unit and mounting it two close to the ceiling will cause ANY future problems to be on your dime IF the installer will violate the space requirements (some will not).

Placing the unit tight to the bookshelf will block the output also. I would go with what they require because a future real problem may be on you that they would have covered if properly mounted.

Ed Beal
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Cooling should work just fine. You can set the vanes to send the air mostly away from the wall (horizontally) and the bookshelf should not matter much then.

Heating might be slightly more affected as it generally likes to send the air straight down. The unit will still heat but may be less effective at sending hot air all the way to the floor. Bottom line: your feet might get a tiny bit colder.

I personally would not hesitate to keep the bookshelf.

Olivier
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