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Community and Q&A

Mitsubishi vs. Fujitsu?

Nina Lafferty | Posted in Energy Efficiency and Durability on

We are ready to install three one-to-one ductless mini-split heat pump/AC units in our 35 year old colonial located in Freetown MA. We have talked to two installers and now are stuck trying to decide which brand is the better choice for us. Note, we chose the installer based on his price, which was significantly less than the other. We just can’t decide whether to go with Mitsubishi or Fujitsu.

Like the appearance of the Fujitsu interior heads better – they are slightly smaller – and the HSPF rating is better than the Mitsubishi 11.5 vs. 10. SEER the same (21). Nstar utility rates are currently 20 cents KWH so this difference is significant to us.

The company has been installing and repairing both brands for about 10 years. Warranty on both companies is the same. He isn’t trying to sway us one way or the other – but his experience has been that Mitsubishi is more responsive if/when there is a problem and their parts are easier to get. Also said that Fujitsu has more “connected” parts – so when one goes, you have to replace a series of parts, not just the defective part.

Leaning towards Fujitsu, hopefully for the right reasons…..

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  1. Jin Kazama | | #1

    May i ask which model/size you are looking at ?

    From my personal experience ( only owned Fujitsu , but used Mits )
    the Mits have a much better control and setup on the head and temps
    the fujitsu usually have a slight advantage on efficiency

    You have to know that there are seldom problems with both manufacturers....
    the head can usually be replaced without touching anything else
    and the outdoor units rarely have problems ..if they do it shows within the first year under the warranty

    both are excellent choices .. make sure you read about efficiency vs load , i believe there was a blog on this with a link to an official testing by GOV agency , showing the effect of over and under sizing , which impacts the efficiency quite alot.

    Dana might be able to explain the phenomen better than i .

  2. Nina Lafferty | | #2

    The models are as follows: (sizes are the same from both manufacturers - 2 15,000 and 1 18,000 - the 15,000 are going in a master bedroom suite and the second in a four season room. The 18,000 is going in our family room and kitchen (which is open to the family room).
    Fujitsu Model # 15RLS2 and #18RLXFW packages

    Mitsubishi is listed a little differenty: Mismszge15na-8 w/ muzge15na same numbers for the larger set-up just "18" instead of "15"

    The room sizes are as follows: sunroom 16 x 20 with lots of glass. Family room 14 x 24 opens to kitchen which is 14 x 18. Master bedroom is 24 x 28 but approx. 1/4 of that square footage is walk-in closet and bathroom. Our home is well insulated and we have hot water baseboard heat (oil - gas is not available in our town). The sunroom doesn't have any heat source other than a free-standing propane fireplace/stove that we don't use because of the grandkids and also because of the expense to get the room really comfortable. Our primary goal is to reduce our dependency on oil but our electricity is pretty pricey as well. Thanks to anyone who can help us with our choice. Thank you
    BTW, I did look at a government report but it was kind of above me with the stats and specs and I'm an accountant - go figure.

  3. Nick Welch | | #3

    An aside: I'm surprised you'd go with the Mitsubishi GE in Massachusetts. Why not the FE? Should perform better in cold weather. Only thing is, there's no FE15, just FE12 and FE18.

  4. Aj Builder, Upstate NY Zone 6a | | #4

    interested in costs quoted, good thread... useful.

  5. Nina Lafferty | | #5

    Total for the install with either Fujitsu or Mitsubishi is $12,500 - this includes all electrical which in our case includes a new 100 amp sub-panel as our 200 amp service into the house was short a couple of "slots'. The price we got from the other installer was approx $16,400 and included the basic electrical but not the upgrade (i.e. new sub - panel) As I said we're leaning towards the Fujitsu based on the higher efficiency ratings, particularly with the heating. Nick, not sure what the difference is between the FE and the GE but the FE was never offered in either proposal.

  6. Expert Member
    Dana Dorsett | | #6

    I"m going to go with "none of the above", as far as the selected models go, but either is a reasonable series to install.

    The -RLS2 series has a heating efficiency advantage over the -GExxNA (11,500 BTU per kwh @ 47F instead of 10,000BTU /kwh @ 47F) The -FExxNA splits the difference, and is better able to handle the the coldest weather extremes. While the -GE- will still run at 0F, the specified lower limit on operating temp is -4F (rare, but it happens in Freetown.) The -FE12NA and -FE18NA have a fully specified outputs at -13F, and will keep running down to about -18F or so, so even during the 50 year cold snap they'll keep running, but they're more expensive than the -GE series. The RLS2 series does not shut down at super-cold temps, but doesn't manage defrost cycles as nicely/automatically as the FE Mitsubishi (I'm not sure about the GE), and can even inflict self-damage on refrozen defrost melt-water in the pan of the outdoor unit (problems they addressed well in the RLS2-H series, presumably targeted to compete with the -FE Mitsubishis)

    Even at 20 cents/kwh a bottom of the line imitation mini-split with a barely-legal HSPF is considerably cheaper than heating with $4/gallon oil in an 85% efficiency burner.

    It's impossible to accurately size them based on the square footage of floor area, but I'd be stunned if the master bedroom zone really needs anywhere NEAR 15KBTU/hr of output unless it's uninsulated or has a lot of single-pane glass ( the oppposite of well insulated). If you oversize by more than 50% the you'll have efficiency and comfort issues, so it's important to get it at least kinda-right. If you have a "K-factor" on a late-winter oil bill it's possible to estimate a reasonable upper bound on the heat load for the whole house based on that number. To come up with a 15K number for the ~675' of bedroom zone sounds sort of like a lazy rule of thumb contractor:

    "Lessee, ya gots 675 feet taimz 25 BTU a foot comes ta 16-17K, but it's a purdy good house and they have a boiler to back it up, so let's round it to 15 and call it done".

    Which is a reliable way to oversize the sucker by about 2x.

    Don't leave it to chance, and don't leave it to the "pros" unless they run a real "Manual-J" type heat load calculation using realistic indoor & outdoor design temps an the actual construction type.. Short of that, you really need do run your own heat load calculation for each zone, based on the exterior surface area of each zone, broken down by surface type: window & window U-factor, wall type & R value, attic area & R value, which goes something like this.

    "Well insulated" has no definition. I'll take a WAG that you have 2x4 wall construction with R13 cellulose or fiberglass cavity fill, R38 in the attic, and clear glass double pane wood sash windows (or single-panes with storms), and 2" solid wood exterior doors.

    A 2x4 R13 wall with a typical 25% framing fraction has a U-factor of about 0.1 BTU/hr per degree of temperature difference.

    An R38 attic at a ~15% framing fraction comes in at about U-0.032.

    A 2" door is about U-0.5, as is the clear glass double panes.

    Your 99% outside design temp is about 8F, and I'll assume it's OK if the room drops to 68F overnight on the coldest nights of the year, for a 60F temperature difference. On a room by room basis, add up exterior surface areas by type, and run the numbers.

    Let's say the master bedroom area (including the walk-in closets, if they are on exterior walls) has 50 square feet of window, 450 square feet of exterior wall (the gross are, minus windows & doors) , and 675 square feet of attic, no exterior doors.

    Window losses: U0.5 x 50' x 60F= 1500 BTU/hr

    Ceiling losses: U0.032 x 675' x 60F= 1300 BTU/hr

    Wall losses: U0.1 x 450' x 60F= 2700 BTU/hr

    Total: 5500 BTU/hr

    With 2 live but sleeping humans and a couple of clock radios, that's more like 5000BTU/hr.

    With a window open you might hit 15K, but even if it's a pretty drafty room over an uninsulated vented crawlspace it's nowhere near 10K, let alone 15K. but if three sides are exterior wall (I was estimating 2 it might bump your wall losses to the 4K range, and if you have a huge viewing window you might have 3K of window loss, but I don't see how it will break 10K, which makes even the 12RLS2 oversized for the actual load, since it can put out ~15KBTU/hr @ +8F, according to Figure 4 in this document: ) Seriously, you're probabaly looking at the much smaller/cheaper 9RLS2 for that zone, but run the actual numbers.

    Since your an accountant, build yourself a spreadsheet with your measured surface areas and surface types, tell us your construction and so can estimate the U-factors, then we'll use some fudge-factor multipliers at the end to account for the net air infiltration losses and interior gains (eg: if you have 2 people sleeping in the master suite , subtract 500BTU/hr. If there's a DVR or other electronics in there, subtract some more.) If you have 2x6 w/ R19s or blown cellulose/fiberglass the wall U-factor is about U0.07, if you have low-E windows assume they're no worse than U-0.35.

    Basements, crawlspaces and uninsulated foundations are also something we'd need to know about. If it's OK that the sun room hit a lower temp than 68F, we need to use your lower-bound temp in the calculation for that room too.

    But with the room by room calculations in hand you can add up the loads for the individual zones, and settle in on what is/isn't a good choice. I'd be stunned if your master suite had a heat load of as much as 10K, (and even if it did, 3/4 tonner like the -9RLS2 or -FE09NA could handle it.)

    So let's run the room by room, zone by zone calculations and see where they come out, then you can solicit bids for them to install them.

    Also note: Many installers are clueless about the snow issues, and mount the compressor units on a small concrete pad out in the open like they would any other air-conditioning compressor, where they can get clobbered by falling ice dams, driftig snow, roof avalanches etc. You get at least 2' of snowpack some years, so bracket mounting them on the wall at least 2' above the ground, protected by the over overhanging rake (best) or eaves (mount it higher if under eaves) so that you're not digging the thing up after every nor'easter. If your house has no roof overhangs, it's worth building a shed-roof /awning over the thing. (In Worcester where I live three feet above grade would be the minimum, four feet if under eaves, since the snow pack is deeper where the snow comes off the roof.)

  7. Expert Member
    Dana Dorsett | | #7

    Sorry if that ran a bit long, but I get really REALLY sick of lazy half-assed HVAC contractors oversizing the hardware. It costs more up front, is less comfortable to live with, is noisier, and runs less efficiently when you oversize a ductless by 2x. Keep it under 1.5x oversizing, or even go with an 0.9x sizing factor (10% undersized) if that's closer to a true fit at the step-sizing of the series.

    If the contractors want to argue the point, make them show you the Manual-J (and scrutinize it for thumbs on the scale, such as 75F indoor and 0F outdoor design temps), then have them snow you extended output tables for the model selected, to figure out the heat it actually delivers at +8F (or +5F or +10F if they only break it out in 5F increments.) It's highly likely the 15RLS2 puts out over 20,000BTU/hr @ +8F, and they're applying it to a load that's probably under 10,000BTU/hr.

    For a quick reference on outdoor design temps, check the +9F design temp for nearby Fall River:

  8. Nina Lafferty | | #8

    Hey Dana - thanks for taking the time to offer up the information. The master bedroom is over the garage and does have high (cathedral) ceilings, two skylights, a large double-pane window on the front of the house, two double hung windows on the side and a slider on the back. The plan is for the units to be placed under a deck off the back of the room . Both companies suggested the same size unit - so I didn't really question whether it was the right size based on two independent quotes. Three walls are exterior, by the way.

  9. Jin Kazama | | #9

    Sifu Dana ... and i thought i was a talkative type ...when i started scrolling your post i thought i had miss a break or two and signatures :p

    There is not a large price difference between the different size units, at least with the FUJ models...

    Don't know much about your weather , ( mass ?? ) but i'd look at the RLS2H model seriously.
    Just for the fact that it gets you much farther down where you still get some benefits out of it.

  10. Nina Lafferty | | #10

    Thanks everyone - we decided to go with the Fujitsu installation - our neighbors (2) - one has Mitsubishi, one has Fujitsu, both recently installed - they are happy with both. Went with the more efficient units and also liked the appearance of the heads. Go Sox!

  11. Expert Member
    Dana Dorsett | | #11

    But they are oversized, they're going to underperform.

    Between the three units there is enough output at +5F to heat my not-so-superinsulated 2400' (+ 1500' of semi-conditioned basement) nearly 2x over.

    I have very little confidence in the contractor sizing if they didn't actually measure up your exterior surfaces by type, and run even the most basic calculation on it. I have a very strong suspicion that you're in the 2x oversizing range for at least the master bedroom zone. It takes a bit of time to measure it all up and run the calculation, and competent HVAC contractor doing that work would have to charge a few hundred for running the calculation, but it would save more than a couple hundred in oversized hard ware up-charges. I've given up on letting most HVAC outfits size the equipment, having observed their methods. But a contractor that offered up the Manual-J as part of the bid, with only budgetary pricing on the WAG-type sizing to be refined when the calculation is in would move to the front of the line.

    There are third party energy assessment companies and insulation contractors etc who offer up load calculations as a separate service. If you don't feel confident in the spreadsheet calculation approach, it's worth paying someone else to do it.

  12. Jin Kazama | | #12

    Always follow Dana's advice ... seriously ! :p

    ( don't want to hijack this thread ..but Dana i would like if you could comment on my window development thread please !! )

  13. Expert Member
    Dana Dorsett | | #13

    Huh? What? NEVER take Dana's advice, he just makes it all up as he goes along! :-)

  14. 1900DisasterHome | | #14

    I got an estimate in Maryland for F-AOU36RLXFZ-H, F-ASU18RLF, F-ASU15RLF NOT including electrical connections, from a Mitsubishi diamond installer asking $10,354. However, a friend who does commercial work and a little residential on the side looked at the two rooms and offered to do two Fujitsu units about 1 ton each for $5,500 including electrical. Big difference in sizing and price. Who should I go with?

    1. Expert Member
      Dana Dorsett | | #15

      Two individual 12RLS3s will at least modulate with load for higher comfort & efficiency, whereas the multi-split heads will just cycle on/off. When in doubt, go with individual single zone mini-splits. (A pair of 12RLS2 for $5.5K all-in seems like you have a REALLY good friend.)

      Whether either solution is right-sized for the loads depends on your actual load numbers.

      The 12RLS3s are good for 17.5KBTU/hr each @ +17F, when running at max speed, for a total of 35,000 BTU/hr.

      The ASU 18RLF is good for a nominal 20K, when married to sufficient compressor, not sure what the nominal output of the ASU15RLF is- probably about 17K, for maybe 37K total. The max capacity of the AOU36RLXFZ compressor @ +17F is 39,341 BTU/hr no matter what heads are plugged into it.

      1. Dreamss | | #16

        Hi Dana, hope all is well. I am resurrecting a really old thread as i have some questions for you. Are you still on this forum?

        Thanks so much!

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