I have a mini-split cassette (ceiling install) in my garage. Two questions for you guys and gals.

  1. Do I need to pour bleach down the drain line for a mini-split? I do this for my HVAC system. There is not an access to the drain line, I would have to add one and figure out how to access it.
  2. If I insulate the attic space with blown-in insulation, do I need to cover the mini-split?

I can't find an answer via google for the using bleach in a mini-split drain line, all my searches reference HVAC systems. As for the insulation issue, some say cover it with insulation and some say don't so I am not sure what to do.

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  • Just to be clear, we're looking down at an attic floor in this picture? Also, this should really be 2 separate questions since you're asking 2 very unrelated things. Yes, they're both about your mini-split, but bleach in the drain line and insulating an attic are 2 different things.
    – FreeMan
    Aug 11 '21 at 12:23
  • Yes, this a picture looking down on the top of the garage ceiling. The mini-split is the black box in the middle of the picture.
    – amrog
    Aug 11 '21 at 19:04

Bleach is not the best option for long life.

there are biocide tablets that will prevent mold and other gunkies from growing without aging the plastic drain tubes and pump seals.

As for freezing there should be no water discharge from the inside unit in the winter because you are in heating mode. With no water there is really no reason to insulate.

In the winter months the outside unit may generate the water, remember a mini split is just a heat pump, moving heat from 1 location to another.

  • Hi Ed, I need to insulate to keep the cool air from dissipating during the hot summer months so I am trying to figure out how to address the mini-split and insulation issue in the attic. Even Mitsubishi doesn't seem to address how to insulate around the mini-split unit.
    – amrog
    Sep 4 '21 at 4:36
  • Adding some insulation helps reduce some losses even foam insulation for pipes that you can get at a big box store will help. I purchase pre insulated most of the time each pipe separately encased. I have rolls of neoprene for the cases where I do it my self, make sure to have some between the 2 pipes you don’t want them touching each other without insulation between them.
    – Ed Beal
    Sep 4 '21 at 14:44

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