How can I install a window air conditioner into my metal framed window?
I recently (well, last summer) did basically the same as buggzzee23 to mount a window a/c into the frame of a sliding window. Since I rent, I couldn’t drill holes in the window frame, so I built an inner frame that fits snugly into the window frame – 2 3×1/2 uprights chamfered slightly top and bottom to fit inside the track, 1 piece of 3×2 with a groove cut lengthwise so it’ll sit in the bottom track, ply to fill in the gap above, and the whole thing screwed together with brackets. The a/c is screwed to the wooden sub-frame and, because it’s such a snug fit, that frame ain’t going nowhere. Any semi-competent chippie should be able to do this for peanuts. I’m an electronics tech who is handy-ish, and it took me half a day to drive across town, buy the timber, cut it to size, chamfer & groove as needed, and test-fit. It actually took longer to paint the pieces before I installed them. The thing to remember is that window a/c units are designed to pretty much balance in the window, with a
The way I did an installation in an aluminim frame: Ripped a 2×4 for 3 pieces; 2 vertical and the bottom horizontal I then fastened 2 verticals and the bottom piece pieces to the house frame just inside of the window, laid a full 2×4 on its side and fastened it to the top of the 2 verticals flush to the inside edge with the overhang under the sliding part of the window for a good seal. I had some 3/4″ plywood laying around in the shop and cut a piece for either side of the AC unit, nailed it to the 2x frame, caulked for a good seal, painted it to match the wall, and installed the AC. Don’t forget to support the back end of the unit if the manufacturer recommends and be sure the unit is level for best results. It’s a good idea to avoid screwing into the metal window frame if possible.
The AC being narrower than the opening is a serious problem and will have a drastic effect on your options, because the units are designed to pass through the window and then wedge themselves against the opening to counteract the weight sticking out. Otherwise you could just screw the anchors into the metal frame anyway by pre-drilling metal holes (assuming it’s no big deal or no one will notice later). In this instance I think all you can do is build a platform for the unit to sit on outside, and then mate the window against the opening with lots of weatherstripping.
An AC normally hangs out the window, and has a lip on top that catches the bottom edge of the opened lower sash. Assuming yours is like that, you should just be able to open the window, balance the AC on its bottom lip on the window frame, close the window on top of the AC, and carefully let the AC “fall” out the window till the lip hits the sash. (More safely done with a helper.) Then just stuff any gaps with foam strips which you can get at the hardware store.
I’ve many times fit the impossibly sized window air conditioner to windows that have nothing to accept screws and are mere millimeters large than the unit. You’re on the right track: there is always a way to cobble together some woody bits to secure the unit in place. I’ve never been fussy with it — the things are too damn ugly to worry about aesthetics. The only caveat is to consider your physics: in what direction do you need to resist the pull from a potential fall of the A/C?
