I have run across this with both single conventional ovens and microwave ovens...that they are to be mounted at countertop height or above. With no explanation as to why this is so. The manufacturers then contradict themselves by showing the microwaves mounted in an undercounter location on their own website, or saying that the conventional oven can be mounted under corresponding cooktop XYZ. (Which means the cooktop would be mounted at about 5 feet off the floor?)

Most of the "built in" models (not all) are countertop models that come with a trim kit.

I have my micro on a shelf in my island. The only problem I ever have is when I open the door, the steam often hits me in the face and it's really hot. Now I'm careful so it's not a problem for me but possibly it's a safety issue and that's why it's recommended at 3 feet. This is just a wild guess.

I would guess that it's to protect themselves from claims if someone found that reaching into it that low was not easy and they spilled something hot or couldn't get a good grip and dropped a hot dish. Then there is also the issue of having a certain height so really little ones (or hungry dogs) can't get into it. My lab would love o turn the micro drawer and warming drawer into food trays, but the sides keep her out -- a swing door might not, especially if I had to turn around.

I'd guess that the reason is to prevent 3 year olds from cooking the cat.

You might want to try this question over on the appliance forum. They are very knowledgeable about this type of detail over there. A while back I asked this question b/c I was considering using an GE advantium. I wanted to place it lower than GE recommended due to the drop down door that I felt would hard for me to reach over since I'm short. I have forgotten the answer from the appliance forum since I ended up not using the advantium. When I asked GE their answer was that they had not tested the oven for use in any other location or height than what they recommended and therefore could not state that it could be used safely in another placement. HTH.

The testing thing makes the most sense. I used to be involved in patient-based clinical research and the parameters of study were sometimes quite narrow, to limit the number of variables. Then, when the new drug application was filed with the FDA and the "labeled use" was determined, the indications of the drug could be interpreted rather narrowly. Using the drug or device outside these parameters often made sense, but it could not be promoted for such.

Its probably a similar thing...it was tested on a standard height kitchen counter so it is "labeled for use" at standard kitchen counter height, when in reality, its use at other heights is not contraindicated.

I recently saw a kitchen where the OTR microwave was 60" off the floor. I think it is much more dangerous to be removing a steaming dish at eye level than below waist level, but it was mounted OTR as tested, so it was not in violation. I have also seen them on top of refrigerators: again, removing something from over the head or while standing on a stool is more dangerous,,,but it is above the 3' height--so its in an okay spot according to the specs. But not in practice.

THANK YOU EVERYONE!! You all make a lot of sense, that contraindicated thing especially. So annoying though.
Well, I think I've found another solution that is going to work, instead of under the island we can put it in an upper cabinet space; will lose a bit of upper storage but it will be easier to use the micro there as it will be higher up, yet not as high as an over-the-range model. I think I will like it better there too, as I will gain another deep drawer plus a regular depth drawer in the island!
SO it all works out in the end....I am so appreciative to you all for taking the time to respond to me. I love this website! THANKS AGAIN!!