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Fujitsu Capacity Charts/ Help Sizing/Deciding Multisplit

HydroNiCK
HydroNiCK Member Posts: 108
I'm trying to decide between Mitsubishi MXZ-3C24NA2 and Fujitsu AOU24RLXFZ. I need 6300 btus for master bedroom, 3500 btus for small bedroom, and a ton for a 420sf lofted room with 23ft vaulted cieling. From my understanding the FH06 is capable of 9k btus. What is the min-max for a Fujitsu ASU7RLF1? Is nominal 7k btu all i can get max? Does anyone have a Fujitsu Capacity chart? Looking at the mitsubishi capacity chart for MXZ-3C24NA2 I take it that when two FH06 and a FH12 are connected all on high setting running simultaneously the output for each looks like this


If a FH06 and FH12 are off and only one FH06 is running it can supply 9,000 btus correct? So as of now without a Fujitsu capacity chart all I can tell is that Mitsubishi can supply me with a colder room if I want. Whereas the Fujitsu ASU7RLF1 supplies 7000 BTUS max no matter what.... Am i correct?




Comments

  • pecmsg
    pecmsg Member Posts: 2,071
    How did you come up with those #'s?
    HydroNiCK
  • HydroNiCK
    HydroNiCK Member Posts: 108
    I have to thank ACCA for developing the Manual J and my 6th grade math teacher Mrs. Hunt for that. The capacity chart is from Mitsubishi's link drive and the Fujitsu numbers are from their website.
    ChrisJHVACNUT
  • HydroNiCK
    HydroNiCK Member Posts: 108
    I may have exagerated a little on my numbers but now that I have the paper work in front of me I need
    Masterbed: 3598(master bath add 1853 btus)
    Nursery: 596 btus
    Loft room :10,225 Btus
  • HydroNiCK
    HydroNiCK Member Posts: 108
    On the other side of the house I am installing an identical 2ton mitsubishi or fujitsu to cool finished basement (6,668 btus) and open living room kitchen(14,682 btu) and hallway(1,901 btus). All numbers are for cooling. Split foyer ranch house with overhang not insulated and second floor addition not part of cooling system. Cold air on 1st floor sinks right down stairs to basement. Uninsulated overhang pulls hot air in. 1961 insulation. I am going to insulate. However im currently trying to decide between the two above systems.
  • pecmsg
    pecmsg Member Posts: 2,071
    HydroNiCK said:

    I have to thank ACCA for developing the Manual J and my 6th grade math teacher Mrs. Hunt for that. The capacity chart is from Mitsubishi's link drive and the Fujitsu numbers are from their website.

    Do Not trust On Line calculators. You need a true Manual "J" calculation. Minis even thou they are variable speed cannot be oversized just like conventual A/C. Proper Sizing is more critical!
  • HydroNiCK
    HydroNiCK Member Posts: 108
    Yes thank you. Anyone have input on my question? Capacity or combination table for Fujitsu? Max output and ratings for their wall units?
  • ratio
    ratio Member Posts: 2,794
    Have you talked to the local vendor? Around here, Johnstone hawks that brand, & they're not adverse to helping out with a little research, as least if the counter's not busy.
  • HydroNiCK
    HydroNiCK Member Posts: 108
    No i haven't. Im getting it installed and trying to decide between systems. At the same time double checking the installer. I have a manual j and know how much i need. However i can find info on mitsubishi butFujitsu isnt as informative. I dont want to get the fujitsu and have all three units running at once only to find the two 7ks are only putting out say 5300 and the one ton puts out 10k when i need 11k. As Ronald Regan said "trust but verify". So does anyone here have experience with Fujitsu? Am i making sense?
  • TAG
    TAG Member Posts: 488
    Just went through this ... each time I have used a mini split it seems both I and the installers learn something.

    The last two systems have been 3x 12BTU on a 30k outside unit. Mitsubishi

    You have to be very careful when doing these multi head systems. First -- you must understand what the max head output will be when the head is on a multi set up .. and you must understand what the turn down is on the compressor.

    My first system was two ceiling units and one wall w/ eye (Mitsubishi) ... When it was going in a few years ago we spoke to an engineer at Mitsubishi who told us what to use. I now understand that it was picked for overall load and the heads while important .. are less so. When looking at ..should I do a 9 or 12 say.

    The multi units do not turn down as much ... so the worst thing I could have down was to put in a 36k to match the 3x 12 heads. You have to understand that non of the information on the single units work when they are on a multi.

    Even when the heads are off -- they have to have some bleed.

    On my newest project I was going to do an 18k for a kitchen and a 9 or 12 for another area that was going to be little used. When I looked at the charts ..the 18k wall on a multi setup was not going to give me the full 18k .. and having it linked to one always off with the turn down of what I though I had to use as a compressor (30k) was going to send too much all the time to the off head. It being a Kitchen in a vacation home with many people in the area possible - I wanted the ability to blast the area.

    I ended up having to do 3 single units -- vs a single and a double.

    The only other possibility was to do branch boxes -- the multi that way get each head more BTU's -- I did not look into it all because I was not going to go that route. It was easier to find a way to hide the extra unit.

    I think the multi head system work best when all the heads are always on and you match that compressor to the load. It's like a proper zoned ducted system in a house. Don't oversize it ... most houses never need the same level of heat or cooling at the same time. You are not cooling bedrooms at the same time as kitchens for example.

  • TAG
    TAG Member Posts: 488
    Fujitsu vs Mitsubishi. I did a single Fujitsu for the loft of a Barn conversion a few years back .. and a good friend used a 7 or 8 head branch box system in an old victorian. I have been in quite a few houses with the Fujitsu branch box system (lots of big Victorians in the area). I have also done LG -- but it was too long ago to be up to date. I used the Fujitsu because the head size fit -- they are not as long as the Mitsubishi unit and they stick out a bit more.

    IMO -- The Mitsubishi wall units with the eye just seem to work better -- less air feeling (unless you want to blast). They seem more responsive. It seems most installers who do both -- like the Mitsubishi a bit more. Fujitsu comes in second. I have had no problems with my LG unit in a small cabin.

    The Mitsubishi systems require add on items to get them to work with the internet
  • HydroNiCK
    HydroNiCK Member Posts: 108
    > @TAG said:
    > Just went through this ... each time I have used a mini split it seems both I and the installers learn something.
    >
    > The last two systems have been 3x 12BTU on a 30k outside unit. Mitsubishi
    >
    > You have to be very careful when doing these multi head systems. First -- you must understand what the max head output will be when the head is on a multi set up .. and you must understand what the turn down is on the compressor.
    >
    > My first system was two ceiling units and one wall w/ eye (Mitsubishi) ... When it was going in a few years ago we spoke to an engineer at Mitsubishi who told us what to use. I now understand that it was picked for overall load and the heads while important .. are less so. When looking at ..should I do a 9 or 12 say.
    >
    > The multi units do not turn down as much ... so the worst thing I could have down was to put in a 36k to match the 3x 12 heads. You have to understand that non of the information on the single units work when they are on a multi.
    >
    > Even when the heads are off -- they have to have some bleed.
    >
    > On my newest project I was going to do an 18k for a kitchen and a 9 or 12 for another area that was going to be little used. When I looked at the charts ..the 18k wall on a multi setup was not going to give me the full 18k .. and having it linked to one always off with the turn down of what I though I had to use as a compressor (30k) was going to send too much all the time to the off head. It being a Kitchen in a vacation home with many people in the area possible - I wanted the ability to blast the area.
    >
    > I ended up having to do 3 single units -- vs a single and a double.
    >
    > The only other possibility was to do branch boxes -- the multi that way get each head more BTU's -- I did not look into it all because I was not going to go that route. It was easier to find a way to hide the extra unit.
    >
    > I think the multi head system work best when all the heads are always on and you match that compressor to the load. It's like a proper zoned ducted system in a house. Don't oversize it ... most houses never need the same level of heat or cooling at the same time. You are not cooling bedrooms at the same time as kitchens for example.

    So you ended up with 11.7btu per unit x3. I know this because I found the charts.....i wanted the charts to avoid your mistake. I do have a reduction in BTU but it now is closer to my heat loss...a little above instead of a lot above. Sensible heat along with enough room for latent.
  • TAG
    TAG Member Posts: 488
    Hydronick --- I don't have the chart in front of me. That still seems too high .... not enough derating.

    When I was looking a few weeks ago at the 18k it was closer to 15k ..max. With a poor turndown when mated with a 12k head and 30k compressor. I wanted to talk to the engineering department again about doing the 2 heads with a 24k compressor as it just fit the over rate table for the compressor and I was thinking the turndown would be better.

    But the max was still around 15k. I needed extra capacity as it was a kitchen. The 15max out of the 18 head was not going to cut it. The performance of the single heads as far as turn down and overdrive are much greater.

    My multi heads work great -- but none are really stressed. The biggest room w/ the 12k ceiling unit is typically calling in the when the others are not.

    If you go Mitsubishi -- the better wall units with twin vane control and the eye are worth the extra money.
    HydroNiCK
  • bio_guy
    bio_guy Member Posts: 69
    edited September 2020
    TAG is right, multis, if you want to run them most efficiently require more planning. One thing that became obvious to me is that you want to have units that will run at the same time on the same outdoor unit if you have more than one outdoor. That way they may be able to taper off to closer to minimum supply and cycle less. It is really similar to trying to use a condensing boiler to power a bunch of small zones. Example, put all the bedrooms on one outdoor unit since demand is low at night. Mine turn down to about 30%, I think. I have one 9K and one 6K on a 20K compressor. It could be better.

    I would not say that they don't turn down as much, they go to about the same percentage or full. They don't go as LOW so powering one indoor unit will obviously get your more cycling than a 1:1 system.
  • HydroNiCK
    HydroNiCK Member Posts: 108
    Thanks, I know.  I was looking for the charts.
  • TAG
    TAG Member Posts: 488
    Thought you had them?

    The common thought is to add up the heads and match the compressor .. this is not the case. The other is when planning a three head system don't think .... 'X" and "y" head will be off ... so "z" head will have more power to do what I want ... again not correct.

    The lack of excess capacity (on the head side) was an eye opener with some set ups on both heat and cooling.



  • bio_guy
    bio_guy Member Posts: 69
    TAG, are your comments about VRF systems, non VRF, or both? My understanding is that the former are not often found in residential, but maybe I am behind the times.
  • HydroNiCK
    HydroNiCK Member Posts: 108
    Yes, I got a hold of the charts. I posted this awhile ago.  Minisplit installed. Everything all good in HVAC land. 
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