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Community and Q&A

Adding a Zone with Older Compressor

Richard White | Posted in Mechanicals on

I have a Mitsubishi MXZ-4B36NA that has been running flawlessly for the past 7 years. We live in Washington, DC so climate zone 4a. We have two zones (9,000 and 18,000) and are thinking of adding more.
Question 1: Can we get compatible air handlers or are they no longer available? I see in a compatibility chart that SEZ-KD09NA4  would be compatible but I have not found a supplier.
SEZ-KD09NA4R1 would seem to be the newer model but I’m not sure it is compatible with our existing compressor
Question 2: How much am I able to overrate the compressor? I’ve heard you can load 45,000 btu on a compressor rated at 36,000 btu but do not have a reference for that.

I appreciate any advice the community has to offer

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Replies

  1. Expert Member
    Akos | | #1

    The only people that can answer this is Mitsubishi. Give them a call.

    On most Mitsu units, you can install indoor heads up to 130% of outdoor unit rated capacity. To make sure, dig up the specification sheet of your 4B36, and see if your proposed setup is in the listed combination table.

    1. Richard White | | #2

      Thanks for the recommendation. I didn't know it could be so simple :) The Mitsubishi rep let me know the current SEZ air handlers are all compatible with my compressor. Further, she confirmed the 130% over-rating. She was unable to provide data on the efficiency loss when operating in an over-rated capacity. I'll have to research that further.

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