Through wall AC

Discussion in 'HVAC Heating & Cooling' started by mar3232, Jul 18, 2012.

  1. mar3232

    mar3232 Member

    Messages:
    108
    Location:
    Indiana
    I need a small air conditioner in my bedroom and I'm probably answering my own question here but other than the fact that a "through wall" unit is built for going through a wall, there's no real reason why you can't use a window unit, right?

    I've done it before 2 or 3 times and it is sort of a pain -- but works.

    Why they charge so much for through wall types, I don't get -- almost twice as much PLUS the housing.

    I know you should keep the vents to the exterior air etc if you're using a window unit.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,346
    Location:
    New England
    Properly supported, sloped, and sealed, a window unit should work in a custom hole. It just may not look all that great around the edges without more work, but should still work. A window unit is likely wider than the stud spacing, and you'd have to frame the wall to support it, and unless you can do all of this yourself, you'd probably find that the cost difference goes away.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    It is done often...mainly because window units cost less! Here are the caveats:
    > The window unit is not spefically designed to be weather sealed thru-the-wall. You will need to engineer that feature.
    > The windo chassis is not structurally as strong as a thru-the-wall. You will need to engineer the securing method.
    > The BIGGY: window units have ventilation louvers on sides, and sometimes top. It is imperative that these are not obstructed by a thick wall, flashing, etc.
    > Window units are non-standard chassis size. Might change every year. You will most likely never be able to just slide the chassis out and slide in a new one at replacement time. Start from scratch
  4. mar3232

    mar3232 Member

    Messages:
    108
    Location:
    Indiana
    yeah -- I've done it a couple of times before but this time I need to go through 8" block + another stud wall, so the side louvers probably won't make it.

    tried a portable AC unit with a vent hole through the wall and took it back the next day -- those damn things are too noisy.

    wish the prices weren't so high on through wall units.

    fact is, what I'd REALLY like to do is mount a small (5000 btu or so) unit high on my bedroom wall and built some sort of chamber that vents it through the attic and to the outside (or just into the attic itself? -- because one of my roof vents is right above where I want to put it).

    THAT is what I'd really like to do but I posted on this forum and it was discouraged.

    But what about if I do a really small window unit (Like I say 5000 btu or so)?

    Obviously, I'd put a drain pan underneath it and run to a pipe.

    a chamber kind of like this? ---

    ATTIC

    I I
    ___I I
    I > I
    I________I
  5. mar3232

    mar3232 Member

    Messages:
    108
    Location:
    Indiana
    my art fell out of sync -- you know what I mean, a backwards L shape chamber.
  6. mar3232

    mar3232 Member

    Messages:
    108
    Location:
    Indiana
  7. jacobsond

    jacobsond DIY Junior Member

    Messages:
    59
    Location:
    ND
    Going through a block wall your going to need a shell like the GE RAB46. The AC that fits into that will vent and exhaust from the back because there is not room for side vents with a wall that is going to be that thick.The shell is only 50 bucks but ACs that fit in there are $500 +. 90% of the apartments in this area have that RAB shell so we deal with them all the time. Service is easy with the pull out chassis and so is the eventual replacement.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,346
    Location:
    New England
    Do you have room to install a minisplit system? MUCH quieter, and better efficiency. Great flexibility on placement, and multiple room support.
  9. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    If you try to duct the air flow in a window shaker unit, it will cool very poorly and FAIL very soon.
  10. mar3232

    mar3232 Member

    Messages:
    108
    Location:
    Indiana
    Ok.

    Doing a mini split in my other 2 rooms next year but want something small for my (small) bedroom.

    I'll just go through the wall then.

    Is it because the window units don't have a fan blowing air out? (like a roll around portable unit has?) -- so they can't be ducted? (what if I use a fan somehow?).

    Hate going through concrete -- no matter how careful I am, I end up just scoring it somehow and banging it out with a sledge hammer. Do you think a concrete block wall will keep it's ^%it together if I do a 19w by 14h opening? (like no lentil?)
  11. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,799
    Location:
    Long Island, NY
    I'm no architect or structural engineer, but I'd not make an opening that big without a lentil holding up the unsupported blocks above that opening. 19 inches wide means at least one mortar joint will be at the top of the opening.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,292
    Location:
    Cave Creek, Arizona
    Ideally, you would cut the hole so the joint between two blocks is "about" centered over the opening. Don't "score" the block actually cut through it, although you will probably have to do it from both sides using a circular saw with an abrasive blade.
  13. mar3232

    mar3232 Member

    Messages:
    108
    Location:
    Indiana
    But still put in a lentil? Block pretty much stays sound the way it's laid doesn't it? -- concerned though because I'll be at a low point in the 8' wall.
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,346
    Location:
    New England
    Without a lentil, you're relying on the strength of the mortar bond to the blocks...I think that this would be risky.
  15. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,398
    Location:
    Yakima WA
    Years ago I built a window AC into the wall of my frame house. The details of how to do it have already been discussed. A couple of things I learned quickly. One, you don't have good circulation for the whole house, but a fan will help. In other words, the room when the AC is located will get very cool, but rooms farther away and with hallways and doors will not be evenly cooled. Two, don't let the house get hot before turning the AC on. It takes these units forever to cool a hot house down. Much more effective to keep it cool be turning it on early in the day, These units will not give you the comfort of a ducted AC, but will not cost as much to buy and install. If you already have ducts for heat, look into a AC that can be incorporated with the furnace, using the same ducts. Initial cost will probably be more, but you'll be happier in the long haul.
  16. rfsmith48

    rfsmith48 Member

    Messages:
    50
    Location:
    Colorado
    I just installed a GE 8300 BTU thru-the-wall unit in our master bedroom. Used the GE shell that is specified for the unit.

    We like it alot. The only qualifier is that the GE unit is more noisy than a comparable LG unit. So, if I were doing the job again. I would use the LG unit and its recommended shell. (About $200 less than the GE unit.)

    Also: If you cut a hole thru a load bearing wall, whether masonry or lumber, you MUST add structure. (Lintel), over the opening. It sounds like you are going to punch a hole thru a wall that is about 12" thick. Don't try to reinvent the wheel. Get one of the thru the wall AC units.

    Rog
  17. JB40

    JB40 New Member

    Messages:
    2
    Location:
    Albany
    Yes and no. Most window units have side intake louvers and a back discharge. If your wall is typical, 2x4 studs + sheetrock + plywood + siding, your side intake louvers will not be "free". This will reduce your cooling capacity. A thru-the-wall unit is designed with solid sides. All air paths in and out of the unit are through the back accessory grille. In addition to separating the air paths, the back grille looks ALOT nicer than the open radiator coil you see on most window units. In general, a thru-the-wall unit is designed to stay put all year round while a window unit is designed to be seasonal. There are 2 types of thru-the-wall units; the hotel style PTAC unit, and the little brother version, "Mini-PTAC" unit. The mini-ptac most closely resembles a window unit in both design and price point. The full size hotel PTAC units are the most expensive, but also the quietest, most efficient, and they have tons of accessories to choose from (wireless controls, architectural grilles, carbon filters, etc.). Here's a good sampling of all styles: http://www.h-mac.com/brands/cooling-brands/amana.html
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