I replaced the microwave in our MH this weekend, and while the job is truly complete, the trim work may never get done (much to my wife's chagrin). I thought somebody might find it interesting, if not useful to see what I did, so here goes my documentation attempt.
The pics are on Flickr if you want to see them directly.
The old microwave (a Sharp R-820) was broken when we bought the RV in 2010: the display didn't show most of the numbers. Since you couldn't tell what time you typed in or power setting or temp (for the convection operations), it didn't get used much. I finally got around to finding something that would fit in the cabinet, so bought this Frigidaire FFCT1278L for around $250 from Airport Appliance (a store we've been shopping at for nearly 2 decades...always good prices and good service).
First discovery after removing the old unit, was some wires coming up from the bottom and heading out the top of the cavity. I pulled up the floor, and found that be re-routing the wires under the floor, I could get enough slack that they wouldn't interfere with the microwave.
Next, I made some cardboard cutouts that lined up with the screw holes on the back of the unit:
I then cut out and bent some 22 gauge steel purchased from a local hardware store (Dale Hardware is awesome) and welded two pieces together for each side:
I'm obviously not a welder, as these are terrible quality, with burn through etc...but they're certainly good enough for this application.
Here they are, installed on the microwave:
I had to cut the opening a little wider; I took off 3/4" off of both sides. To do that, I put painter's tape (the wide blue stuff) on the wall and then drew a line on it. A jig saw with a high quality blade made the cuts, with no tear-out; free-handing the cut I'm pretty happy with how straight they are
After sliding the microwave and brackets into place, the brackets hooked the cabinet just like I wanted:
I decided that I didn't need to drill holes in the bracket flanges, and just added screws to hold them in place:
So far, this all I've done. I do need to add some kind of trim around the microwave, to hide the bracket flanges and cover up the opening. I'm intending to put a fan in the back that will vent out of the cavity, controlled by a switch. That way, any heat that does build up has a place to go. I've run it up to 400 degrees and had it there for about 20 minutes, and the cavity had no significant heat build-up. I attribute that to the fact that there is a half inch gap on the sides and bottom and a 2" gap above the unit. The trim will probably make the fan necessary.
2004 Four Winds Fun Mover 39C (39' including 14' toy hauler garage)
Cat 3126E 300hp Allison MD3066P Pics of the FunMover
Nice job. Had to replace our mw last year. Went to local wm and purchased three units that could possibly fit. Once at home I dry fitted each and decided to keep the best one. Cost me $95 and a couple hours of work.