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Through the wall heat pumps

Post in 'DIY and General non-hearth advice' started by SlyFerret, Sep 23, 2012.

  1. SlyFerret

    SlyFerret Minister of Fire

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    Hi folks!
    A few years ago, we built a new detached garage with the intention of turning the attached garage into art studio space for my wife. Well, the time has come. She has quit her full time job to stay home with our son and start focusing on getting her art business off the ground. Finishing the attached garage into studio space is now on my list!

    I intend to tear off the old 2-car garage door and then frame in the old opening. We'll put a set of french doors in at one end of where the garage door is now, and the rest of the wall will have windows to let in lots of natural light (no, not the kind that comes in a can...).

    I will be insulating the space (~300 square feet), adding a ceiling, putting in lighting, putting down some flooring, and essentially "white boxing" it for her.

    One key item that I need to take care of is air conditioning and backup heat. Since my HVAC system was never designed to heat that space, I don't want to tie it into the existing system. For primary heat, the stove will be able to handle that. The stove is near the door from the kitchen into the studio, and getting warm air circulated into the studio should be easy enough.

    My thought is that a through the wall heat pump would be a great solution. Have any of you guys had any experience with these types of units? Who makes good ones? Any lessons learned that you can share?

    I need to plan what I'm going to install before I tear off the old garage door and start framing, since that will be the wall where the unit will be mounted.

    -SF

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  2. begreen

    begreen Mooderator Staff Member

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    A small mini-split heat pump would be perfect for this type of installation. They are super efficient and quiet. I would look at a 9kw unit from Mitsubishi or Fujitsu for this application.
  3. SlyFerret

    SlyFerret Minister of Fire

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    Thanks Begreen!

    So far, everything that I'm seeing requires a separate compressor module that sits on the ground outside. The system will be located on the front corner of my house, so I want to avoid a compressor sitting out in view from the street. I might have trouble getting that approved by the aesthetics committee here at the house!

    I'm hoping to find one where the external unit is wall mountable as well.

    -SF
  4. fossil

    fossil Accidental Moderator Staff Member

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  5. MasterMech

    MasterMech Guest

    Have no idea of the model but at the wife's job they have a Mitsu with a wall mounted exterior unit heating/cooling a a 2nd story deck converted into a sun room. Unit is pretty good size and I'd think it be easier to conceal a conventional condensor with a shrub or short fence as oppsed to this thing. Unit is located in an area where aesthetics are not a primary concern.
  6. SlyFerret

    SlyFerret Minister of Fire

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    As long as I could wall mount the external unit, that would be OK. I just don't want it sitting on the ground in that spot.

    Thanks again for the responses so far guys!

    -SF
  7. begreen

    begreen Mooderator Staff Member

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    It doesn't necessarily need to be co-located. The refrigerant line can be on the opposite side. Or just install both the compressor and indoor unit on the opposite side of the building. Or just put a bush in front of it, they unit is not very deep.
  8. Hogwildz

    Hogwildz Minister of Fire

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    Put the compressor out back, and just run the lines through the attic space to wherever you want the head to be. If it is wide open inside, put them both on the back.
  9. RichVT

    RichVT Member

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    Chances are your existing HVAC system is grossly oversized and would have no problem conditioning the extra space if you can get some ducts in there.
  10. SlyFerret

    SlyFerret Minister of Fire

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    I can get ducts in there, but I was concerned about adding space that the system wasn't originally designed for.

    What sort of information should I look for to determine what it's capabilities are?

    -SF
  11. RichVT

    RichVT Member

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    Heating systems are supposed to be sized to keep your house warm on the coldest day of the year which means that they should be running more or less continuously at that time (every other day the system is oversized and less efficient).

    Heating contractors NEVER want you to call them an say that your house is cold so they will typically oversize the system often by a substantial amount.

    Same applies to cooling. Oversized cooling systems can lead to comfort issues because they don't run long enough to dehumidify the air which can lead to a house that is cold and clammy.

    Newer systems can run at variable speeds to better match their output to the house's needs.

    Simple answer is to monitor how much time your system runs during very cold and hot weather. If your furnace only runs for say 30 minutes out of every hour in the dead of winter then it is capable of heating twice as much space as it is (assuming similar construction).

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