Hoods, Noise and Venting Q & A
Q.
At 12:46 PM 9/5/2006, you wrote:
Hi Peggy,
Quick question:
I went to purchase our Viking Range and Hood and was asked and/or told the following so before I purchase, I want to make sure what I order will be accomodated in our kitchen plan.
1- I was told I had to order the 27 inch depth hood. Although, we talked about 24 inch depth.
Do you know of a reason why I should consider the 27 inch?
2- I have a choice between a 1200 or a 1500 CFM external motor for the hood.
Do you have a preference? (Which by the way, I didn't realize that the motor didn't come with the hood. Note to self.)
Thanks for getting back to me as soon as you can.
I would like to place our appliance order in the next day or so.
Hope all is well,
Monica
A.
The 27" deep hood will capture more of the smoke and steam and fumes off of the range than a 24" deep hood would.
A column of heated, greasy, air comes off a pan and spreads 3" in a 30" rise from the pan surface to the hood.
That means a 12" fry pan gives off an 18" diameter plume by the time it gets to the hood.
If there is no hood over part of the column, some of the greasy steam will rise to the ceiling and spread into the room.
There is no such thing as a hood that can capture and pull grease-laden air beyond its overall dimensions.
This becomes a cleaning issue over time.
There are other considerations though...
The height of the user(s) is definitely an issue.
I would hang some cardboard to mock up the bottom of the hood at 66" from the floor, sticking out 27", to see if it is an issue for the cook.
It likely could be...in fact, the 24" deep one could be an issue too.
Another option of course is to hang the hood higher to get it up out of the way.
Viking says we can go up to 72" high (although that is really marginal in my mind...it defies physics).
We already are using a 54" wide hood with a 48" range so we have the capture of the 3" in 30" rise covered on the sides.
If you go with the 27" deep hood we will have it covered in the front.
BUT the column of steam keeps expanding as it rises, so the higher the hood the bigger it needs to be to capture everything.
Raising the hood above 66" will again lose some of the steam in the front.
There is also the issue of venting the hood to the rear, which is desirable in this case.
If we raise the hood, that option likely goes away, since Viking recommends 24" of vertical rise before turning the vent pipe to the rear.
Unless your house has balloon construction (wall studs that go from the foundation all the way up to the roof), we only have about 24" available if the hood is mounted at 66".
I would use the 27" only if it is comfortable (or you can LEARN to be comfortable) using the range with the hood at 66".
If it's not, I would skip it and stick with the 24".
Now, on the hood motor choices:
I strongly recommend an INTERNAL motor for your hood rather than the external ones they want you to buy.
The reason to buy an external motor is touted as the noise factor.
This is a fallacy.
The noise a hood makes is directly related to how it is vented.
This is why I asked you to be sure to read the caveats about hood venting on your appliance specifications.
If you plug in a hood fan without having it attached to the vent and run it, you will find it makes almost NO NOISE.
The noise you hear when it is all assembled and installed is the noise of the air rushing through the vent pipes.
This is why I specify that all hood vent pipes be as LARGE as possible and as STRAIGHT as possible.
And, when turns in the pipes are necessary, that they be 45 and 45 degree turns rather than 90 degree turns.
90 degree turns cause AIR TURBULENCE in the pipes and contribute to noise.
I also specify that the pipes be supported and thoroughly sealed and insulated with pink fiberglass around them.
This is so they do not VIBRATE and create noise.
Vibration and turbulence are what creates the noise that people object to with their hoods.
Such vibration will be there, or not, no matter where the motor is.
Back to the hood motor...which should be 600CFM.
An internal motor pushes the air.
An external motor PULLS the air.
If you ever have a fire on the cooking surface, an external motor will pull the fire up through the pipes.
Cooking fires are the most common fires in the home.
An internal motor with a squirrel cage fan will cut off fire at the motor, so it will not get into the vent pipes.
This is why I recommend internal motors (they are also cheaper).
Safety, economy, nearly-quiet (when properly installed)...What more can you ask?
Share this email with your contractor.
Best,
Peggy
Posts
We just read and have a related question.
ReplyDeleteWe are going to get the 48" wide dual fuel viking range. It is 24" deep.
What cabinet depth do you typically use when this range is used? Also, what hood dimensions are appropriate, particularly with my wife being 5' 11" tall (66 probably would be too low)?
We are struggling as we need to use as shallow a cabinet as possible since the overall kitchen is very narrow.
The architects say they typically use 30" deep cabinets with this range, but we would like to use something less deep.
Would 24" work? How about 27"
Thanks.
Tom
I would normally use 24" deep base cabinets and 12-13" deep upper cabinets with a 24" deep Viking range.
ReplyDeleteI often work with "tight" kitchens and providing enough "negative space" is really important, so that the room does not feel cramped.
The hood size is more difficult for a tall person like your wife.
But, in fact, she will probably find that she can use a hood just fine as long as it is not at a height where it would hit her just above her eyebrow. For her that would likely be about the recommended 66" from the floor. Measure it and plan for an inch higher. It really doesn't need to be above her head.
To test this, go out into a clear area in your garage and pin up a cardboard box on the wall, at the right height and depth. Then some more boxes at the bottom to simulate the range size.
Cardboard is great, free, and keeps lots of mistakes from happening in my practice!
Then, both of you should get out your pots and practice "cooking" with the arrangement and adjust the "hood" as low as you can tolerate it.
As to hood size:
A hood 30" above a high-BTU, commercial-type range like the Viking should be at least 3" wider on each side than the range.
Since you will need to go higher, a 60" wide hood would certainly capture more than a 54" one would. I would only go with a deeper than 24" hood if you decide to mount it above her head. Aesthetically, that would look pretty awful.
Sometimes I have also done a recess and canopy IN the ceiling when I have needed a really big hood. They also work quite well, but are not as reachable for cleaning purposes.
There is a photo of one on a contractor's web story of his kitchen remodel, which I designed. It is on the LINKS page of my web site.
www.kitchenartworks.com/links.htm
Unfortunately my site has been down all day today. I'll tend to that tomorrow.
Good Luck Tom,
Peggy
There's a great discussion on venting bath fans on This Old House Discussions at:
ReplyDeletehttp://advice.thisoldhouse.com/showthread.php?t=969
Much of the advice pertains to hood venting as well.
Peggy
Hi Peggy,
ReplyDeleteWhenever it is windy outside, my viking hood is making terrible noise. It sounds like someone picking up a piece of sheet metal and droping it every few seconds, in a metal tunnel. My contractor came back and connected a turbine vent on the roof. Now it only added the squeaking noise and didn't fax the original problem.
What went wrong with the installation at the first place?
Thank you in advance for your advice.
Dan
Well Dan, it sounds like you have a real problem there. Not one you can learn to live with either.
ReplyDeleteThe only normal thing I can think of that would cause it is the back-draft damper in the roof cap blowing in the wind.
I used to have that problem with my own hood outlet which is in a roof eave just outside the kitchen. Whenever it was windy the damper would clatter. We fixed it by replacing the cap with another.
Sounds like your contractor has already tried that.
The next step would be to dismantle the entire ductwork run to see if there is a loose piece of sheet metal; and rebuild it with new material, or the existing material if something is discovered.
If you decide to go with rebuilding the entire duct run, good guidance on how to make it a quiet as possible can be found at:
http://www.abbaka.com/quiet-hood-design.htm
Peggy