Quietest inline fan for range hood exhaust

I'm planning to use an inline fan for a range hood - I'm going to have the canopy made by a metal fabricator. I'm putting the fan in the attic. I'm looking for something
- about 300 CFM max - can be speed controlled about all the way to 0. - doesn't make a hum or whatever when speed controlled. - Absolutely as quiet as possible.
I've heard that if you compare a small fan with a large fan that's turned down with a speed control to move the same CFM as the small fan, the large fan will be quieter.
Somebody at Fantech told me this wasn't true, that the noise just depends on the CFM the fan is moving. I don't believe this (she said other very dubious things), because I've heard elsewhere that a larger fan will be moving with a lower RPM when it's moving the same amount of air, so it would be quieter.
So, I figure I'd get about a 300 CFM fan and turn it down with a speed control. My range is very small and it doesn't need a big fan.
Some fans make a low-voltage hum when you use a speed control on them. Fantech said their fans do. Someone at Broan told me their inline duct fan doesn't have a low-voltage hum when speed controlled. I don't know how big of a deal the low-voltage hum is, compared to the noise from the fan motor.
What inline fans are quietest? They don't have a standard way of testing the noise from them, unfortunately.
I know stuff about reducing the noise that's moving through the duct - duct silencer, liquid soundproofing you can spray inside the duct. Etc. etc. My question though is about the quietest *fan*.
Laura
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snipped-for-privacy@adore.lightlink.com (Lacustral) wrote:

You might want to check what code is before you invest a lot in this setup. Seems to me there's issues with potential grease buildup on a remote fan for a range vent that causes this to not be allowed.
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Rick Blaine wrote:

That makes sense, considering what the newspapers here in Red Sox Nation said a couple of weeks ago when two Boston Firefighters lost their lives because a burning double ceiling above the kitchen in a Chinese restaurant collapsed on them.
A fire started above the "upper" of the two ceilings and it was stated that it may have been burning for a couple of hours before the staff noticed it and the Fire Department arrived.
The proximate cause was blamed on grease leaking from unsealed joints in the stove exhaust hood duct and collecting above the higher of the two ceilings for ages before something touched it off.
The article stated that the restaurant owner had dutifully paid a "grease cleaning" contractor to service the exhaust system as required, but whoever did the job skimped on checking the full duct run and/or didn't refuse to do the job because they couldn't access to the full run of the duct due to the "double ceiling" situation.
Jeff
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Lacustral wrote:

I have no idea which is quietest; however...
1. I have a Broan. Don't recall the CFM but it is maybe 10-12". No speed control
2. It is about 25' from cooktop
3. The only way we can tell it is running is by looking at the switch...I used a switch that lights an LED when the switch is on.
Be sure your hood fabricator includes a grease trap - that's just coarse wire mesh - that is easily removed for cleaning.
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dadiOH
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This is nice and quiet, and IMO, better quality then the others you'd mentioned.
http://us.exhausto.com/files/pdf/Brochures/3921002.pdf
-zero

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Hope their fan is better than their home page. I got cross-eyed and still know nothing about their fans.

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-zero (sometimes.zero snipped-for-privacy@gmail.com) wrote:

Their fans seem mostly too big, I need something about 300 CFM. But I could check out the smallest pizza oven fan. I need something inline though, that's meant to be inline in the ductwork, I'm not sure if their fans are inline fans.
What I'm looking for is an inline fan that's engineered to be quiet. You can have fans pulling a lot of CFM that are quiet. The motor has low RPM, so that cuts down on motor noise.
Broan says their inline blower has a "low RPM" and is quiet. But they didn't know what the max RPM is, though the technical support person said she'd try to find out.
The whole arrangement, having a range hood fan inline in the ductwork in the attic, is something you can buy as a high-quality range hood. Some of Broan's range hoods can be used with an external blower. The Broan blower ILB3 is what I was looking at. I know this arrangement isn't contrary to code. All the code says about kitchen exhaust so far as I know is that it has to be rigid metal ductwork and a backdraft damper. Yes, I would put a filter in it. You can buy custom size filters for range hoods online.
I eat a very lowfat diet and don't use grease for cooking myself, but I do want to allow for the possibility that someone else might use the arrangement for cooking with grease. My ceiling over the stove hasn't gotten dirty, even without a range hood.
Laura

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Check in bathroom supplies I will sale you one $50.00 6" OD or 8" presently not sure
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-zero (sometimes.zero snipped-for-privacy@gmail.com) wrote:

I wanted to say thanks for telling me about exhausto. They have inline fans, they have one that's meant for chimney ventilation which should be fine for a range hood. It's speed controllable, the guy said it doesn't make a low-voltage hum. It's almost 500 CFM, which is a little more than I was thinking of, but actually this much CFM would be useful. I don't need that much for the range hood, but it'll be useful for times I want to clean the air out of my house quickly. It's 1600 max RPM, so it's very quiet. Fantech's fans run at about 2600-3000 max RPM. And I like exhausto's speed control. It has numbers on the dial, which is useful.
So anyway, this is helpful.
Laura
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wrote:

Good. Your much welcome!
-zero
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On Sep 14, 6:58 pm, snipped-for-privacy@adore.lightlink.com (Lacustral) wrote:

Consider an exterior wall fan, then you wont have to worry about grease in the attic, or noise, heres one:
http://www.rewci.com/faexfa.html
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Any fan rated "Suitable for use over cooking equipment" (within 10' of a range or cooktop) will NOT be able to be varied in fan speed. For one thing the motors are usually rated "continuous air over" (meaning that a continuous airflow of a specific minimum is needed to cool the motor), and (as others have stated) that duct and fan would become coated with grease is short time. This is an extreme fire hazard (whether you cook a lot with grease or now. Just the products of cooking alone can become a problem in a duct.)
Were you looking for home use or commercial?
For home use, the quietest fans are the ones located on the roof, inside the exterior weather cover. And they are also the most expensive.

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Dennis ( snipped-for-privacy@npcc.net) wrote:

That isn't true. There are "infinitely variable" inline fans for range hood exhaust. Maybe some range hoods come with an "infinite variable" fan in the hood (you turn a dial to turn the fan down allthe way to 0). Fantech's fans can be speed controlled to 0. Exhausto's fan is nice in that it has a door that you can open to clean it, so it can be cleaned at home with soap and water, they say. I don't think Fantech's fans are openable. Apparently either BESF or RSIF from Exhausto is good for inline range hood exhaust.
Laura
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I stand corrected. I wasn't aware of these fans (a little more pricy than what I'm used to seeing in my inspection in the plan's materials.) They do advertise that they include an infinite speed control for the fan, which would appear to be exactly what you were looking for. Definitely not your everyday range hood (as the price would indicate).

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