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Different spec values reported by Mitsubishi and NEEP for heat pumps

Cgalgowski | Posted in Mechanicals on

I am in Storrs, CT climate zone V.

The attached document shows the Mitsubishi M Series Catalog and the Northeast Energy Efficiency Partnership (NEEP) Cold Climate Air Source Heat Pump Specification Website report different values for a few Mitsubishi Hyper-Heat Heat Pumps.  The differences occur in output at 47 and 17 degree temperatures.

Does anyone know what the correct values are?  I am trying to select the pumps which will perform best in my house.  Knowing the minimum output at both 47 and 17 degree temps along with the heat demand of my house will help me determine at what temperature the various heat pumps will start to cycle.   I use the two values to get a range of minimums from 17 up to 47 degrees. This helps me know at what temperature the pump will start to cycle.  Then knowing the percent of the time the average climate is above that temperature lets me know how frequently the pump cycles.  This will help prevent over-sizing the pump and getting a low HSPF and COP.

Also, knowing the correct maximum will prevent me from using a pump that is too small.

The following items in the table are of concern:

1) The NEEP values at 47 degrees are high as compared to values of other brands of heat pumps.
2) The NEEP minimum values at 17 degrees also appear high.
3) The Mitsubishi Catalog does not report the minimum values at 17 degrees.  How did NEEP get the values?
4)  The constant value of 7,200 BTU/hr reported by Mitsubishi for the 4 pumps (which are listed from smallest to largest) is unique.  Typically the minimum output for other brands of inverter type pumps increase as the pumps get larger.  Do Mitsubishi heat pumps have a special feature that allow a constant minimum value, even as the pumps get larger? Or are the 7,200 reported values at 47 degrees incorrect?

I was not able to get answers to these questions by calling Mitsubishi or NEEP.  I saw a transcript of a podcast by Dana Fischer, a Mitsubishi rep in Maine.  He spoke very knowledgably about how to avoid heat pump cycling.  Possibly, he would know how to determine the correct specifications for these 4 heat pumps.  I do not have any contact information for him.

Any help is appreciated.  Thanks,

Charlie Galgowski

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Replies

  1. CollieGuy | | #1

    I can offer no answers, but I'll just add that my two inquiries to Mitsubishi's customer support group went unacknowledged and unanswered, so I decided to take my business elsewhere.

    This fall, I'm replacing one of my two ductless mini-splits with a new cold climate model from another manufacturer that provides 100 per cent of its nominal rated capacity at -15°C and 80 per cent at -30°C. And with an HSPF of 14.0 with pan heater, on average, I'll receive just over four kWh(e) of heat for every one kWh consumed. Much better performance than the top of the line Mitsu and at nearly half the installed cost.

    1. this_page_left_blank | | #2

      Don't leave us in suspense, what is the brand? Those specs look like a Fujitsu RLS3H series, but the installed cost of one of those would usually be similar to a Mitsubishi of equivalent specs.

      1. CollieGuy | | #3

        The brand is Ouellet, and I'm not sure if they're sold in the United States. The model is the UHD12KCH31S, which comes with WIFI functionality. That's an extra cost option with the Mitsu, and requires that a separate external module be installed next to the head; with this Ouellet, it's no charge and integrated within the head itself.

        The particulars for the 9 and 12K models are as follows :

        1. this_page_left_blank | | #4

          Interesting. No certified installers in Ontario, either. They have distributors, but I don't know who they'd be selling the units to. The manual says it needs to be installed by a certified installer to get even the basic warranty, which is already pretty minimal - 1 year parts, no labour covered, 5 years on compressor.

          Where did you find the extended performance specs? Oulette has some models listed on the NEEP cold climate product listing, but not those ones.

          I note that the rated heating capacity is only the same as the rated cooling capacity - typically, the heating capacity on a cold climate model is a step higher than the cooling (e.g. for a Fujitsu 12RLS3H, the cooling is rated at 12kBTU, heating 16kBTU). If I extrapolate the information you provided (100% at -15C, 80% at -30C), then the output of the 12k Ouellette unit is 12kBTU at -15C and 9.6kBTU at -30C. In comparison, the equivalent sized Fujitsu is 16.5kBTU at -15C and 11.5kBTU at -26C.

          What is the installed cost you were quoted?

        2. Expert Member
          Dana Dorsett | | #7

          >"The model is the UHD12KCH31S..."

          That model number shows up under a number of different brand-names:

          http://www.willisac.com/wp-content/uploads/2018/02/UHD12KCH31S.pdf

          https://airtempo.ca/en/vulcan-single-zone/

          The cabinet work for the indoor unit looks a lot like a Gree Livo, the outdoor unit looks a lot like a Gree Crown. I'm guessing this could be a model Gree OEMs to a number of different vendors.

  2. Expert Member
    Dana Dorsett | | #5

    There are several differences between AHRI testing submittals and the information required by NEEP from the manufacturers for listing. For one, AHRI tests insist on running the inverter at 60Hz rather than the speed at which it's most efficient or has the greatest capacity, and doesn't require minimum modulation capacity (at that 60Hz inverter speed) at any temperature other than +47F.

    The "rated" capacity in an AHRI submittal is the modulation rate at which it's efficiency is tested, with the inverter locked at 60Hz. That isn't likely to be the most efficient frequency or modulation level for this type of equipment, but that's what's required for the AHRI cert.

    All of the values NEEP reports are whatever the manufacturer filled in for the sheet. There is no independent third party testing (other than if a competitor wants to call BS on some other vendor they suspect was cheating), and there are (rare but) occasional data-entry errors on the NEEP site. Their intake sheet is posted online here:

    https://neep.org/sites/default/files/ColdClimateAir-sourceHeatPumpSpecification-Version3.0FINAL_0.pdf

    Mitsubishi (and others) get to choose any minimum value they like for the firmware in their system controllers. Going too low results in lower efficiency on the compressor- I suspect 7200 BTU/hr @ 47F was chosen for their multi-splits because that can still be delivered by any of their half-ton heads without forcing the compressor to cycle inefficiently when only one head is calling, or forcing it modulate down to a sub-optimally inefficient (for the compressor) level.

    If you look you'll also find that all Fujitsu single zone mini-splits modulate down to 3100 BTU/hr @ 47F independent of size, probably for similar reasons.

  3. CollieGuy | | #6

    Hi Trevor,

    Mine will be installed by an authorized agent and I'm also purchasing the extended ten year parts and labour warranty (just waiting to confirm the cost on this). I guess your best bet is to contact Ouellet directly or one of the distributors listed on their website to see who serves your area.

    I'd like to keep the quoted price confidential if I may. I can tell you that it was thousands less than the MUZ-FH12NAH I had initially selected as a replacement. Good luck !

  4. Cgalgowski | | #8

    Thanks Dana for explaining more about the minimum operating values. I would like to know what are the minimum operating outputs in BTU/Hr for the following 4 Mitsubishi hyperheat compressors for outdoor temperatures ranging from 17 degrees to 65 degrees and indoor temperatures at 68 degrees (or 70 degrees if that is more common). The compressor model numbers are all of the MXZ- Series. The indoor heads are all the MSZ-FH Series.

    MXZ-2C20NAHZ2 with indoor heads MSZ-FH12, FH09,

    MXZ-3C24NAHZ2 with indoor heads, MSZ-FH06, FH06, and FH06

    MXZ-3C30NAHZ2 with indoor heads MSZ-FH15, FH09, and FH06

    MXZ-4C36NAHZ. with indoor heads MSZ-FH09, FH06, FH06, and 3 duct air hand- ler that delivers a total of 13,000 BTU/Hr peak (when outside temp = 6 degrees)

    Again, the objective is select heat pumps with a minimum of cycling.
    Thanks, Charles Galgowski

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