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Community and Q&A

Mitsubishi Rated Minimum Capacity vs Part Load Capacity Charts

1905_one_and_a_half | Posted in General Questions on

Hi all,

I’m a homeowner looking to get a 2-zone minisplit system installed in my home and I’m trying to decide between the 20k and 24k Mistubishi MXZ outdoor units. My goal is to undersize the unit relative to the Manual J calc load as this is mostly for cooling and light load heating (located in PNW and I have a furnace for backup heat).

Of these two units (MXZ-2C20NA4 vs MXZ-3C24NA4), I would like to choose the unit with the lowest minimum cooling capacity (i.e greatest turn-down). This should be easy to identify, as the “Minimum Capacity” (for heating and cooling) is listed on the ‘submittal’ pdfs. The 20k unit has a minimum cooling capacity of 5,700 btu/hr, and the 24k unit is 11,600 btu/hr (at 67F WB indoor & 95F DB outdoor). So it seems like the 20k is an easy choice. However, when I look at the “Part load capacity chart” in the ‘Technical Data’ sheet for these units, the 20k unit has a minimum output of 8149 btu/hr and the 24k unit has a minimum capacity of 6452 btu/hr (at 67F WB indoor & 94F DB outdoor), so this suggests I should opt for the 24k unit as it has a greater turndown and uses much less power at minimum capacity (498W vs 774W).

Can anyone explain why the “Minimum Capacity” listed on the submittal sheets does not line up with the minimum output shown on the Part-load capacity charts? I’ve attached a screengrab of the partload capacity chart and submittal data for the 24k unit (MXZ-3C24NA4). 

There have been a few other posts on this forum about the minimum capacity of the Mitsu units but I have not seen any discussion of this.

Thank you!

GBA Prime

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