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Purchasing/DIY single mini-split

FrankFulton | Posted in General Questions on

We have a poorly insulated, 260sqft finished bonus room above our garage. I just removed a 23yo TWO TON AC unit (!). There is baseboard electric heating.

What is the best way to purchase a single minisplit for this space and hire an hourly HVAC installer (eg, someone moonlighting by the hour)?

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Replies

  1. User avatar GBA Editor
    Martin Holladay | | #1

    Emerson,
    You need an HVAC professional certified for handling refrigerant tubing. You'll have to call up local HVAC contractors to see if any of them are willing to work with you on the installation of a minisplit unit purchased by a homeowner.

  2. FrankFulton | | #2

    Thanks Martin. Is there a best/are others reporting a best spot to purchase the unit?

  3. User avatar GBA Editor
    Martin Holladay | | #3

    Emerson,
    I'm not endorsing your idea. Frankly, you will probably find that it's difficult to get an HVAC contractor to agree to your plan.

    I used to be a contractor. Contractors provide valuable services. If contractors are competent, they know their trade, and since they've performed a task multiple times, they are unlikely to make rookie mistakes. And a good contractor provides warranty service in the case of problems.

    Most contractors want to purchase their own equipment, and to control all aspects of the installation.

  4. User avatar GBA Editor
    Martin Holladay | | #4

    Emerson,
    For more information on do-it-yourself minisplit installations, see these links:

    Friedrich Pulls Back on DIY Minisplit Launch

    Dare to DIY a mini split install?

    Are Ductless Minisplits Overpriced?

    Mini-split final install Qs

  5. User avatar
    Dana Dorsett | | #5

    It's unlikely that the cooling load of that space is anywhere near 3/4 ton (even with poor insulation) and it might be better suited for a half-ton PTHP than a mini-split.

    Most 3/4 ton DIY mini-splits don't modulate down to even 3500 BTU/hr (probably more than your cooling load) so even a mini-split isn't going to modulate much unless you buy something like a an LG Art Cool or cold climate Mitsusbishi FH06, both of which will throttle back to well under 2000 BTU/hr under light loads.

    If the 2-tonner was in a wall sleeve that you'll be replacing with finished wall, you already have the hole that's bigger than the wall sleeve for a half-ton PTHP, which would also heat the place with efficiency that would challenge that of an oversized low-end mini-split. There are several PTHPs with quiet scroll compressors out there in the ~6000-7000 BTU//hr range (both heating & cooling output), this isn't a comprehensive list:

    LG LP073HD2B

    Amana PTH073G35AXXX

    MrCool PTHP07325

    Gree ETAC-07HP230V15A-A

    Run a heating and cooling load calculation on that space using a freebie tool such as loadcalc (http://loadcalc.net/ ) until you're comfortable with the sizing. Ideally any mini-split you installed could modulate down to less than have your design cooling or heating load. If it can't go that low there's less of an argument for mini-split than an easier-to-DIY PTHP in a wall sleeve.

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