Replies

1. GBA Editor
   Martin Holladay | Jun 10, 2015 06:50am | #1

   John,
   The three leading names are Mitsubishi, Fujitsu, and Daikin. You should have good luck with any of these brands.

   What matters most is good local service and support. If there is an HVAC contractor in your area who installs and services one of these brands -- an HVAC contractor with a good reputation -- that's the company to call.

2. 
   JohnBoy28 | Jun 10, 2015 07:37am | #2

   Thanks Martin
   All of those companies are represented in my area. What about Samsung (Quietside)?

3. 
   bobhol | Jun 10, 2015 09:13am | #3

   Hi John...I have just finished a house in zone 6 (Ontario,Canada) and have installed a pair of Fujitsu XLT(extra low temperature ) mini splits .In all my research over the last two years only Mitsubishi and Fujitsu consistently met my needs.There are lots of others but I needed efficiency at low temps and these companies lead the industry.Good luck with your build ,regards Bob

4. 
   JohnBoy28 | Jun 10, 2015 09:37am | #4

   Thanks Bob.,
   I will check them out, I wasn't aware of the XLT models. My only problem is I need the ducted version and they will probable not be available in XLT models.

5. Expert Member
   Dana Dorsett | Jun 10, 2015 04:52pm | #5

   Climate is important. If going with a ducted mini-split in a US climate zone 6 climate the only realistic option is the Fujitsu xxRLFCD series. They at least have a rated output down to -5F.

   The Mitsubishi SUZ/SEZ units have rated output down to +5F, but the output and efficiency is comparatively poorer. But in a US climate zone 4 or warmer they'd do just fine, and there is a lot more distributor support for Mitsubishi than Fujitsu in many markets.

   So, where are you located, and what are your heating/cooling design loads? The answers to both are critical to finding the right solution.

6. 
   rsmith02 | Jun 11, 2015 09:32pm | #6

   This isn't a list of recommendations but rather a compilation of manufacturer supplied data about heat pump performance at low temperatures. It might help compare apples to apples.

   http://www.neep.org/initiatives/high-efficiency-products/emerging-technologies/ashp/cold-climate-air-source-heat-pump

   Here is a list of units that have met Efficiency Vermont's specifications for that climate.
   https://www.efficiencyvermont.com/docs/for_partners/contractors/evt-cchp-qpl-bymanufacturer.pdf?v=9

7. 
   jackofalltrades777 | Jun 12, 2015 02:42am | #7

   This is a new and interesting study on Mitsubishi mini splits:

   http://r20.rs6.net/tn.jsp?f=001skUCV0BVjaa_kBxSxlVxEOT-mrVHpK0ttTgCT-m6W0XFp5Jx1GrqWKzI74MjzPuEfrw5UO-L9XfMTEwxcXi5-AssZAB8xq8Uk6orBHcHcmOkocis2euyoG_-_DPv_VOcvTwHxGyQRQrvLzKCrQzIuqW7m-v5YmQnUHD1WfWibnppzwidGlYtLyj6ml265t0cPcYbc-ZncfVpVTgeHpgsrl45NCbmy1lV_942YAa6uyfgcNY-b4bISTVMokSlAHkMejHnEI2Y8uROZmgvQZzVMnS-HzrX4-My&c=a5bp4rLqpGyv7X3KxJ4rgK8cRauSc9MMwSod9mHnNGSqMRjDiGBePQ==&ch=n29qiLsch9cvVV_7lasGlHxgZ9JzVZogHVL-cPvhbmTQR8vNQ53wqA==

8. 
   JohnBoy28 | Jun 12, 2015 05:47am | #8

   Thanks All
   The information and links provide will be helpful. I don't expect the system to be economical in the middle of winter here in Zone 7.

9. 
   JohnBoy28 | Jun 12, 2015 06:16am | #9

   Roger
   The spreadsheet is very helpful. As mentioned, I am in zone 7 so need a system that is efficient at low temperatures. I have seen different units advertised to -5F and lower but obviously performance suffers. For this I understand I am looking for a high SEER rating but how do EER and HSPF ratings tie in?

10. 
    rsmith02 | Jun 15, 2015 12:21am | #10

    The spreadsheet gives you a sense of how much the efficiency suffers at low temperatures, not just that it will provide any output as some manufacturers claim. Personally I am using a low-temperature optimized Fujitsu minisplit in a southern New England-like climate. It is overkill for here and I have had no problems with it not working on cold nights. I think well north of here you'd use a similar unit but with a base heater? Not sure how cold your area gets.

    SEER and EER are for cooling I believe. SEER is an average over the cooling season and EER is for peak performance on a 95 degree day. HSPF is for heatpump heating. Truthfully none of these metrics really tell you how much a given unit will use in a given climate. The DOE had a tool to derate heat pumps for colder climates than what the HSPF rating assumed but wasn't meant for ductless minisplits and assumed it would run in electric resistance mode at cold temps.
    So look for relatively high COP/HSPF and a decent amount of output capacity for the temperatures you can expect to ordinarily experience.

    I would assume that it will be economical year round vs electric resistance and oil though you may need some supplemental heat source through the coldest part of the winter..

    I'd see what dealers are selling in your area and what works there. Minisplit heat pumps are doing fine from coastal Maine to New Hampshire to Southern Alaska so I think you'll find a unit that would works for you for at least for most of the year. I'd consider starting with that Vermont rebated list to narrow them down a bit and then maybe search for experiences with those units by people in your area.

11. 
    JohnBoy28 | Jun 15, 2015 05:32am | #11

    Roger, Thanks, good advice.

    FYI we get one or two days approaching -40F but -5F is closer to average in February.

12. 
    dburgoyne | Jun 15, 2015 11:12am | #12

    My mechanical contractor said all three that Martin recommended were great units, and he works on all three without many problems. He recommended the Daikin, primarily because of the 10-12 year warranty, and said either option would not affect the price (in my case). The other two have a 5-7 year warranty. I followed his advice and will be installing a Daikin in a few weeks.

13. Expert Member
    Dana Dorsett | Jun 15, 2015 12:09pm | #13

    "HSPF is for heatpump heating. Truthfully none of these metrics really tell you how much a given unit will use in a given climate. "

    Actually, HSPF testing is model developed to predict approximate average performance in a US DOE climate zone 4 location, but a separate HSPF map was developed with it's own "heating load hours" zone map (see: http://www.fsec.ucf.edu/en/publications/html/fsec-pf-413-04/images/Figure5_lg.gif ) to deal with the wide variance peak vs. average loads, average humidity, and total numbers of hours of heating load, all of which affect air source heat pump efficiency. DOE climate zones are more about heating degree day averages. It's not a particularly good model for modulating equipment like mini-splits though, since An HSPF number is the approximate seasonal efficiency for zone IV in the heat load hours map. There are fudge-factor tables to predict the performance in zones other than zone IV based on the HSPF zone IV numbers, none of which are very accurate even for 1 stage ASHPs.

    https://www.federalregister.gov/articles/2005/10/11/05-15601/energy-conservation-program-for-consumer-products-test-procedure-for-residential-central-air

    http://www.heat-pump-pro.com/heatpumpefficiency.html

    At moderate to cool outdoor temps modulating ASHPs have much higher efficiency at part load than when running full-blase, but the range of efficiency narrows as outdoor temperatures fall. But that high part load efficiency means that with some amount of oversizing the seasonal efficiency goes up, often substantially. The limitation comes to where the oversizing factor is high enough that it is always cycling on/off rather than modulating during the spring/autumn shoulder seasons. Part of the specifications on an HSFP test submittal sheet is both the minimum & maximum modulated output at +47F. It can be important to know your heat load at +47F when selecting the equipment. If the minimum output of the equipment @ +47F is 2x your actual heat load @ +47F both efficiency and comfort are going to suffer, since it'll begin cycling on/off at temps well below +47F, with wide swings in room temperature. From a modulation range point of view, among the cold-climtate mini-splits the Mitsubishi -FHxxNA series has a distinct edge over the competition. The FH09 cranks down to 1600 BTU/hr @ +47F, but still delivers 10,900 BTU/hr @ +5F, and has a rated output down to -13F.

    In a US climate zone 7 location what you would be most interested in is the low temp capacity of the mini-split, not it's cooling efficiency or cooling capacity. The Mitsubishi -FHxxNA units are pretty efficient, but have a much reduced capacity at -10F than their rated +5F capacity, and they are designed to turn off at -18F or lower (!), though internet scuttlebutt has it that the true turn-off temp is somewhere in the -20s. The Fujitsu -xxRLS3H series has similar (slightly better) HSPF tested efficiency, but somewhat more capacity, and the keep running no matter how cold it gets. In locations that get at cold as -40F you'll be better off with the Fujistu -xxRLS3H series, despite the fact that the min-mod @ +47F is 3100 BTU/hr, even for the 3/4 tonner. The 3/4 ton Fujitsu -9RLS3H delivers more heat at -5F than the 1-ton Mitsubishi -FH12NA does at +5F, despite having substantially lower rated cooling capacity.

14. 
    rsmith02 | Jun 16, 2015 01:41am | #14

    Thanks Dana, this all great info!

    I'm still waiting for someone to help come up with a reasonably accurate way to compare heat pump cost-effectiveness in different temperatures that isn't too hard for contractors or end-users to figure out. The estimates in the EIA heatcalc tool just doesn't seem to apply to minisplits and derates the HSPF too much.

    "An accurate savings tool for DHPs is needed. HeatCalc, a DOE‐supported
    downloadable spreadsheet tool, includes a calculator to adjust published HSPF
    ratings for the local climate.3 However, the adjustment factors were formulated prior
    to the introduction of cold‐weather performing heat pumps and these factors assume
    that electric resistance coils contribute part or all of the heating at colder
    temperatures. Updating the tool to be consistent with the cold‐weather performance
    of cold‐climate DHPs would provide program administrators, as well as market
    actors, a simple tool for estimating DHP savings."
    http://www.neep.org/primary-research-ductless-mini-split-heat-pumps

    For New Hampshire this study ended up derating the HSPF 10% for northern New England.

15. 
    JohnBoy28 | Jun 16, 2015 05:38am | #15

    Dan & Dana
    Great feedback, thanks

16. 
    JohnBoy28 | Jun 16, 2015 05:42am | #16

    Wondering if anyone has a Consumer Report subscription and has seen any reviews of mini splits there.

17. Expert Member
    Dana Dorsett | Jun 16, 2015 06:49pm | #17

    In a zone 7 climate with a cold-climate mini-split sized to cover your load at -10F with a bit of margin you can figure on a seasonal average COP of about 2.5, give or take a little bit. If you under-size it you'll average closer to 2.0, since running flat-out most of them won't do better than about 2 anytime it's below +5F or so. In high-defrost cycle weather conditioned when it's +10F out it might not even make 1.5, but we're talking seasonal averages.) At -10F you're looking at a COP of about 1.8 even without the defrost discounting.

    You'll note that the measured COP in Table 6-1 on page 42 (pdf pagination) of the NEEP document looks pretty crummy at 10-20F:

    http://www.neep.org/sites/default/files/resources/NEEP%20DHP%20Report%20Final%205-28-14%20and%20Appendices_0.pdf

    But it's important to consider that this was a first-generation cold-climate mini split, the Mitsubishi -FE12NA, that was woefully undersized for the heat load of the zone it was heating, which was a 600 square foot sunroom. It's highly likely that even at +25F it had to run full-tilt/lower efficiency to keep (or not quite keep up). The temperature vs. efficiency vs. modulation level curves for an FE12 in a bench test can be found in figure 9, p.22 of this document:

    http://www.nrel.gov/docs/fy11osti/52175.pdf

    If you presume that it was running full-tilt any time the outdoor temps were below freezing (which is probably the case) the site-9 data from the NEEP document aren't surprising, when comparing it to the bench-tested efficiency.

    The modulated efficiency of the Fujitsu 1-ton -12RLS2 in the bench testing shows a more consistent and somewhat higher efficiency pattern (see Figure 5, p10), which would be consistent with the higher tested HSPF (about 12 for the Fujitsu, 10.5 for the Mitsubishi).

    The second generation cold-climate mini-splits from both vendors are 15-20% more efficient than those in the bench tests, but the basic pattern would be the same. If your binned hourly average mid-winter temp is +5F you'll do a COP of about 2 during cold weather, and higher the rest of the season, provided it's sized sufficiently to handle your -5F or -10F load.

18. 
    rsmith02 | Jun 17, 2015 12:47am | #18

    Dana, thank you for this informed analysis. I learn a lot each time you write.

    John, I have a subscription and don't recall anything detailed about minisplits. What Dana is giving you is a lot more expert and relevant. There are very few units that meet your specifications and you got a bunch of model numbers in this thread to pursue. Consumer Reports doesn't have the type of data that NEEP got from manufacturers or others got from field testing units as far as I'm aware.

19. 
    JohnBoy28 | Jun 17, 2015 05:51am | #19

    Dana: Thanks for the great information. It will be very helpful in making my decision.