Choosing a Fan for Oven Venting
NICK KEENAN
| Posted in General Questions on
I’m working with someone who wants to install a wall oven but wants it to have a vent fan to suck up smoke when it’s broiling. My initial suggestion was just to turn on the vent over the cook top a few feet away but that was shot down.
So now I’m thinking of putting a cabinet with a top-hinge door above the oven, putting a fan in the cabinet, and a switch on the door so that when the door is opened the fan turns on. The question is, what kind of fan? Can I just use an inline fan with a regular register? Or do I need a kitchen specific fan? Do they make those for horizontal installation?
Thanks.
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We did this in a kitchen in one of our houses. No photos to post unfortunately. We built a box that stood out from the wall about 8", the width of the ovens. It was integrated with the design of the oven surround, and the crown molding wrapped around the box. Inside, we covered it with copper to make it somewhat easier to clean. There was a wall register inside connected to a duct and inline fan, just as you suggest above. Decent damper on the exterior. It was switch controlled. Worked very well. It didn't collect all the smoke from really aggressive broiling, but most of it. It certainly made a difference. Your hinged cabinet would probably work well. I'd probably include side flaps that slide into the cabinet when closed. Do consider cleaning, as the interior will collect quite a bit of grease from the smoke.
I would use a "muffin fan" for this application. You need one that will run on the voltage you have available (probably 120v), and I'd use a ball bearing fan for long life. Larger fans running slower speeds for the same CFM are quieter than smaller fans running higher speeds, so I'd try to go with at least a 4" or so fan. I've tried to pre-set some of the selections for you to find a suitable fan here, but I'm not sure if it will carry through the link:
https://www.digikey.com/en/products/filter/ac-fans/216?s=N4IgjCBcpgLFoDGUBmBDANgZwKYBoQB7KAbRACYBOADgHYAGANhAIGZ6xLbqWRHbYlZgX7VqAVl6MhdXrQbjWchZILzBqkN3Hkea6o3LCtB3XOo16varFbsQAXQIAHAC5QQAZVcAnAJYAdgDmIAC%2BBOI80CDIkOjY%2BESkIKxg3ByOLu6QXr6BIeEgALTkCDFQvgCuicSQZJIOhUWUZbFVNckQjYWldSDoAY6hQA
Note that you can get "current relays" that will turn a load on automatically when current is sensed in a wire. You could use one of these to make the fan come on automatically when a heating element in the oven comes on, and it wouldn't require any modification to the oven to make that work. A time delay relay could then be used to keep the fan on for some amount of time (10 minutes or so) AFTER the oven finishes running, to make sure you get any remaining smoke. All of those relays are readily available from Grainger.
Bill
Thanks Bill, I've been a Digikey customer for over 40 years and I wouldn't have thought to look at them for this application.
What about a grease filter? I assume the intake should have one? I guess what I'm asking is whether there is a combination grease filter and intake I can buy rather than having to cobble it together. And is mounting it vertically going to be an issue?
Thanks.
I've been with them for a long time too, back since the paper catalog was less than 1/4" thick :-)
Those fans don't care what orientation they are mounted in. I've used them vertically, horizontally, and probably a bunch of oddball angles in between. I haven't used one for a range hood applicaiton before, but I have used them for greenhouse applications. Expect somewhat shorter life in these kinds of harsh applications compared to the more common "cool of the electronic gizmo" applications, but they WILL work.
I would use one of the wire mesh filters as a sort of grease pre-filter, but you'll never get all the grease out. Just make sure the fan is serviceable since at some point you'll need to replace it, but that should be many years in the future. As an example, I have use Comair Rotron Tarzan fans in a greenhouse for decades, and they typically last around 15-20 years or so. That's in 24x7 service, in a high humidity location, and they even get watered ocassionally.
Try to get a fan with wire leads and not solder terminals or the small plug connectors. This will make installation easier. If you can only find the fan you want with the small two-prong connector, get a "fan cable" with the fan connector on it. You can also use the 1/8" faston terminals (I recommend AMP's Solistrand termainals here, with vinyl boots), but the premade fan cables are easier.
Note that if you will be concealing the fan in the back of a cabinet, an inline fuse is probably a good idea.
Bill
I would recommend something like this GE hood it is 21 inches deep. I would recess it in the wall so it stuck out 6 to 9 inches.
https://www.geappliances.com/appliance/30-Commercial-Hood-UVW93042PSS
It is designed for kitchen use with the correct filters and safety testing.
Thanks.
"It is designed for kitchen use with the correct filters and safety testing." That's more like what I had in mind. But the instructions say it has to be installed according to the instructions, and the only installation method in the instructions is over a cooktop.
Still looking for a kitchen exhaust fan that can be installed with the intake vertical.
My guess is if you refuse to install any product whose instructions do not show it over an oven will stall this project because your client has requested a solution for something very few people see as a problem want to spend money to solve.
From a liability point of view buying a random fan and building your own set of controls for a custom hood used in such a harsh environment put you at a lot of risk for what seems like very reward.
Walta
Thanks Walta. I agree with everything you're saying.
You can look at something like a Fantech RVF 6 which is rated for kitchen exhaust. You can do a simple setup with the fan outside and short run of metal duct to a liner bar grille mounted above the oven.
This is something I've been thinking about for a while, and not just for broiling. Any cooking or baking in the oven is producing particulates at a similar rate to using a cooktop. I guess most people subconsciously think that their oven is hermetically sealed when it's closed, but it's far from it. Cooking in the oven shoots up PM2.5 counts just like cooktop cooking does. I suspect this would even be the case with a combined oven/cooktop (range) with the range hood operating. I think a lot of the particles will be exiting the oven too far away from the hood to be sucked up.
> Cooking in the oven shoots up PM2.5 counts just like cooktop cooking does
Data? In my experience and based on visuals, the stove top is far more more likely to produce significant indoor pollution. Evidently a rotisserie oven can be an exception. Some commercial ovens are reported to have built-in vents (which makes a lot more sense than trying to capture pollution after it leaves the oven).
I only have the particle counts in my own house as data. But I think the burden of proof is being misplaced. We should assume it's a problem until proven otherwise. There's really no good reason to think, especially knowing what we know about air leakage in general from building science, that just enclosing the cooking inside a loosely shut box is going to effectively eliminate the air pollution associated with cooking.
When I say similar rates, I mean in the context of how it affects human health, i.e. within the same order of magnitude, not within 10 or 20%. Maybe the oven reduces the particles in the air by half versus a cooktop (that which sticks to the oven's inside walls). Would anyone consider a range hood that captured 50% of the smoke a good setup? Even if it was a 90% reduction, when you consider how much longer run times the oven gets in some homes, it might still be a concern. How does frying a couple of eggs for three minutes to roasting a chicken for 2 hours?
Vents inside the oven would be good for capture, but at a very high energy penalty unless there's some kind of heat exchange going on.
> vents inside ... a very high energy penalty unless
I disagree. The flow rate could be incredibly low, just enough that oven smoke exits via the exhaust vs the gaps around the door.
Interesting discussion! This begs the question, if the whole kitchen should have an exhaust, not just the range.
I know it's good practice with HRV's to have an exhaust in kitchens, but this is in adjunct to a range hood and isn't supposed to see kitchen products of combustion.
But with a wall oven added to the mix, and even toasters, griddles, waffle irons etc. In design considerations, would it be prudent to consider having a dedicated high cfm exhaust at the ceiling of the kitchen to catch everything? In lieu or in addition In addition to a range hood/ wall oven hood?
Thoughts?
PS. DC, I like akos's solution the best, a planar grille above the oven, basically a custom box from the cabinetry above the oven, lined with a tin plenum that transitions to 6" round, and 6" round duct to the RVF6 exterior fan. The grill sits flush with the oven face and with enough CFM, it 'should' suck the majority of the hot fumes as it rises.
The exterior fan approach is quiet and easily replaced from the exterior. Personally I wouldn't try to implement a grease catch if I couldn't find a simple solution, I expect most oven work to produce dry fumes from baking and broiling, vs ranges where people pan fry with oils or deep fry (my personal favourite for long term disgusting kitchen) which produce lots of airborne oil. This is my speculation from observation, I haven't done something like this.
In a couple of articles there has been the suggestion that an ideal kitchen would actually be closed and air sealed off from the rest of the house. That's the only way a general exhaust could be effective. That's obviously in conflict with how most people view the kitchen as part of the social environment of the house.
I have thought about this as well. A small fantech like: https://shop.fantech.net/en-US/hl--30--kitchen--hood--liner/p106628 (I bet there is plenty of grease in this smoke, so the way these inserts work captures that).
Our oven produces giant plumes of smoke when opened and roasting etc. Seems ironic that the induction cooktop just nearby got all the particulate removal love (a Fantech hood insert with an inline fan). I had hoped that the wall oven facing the hood would help, but the smoke goes straight up to the roof (there is a 4' hallway and a 12" cabinet between the wall oven and the cooktop) and very little makes it over to the hood.
I think it makes sense to have an inline fan and duct system serving two separate hoods, one for the cooktop and one for the wall oven (probably with a switched damper between them). Judging by where our smoke goes, the hood for the wall oven should go at roof height in front of the oven (either in a cabinet style drop down) or, ideally, recessed into the ceiling. A variable speed inline fan would be great for slow removal during long bakes. I suppose another interesting option would be to have a flexible duct so that you could pull the hood out like a drawer from the cabinet above the stove (mount the insert on drawer slides).
Better still, ovens should have a duct connected to them, with a button that one presses before opening the oven that sucks all the smoke out before releasing the door (sure, you loose some heat, but do you want it in your kitchen anyway, my air-conditioner says nope, in any case most of the heat is in the thermal mass of the metal of the oven, not the air). Doesn't do much for slow particulate creation over time.
Those saying this isn't a problem: where do the particulates from 2 hours of baking go? I suppose they might be incinerated or behave differently then when cooking on the stove, but my nose when I bake bacon says there's definitely something in the air!
> pull the hood out like a drawer
My cooking style is such that it's only the occasional single stove burner that needs exhaust ventilation. So a small movable hood would work at low CFM and otherwise be completely out of the way. Similar to a "Portable Fume Extractor".
> ovens should have a duct connected to them
Agreed.
Imagine this a few inches above a frying pan:
Yup, that's the ticket! PM2.5 seeking robotic arms :)
This is very helpful because it tells me what I should be searching for: a "range hood liner." Sometimes getting the right keyword is half the battle.
So rather than pull the hood out like a drawer what I was proposing was a top-hinge cabinet (like this: https://www.rockler.com/overhead-bin-hinge?country=US&sid=V91040&promo=shopping&utm_source=google&utm_medium=cpc&utm_term=&utm_content=&utm_campaign=PL&gclid=CjwKCAjw1JeJBhB9EiwAV612y9r7VL7ESGCKYFtFVh7NP2ytPJMmhDSWPJXiaMEzukikWy0IomW_DBoCtKIQAvD_BwE) with the hood mounted vertically in a vertical panel just inside the door.
I think having the hood move is going to be problematic. Of course, mounting the hood vertically is also problematic because it's non-standard.
One enhancement I'm thinking of is to have a door switch so the fan comes on when you open the hood and goes off when you close it.
Ok, so I have the solution! A flexible pull down hood thing :)
https://www.psalaboratoryfurniture.com/FumeHoodTypes/Snorkel
Actually I've thought this would be the right addition to a cooktop, especially an island cooktop. Something unobtrusive that pulls down from the hood liner or pops up from behind the island stovetop.
Hmmm, this one is sorta suspicious: https://fumehoodsinstock.com/laboratory-fume-hoods/exhaust-snorkel/
I'm still trying to persuade the home-owner that just turning on the range hood will clear the smoke from the oven -- so your post is really bad news for me!
Actually it's very helpful. Thanks.
hi guys,
I'm a bit late to this discussion but am having the same dilemma as I often broil in my wall oven and set off the alarm in my old house. As it turns out I'm actually having the external fantech fan mentioned above installed for my range hood anyway. Since the range hood is right next to the wall oven, would it be a mistake to add a mechanical damper to the range hood exhaust duct that I could then divert to a builtin hood liner above the wall oven when needed? Would the damper cause issues for such a greasy area? It seems like such a waste to install a second external fan when I have a perfectly good one attached to the duct right next to it... but I'm a bit hesitant to try a risky assembly that may one day cause a fire if there are valid concerns with such a setup.
A second thought would be to just install a passive grille into the side of the cabinet, so that air from the cabinet gets sucked through the side of the cabinet and into the range hood following those nice arrows that people on here love so much. But I'm not sure how helpful that would be given that the ovens seem to be designed to vent out the bottom front of the oven. Perhaps that could be modified, however...