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Air handler location for Mitsubishi heat pump system

Kieran973 | Posted in General Questions on

Hi, is it a bad idea noise-level-wise to put a Mitsubishi heat pump air handler in a conditioned attic that is frequently being used as an office? I see a lot of the specs on them are in the 50-55 decibel range. In my basement, I have a Gen 5 Rheem heat pump water heater with an official spec of 49 decibels but which I can hear all the way up on the second floor. The attic office is something that I would use 8–10 hours a day. Will I be able to get any work done if there’s an air handler in the attic outside the office? 

The air handler would be for ducted heating and cooling supplied to three small bedrooms below the attic on the second floor. Heating and cooling in the attic itself would be from a separate ductless wall unit. Doing it this way would allow the second floor to have “central air conditioning” in the summer and I could toss the window unit ACs we currently have there. 

But if it’s not a good idea to have the air handler in the attic, then the alternative for second floor HVAC would be a ductless unit on a hallway wall for heat (I’m aware that we’d have to leave the bedroom doors open often for this to work), but cooling would continue to come from window units. Thanks. 

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Replies

  1. Patrick OSullivan | | #1

    I suspect it will be nearly silent. I have a Fujitsu 18,000 BTU/h medium static unit and when we first powered it on, neither the techs nor I could tell if it was actually on until we felt the registers.

    The unit itself is barely audible even at the highest fan speed.

    What makes noise, however, is an undersized return. Make sure the ducts are designed (not guestimated!) and work with the designer to make the return as large as practicable. This is good for sound as well as for minimizing static pressure losses due to filtration. My particular setup has a 24"x30" return grille where I put a 1" filter and then an Aprilaire 2210 downstream (https://www.aprilaire.com/whole-house-products/air-purifiers/model-2210).

    Do it right and you'll be *shocked* how quiet good systems can be.

  2. Kieran973 | | #2

    OK, thanks. Good to know. I hadn’t considered the size of the return. If I do end up putting the air handler and ducts in the attic, I would prefer to put the air handler as close to the bedrooms as possible and use the shortest amount of duct work possible since I’m a little out of my league in terms of making sure that the ducts are efficient, plus I don’t want to compromise the future usability of the attic space….

  3. Paul Wiedefeld | | #3

    I think your sound rating is for the outdoor portion. This puts it at 33-41 dB based on fan setting.
    https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.com.s3.amazonaws.com/DAMRoot/Original/10006\M_SUBMITTAL_SVZ-KP24NA_SUZ-KA24NAHZ_en.pdf

    I believe the Fujitsu is even quieter than the Mitsubishi, but all will be dependent on duct design.

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