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Mitsubishi Heating Correction confusion

Doug L. | Posted in Mechanicals on

I am in the process of estimating the size of Mitsubishi FH series minisplits needed for a modular home in order to receive quotes from HVAC companies based on specific equipment requests and not their WAG assumptions. Will shortly be receiving a room by room Manual J heat loss calc.. The house will be located in zip code 12833 and so I am keenly interested in the minisplits ability to provide primary heating in an Upstate NY winter climate.

My confusion comes when reading Mitsubishi’s engineering manual on the FH series and their heating correction tables based on outdoor wet bulb temps and indoor dry bulb temps. For instance when looking at page 24 of the specs, it states that correction ratio for the FH12na at -13 outdoor temp and 65 indoor temp is 0.75. When you look at a similar specs on page 25 it states the same conditions (-13outdoor/65indoor) for the same FH12na prescribe a correction ratio of 0.84. Am I reading the tables wrong or am I completely missing an important difference between the two tables?

And as a followup, and please forgive my ignorance, are the heating correction ratios applied to the rated heat output of the unit (13,600) or to the maximum heat output of the unit (21,000)? Thanks to all and anyone who can clear this up for me.

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  1. Doug L. | | #1

    Anyone? Bueller? Anyone, anyone? Martin, Dana?

    Seems like this question disappeared to the bottom of the pile. Anyone willing to take a stab at the apparent contradiction in the Mitsu engineering specs in section 3-7. The manual I'm referring to is at the following link:

    Thanks everyone.

  2. user-2310254 | | #2

    Doug. Have you contacted Mitsubishi technical support? Errors in technical documentation are not uncommon.

  3. Doug L. | | #3

    Hi Steve, haven't contacted Mitsubishi about this. I was hoping to see if anyone here has encountered this discrepancy before or to confirm that my feeble mind is just misinterpreting the correction tables.

  4. GBA Editor
    Martin Holladay | | #4

    Like Steve, I suggest that you call the Mitsubishi technical support phone number. My speculations will be less useful than their interpretation.

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