[GoofyPotsticker]

Hi Forum-

This is my first post, so good to meet you all and thanks for your help here. I'm thinking about how to design a kitchen remodel, specifically what to do with over the range.

The existing solution is something that as far as I can tell is not made anymore - a metal shelf with power and a fan that supports a standalone microwave in an over-the-range position. The fan blows air from over the range and out forward near the ceiling. There is an old defunct ceiling vent next to the output of the fan-shelf. That ceiling vent probably goes into the house's original furnace exhaust. It is appears to have been plated over two furnaces ago, and the current furnace saw a new and completely separate furnace exhaust installed.

The current system is terrible - a smoky kitchen incident just stinks up the whole house and the existing fan does zero to mitigate it.

I had the roof done two summers ago and I had the roofers install vent lines with flex hoses through the attic for each upstairs bathroom, and the kitchen. Unfortunately, we discovered the above system had nothing to connect the hose to, so the exhaust line is just dangling in the attic waiting for the kitchen to be done.

So, I have an over-the-range spot for a vent/hood appliance of some kind and an overhead exhaust line direct to outside. But, this volume above the range has to serve a lot of functions. This kitchen is not too big, and the existing shelf provides a location for the microwave, plus some handy storage for cutting boards, cookie sheets, and other flat kitchen equipment that fits nicely next to the microwave. Also the spot is between an interior wall and a cabinet, so a standalone hood with tube up to the ceiling would look weird and waste valuable volume. This spot is also under a cornice the extends down from the main ceiling level about a foot. I don't know if this only conceals a void or if there is some concealed duct work.

So, the first problem I have is it seems hard to shop for range hoods or over-the range microwaves by how they vent. My understanding is some vent into the room, like I have now, and some are designed to vent to the back through an exterior wall (but the wall behind the range is an interior wall). Is there a way to figure out which appliances vent to the top?

Second, assuming we have a top venting appliance, can either a dedicated hood or an over-the-range microwave work in this case? Can either go under a cabinet piece? (the assumption being that the exhaust tube just goes into the cabinet through the top) Are over-the-range microwaves that function as a fan and vent even available?

Thanks so much for your insights!

 

[huesmann]

Can you post pics of what you have?

 

[HotRodx10]

So, the first problem I have is it seems hard to shop for range hoods or over-the range microwaves by how they vent. My understanding is some vent into the room, like I have now, and some are designed to vent to the back through an exterior wall (but the wall behind the range is an interior wall). Is there a way to figure out which appliances vent to the top?

The over-the-range microwaves typically allow you to rotate the internal vent housing to vent out the front of the unit, out the top, or out the back.

 

[GoofyPotsticker]

Can you post pics of what you have?

Yes, here is a picture of the setup. The main thing that isn't immediately visible is that the ceiling intake in front of the fan output is defunct, so the shelf just blows smoke from the range back into the room.

https://drive.google.com/file/d/165feIsNHgLWyqgZCBLUkHEejV6O4nAzY/view?usp=sharing

 

[GoofyPotsticker]

The over-the-range microwaves typically allow you to rotate the internal vent housing to vent out the front of the unit, out the top, or out the back.

Ah, thanks for that! That helps explain things. So, supposing the over-range microwave is mounted under cabinets, is it appropriate to simply open holes in the ceiling and cabinets to connect the exhaust tube directly to the vent housing on the microwave, or do I need some kind of intermediate equipment?

 

[huesmann]

The vent flange on the microwave is typically a 3.25x10 or so rectangular duct size. Depending where your microwave is located, you can vent out through the back, up through cabinet and ceiling, or back to the room (which really isn't venting at all). Where is your microwave w.r.t. any exterior walls?

 

[Oso954]

There is an old defunct ceiling vent next to the output of the fan-shelf. That ceiling vent probably goes into the house's original furnace exhaust. It is appears to have been plated over two furnaces ago, and the current furnace saw a new and completely separate furnace exhaust installed.

A vent grill in that location was typically an exhaust fan and would typically be ducted out thru the roof or a sidewall. No connection to any furnace exhaust.

A lot of them housed the fan directly behind the grill and had a 2 prong plug that plugged into a receptacle inside the duct or fan housing section. Unfortunately, they also collected a lot of cooking grease and dust so they would run hot and eventually fail after many years of service, if not being periodically cleaned.

Many homeowners didn't bother with replacing them. Accumulating grease could also lock the damper open which would create cold down drafts. That would be the reason someone might block it off if they are no longer using it.

If you have attic immediately above that kitchen, the duct usually goes straight up. You can often spot the roof vent in that location just by looking for it from the ground, or spot that duct from the attic access hatch if you have a good flashlight.

You need to investigate it.

 

[HotRodx10]

So, supposing the over-range microwave is mounted under cabinets, is it appropriate to simply open holes in the ceiling and cabinets to connect the exhaust tube directly to the vent housing on the microwave, or do I need some kind of intermediate equipment?

You just need the duct pieces and transitions to connect, but it should be connected to a roof vent. Venting into the attic space will develop into a fire hazard.

 

[GoofyPotsticker]

You just need the duct pieces and transitions to connect, but it should be connected to a roof vent. Venting into the attic space will develop into a fire hazard.

Yes, we had the roofers put in a vent with flex tube, so that is what would connect to the duct piece of the microwave. This is making sense, thanks!

You need to investigate it.

Yeah, I'm thinking that has to get opened up before we make any firm plans. Thanks again!

 

[HotRodx10]

...a vent with flex tube...

Make sure it's at least a metal flex duct. The semi-rigid aluminum duct would be better. Rigid metal would be the best. Over time, grease and other flammables will build up in the duct, especially with the flex, because it has so many crevices and pockets. It could eventually become a fire hazard. There may be building code requirements for that reason, also.