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Community and Q&A

Ductless minisplit for cooling only

Trevor Lambert | Posted in General Questions on

After living with a heat pump on the main floor for a couple of months now, I’ve come to the (unsurprising) conclusion that it has negligible cooling effect on the 2nd floor. The main floor unit was purchased mainly for heating, but I thought I’d just see what it was like with no cooling upstairs. It’s not great. I keep the main floor at 23C, 55-60%RH. The upstairs is typically 2-2.5C warmer, and much more humid.

Anyway, looking for recommendations for models for the upstairs, given that it will essentially never be used for heating. My energy monitoring last winter showed only 10% of the heat delivered to the house was on the second floor; and of that small amount, all of it was to bedrooms, whereas this minisplit will be in the hallway.

I went with a Fujitsu 9kRLS3H for the main floor, based on its cold climate heating performance. Since that isn’t even a consideration this time, is there a more cost effective alternative? Looking for something in the 6k-9k range again. I feel like 6k is probably enough, but I’m guessing there’s not much price difference between 6k and 9k anyway.

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Replies

  1. User avatar
    Dana Dorsett | | #1

    Try calculating the room-by-room cooling loads for the second floor. (The actual load is probably smaller than you think.) Without the load number there's no way to make reasonable model recommendations.

    >"Since that isn’t even a consideration this time, is there a more cost effective alternative? Looking for something in the 6k-9k range again. I feel like 6k is probably enough, but I’m guessing there’s not much price difference between 6k and 9k anyway."

    I'm not aware of any vendors selling cooling-only half tonners. Mitsubishi's only half ton heating & cooling heat pump (the -FH06NA) is about USD$200 cheaper than the 3/4 tonner in the same series (-FH09NA), but still more expensive than 3/4" ton cooling-only minisplit or 3/4 ton minisplits not designed for cold climate heating.

    1. Deleted | | #3

      Deleted

  2. Akos | | #2

    Trevor,

    Don't underestimate the size of the upstairs unit. With a hallway mounted unit, most of the cooling will go downstairs, a good chunk of the cooling load of the whole house will have to be handled by the new unit.

    If you want a smaller A/C, you would need a ducted unit feeding the bedrooms directly. This might be more work than it is worth as a retrofit but much better for overall comfort.

    As for a unit, it will come down to what your local installers have. As long as it is an inverter unit with an electronic TXV, it should be pretty efficient. I've had good luck with low cost Chinese units.

    1. Trevor Lambert | | #4

      The cooling load for the whole house is around 12k, so if I put a 12k one upstairs it should be able to handle it. I'm not too concerned about sizing the unit smaller, but putting even a slim ducted unit into the house now would be a lot of work, and the result would be pretty unsightly.

      I've been offered a Daikin 12k "new old stock", which was a demo unit for "a good price". Still waiting for the specs on that unit, and the exact price. I'm also considering a DIY unit:

      https://www.sogoodtobuy.ca/12000-btu-mini-split-air-conditioner-senl-12cd/

    2. Trevor Lambert | | #5

      The cooling load for the whole house is 12k, so a 12k unit upstairs should be able to handle it. Ducting to the bedrooms would be nice, but with the design of the house it would mean a bulkhead below the ceiling to house the unit and ducts. A lot of work, and somewhat unsightly.

      I'm waiting for a quote on a "new, old stock" Daikin, which the guy tells me will be a very good deal. Also considering a DIY unit:
      https://www.sogoodtobuy.ca/12000-btu-mini-split-air-conditioner-senl-12cd/

    3. Trevor Lambert | | #6

      The cooling load for the whole house is 12k, so a 12k unit upstairs should be able to handle it. Ducting to the bedrooms would be nice, but with the design of the house it would mean a bulkhead below the ceiling to house the unit and ducts. A lot of work, and somewhat unsightly.

      I'm waiting for a quote on a "new, old stock" Daikin, which the guy tells me will be a very good deal. Also considering a DIY unit, a Senville 12CD for C$1100, includes an install kit, even tools I believe.

      1. Akos | | #7

        Be careful with DIY and install kits. Unless it has the quick connect pre-charge line set (I think MrCool is the only one), you need the full setup: a gauge set, high pressure nitrogen, vacuum pump and micron gauge to do it.

        If you are looking for budget DIY, one option would be to T one of these into your bedroom fresh air feeds:

        https://climateright.com/climateright-5000-btu-a-c-heater-2.html

        1. Trevor Lambert | | #8

          I'll look into that, thanks. I know someone who bought the Senville, so I'll ask him what it came with. I don't see anywhere I can buy the MrCool.

          I just looked through the full install manual of the Senville, and there is no mention of nitrogen or a micron gauge. They do show a gauge set and vacuum pump; basically the same equipment you'd use for charging an automobile A/C system (less a scale).

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