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Best Configuration for Mitsubishi Multisplit

Aston01 | Posted in Mechanicals on

Looking to replace an existing HVAC system with a Mitsubishi multi split and just so happened to run across a previous post talking about issues with multi split systems efficiency when they aren’t configured properly.

The equipment currently being spec’d

MXZ-4C36NAHZ2
PEAD-A09AA7
PEAD-A24AA7
SEZ-KD09NA4R1.TH
PAC-MKA32BC

I’ve had a Manual J,S & D done, but I was curious if anything about the above configuration that stands out in a bad way to someone with experience in Mitsubishi systems?

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Replies

  1. BFW577 | | #1

    Even if they are configured properly 1 to 1 splits are significantly more efficient and have much better lower minimum capacities.

    It looks like your outdoor unit is the same as a recent poster. The minimum capacity is 22k which is going to be ridiculously oversized under any low load conditions.

  2. Expert Member
    Akos | | #2

    I would put the PEAD-A24AA7 on its own outdoor unit ( https://ashp.neep.org/#!/product/34519 ) and put the remaining two zones on a MXZ-2C20NAHZ2 ( https://ashp.neep.org/#!/product/29016 ).

    This will make the largest unit fully modulating (multi splits don't modulate as well as one-to-one) thus more efficient.

    The BOM cost is a bit less since you don't need a 4C unit with a branch box and install cost is a bit more, even than it should be cheaper. You would get a much better setup this way for about the same money.

    If you are in snow country, make sure all your units come with a pan heater. Usually built in, but sometimes this is an accessory.

    P.S. I would doublecheck the load on the 24k unit, most likely this can work and has even better modulation:
    https://ashp.neep.org/#!/product/34564

    1. Aston01 | | #3

      So you think the following would provide better modulation for about the same money?

      1.) PEAD-A24AA7 and PUZ-HA24NHA1
      2.) PEAD-A09AA7, SEZ-KD09NA4R1.TH and MXZ-2C20NAHZ2

      Is the primary difference between the PUZ & MXZ outdoor units that one is for a single zone and the other is multizone?

      BTW - Unfortunately, I think the 24k unit is sized pretty close so there isn't much room to downsize on that one (I attached a pic of the Manual J on that zone)

      1. Charlie Sullivan | | #5

        I'm not sure what your design temperature is, so I'm not sure how much room you have to downsize for that zone. The 26,000 BTU/h listed at 47 F is more than 1.4X the load, but presumably the design temperature is lower, where the heat output is less.

  3. Expert Member
    Akos | | #4

    One to one setups always have much better modulation. There is a lot of threads on here with people with multi splits with excessive power use. Sized just right they can work, just never as well as dedicated units.

    Looking at your man J, your cooling is above heating loads, which generally means milder climate. You can probably also save some money by not going with hyper heat units, or not all hyper heat. Even in colder climates you can do this for something that would be heating rooms on the 2nd floor.

    If you do need the 24k of cooling, there is also an SUZ-KA24NA2 or SUZ-KA24NAHZ that can be paired with the PEAD-A24 that is lower cost.

    1. Aston01 | | #6

      Just an update.

      I ended up going with your suggestion of
      1.) PEAD-A24AA7 and PUZ-HA24NHA1
      2.) PEAD-A09AA7, SEZ-KD09NA4R1.TH and MXZ-2C20NAHZ2

      Once they were up and running I could see the benefit of leaning towards 1:1 configurations. From an installation footprint standpoint I couldn't have gone 1:1 on the 9k btu units without taking up too much wall space in my situation, so that trade off was a workable compromise.

      1. Expert Member
        Akos | | #7

        Lot of times design is about making compromises. The impartant part is that you ended up with a much better system than the original design.

        Would be interesting to see how the system performs over the winter months.

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