Is this mostly due to safety and combustibles or is it more of a lack of ventilation. I am wondering if it is an absolute NO.

Both. And yes it is an absolute no. I hate OTR microwaves, they are cheap made in China junk and are house fires waiting to happen.

If I look at more traditional grade gas ranges they don't seem so strict on not using an OTR microwave and many of them have the same BTUs.

On the Thermador all the burners are a powerful 18,000 BTU. On a standard gas range you might get one 15-18,000 BTU power burner. The rest will be much less powerful.

We don't have the counter or cabinet space to sacrifice on a microwave.

Have you looked into an over-the-counter microwave? GE and Sharp have them. They are easy to install yourself and mount to the bottom of your cabinet wherever you want.

This post was edited by hvtech42 on Sun, Feb 8, 15 at 11:21

Thanks for your advice. Maybe an induction range my be a good alternative as well. In the meantime I will also look into other microwave options.

This post was edited by RSNovi on Sun, Feb 8, 15 at 20:40

Maybe you could look into the Viking induction range? I understand that may not be in your budget, especially when you factor in that the Thermador comes with a free dishwasher.

While we're not fire-safety experts and thus can't comment on the safety issues with OTR microwaves, we can definitely tell you that in comparison to actual, full-size range hoods, OTR microwaves suffer in more than a few ways:

1.) Ventilation power - the size of the microwave prohibits using a powerful blower. As a result, you're stuck with 100-300 CFM, while full-size range hoods can provide 600-1200 CFM.

2.) Speeds - many OTR hoods have only an "on/off" switch; with a few, you may be lucky enough to have 2 selectable speeds. Meanwhile, full-size range hoods offer 3, 4, or more speeds, letting you have a finer balance between airflow and noise.

3.) Speaking of noise... a smaller blower working at its top speed is going to be louder than a larger blower working at a fraction of its power. For example, let's say you need 300 CFM of airflow, for your particular cooking situation. A 300-CFM OTR at full blast is going to be noisier than a 900-CFM hood running at 1/3 of its speed - typically 2 to 3 times louder!

According to customer feedback, the #1 reason for upgrading from an OTR to a full-size hood is - noise! What's the point of having an appliance when you don't ever want to use it because it's too loud?

4.) Filter area - the 3 or 4 full-size filters on a full-size hood will provide much better suction performance than the undersized single filter on most OTR's.

5.) Filter capacity - high-quality full-size range hood filters are usually made from 5 or more layers of mesh (our filters are 7-layer, for example), while the OTR filters have 1-3 layers. More filter capacity lets it absorb more grease before needing to be washed.

6.) Lighting. To put it bluntly, most OTR microwave lighting is terrible. It's getting better as manufacturers are listening to consumer feedback, but it still has a long way to go before it matches the level of illumination that full-size range hoods provide, with high-power halogen or LED bulbs.

All great feedback and I appreciate it.

You guys have me convinced that if I ever fully redo the kitchen I will go with a better ventilation system. Right now I am not able to make the changes needed for a Pro Style range. I think I have pretty much made up my mind to go with the Bosch induction range. Thanks.