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Mitsubishi minisplits – Dramatic drop in COP at 17 degrees on submittal

evantful | Posted in Mechanicals on

I was browsing the Submittals today on Mitsubishi’s MyLinkDrive for the FH12NA and FH09NA. I noticed that they been updated this year at some point in the last few months.

Something that stuck out was the COP numbers on both units at 17 degrees dropped dramatically from what they were previously listed as on Mitsubishi’s previous Submittals.

The FH09 went from a [email protected] of 3.33 to 2.48
The FH12 went from a [email protected] of 3.34 to 2.10

Ive attached the previous table showing the efficacies, as the old submittals seems to be eliminated. The new submittals can be viewed on MyLinkDrive.

Any explanation to what happened? This really changes the dynamic of what these units can do in cold climate environments.

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Replies

  1. Josh Durston | | #1

    I'm curious as well under what conditions the data was generated since I'm in the process of purchasing a FH09na. When I started looking at them the COP was still listed at the higher value making it appear to be a no brainer, but as I'm finalizing my equipment selection I saw the lower numbers and got a little nervous. I wonder if other equipment manufacturers (notably Fujitsu) have adjusted their numbers?

    On the submittal data sheet there is a note saying that the COP is under maximum capacity, at 17F I would expect to modulated down quite a bit since it is so far above my design OAT.

    I know the published stats are really only valid on certain BTU/hr load, in/out temperature conditions, and sometimes under a fixed compressor RPM. Mits has stated that in some cases they had to run the compressor at a fixed 60hz since the test process did not have a way to deal with VFD compressors and fans.

  2. evantful | | #2

    I don't blame you, I would really like to know if testing specification from AHRI Efficiency Ratings changed this year resulting in the lower number.

    I purchased both a FH09 and FH12 back in May and it's alittle disappointing to see this revision.

  3. Expert Member
    Dana Dorsett | | #3

    It's a bit of a tempest in a testing-teapot. The COP listed is at the manufacturers' selected ARHI output modulation levels, not the COP at your actual heat load at your 99% outside design temp.

    Getting the sizing right for your actual heating loads and the modulation turn-down range during more temperature temperatures is far more important to the as-used efficiency than a specified COP at some specified output level & temperature unrelated to yours.

  4. Rich Cowen | | #4

    If they really misled consumers it would be grounds for a class action lawsuit. One thing I noticed is the my unit (FH18) runs far better now that I have the external thermostat installed.

    Is there any way to retrieve data from these units to find out the efficiency at which they operate?

  5. Expert Member
    Dana Dorsett | | #5

    >"Is there any way to retrieve data from these units to find out the efficiency at which they operate?"

    I don't believe there is any internal datalogging in the FH series minisplits or their various remotes.

    Regarding published efficiency data, the new NEEP format for information on cold climate mini-splits is now active. It's not as complete as the information in their prior (but bulky) spreadsheet of all units, but has the min/max output capacity and COP at +5F, +17F and +47F, as well as a description of the pan heater control algorithms. eg: here's the FH12NAH: https://ashp.neep.org/#!/product/26102

    FH18: https://ashp.neep.org/#!/product/26105

    FH09: https://ashp.neep.org/#!/product/25894

    The product search parameters can be selected here:

    https://ashp.neep.org/#!/product_list/

    (Notice the handy heating capacity min/max slider in the upper right.)

    It would be nice if the website remembered your parameter selections when you hit "back" after viewing the details of a particular model . It would also be useful to also include the capacities at the manufacturer's minimum operating temperature (which used to be included in the spreadsheet version that was in use up until January this year.)

    1. BFW577 | | #9

      Interesting link and data. I have been monitoring my mini split with an electricity monitor, duct/return and outdoor temp sensor. I noticed impressive performance lately with the damp mild spring weather with temps in the 50-60's. I installed my split in Jan 2019. My electric consumption matches up exactly on this chart with my Midea. The cop of 6.36 is impressive at the lowest modulation at 47. Mine pretty much always runs at lower modulation and barely runs at its 1.1 kw full output. Here was sundays electric consumption.

      Heating 47℉ 70℉
      Btu/h 3,690 11,800 12,810
      kW 0.17 1.08 1.07
      COP 6.36 3.2 3.51

  6. Walter Ahlgrim | | #6

    This is a wild guess but I bet there was a change or clarification in the testing procedures.

    Walta

  7. BFW577 | | #7

    I have been looking at the Gree Sapphire line and noticed the data sheets were all just updated as well. Just like Mitsubishi did everything was downgraded significantly.

    1. Tom May | | #8

      Just goes to show you, new products that are not time tested may not operate up to specs that are initially reported, especially in real world situations, so taking manufacturers specs as absolute may not always work out. This goes for most products, which is why there is always a "new and improved" model that comes out years later.

      1. Expert Member
        Dana Dorsett | | #10

        AHRI test procedure changes don't change the operation of the heat pump any more than changing the AFUE test procedure does for a boiler or furnace or changing the EPA Fuel Economy Test Methods and Calculations does for the fuel economy of your car. Mini-splits have a 40 year track record, split heat pumps nearly twice that. Personally I'd call that "time tested", but clearly YMMV (depending on which version of the EPA test you're referencing, of course. :-) )

        1. Tom May | | #11

          Yes, but new models and new designs don't fit into the track record.

          1. Expert Member
            Dana Dorsett | | #12

            Doesn't the 2019 F250 fit into the track record that began with the Model T pickup?

            I suppose not- it's a new design that can't be counted on. It's too dissimilar to the F150s, the F100s, and all those prior models, and it doesn't say "Model T" on it anywhere.

            The "new improved" models of mini-splits are definitely incrementally improving along the track of prior versions, with the occasional larger step improvements along the way such as vapor injection compressor technology and inverter drive variable speed motors.

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