"Is there such a thing as an OTR microwave that vents to the outside?"

Totally! All the OTR microwaves I've ever had have vented out.

Though many on this forum bash them, OTR microwaves work fine in most people's kitchens. However the ranges you're considering are a step up from most kitchens and, while not full on "pro" ranges, they will have higher BTU burners than your average range. An OTR microwave will probably *work* but if you can give up enough space to get a hood, you should.

The main drawbacks to OTR microwaves is that they only go up to about 300-400 CFM, their physical design isn't conducive to the best capture area/performance, and some say that if placed above ranges that are too powerful the life of the microwave components could be shortened.

This post was edited by hvtech42 on Mon, Jul 28, 14 at 22:24

Thanks, HVtech42. Any specific products you'd recommend for my renovation? Space is at a premium.

The other thing I forgot to mention is that most microwaves these days are cheap imported junk. By separating the components, when the microwave dies all you have to do is go buy a new cheap one rather than having to go through the ordeal of selecting a new OTR unit and replacing. Hoods, on the other hand, will last a long time because there is so little to go wrong.

As for specific products... I can't really recommend any OTR microwaves because all the new ones I've seen are equally crappy, and hoods are hard to recommend, because they're so similar mechanically. Pick one with the looks and price you like.

The one product I can recommend based on a friend's experience (plus the feedback on this forum) is the Sharp microwave drawer. It actually seems to be pretty decent quality and although it is more expensive, it will get you a microwave while saving counter space and not having to go OTR.

For me the bigger advantage of a separate built-in microwave is that the interior is much deeper than possible with an over-the-cooktop MW/fan combo. Those have to fit between 12" deep cabinets, so the microwave interior is typically wide but shallow. Common items like a pizza box won't fit. Whereas a microwave that's designed to fit into an oven cabinet or below the countertop can be up to 24" deep.

lee676, that's a very good point regarding depth. Thank you!

As far as OTR microwave vs range hood debate goes, I'm very much in the pro-range-hood camp. They're a LOT quieter, built much better, and as hvtech42 pointed out, much more reliable because there are only a few components (blower, controller, buttons, transformer, and lights).

Plus, you get to pick from a huge variety of styles and materials. Whereas a microwave is a black or stainless-steel box. No options, really.

Not a question- go with the hood. Wish I had...

Okay. Message received, decision made: OTR MV is out, Sharp MV Drawer is in. Now need advice on the hood. SS or wood sheathed? A matter of taste or are there functional considerations? Gas range will be 30-inch, GE Cafe or Thermador or KitchenAid......I think. Thoughts?

Hoods should be SS whether sheathed or not. However, the SS exterior hoods require perfectly welded and polished SS whereas a liner under wood can stand less expensive workmanship. Whether liner hoods are significantly less costly to make, however, may depend on the degree of automation applied to each type by any particular manufacturer.

Also I would add that baffles will have several advantages over mesh filters, assuming the baffles are correctly designed and the air velocity past the baffles is high enough for them to function as centrifugal grease separators:
o won't discolor like aluminum meshes
o may clean more easily in the dishwasher -- varies with the mesh design
o remains effective even when very greasy
o burnt grease on meshes is very difficult to remove, whereas SS baffles won't be easily stained
o It is likely (although I don't have any data at hand) that baffles present a lower pressure drop for the blower path, thereby (all else being equal) improving the CFM available from a given blower / duct combination.

Advantages of meshes over baffles would include:
o better grease collection at low fan speeds once some lint has been collected
o lower risk of a cut handling them

Generally, if one considers that commercial kitchens (including restaurants) have one of their highest costs associated with powering the ventilation, hoods that emulate commercial hoods within the limits of tolerable aesthetics should be superior to those that don't. Baffles are a key feature of most commercial hoods, although there are other technologies available for particular parts of the grease particle size spectrum that have been developed.

Search "hoods" on this forum for vastly more commentary on residential kitchen hoods. For more technical information, please see the references noted in My Clippings.

kas

We're renovating a small kitchen, and after a lot of angst we've decided to go with an OTR microwave/convection oven with outside venting.

Space is at a premium, and I don't want to give up any more cupboard/storage space to put in a separate microwave.

We are considering the BlueStar RNB 30". BlueStar suggests a 36" vent, but says a 30" would be fine. They also say 300cfm is required. This stove will be retrofitted into our kitchen, replacing an electric stove. We have an OTR microwave right now that can vent outside but doesn't. The BS hood that matches the range is what I really want, but at $3500 to get the color I want, that's not going to happen. It's not hard to find a 300cfm hood. Then we discovered that the vent on our microwave is 300cfm, and we can vent it outside. This is our plan. Also, no one ever mentions that return air thing (that's not what it's really called, but I can't remember the term). The guy at our BS appliance store told us any vent over 400cfm must have something else done in the house (because the vent sucks the air out of the house and the air must be replaced and this is usually done by sucking air out of the furnace or hot water tank, etc. He said it's about a $5000 fix. So we definitely don't want to go above 400cfm. Anyway, I found a 300cfm under the cabinet hood in white (to match my cabs - don't have or want any stainless steel in my kitchen), and I thought we could go with that, but then realized the tile backsplash doesn't go past the bottom of the current microwave. That's when we looked up the cfm on the microwave and found it was 300 and we could vent it outside. So our plan is to stay with that. I can't really see any reason not to.

It's called "make-up air", and it does become an issue with high-CFM exhaust fan hoods, though I wouldn't have thought 500CFM would require much if any alteration to your house, much less a $5000 upgrade.

"So our plan is to stay with that"

OTR microwaves over powerful ranges are a bad idea.

"I can't really see any reason not to."

Did you read my posts above? I clearly outlined why it is a bad idea. I was responding to the original poster who was considering ranges less powerful than your RNB. In your case, I wouldn't even say "avoid OTR microwaves if possible." Avoid them entirely.

"He said it's about a $5000 fix"

Nonsense.

Makeup air is a safety issue. If you have a tight house, there can be issues with high CFM hoods sucking air back through the chimney or flues of gas appliances. I don't think you need more than a 600 CFM hood but I wouldn't go under that. It also depends on how strict the inspector is. In many places they are not enforcing the 400 CFM rule. That does not mean you should ignore it entirely, however.

So, the questions are: how tight is your house, and what other gas appliances do you have?

If it is not going to be a safety issue for you, opening a window on the highest setting should be fine.

If you do end up needing makeup air, either for safety reasons or because the inspector requires it, it is not as big of a deal as some make it out to be. See my link for a brief overview. Obviously labor costs will vary by house and area but as you can see, the components are not that expensive.

Here is a link that might be useful: Makeup air

This post was edited by hvtech42 on Mon, Aug 4, 14 at 14:53