Mini split heat pump in a garage workshop?

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  • Mini split heat pump in a garage workshop?

    Anyone done it? Looking at a Cooper & Hunter 18k btu unit..

    https://minisplitsforless.com/collec...39549631299776

    396 sq ft garage, 8ft ish ceilings.. 12k is called for but rollup doors even insulated are lousy,, and Houston climate..

    Already have the 230v breaker / outlet in place.

    Any advice?
    Last edited by dbhost; 01-22-2023, 11:14 AM.
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  • #2
    Advice? Do it now before it gets hot. I’m not familiar with that brand. I did the site inspection and specifications for many dozens of mini split installations on our local marine base. We could not designate manufacturers/brands in our specifications but we could require a 1 year service warranty. I do not recall seeing any brand besides Mitsubishi and MrCool being installed. Our contractors did not want to get called back on a warranty service call.
    I cooled my 750sf shop with a already used 14000 btu Westinghouse heat pump through the wall unit for 12 years until it died of overwork due to Hurricane Michael sucking all the insulation out of my attic. It was replaced with a 24000 btu Amana heat pump through the wall unit and the attic insulation was replaced with spray foam. This new smart AC doesn’t heat and cool as well as the 14,000 btu unit and I had to add a garage door insulation package to the existing insulated garage door to get this air conditioner to be able to cycle on and off properly. …… So you will most certainly have to insulate your garage door. I also blocked the garage door windows with bubble insulation and could tell a noticeable difference. Click image for larger version

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    • dbhost

      dbhost
      commented
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      My doors are insulated with 2 layers of R-Max 5 so a combined total of R10 is all I could fit... Due to the face I actually still use the doors to get material and my happy behind in / out when I am working in the driveway, I can't tape the joints. I need to replace the door gaskets. I have them all around but after 12 years fo Texas sun they are hurting...I will be adding a 10x12 shed as soon as I rip out a crepe myrtle in the back yard that is in the way, and I have NEVER liked... Nice in the front yard, ticks me off out back... Once my lawn and garden, and camping stuff is in the shed, I move my lumber off the racks and blow in insulation on the remaining wall, then patch the wall, paint and enjoy HVAC space... They jump from 12K to 18K BTU, I have the outlet ready to go, just need to figure out where to put the ouside unit.... I am going to plant new bushes so I may be able to conceal it behind a bush and keep the HOA off my tail...

    • dbhost

      dbhost
      commented
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      Not sure how I didn't notice earlier. What's with the hurricane lanterns?

  • #3
    Ductless, Split Units - is all we had in Japan. Used them long before they were accepted in the USA. Very efficient too.

    Here in the USA, I helped in building a church destroyed by a tornado back in 2012. In the rebuild in 2014, I had talked the church into the Split Units in a 2400 Sq foot building - 1200 sanctuary and 1200 for fellowship and bible Study rooms. The pastor was intrigued but a little scared of it. It was difficult getting anyone (AC guys) in the Memphis TN area to order and install one. One guy who did AC repair and was a qualified electrician also, agreed to install it if we ordered it. We ordered two separate split units; got them installed. The pastor and deacons are ecstatic about it. Heating and cooling; utilitiy (electricity) much less than they were expecting. 9 years on and doing well.

    The decision was made when they got to the point of: Do we install duct work through the attic before installing sheet rock in the ceiling or do we go with ductless. When comparing the prices and time line for duct install - Volunteer workers with qualified contractors overseeing - would add 3 months to the work. (They had to wait until the volunteer workers and contractors could coordinate their work together.) When the approximately 3 months delay and cost of duct work and inside install of the AC work was figured in, they decided on the Ductless/Split units. It was much easier to do, and less personnel work involved.
    Last edited by leehljp; 01-22-2023, 05:14 PM.
    Hank Lee

    Experience is what you get when you don't get what you wanted!

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    • dbhost

      dbhost
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      Have you used one in a shop environment? Anything to watch out for maintenance wise? Getting it installed is no issue (I have a friend that is certified / licensed and willing to do the install on a beer & pizza basis...)

    • leehljp
      leehljp commented
      Editing a comment
      I personally haven't seen one used in a shop environment but I know that keeping the filter clean is a necessity. I did something last year that worked greatly but I got criticized that it would cause too much drag and decrease the air pressure pull from the fans. I got some cloth/nylon screen used for screen doors and put it on my outside AC coils all the way around and used those bar magnets from HF to hold it in place. It caught tons of debris and cottonwood fuzz. I cleaned it off every month and the coils were much cleaner both last year and this year. I would put something like that - to catch the big stuff and let the filter catch the small stuff.
      Last edited by leehljp; 01-22-2023, 10:02 PM.

  • #4
    12K BTU sounds kind of low, especially for Houston. Are all walls and ceiling of your garage insulated 3-1/2 inches of batting plus drywall an sheathing or attached to the house?
    Oh, on second read I see its going to be 18K.Still may be optimistic with one wall being a lightly insulated door. are all the other walls insulated and the ceiling?
    Last edited by LCHIEN; 01-22-2023, 06:13 PM.
    Loring in Katy, TX USA
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    • dbhost

      dbhost
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      Other walls are radiant barrier and R15 (2x4 wall studs), or attached to the house. Ceiling is R30 batts.

      The portable AC keeps it tolerable in August here, maybe chugs along at mid 70s and is 13.5K BTU. I figure as inefficient as those things are, and upsizing to 18K should do the trick...IF need be I can add a flase wall in the front and pack more insulation but that kind of kills entry / exit...

  • #5
    Portable ACs are the lowest form of ACs, just one step below a tub of ice! The reason is the hot compressor returns heat to the room and usually the evaporator coils leak heat as well.
    I have one neighbor that has a mini split in his garage shop with a factory insulated 2 car door. He says it cools ok. I’m not sure of his building insulation.

    My replacement unit was a Through the Wall AC ( these units have a large solid sheet metal casing that does not have long louvers cut to allow it to be imbedded in the wall, and can also be used in windows ). I wanted a Mini Split but when I needed an AC there were NO Mini Splits, window or through the wall units available anywhere due to Covid and Hurricane Michael. People were buying them up because they can be powered with a portable generator whereas a home AC requires a much larger stationary generator. I found them available online through Home Depot with a 2 week delivery time. Note. I previously said it was 24,000 BTU, but that unit was not available so I purchased 18,000 BTU.

    The door insulation in my photo shows the hinges covered by Reflectix Tin foil bubble wrap type insulation that allows the hinges to flex so the door easily opens. The hurricane lanterns are something that I collected and used on our patio.

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    • #6
      I have a Lennox mini split in my shop and the only thing I've needed to do is keep the filter screens clean and blow out the entire unit with compressed air fairly often.
      Chr's
      __________
      An ethical man knows the right thing to do.
      A moral man does it.

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      • dbhost

        dbhost
        commented
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        Do you run an ambient air cleaner? (I don't use mine as often as I should...)

      • twistsol
        twistsol commented
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        I have a Jet AFS-2000 air filter, the machines are all connected to 3hp cyclone, and the handheld and bench tools are tied to one of my HEPA vacs. The only thing not connected to dust collection are hand planes and my drills.

        The air handler for the mini split has fine mesh screens but no actual filters. I clean those a couple of times a month and blow out the unit whenever I do.

    • #7
      Regardless to ambient air cleaner you still must clean the AC air filters. Filters in every Mini Split, window/through the wall and terminal units are pitifully inadequate for workshops with lots of dust. Proper dust collection should be high on your list of must do’s for your shop. I augmented my ACs pitiful filter with a thin sheet of pre-filter material used on room air filters.
      Concerning mini splits, the main complaint that I recall from maintenance crews servicing them on the marine base was their condensation drains. Wall mounted units create lots of water that must be piped out of the building. Most installers use clear vinyl tubing hooked up to the optional condensate pump inside the mini split. (Don’t forget to order it if it is offred)

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