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#723128 - 07/28/12 12:22 AM Window AC Support
Steve_S Offline


Registered: 04/27/10
Posts: 105
Loc: Central NJ
I'm putting a window unit upstairs to supplement my central air, and we got a good deal on a used 10k BTU unit.

It's pretty heavy, though, so I'm pretty sure I should install one of these:

However, I have relatively new vinyl windows, and the window frame is capped with aluminum on the outside, so I'd really like to avoid putting screws or holes anywhere. The only place I'd be ok is on the inside sill where there is still wood.

Any suggestions on how to do this? Do these brackets typically install to the inside sill? The photos show it on the outside sill.

Just wondering if anyone knows a time-tested way of putting this in safely to the second story window.

Thanks in advance for the advice.

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#723134 - 07/28/12 05:48 AM Re: Window AC Support [Re: Steve_S]
Clint_Robbins Offline

Carpal Tunnel

Registered: 09/19/01
Posts: 11270
Loc: Akron, OH
Many window ACs are designed to be supported in a typical window opening without additional support. If you don't have the installation instructions, check online for your unit.

In cases where I've installed window ACs in windows with aftermarket storm windows, I've had to install some wood spacers in the bottom of the interior double hung window channel in order to raise the support area to the level of the storm window opening.

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#723136 - 07/28/12 06:21 AM Re: Window AC Support [Re: Steve_S]
Bob_Fleming Offline

Carpal Tunnel

Registered: 06/28/01
Posts: 30073
Loc: Ft Collins, CO USA
I installed several of these in varying situations, and I usually made my own shelf, since at that time there were no ready-made shelves. All of these were relatively heavy units so I had to be sure the shelf was secure.

I started with a plywood shelf the size of the base of the unit and I fastened it with screws to the window sill, toward the inside. Alternatively you can fasten something like a 2x2 to the inside bottom of the shelf and just hook that over the window sill.

I made diagonal bracket supports of 2x4s angled back toward the outside wall, very much like the one in your photo. To keep from having to screw through the siding, I added braces to fix the angle of the braces.

To use the ready-made shelf in your photo, you could make a lip to fit under the inside of the shelf and then hook that over the window sill. Then you will have to fix the angle of the outside braces so they will not sag or spread.

Regardless of the type of shelf you use, do make sure the unit sets slightly down on the outside. Those I worked with had a condensate tray under the unit that was intended to drain outside. If that drains inside, it will make a mess that could be costly to repair.

The shelf and braces will have to be painted to protect them from the weather, and it is nice to paint them to match the color of the siding. If you use the ready-made thing, it should be powder coated so it will not rust; then a color coat to match the siding will be a simple task.

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#723295 - 07/30/12 11:57 AM Re: Window AC Support [Re: Bob_Fleming]
Steve_S Offline


Registered: 04/27/10
Posts: 105
Loc: Central NJ
Thanks for all the quick replies & advice.

After thinking about building a custom support, I decided to take my chances and give this one a try, so I bought the support in the photo, for a $30 investment I figured it saved me a lot of time.

It ended up working just fine, however I did have to put two screws in the outside sill, but the damage to the cladding is minimal. I'm going to remove this bracket for most of the year, as I hope to only need this supplemental cooling unit for a couple of the hottest months of the year. As long as I can reuse the same holes each summer, I'm hoping that I won't have to replace the sill or the cladding for quite some time.

Thanks again for the quick feedback.

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