Creating External Exhaust for Microwave over Range - Need Reality Check

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Nearly A Moose
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Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Nearly A Moose » Mon Nov 13, 2017 10:11 pm

Question for all the home improvement DIY'ers out there. How difficult is it to run an external exhaust conduit for a microwave mounted over a range? One of the many pet peeves I have about my house is that the microwave (mounted over the range), despite being on an external wall, is setup to vent back into the kitchen. I like to cook meat in a hot pan on the stove, which means I have gotten extremely skilled at waving a towel in front of my smoke detector while my wife and children huddle in the corner and ask whether the house is going to burn down. I'm going to replace my microwave (broken handle that I can't figure out how to fix, and not worth paying for it to be serviced). I had mostly resigned myself to viewing an external venting over-the-range exhaust fan as something for my next house, but if I'm going to pull the microwave off the wall anyway, I'm now wondering if it's worth trying to do an external vent.

Here's the setup: The microwave (and range) are against an external wall. My house is brick, but part of the back wall obviously had been a window or door at some point because it is filled in with a plaster-like substance rather than the surrounding brick. I can't quite tell whether the microwave butts up against this plaster substance or the brick; it's close (and I'd certainly measure and/or pull an outlet out of the wall to check before making any moves). The area on the other side of the wall is my back patio, and the back of the microwave is either up against my general patio or a storage shed I have a couple inches away from my wall (again, it's close and I'd have to measure to be sure). So, as I see it, I'd essentially be punching a hole straight back through my wall, about 6 inches. I wouldn't have to run a conduit across my cabinetry or up a story. But for anyone who has done this:
1. Can you set up an exhaust line this way (ie straight out the back of the microwave, or up into the upper cabinet and then straight out the back of the house)?
2. Will it negatively affect my patio? E.g., will I eventually build up a grease stain on the pavers or something? Or would it mess up my shed and/or make everything inside smell like perfectly pan-seared steaks?
3. Is it particularly hard to punch through the exterior wall of a house by yourself?
4. Anyone know of a good, accurate video or tutorial online?
5. Or how costly of a project would this be if I hired a professional, and what trade would I even hire?

I'm reasonably handy, not afraid to mess with things, but I also don't have days to spend tinkering - I'd need to be able to get this done in a couple hours over the course of one weekend to maintain household harmony. Thanks!
Pardon typos, I'm probably using my fat thumbs on a tiny phone.

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Sandtrap
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Sandtrap » Mon Nov 13, 2017 10:45 pm

Nearly A Moose wrote:
Mon Nov 13, 2017 10:11 pm
Question for all the home improvement DIY'ers out there. How difficult is it to run an external exhaust conduit for a microwave mounted over a range? One of the many pet peeves I have about my house is that the microwave (mounted over the range), despite being on an external wall, is setup to vent back into the kitchen. I like to cook meat in a hot pan on the stove, which means I have gotten extremely skilled at waving a towel in front of my smoke detector while my wife and children huddle in the corner and ask whether the house is going to burn down. I'm going to replace my microwave (broken handle that I can't figure out how to fix, and not worth paying for it to be serviced). I had mostly resigned myself to viewing an external venting over-the-range exhaust fan as something for my next house, but if I'm going to pull the microwave off the wall anyway, I'm now wondering if it's worth trying to do an external vent.

Here's the setup: The microwave (and range) are against an external wall. My house is brick, but part of the back wall obviously had been a window or door at some point because it is filled in with a plaster-like substance rather than the surrounding brick. I can't quite tell whether the microwave butts up against this plaster substance or the brick; it's close (and I'd certainly measure and/or pull an outlet out of the wall to check before making any moves). The area on the other side of the wall is my back patio, and the back of the microwave is either up against my general patio or a storage shed I have a couple inches away from my wall (again, it's close and I'd have to measure to be sure). So, as I see it, I'd essentially be punching a hole straight back through my wall, about 6 inches. I wouldn't have to run a conduit across my cabinetry or up a story. But for anyone who has done this:
1. Can you set up an exhaust line this way (ie straight out the back of the microwave, or up into the upper cabinet and then straight out the back of the house)?some overhead microwaves have an exhaust system built into them. The duct will be overhead and routed into the cabinet then out to the exterior wall. Or it may a direct line to the exterior wall depending on the kit and your setup. I don't know the practicality of installing a range hood under a replacement microwave. Might be funky logistics.
2. Will it negatively affect my patio? E.g., will I eventually build up a grease stain on the pavers or something? Or would it mess up my shed and/or make everything inside smell like perfectly pan-seared steaks?the exhaust system has grease filters
3. Is it particularly hard to punch through the exterior wall of a house by yourself?no as long as you don't hit studs, wiring, pipes and are patient and careful not to make a mess. The better the cutout the less patching to do later.
4. Anyone know of a good, accurate video or tutorial online? links below
5. Or how costly of a project would this be if I hired a professional, and what trade would I even hire?a competent journeyman carpenter should be able to handle all of it from cabinet to duct to install to repair. Carpentry overlaps the other trades. If you have everything ready it should be done in a short day depending on the skill and efficiency of the carpenter. Do the exterior and interior touch up paint and cosmetics yourself.

I'm reasonably handy, not afraid to mess with things, but I also don't have days to spend tinkering - I'd need to be able to get this done in a couple hours over the course of one weekend to maintain household harmony. Thanks!it will take a lot more than a couple of hours.
Can you take a picture of the interior and exterior wall?
https://www.youtube.com/watch?v=cVJgTn ... 855VYKHa6E
https://www.youtube.com/watch?v=-rh8_NBeDcA
For microwave venting. Amazon.com has a number of kits.

If you are not handy this may be a job for a carpenter as he will be able to route the exhaust duct the best way to avoid wires and studs and water pipes, etc. This is the type of job that done well can look slick and done poorly looks funky. It is also the kind of project that can go smoothly like the youtube videos or not so. You will also have to wire in the exhaust fan to best exhaust cooking fumes.
It would not hurt to call a bunch of carpenters for estimates and get some ideas as you talk it over with them. Then decide if you want to tackle it yourself. I would do it myself but I'm a carpenter/builder so that's a different thing altogether.
It can be a fun project.

Nearly A Moose
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Nearly A Moose » Mon Nov 13, 2017 10:58 pm

Thanks ^^

I'm afraid I haven't figured out how to post photos here yet. But to clarify, I'm envisioning a microwave with a built it exhaust system, not a microwave plus a separate exhaust fan unit, which I agree would look funky. I'll take a look at the videos. And if I can sort out the pictures I'll post. But suspecting I'll end up soliciting a few Bids...
Pardon typos, I'm probably using my fat thumbs on a tiny phone.

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Sandtrap
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Sandtrap » Mon Nov 13, 2017 11:05 pm

Nearly A Moose wrote:
Mon Nov 13, 2017 10:58 pm
Thanks ^^

I'm afraid I haven't figured out how to post photos here yet. But to clarify, I'm envisioning a microwave with a built it exhaust system, not a microwave plus a separate exhaust fan unit, which I agree would look funky. I'll take a look at the videos. And if I can sort out the pictures I'll post. But suspecting I'll end up soliciting a few Bids...
Okay. Great. Tons of vids on that setup. Get the outside exhaust kit. Put it together like "legos". Plan the outside hole carefully. Done. Hardest part will be lifting the microwave into place and mounting it. Good luck. :D

Frisco Kid
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Frisco Kid » Tue Nov 14, 2017 9:02 am

For the type of cooking you are doing a "properly sized" externally vented hood would do a much better job of ventilating your kitchen. People in the trades have told me a microwave with a vent is marginal at best, regardless of how it is vented.

Rupert
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Rupert » Tue Nov 14, 2017 9:13 am

I've also heard bad things about the effectiveness of vented microwaves. Have you considered putting your microwave on a countertop and installing a proper hood over your stove? And in my area, the microwave-over-the-stove look has gone out of style. Builders are incorporating microwave shelves into the cabinetry these days, so that short people don't have to reach over their heads to get hot food out of the microwave. A well-placed exhaust fan (like the one in your bathroom) is another option that would likely work better than the vented microwave.

barnaclebob
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by barnaclebob » Tue Nov 14, 2017 9:42 am

First of all an OTR microwave is garbage for collecting smoke and grease. You'll be much happier if you find a new location for your microwave and replace it with a proper hood.

However venting to the outside wall is pretty easy and there is practically no excuse when the hood is on an exterior wall. Cut the hole, make sure its properly reinforced, put in the duct penetration and make sure its sealed from the elements on the outside. A couple of hours may be sporty but a dedicated weekend should get the job done with time to make dinner on Sunday if you research properly ahead of time.

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lthenderson
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by lthenderson » Tue Nov 14, 2017 10:59 am

Nearly A Moose wrote:
Mon Nov 13, 2017 10:11 pm

1. Can you set up an exhaust line this way (ie straight out the back of the microwave, or up into the upper cabinet and then straight out the back of the house)?
2. Will it negatively affect my patio? E.g., will I eventually build up a grease stain on the pavers or something? Or would it mess up my shed and/or make everything inside smell like perfectly pan-seared steaks?
3. Is it particularly hard to punch through the exterior wall of a house by yourself?
4. Anyone know of a good, accurate video or tutorial online?
5. Or how costly of a project would this be if I hired a professional, and what trade would I even hire?

I'm reasonably handy, not afraid to mess with things, but I also don't have days to spend tinkering - I'd need to be able to get this done in a couple hours over the course of one weekend to maintain household harmony. Thanks!
1. The last three microwaves I've installed allow you to vent it directly out the back, straight up or back into the house. It is a matter of undoing a panel, flipping the fan according to your preferences and putting the panel back on. I think this is the way most new microwaves are sold.

2. They come with replaceable grease filters but it will smell up the area it vents too. My wife cooks a lot of fish and when I'm working outside, I can definitely smell what's for supper.

3. Depends greatly on your individual circumstances. I've had some that were very difficult because of materials and what was routed between the microwave and the outside. Other's have been extremely easy 15 minute jobs.

4. Google "installing vented microwave" and you will find hundreds of videos.

5. Depends on number 3. Most appliance stores where you can buy microwaves also have contractors to install them.

p14175
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by p14175 » Tue Nov 14, 2017 11:58 am

We had a GE Americana range in our old house. An avocado one just like in the ad below. The oven was over the range. Ours didn't have the bottom oven. The model in the picture is probably 5'10" (or taller) w/heels so she makes it look like the top oven is okay. The Americana had a built in exhaust under the top oven, and the flap over the oven was a secondary exhaust if you needed it. The vent to the roof was attached to the top.

After cooking a turkey in the top oven we decided it was just too dangerous to have an oven or microwave that high up. All it takes is one accident. Yeah, I know it's standard setup in houses these days to install the microwave over the range so doesn't take up space on the counter or on a movable cart that doesn't fit anywhere in the kitchen. When we replaced the Americana, we installed a regular exhaust over the new range and moved the microwave we had on the counter into a kitchen cabinet shelf (w/doors to hide it) that was about the same height as the counter top. We added an electrical outlet inside the cabinet for the microwave. The setup worked well.

Image

ref:
https://thisoddhouseblog.wordpress.com/ ... americana/

Afty
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Afty » Tue Nov 14, 2017 12:39 pm

Nearly A Moose wrote:
Mon Nov 13, 2017 10:11 pm
I like to cook meat in a hot pan on the stove, which means I have gotten extremely skilled at waving a towel in front of my smoke detector while my wife and children huddle in the corner and ask whether the house is going to burn down.
I don't have anything useful to add, but I laughed out loud at this. We had this *exact* experience last weekend when I was cooking bacon in a skillet.

GreatLaker
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by GreatLaker » Tue Nov 14, 2017 2:09 pm

I agree with ditching the OTR microwave and going with a dedicated range hood with separate microwave on a counter or shelf. OTR microwaves just are not that effective at exhausting cooking fumes and smoke. They are an OK compromise for a small kitchen, but the way you described your cooking leads to a real range hood.

Added: I do miss the size of my over-the-range microwave. It could fit a 3qt glass baking dish on a shelf which was useful for cooking (as opposed to just warming things).

Another thing I recently learned is that ionization smoke detectors are very susceptible to false alarms from even a small amount of smoke from frying or opening an oven. Photoelectric detectors are much less prone to false alarms from cooking. I recently got one for my kitchen and have not had a false alarm since.

Here is one example:
http://www.kidde.com/fire-safety/en/ca/ ... P3010K-CA/
Last edited by GreatLaker on Tue Nov 14, 2017 2:27 pm, edited 1 time in total.

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Sandtrap
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Sandtrap » Tue Nov 14, 2017 2:15 pm

Rupert wrote:
Tue Nov 14, 2017 9:13 am
I've also heard bad things about the effectiveness of vented microwaves. Have you considered putting your microwave on a countertop and installing a proper hood over your stove? And in my area, the microwave-over-the-stove look has gone out of style. Builders are incorporating microwave shelves into the cabinetry these days, so that short people don't have to reach over their heads to get hot food out of the microwave. A well-placed exhaust fan (like the one in your bathroom) is another option that would likely work better than the vented microwave.
DW is short. We ended up relocating the microwave. Also, the over range types and others cost a whole lot more than a shelf one and are also not as vulnerable to electronic issues because of unvented heat.

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Earl Lemongrab
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Earl Lemongrab » Tue Nov 14, 2017 4:53 pm

While an over range microwave isn't great, my kitchen doesn't have a huge amount of counter space and trying to place an individual unit there would really cause a shortage.
Last edited by Earl Lemongrab on Tue Nov 14, 2017 5:25 pm, edited 1 time in total.
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by mrc » Tue Nov 14, 2017 5:04 pm

Frisco Kid wrote:
Tue Nov 14, 2017 9:02 am
For the type of cooking you are doing a "properly sized" externally vented hood would do a much better job of ventilating your kitchen. People in the trades have told me a microwave with a vent is marginal at best, regardless of how it is vented.
We have a GE SpaceSaver with a built in vent. It's nearly useless. It has a small squirrel cage fan in the back, about 2" in diameter and maybe 10" long. Mine's on an interior wall, the MW vents to the rear, then up and out to the exterior. The pipe is 4". Every part of this system is undersized.

I sear steaks outdoors on the grill, otherwise I set off smoke alarms. If we had decent counter space, I would install a real hood, vent it up and out the wall cabinet space, and put a free-standing MW someplace else.
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z0r
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by z0r » Tue Nov 14, 2017 5:15 pm

LG has a line of OTR microwaves with powerful fans and an extending tray to get more collecting area:

http://www.lg.com/us/cooking-appliances ... -microwave

by the numbers, they're better than some builder-grade dedicated hoods. I demoed one in home depot and plan to use this type in my small kitchen. They're $$$ though and don't seem to go on sale.

Gryphon
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Gryphon » Tue Nov 14, 2017 11:40 pm

z0r wrote:
Tue Nov 14, 2017 5:15 pm
LG has a line of OTR microwaves with powerful fans and an extending tray to get more collecting area:
Costco sells one of those. The only potential issue (at least for me) is that they're a few inches taller than a regular microwave, which means a few inches less clearance between the microwave & the stovetop. I already have to bend down slightly to see the controls on the stove, I'm not sure I want to make it any worse.

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celia
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by celia » Wed Nov 15, 2017 12:27 am

Nearly A Moose wrote:
Mon Nov 13, 2017 10:11 pm
... I have gotten extremely skilled at waving a towel in front of my smoke detector while my wife and children huddle in the corner and ask whether the house is going to burn down.
OMG! It sounds like you have a fire hazard. People are trying to tell you about it, but you are ignoring them. :!:

First, the range and the microwave (and the dishwasher and refrigerator) each need to be on a dedicated circuit--no other appliances, wall outlets, or lighting can be on the same circuit.

Second, the top of the counter (and range) is usually about 36" above the floor. And you are usually required to have clearance above the range to prevent fires. No wood or wallboard or anything flammable can be within 32" above the range (per our building code in S. California). That would put the bottom of the microwave at 6 feet off the floor. The range is usually required to have a venting system at that height (unless it has a built-in venting system?).

Now imagine this. Something is cooking away on the range. Then someone wants to use the microwave. Not only is it over 6 feet above the floor, but it doesn't stick out from the wall as much as the range does. If you build in a microwave, I think you have to have a flat surface nearby to hold anything hot that comes out of the microwave. Where do you put that cup of boiling water that just finished in the microwave? Do you have to lean over the food cooking on the range?

I suggest you start with the city building codes and find out the requirements for all your built-in appliances. Then read the manufacturer's installation instructions for each appliance (which are usually available online). Have you followed all the recommendations/rules/building codes involved?

When your house burns down, your fire insurance may not pay you if you were not following building codes.

voltaire
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by voltaire » Wed Nov 15, 2017 2:48 am

I had an over the range microwave installed recently with a built-in exhaust fan installed recently.

The very competent installer charged me $119 to open up the wall behind the microwave, install a rain protected vent on the outside stucco wall. He also told me the outside vent didn't make a big difference because the fan was not nearly as big as a dedicated stove fan would be. He was right, the vented micro works better than one without a vent--but not a giant difference.

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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by michaeljc70 » Wed Nov 15, 2017 10:24 am

I agree with the suggestions to get a real vent hood and relocate the microwave. You are not going to get a powerful fan with a microwave. You can get pretty decent range hoods that recirculate and have carbon filters if you don't want to make a hole in the side of your house.

Look at the CFMs which indicates how much air hoods move. The more powerful ones are very loud. You can get ones where the actual fan is placed in the attic or on the roof and they are quieter. I had a huge Viking hood because my range had a grill and it sounded like an airplane was over the house when I ran it, but it did the job.

tev9876
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by tev9876 » Wed Nov 15, 2017 11:32 am

I did this a few months ago and the difficulty depends on what is in that wall. Most microwaves have a 3.25x10" exhaust that can be directed out the back, top or front by removing the blower motor (a couple screws) and flipping it around.

In my case a stud ran right through the center of the microwave so back venting was not an option as that requires a rectangular hole in the wall. I went with a top vent. I also decided to replace the microwave since the existing one was 13 years old and Murphy's law says it would have died 10 minutes after I put it back up.

My house was built in the 1950s and at one time had an exhaust fan through the kitchen wall. The inside had been drywalled over and the cabinet adjacent to the microwave is covering it. The metal cover was still on the outside, so I decided to use that same hole to avoid having to remove more brick. My parts list consisted of:
3.25x10 to 6" round transition
6" elbow
6" flexible vent
Wall vent (https://www.lowes.com/pd/IMPERIAL-Metal ... nt/4598558)
Aluminum duct tape
Caulk

Everything came from Lowes except for the transition which I found on Amazon. It was a pain to cut thorough the cabinets in such a confined space. It took some trial and error but the best tool for the job was a Dremel with a saw bit. I also had to trim the transition with tin snips to get enough top clearance for the elbow. The wall vent is the same size as the existing hole so that helped, but I did have to do some creative attachment of scrap wood to the framing to bring something out to the edge of the brick to screw the vent to.

It is not pretty and I lost some cabinet space, but it works so much better now. I always crack a nearby window so it can get good airflow.

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CaliJim
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by CaliJim » Wed Nov 15, 2017 11:44 am

Present several options to your spouse.
Let your spouse decide.

:P
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z0r
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by z0r » Wed Nov 15, 2017 3:10 pm

celia wrote:
Wed Nov 15, 2017 12:27 am
Nearly A Moose wrote:
Mon Nov 13, 2017 10:11 pm
... I have gotten extremely skilled at waving a towel in front of my smoke detector while my wife and children huddle in the corner and ask whether the house is going to burn down.
OMG! It sounds like you have a fire hazard. People are trying to tell you about it, but you are ignoring them. :!:

First, the range and the microwave (and the dishwasher and refrigerator) each need to be on a dedicated circuit--no other appliances, wall outlets, or lighting can be on the same circuit.
Virtually everywhere in the US allows grandfathered electrical work, all the way back to knob and tube. This grandfathered work is by and large safe to continue using. The codes have evolved in the areas you mention not necessarily because of safety; consider that they're influenced by powerful industry members who want to sell more wire and bill for more circuits, combined with a bias for being extremely conservative. In the case of a microwave on an old shared circuit, it's safe because the load is intermittent and the circuit is presumed to be current-limited by a fuse or breaker.

Modifying the exhaust is not going to trigger a reevaluation of any grandfathered electrical status here. Presuming the wiring is correct for a grandfathered situation (and that situation was disclosed when purchasing the insurance) insurance won't have standing to now deny coverage.
celia wrote:
Wed Nov 15, 2017 12:27 am
Second, the top of the counter (and range) is usually about 36" above the floor. And you are usually required to have clearance above the range to prevent fires. No wood or wallboard or anything flammable can be within 32" above the range (per our building code in S. California). That would put the bottom of the microwave at 6 feet off the floor. The range is usually required to have a venting system at that height (unless it has a built-in venting system?).
OTR microwaves are designed to sit closer than 36" by being made out of things that don't burn, and including vents.

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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by Nearly A Moose » Wed Nov 15, 2017 9:31 pm

Many thanks to everyone who chimed in - such a valuable DIY home improvement forum :D

I should have mentioned in the OP that counter space is far too precious to devote it to a microwave. And I'm not dying to make massive revisions to my kitchen only to sell in a few years, so I think I'll replace the microwave in the over-the-range position and see how it works. If it seems cheap enough to have someone make an exterior vent, I'll do that and see if it works, otherwise I'll just keep dreaming of a real hood vent in my next house...

Thanks, again, everyone. (And, yes, I have a grill for the steaks, too)
Pardon typos, I'm probably using my fat thumbs on a tiny phone.

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CaliJim
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by CaliJim » Wed Nov 15, 2017 11:23 pm

Nearly A Moose wrote:
Wed Nov 15, 2017 9:31 pm
Many thanks to everyone who chimed in - such a valuable DIY home improvement forum :D

I should have mentioned in the OP that counter space is far too precious to devote it to a microwave. And I'm not dying to make massive revisions to my kitchen only to sell in a few years, so I think I'll replace the microwave in the over-the-range position and see how it works. If it seems cheap enough to have someone make an exterior vent, I'll do that and see if it works, otherwise I'll just keep dreaming of a real hood vent in my next house...

Thanks, again, everyone. (And, yes, I have a grill for the steaks, too)
Nearly a Mouse is sounding nearly like a boglehead.... he's got the frugal part nailed down. Waving dish towels doesn't cost anything and is good exercise.
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Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by 2comma » Thu Nov 16, 2017 12:09 am

z0r wrote:
Wed Nov 15, 2017 3:10 pm
celia wrote:
Wed Nov 15, 2017 12:27 am
Nearly A Moose wrote:
Mon Nov 13, 2017 10:11 pm
... I have gotten extremely skilled at waving a towel in front of my smoke detector while my wife and children huddle in the corner and ask whether the house is going to burn down.
OMG! It sounds like you have a fire hazard. People are trying to tell you about it, but you are ignoring them. :!:

First, the range and the microwave (and the dishwasher and refrigerator) each need to be on a dedicated circuit--no other appliances, wall outlets, or lighting can be on the same circuit.
Virtually everywhere in the US allows grandfathered electrical work, all the way back to knob and tube. This grandfathered work is by and large safe to continue using. The codes have evolved in the areas you mention not necessarily because of safety; consider that they're influenced by powerful industry members who want to sell more wire and bill for more circuits, combined with a bias for being extremely conservative. In the case of a microwave on an old shared circuit, it's safe because the load is intermittent and the circuit is presumed to be current-limited by a fuse or breaker.

Modifying the exhaust is not going to trigger a reevaluation of any grandfathered electrical status here. Presuming the wiring is correct for a grandfathered situation (and that situation was disclosed when purchasing the insurance) insurance won't have standing to now deny coverage.
celia wrote:
Wed Nov 15, 2017 12:27 am
Second, the top of the counter (and range) is usually about 36" above the floor. And you are usually required to have clearance above the range to prevent fires. No wood or wallboard or anything flammable can be within 32" above the range (per our building code in S. California). That would put the bottom of the microwave at 6 feet off the floor. The range is usually required to have a venting system at that height (unless it has a built-in venting system?).
OTR microwaves are designed to sit closer than 36" by being made out of things that don't burn, and including vents.
Celia,

I think the issue with the smoke alarm was that he was grilling steaks in a hot skillet. UL specs is 18" above the 36" stove top so the bottom of the MW is at 54". We don't have the extra counter top space so it's a good solution for us - I'm still mad nobody seems to make under cabinet coffee makers any more...

I see a lot of people here say they are out of style but I like the way they look and still see this installation frequently. Others have said above the stove is a rough environment for electronics heat/smoke/grease and such (they do have grease filters) but our last one lasted over 12 years and was replaced only because it was looking old and didn't match the new SS appliances, our new one has been in place almost 10 years. I'll admit I couldn't find a model with a quiet fan and even though ours vents straight up it is adequate at best and sounds similar to a jet landing.
If I am stupid I will pay.

random_walker_77
Posts: 459
Joined: Tue May 21, 2013 8:49 pm

Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by random_walker_77 » Thu Nov 16, 2017 12:30 am

Not for the OP, but maybe for other readers, if you're going to replace your hood, consider one of the ones designed for Asian cooking. They've got massive airflow, and can eliminate most smoke and odor even when frying bacon. Something like this

https://www.pacairusa.com/mainThisRHPro ... ID=SP-730S

You can tell it's strong if the suction can hold up a pot lid... (no joke)

(Link is to a representative unit. Prices seem to be in the $300-600 range. Here's another one http://www.posharpstore.com/en/cyber-sr ... range-hood)

hudson
Posts: 1223
Joined: Fri Apr 06, 2007 9:15 am

Re: Creating External Exhaust for Microwave over Range - Need Reality Check

Post by hudson » Thu Nov 16, 2017 6:14 am

Nearly A Moose,

I don't know if this will help, but this is my experience on the same sort of project.

As a DIY project, years ago, I vented my stove straight up through the cabinets to the roof with large sheet metal ducting. I put in a powerful overhead vent that worked well. The leaks were minor. A new roof fixed the leak.

I hired a contractor to remodel the kitchen. I wanted a microwave over the stove just like your project. The contractor hired a heating and air conditioning company to work around the new cabinets and add the ducting. I bought a microwave with the most powerful fan that I could find.
The vent setup looks good, but the microwave fan is loud and doesn't vent steam well. Maybe I need some kind of in duct blower?

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