The range in my house is one of those big honking Viking things (36″) with four burners and a griddle, but I can’t stand the sound of the fan in the hood and was thinking of removing it and mounting a remote/external one (the 6″ pipe goes about four feet over above the cabinets and exits out a wall).
One thing I read said you calculate the CFM you need by multiplying every foot of range you have by 50. That would mean the 350 CFM inline fan the guy at the store told me about would be adenquate. But then the Viking people tell me I need a 1,000 CFM sucker. I don’t know who/what to believe. Can anyone provide any guidance?
Thanks in advance.
Replies
you might try also posting in fine cooking forum
350 CFM for a 36" stove? Sounds very inadequte
bobl Volo Non Voleo Joe's cheat sheet
Two things,
My appliance guy makes his recommendations on size of exhaust fan based on BTUs produced on that range rather than size of range. Some 36" ranges have bigger burners than others.
It also depends onlength of pipe, size of pipe and number of elbows. I'm not sure that 6" pipe will carry more than 600 CFM. You might have to up it to 7" or 8".
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Those big honking Viking things are typically installed with more than a 6" pipe. The pipe may be acting as a choke point, creating turbulent flow, and thus noise. I consider 8" vnet pipe a minimum for exterior wall applications, with 10" being preferable for longer runs.
I'd venture that your range has the standard honking 15000BTU burners. A vent approaching 1000cfm would be accurate. I like 1200 CFM, with the fan being on a rheostat so you can adjust the CFM for one burner on a low setting to four burners on full flame. Typically, though, you'll never see all burners on full blast.
Two schools of thought on remote fans:
If the fan is located in the hood, a qualtity fan will have "squirrel cages" or centrifugal fans, that will spin the vaproized grease out of the exhaust before sending the exhaust into the vent pipe buried in your ceilings and walls. Realizew that the exhaust pipe is under positive pressure, so unsealed seams in the pipe will result in escaping exhaust getting into the ceiling and wall cavities. The fan noise is heard since it is in the fan itself.
If the fan is remote, their is usually a screen filter at the top of the hood to screen out grease droplets. While the fan is remote, the screen often causes turbulent airflow noise as the exhaust passes through it. Also, the more dirty the screen gets, the less airflow you get, and more noise is created by increased turbulence. If the screen does an inadequate job of removing grease, you're pulling hot, greasy air through cool metal pipe. With restricted airflow, the grease and moisture can condense out in the pipe. The exhaust pipe is under negative pressure, so any unsealed joints or leaks will result in ambient air in the framing cavitites being brought into the exhaust pipe, reducing effective airflow from the hood itself.
The above are the extremes. Not many installations reach those extremes.
Sizing the vent? Use the manufacturer's recommendation as a minimum. As piffin wrote, a 24" gas cooktop with four 15K BTU burners will need more exhaust capability than 24" four burner resistance cooktop. And again...though you need to take into consideration the output of all burners, it's unlikely they'll ever all be fired up at max output at the same time.
In your system, I think the 6" pipe is the weak point. With a pipe run as short as your run, a remote fan may be a good option. Still, a remote fan pulling air through a 6" pipe may still be too noisy.
I have a 36" Dacor range with 6 15000 btu burners and a Viking range hood with a roof mounted 900 cfm blower. I think we have 10" duct work and two bends that are a little less than 90 degrees. The remote blower does cut down on the noise significantly but you'll still hear it. At the lower settings it's very quiet but when it's cranked up all the way there is a fair amount of wind noise. The 900 cfm blower moves plenty of air through the hood in our installation. I can create lots of smoke while cooking and it moves it on out.
Gary
Dacor makes a nice product...good choice. It also sounds like you have a well designed set of ducting.
JD, you're welcome.
If anyone cares, I think Vent-a-Hood makes the best vents and blowers.
I smell dinner...
I haven't seen a vent-a-hood. I like the dacor better than the viking but that viking remote fan definitely is quieter.
I think there are actually three sounds,
Turbulence/air flow
the Motor itself
vibrations from the motor and the turbulance druming on the metal vent.
so you can reduce a lot of noise by using heavy duty vent and stabilizing it well..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
If you're interested:
http://www.ventahood.com/
They have general price ranges on the site, though I don't know why. No one around here even comes close to approaching the low end of their published price ranges.
Thanks to you and the others for the thoughts. Helps a lot.
I forgot to mention in my previous post that Viking's web site says that you will void your warranty if you use another manufacturer's blower with their hood...
"I forgot to mention in my previous post that Viking's web site says that you will void
your warranty if you use another manufacturer's blower with their hood..."
What is there to fail in a hood other than the blower anyway?
It might be they are worried about it failing to su_ck stuff but that's tough stuff shore 'nuff..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Most Viking hood include halogen lights, a heat lamp, and sensors that automatically activate the blower when it gets too hot.
But another blower wired in the same way would still be activated by the same control. No sweat.
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Yes, but that is notthing significant to replace if it does fail and there is no real reason to expect that it would fail using a different blowers.
Makes no difference to me--I was just mentioning it so he would know.