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Hate to ask again about Mitsubishi mini-split and when a branch-box is needed

Hi, I'm trying to identify the requirements for a 3-zone Mitsubishi mini-split system.
We are looking at either 3 of the MLZ-KP09NA cassettes, or 2 of them and one KP12NA cassette.
We are not looking at a Hyper-heat system.
The question is whether we need a branch-box or not?
If we go to 3 KP12NA heads does that increase in capacity on the system then require a branch-box?
Last question - any issue with a lineset run on one of the heads at about 72 feet?
Really appreciate any info as there's just not an easy way to find this info elsewhere.
Thanks very much.
Seth M.


  • TAG
    TAG Member Posts: 755
    Mitsubishi publishes info with the various heads matched to various outside units ... google around. You need to check that out as it will give you the operating range of the heads.

    I have a 3 head system using two of the older style square cassettes and one wall unit .... all three are 12k heads connected back to a single 3 port 30k BTU compressor.

    Make sure you do a proper load on the spaces -- and the area as a whole. You don't want to oversize the compressor as the turn down ratio can be a problem. Also -- I think all those new narrow heads come with the "eye" ..... makes a difference and well worth getting the unit that does if not standard. The old units did not initially have the eye
  • seth_1234
    seth_1234 Member Posts: 3
    Thank you very much for the tip to search for Mitsubishi provided data.
    I found this catalog:
    It has clear reference to when a branch-box is needed - and it's not needed for my installation.
    So for anyone else needing to find this stuff - above link should help.
  • TAG
    TAG Member Posts: 755
    There is also a grid were they list the outdoor unit and the various combination of heads and what the heads will produce. I'm not seeing the multi head grid ..... just the compatibility grid
  • ratio
    ratio Member Posts: 3,696
    Mitsubishi's design software (Diamond System Builder) is available on mylinkdrive.com. It does mini splits as well as VRF systems, won't allow incompatible configurations, & is reasonably easy to use. IIRC It gives you the manuals for selected equipment as well. Most important in my eyes is that it will cypher up any field charge necessary, although I suppose that's not quite the issue with a mini split than a VRF system.
  • TAG
    TAG Member Posts: 755
    seth_1234 said:
    That is telling you if it will work ..... you also want the one that tells you how it will work. What each head will produce.

    With multi mini splits you don't just add up the heads and pick that compressor. As I said -- both of my systems are 3x 12k btu on a 30k compressor. We did the individual loads and the whole space load. The compressors also have a capacity of 110% . Watch you design temps so you size correctly .... I have zoned all my projects and you never need full capacity in every room. You have to think about how the space will be used. Bedrooms are used in the evenings when it's colder ... rest of house not occupied.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
    I have always gone the the branch manager for this question.

    Often the assistant branch manager can help in the managers absence.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?