External would be much quieter, and pretty easy to install.
Use a continuously variable control to turn it down (More quiet too) we rarely need to run ours on anything more than the slowest speed, and at that speed all you hear is a very "Slight" hum.

Gary

Even if I only have 4' of pipe between hood and fan?

I will measure mine tomorrow, but I suspect mine is even shorter that 4 feet.

Gary

I was told that if you're vent straight out the wall an external blower of the kind I was looking at would actually be louder because the unit itself is louder and it's right there on the same wall. Don't know if that's true, but it came from a knowledgeable source.

Gary, can you also say which equipment you're using?

It all depends on the SPECIFICS of the models you are considering. A really nice internal blower is likely to be more quiet than a POS external blower.

An internal blower is almost always easier to install, no separate power line, no getting a ladder outside in the heat or cold or drizzle or up on the roof ect...

A lot of noise is generated from the movement of air through the ducts, and especially through the filters. The noise from good quality motors is likely a relatively small component of the overall noise.

Small ducts make more noise than large ducts.

Mesh filters are louder than baffle, which are in turn louder than filter-less models (such Vent-A-Hood and some Cyclone type designs).

The noise from good quality motors is likely a relatively small component of the overall noise.

Agreed, but those pesky squirrel cages or fan blades that those motors are attached to make a bunch of noise.

Mesh filters are louder than baffle, which are in turn louder than filter-less models

Yeah, so I've heard. Someday someone will tell me why there's no noticable difference in noise of my mom's 360CFM hood whether the mesh filters are in or out.

To the OP - Sorry, but I don't know the answer. This topic has come up before and is always met with vague answers and conflicting opinions.

Agreed, but those pesky squirrel cages or fan blades that those motors are attached to make a bunch of noise.

They do. Centrifugal (squirrel) fans are quieter than bladed fans though.

Yeah, so I've heard. Someday someone will tell me why there's no noticable difference in noise of my mom's 360CFM hood whether the mesh filters are in or out.

That's a good point - probably at the lower CFM ratings, there isn't enough air movement, so the motor is louder than the air. Any hood putting out 400 CFM or less isn't going to make a lot of noise (~1-3 sones).

Unfortunately, as with most other things, a lot of different factors play into the final answer, and it will differ based on your specific application. What I did was I went to a place that had a number of different models hooked up, and I found the Vent-A-Hood was incredibly quiet, yet still moved a lot of air (900 CFM equivalent). All the other ones I tried were extremely loud at their highest settings. I tried some Viking hoods with remote blowers (roof mount) at the local distributor, and they were pretty quiet, but also didn't seem to move much air (I was quite surprised).

"900 CFM equivalent"

what are you basing this on?

Anytime you read this you can bank on the fact that the marketing huchsters have been massaging the copy. It EITHER moves 900 cfm or IT DOESN'T.

Kinda like I weigh the equivalent of 276lbs. Or it the equiv. of 6 gallons a minute.

Air moving through pipes is measured in CFM be it in the kitchen exhaust industry or the woodworking dust extraction , or materials handling (cereal production) industries.

Also find it interesting you find the VAH quieter, someone around here has compared theirs to another unit in the real world with a SPL meter and found the VAH much louder.

I was in a store that had a number of hoods hooked up. I ran them all at maximum speed, and found the VAH to be the quietest.

CFM ratings are a bit of marketing massage, it's true. The vast majority of companies measure CFM and sones/dB without the filter installed - the filter itself will reduce the actual CFM and increase loudness. VAH hoods don't have a filter, so while they are *actually* moving 600 CFM, they are equivalent to other companies' 900 CFM rated products, because other companies lose 33% effectiveness due to the filter (i.e., other companies quote 900 CFM, but they only ACTUALLY move 600 CFM in real-life usage).

The analog would be that you weight 276 lbs - on Earth. You could say you weight the equivalent of 276 Earth-lbs on the moon, but you'd actually weight much less than that.

It's possible I've bought into VAH's product marketing. I can't provide any measurements - I do not have the equipment to measure sound pressure, or air movement. But I do have a hand to gauge air movement, and ears to gauge noise, and that's what I concluded based on the models I checked out. It's enough that I'm purchasing a VAH for my kitchen remodel.

I've also had three independent appliance chain salespersons tell me VAH is among the quieter models available. They may or may not be in the pocket of VAH, or just beholden to marketing hype, but I have yet to come across any evidence to dispute VAH's claims (whereas I have first-hand experience in favour of them).

Of course, my experience applies only to the particular models I tried, so whomever else tried the measurements with the SPL meter may still be correct (I'd be interested to know which model was quieter than the VAH, so I could investigate it). Of course, using an SPL meter is a science as well, so if the hoods were in completely different environments, that's not an apples-to-apples comparison either.

"because other companies lose 33% effectiveness due to the filter"

According to whom? VAH ?

Sure they loose cfm, but and average 33% is not only inaccurate it's a pretty nice neat number for VAH wouldn't you agree? Not all companies flub their ratings, and there is industry movement to conform to a standard so the consume can get a good picture on a level playing field. HVI is setting standards and those firms that have good products, service and reputations are getting on board.

It all depends on the type of filters, the ACTUAL fan moving the air, the install, 5" pipe or 12", straight shot or 16 90 deg. bends, ect...

Filters don't always increase loudness, with an internal powerpak and mesh filters many hoods actually are quieter at the cooks ear because the filters block out the motor noise which can be louder than the noise of the air passing through the filters.

"The analog would be that you weight 276 lbs - on Earth. You could say you weight the equivalent of 276 Earth-lbs on the moon, but you'd actually weight much less than that. "

This is the same clever BS that VAH is clouding the pool with. I weigh 276 pounds on earth, in the ocean, on Pluto, or anywhere. The readings of my weight might vary depending on locale and measuring devices but I'D STILL WEIGH 276lbs. Same as a blower system moves 900 cfm -or- it doesn't. If my hood moves 900 cfm at the inlet and yours moves only 600 then you have a problem with customers comparing specs, especially in the USA where many think bigger is better. You might then try to point out that my measrements are flawed (and many hood co. do this) but how am I to really know that YOUR measurements of 600 cfm aren't puffed too? I really despise people who resort to banging on someone else's product or service instead of focusing on why theirs is good.

Showroom setting are not the best place to guage a hood's performance or loudness. They are rarely if ever hooked up to ducting to the outside or with remote or inline blowers.

"o if the hoods were in completely different environments, that's not an apples-to-apples comparison either."

this illustrates my point exactly which goes to show you you can't trust your ear or the marketing dept. Also ask to see someone's 5 year old magic lung in a home setting , take it apart and see if you'd like to clean it out.

My questions would be "Why is Vent a Hood the only hood that introduces Grease into the blower" Everyone one else tries desperately to keep it away from the inside of the blower with baffles or mesh filters.

As to Vent a Hoods claims of less noise, more cfm's with a smaller blower i feel its smoke and mirrors, they also claim they have never had a fire start inside a hood in a residential kitchen, i was a fireman for 10 years now selling appliances for 5 years and i have never heard of ANYONE who has had a fire start in the hood again smoke and mirrors.

ants.....makes a good point about cleaning the blower, because the vent a hood has sucked so much grease into the blower it needs cleaning, to remove the tray is easy BUT to take the actual blower down and clean and put it back in place is not so easy, maybe someone has been to a store and seen a sales person take a blower down with a range below it for cleaning and then replace it? if they have i feel confident its not as easy as the sales person first suggested.

Noise has a direct relationship to movement of a large volumes of air, (which is why we buy hoods) if you don't have much noise it can be said that its not moving enough air to do its job, just wave a stick in the air slowly it wont make any noise move it fast it make noise because the air is been moved / disturbed. Installing the correct size duct is also important, make the duct work too small and you will get more noise than if you used a large duct, again blow down a 8" straw and then an 8" garden hose the hose is much quieter, then we come to how many turns and what angle those turns are, then comes how far do you need to blow the smoke once you suck it into the hood.

IMO people make this a hood decision too complicated its not, it comes down to the following.

1) Function or form

THEN

1) Location of blower
2) Duct size
3) Distance

Which brings us back to the original question "will my hood be quieter"

IMO if you don't have distance between hood and blower you will not significantly reduce the noise.

When you are the biggest name in your field you can say anything and it will be believed.

I don't know that much about the technical stuff, but when I was looking at some installed hoods at the showroom, and was startled at how loud the one that was like my old hood was, the salesclerk said that it was because there was no ductwork attached so that all the noise just escaped out of the top, whereas other hoods had some dampening because of cabinetry around them, and stuff like that. This made more sense than that they'd have made them louder in the intervening 8 years.

I am going to address a number of points raised here. I am not a Vent-A-Hood employee, nor a shill, but I do like to make sure everything is stated with accuracy and clarity. My only association with Vent-A-Hood is that they are currently the leading selection in my own kitchen remodel (and is subject to change if someone shows me something better). I like to see people's opinions, so I'm enjoying the debate, I hope atct86 is too.

[To antss]

My statement on others products losing 33% effectiveness is not directly from VAH. It is a calculation I made based on their "effective" CFM ratings. However, the explanation for the effectiveness is plausible, even if one doesn't necessarily buy the exact figure (33%). If someone has a working knowledge of fluid dynamics, I would be glad to know if 33% is a reasonable number to use for diminished air moving capacity due to filters.

I am quite aware of HVI, but I am also aware that not all companies submit their products to be HVI certified, and the HVI documents do not state whether filters (if part of the product) are a mandatory part of the testing.

So yes, while I would love to see every product tested by HVI approved labs for objective testing, that's not something that occurs now. It's useless to me unless the products I am considering are HVI certified.

In terms of comparing internal to external fans, yes, the exact configuration of the ducting matters. Clearly, the farther away the external blower is, the quieter that noise component will be - but also the less effective it will be.

For internal to internal, ducting matters only for CFM. But my assumption when comparing internal blowers is that the ducting is the same for all of them, since regardless of which one you buy, it will be used in the environment. At the showrooms, each blower is the same in terms of ducting - as in, they have none. But the blower is right there by your head (again internal blowers only), so the comparison (both CFM and noise) is legitimate. Even in my kitchen, an additional 3 feet of ducting + one 90 elbow won't matter, because the relative results of my product comparison would be the same.

I can trust my ear and I do, because it's what I use to hear things with. It's a bit of a silly statement to make - I should trust some SPL meter more than my ear? Are you going to tell me if I find a VAH at max settings quieter than product X at max settings, that the VAH can be louder in my kitchen than product X? (Assuming both are internal blowers, again.)

I have taken a VAH apart, in the store. Easy enough to do, easy enough to clean. The housing is nice and large, if you clean it regularly (like you would a filter), should be a snap. The motors as (supposedly) not in the grease flow - not sure how they manage that.

My weight analogy is dead on - the fact is that you do NOT weight 276 lbs anywhere but Earth, or places with very similar Earth gravity. You have the same mass everywhere, but not the same weight. Unit definitions aside, it isn't clear to me why I'm spouting BS, nor am I "banging on someone else's product" as you claim. If instead you are talking about VAH, well aren't really bashing other products - they are simply promoting their own effectiveness. They also claim their sound ratings were verified by an independent lab, for whatever that's worth. You can believe them, or not believe them. I went first-hand to verify their claims. What VAH is trying to do is say, hey, our blower moves 600 CFM after you install it. This is (supposedly) equivalent to 900 CFM rating from competitors, because those products only really move 600 CFM after it's installed with the filter. That is VAH's perspective. Maybe it's true, maybe it's not, I don't know. I do know that the VAH moved a lot of air (no ducting), and some other products weren't nearly as effective (again, no ducting) but at the same time louder.

[To trevorlawson]

For the record, VAH claims not to introduce grease into the blower ("The Magic Lung motor is also enclosed in a specially designed housing to keep it out of the grease flow"). But VAH is NOT the only vendor to be filterless. Cyclone range hoods (http://www.cyclonerangehoods.com/) also has filterless designs, and I think there was another brand I saw (forget exactly who).

More CFMs, quieter and less noise with a smaller noise is not impossible (just unlikely), if you have a significantly more efficient design. It is, however, easier to make a quieter, more powerful blower that is the same size or bigger. (For the record, you can get the same or more air movement from larger blades, and you can get quieter because the larger blades don't need to rotate as quickly - fewer RPMs.) I don't think VAH claims to have a smaller blower, from what I've read.

VAH does NOT claim they have never had a fire start inside a hood in a residential kitchen - their exact quote is "prevents fire from entering the ductwork." Of course, any internal blower could have an electrical fire, but VAH is just saying a fire in the kitchen will not travel up the ducts (into, say, an attic) while the blower is on. Smoke and mirrors indeed.

I will reiterate that, in a showroom, first-hand, I heard how little noise the VAH put out while still moving significant air, compared to the other models I tried in the same showroom.

Back to the original question, you are very absolutely right. The distance of the external blower to the vent hood matters for noise. If it's just outside the external wall, it may even be louder than an internal blower. If it's far away - it probably won't be - but it may (or may not) introduce a lot of noise into some other room if not installed properly with sound isolation to the wall or roof it is installed on.

I don't imagine an external blower is any easier or more difficult to install than an internal blower.

basilisk - Do a search for clinresga's post titled something like "the truth about VAH". He has a VAH with a straight-forward duct run in a vacation home and a ModernAire liner coupled with a Fantech inline and a convoluted duct run in his main home and claims the latter to be much more efficient, much more quiet.

If you want to get technical seach out posts buy a guy named kaseki (I think) and read them till your eyes roll.

Everyone's got their own anecdotes. Many people have VAH's and are happy with them. Some people like you have seen them somewhere and think they're nice and quiet. Some people like me have seen them in a home with a short straight duct run and couldn't be paid to have that racket in my house. Take your pick on whose anecdote/propaganda you feel like following. Unfortunately there are a TON of variables in this field and to date I have yet to see anyone who can put them in writing objectively and succinctly.

"the farther away the external blower is, the quieter that noise component will be - but also the less effective it will be. "

Not the whole story. Sure it will draw more cfm at the inlet then 10 feet down a duct, but you don't really know where the rating was taken at do you? Anyone reputable will have some sort of duct length in their CFM calc. , especially if participating in HVI.

"Are you going to tell me if I find a VAH at max settings quieter than product X at max settings, that the VAH can be louder in my kitchen than product X"

Yep - that's exactly what I'm saying, an SPL meter is more accurate than your ear. However , sound is a tricky animal, so I DO NOT discount what you perceive or even like. I'm simply saying perception isn't always the whole story.

"VAH claims not to introduce grease into the blower "

Yep, they won't guarantee it though. Take apart one that's been in service a while and have a look see.

"More CFMs, quieter and less noise with a smaller noise is not impossible (just unlikely), if you have a significantly more efficient design. It is, however, easier to make a quieter, more powerful blower that is the same size or bigger. (For the record, you can get the same or more air movement from larger blades, and you can get quieter because the larger blades don't need to rotate as quickly - fewer RPMs"

You best pull out your fluid dynamics tomes as this isn't the place have this discussion. Fan size / rpm / and cfm do not follow a linear relationship. Posibility, and what happen in the real world are way different - especially when you have a limited budget and a small market share.

"I don't imagine an external blower is any easier or more difficult to install than an internal blower"

Oh yes the are, well the majority of them anyway.

"I will reiterate that, in a showroom, first-hand, I heard how little noise the VAH put out while still moving significant air, compared to the other models I tried in the same showroom. "

Don't doubt it, but that's not a real world situation and the showroom can't do justice to a 1500 CFM external powerpak that I might need for say a 24" BBQ grill or 40,ooo btu wok burner. Or a really long duct run with many turns. What's the max cfm for VAH these day 1000, 1200? Might not be enough in some instances.

"never had a fire start inside a hood in a residential kitchen"

so what - if it's a concern you'll get a fire supression system like a commercial kitchen - and they all have external mounted blowers, that should tell you something right there.

I'm not a VAH hater, have speced them before , even to good friends. They are just not everything they claim.

[ya_think]

I did a search ... and it came up empty. Perhaps the thread has dropped off the archive. I did a search on clinresga, and another ventilation thread came up, but I didn't not see anything posted in that thread, either by clinresga or kaseki that contradicts any of my statements.

That being said, the setup is comparing a VAH internal blower to a Fantech inline blower. Convoluted ducting or not, you can always use a significantly more powerful inline or external blower and get the same capacity as any internal blower, and it will (from a motor noise point of view) be significantly quieter as long as the blower is sufficiently far away.

The key here is that the original poster is already on an external wall - so my assumption is that the external blower would not be that far away from the hood itself.

You are absolutely right about a tonne of variables impacting the actual characteristics (efficiency and noise). I really wish HVI certification were required for all fans (with filters) - that would give everybody a true relative assessment between products. But unfortunately, we don't have that now. All we can say is what we have personally experienced, and how some aspects of physics plays into things.

[antss]

I am pretty sure all blower manufacturers provide CFM ratings at the inlet of the motor with zero ducting. In my research, I have not seen any indication otherwise. As far as I know, HVI testing doesn't using ducting either. Maybe my statement should be: "for the exact same blower, a longer duct will reduce the air moving capacity at the same effort level, or will increase the power required for the same air movement."

And, actually, an SPL meter is NOT more accurate than my ear - perception is everything. The SPL, which gives you a single dB measurement, actually weighs all the various frequency components into one number (there are actually a number of different weightings that are defined, including a flat distribution, none of which match the frequency response of my ear). My point is that, the SPL could detect a peak in a frequency that nobody can hear. If nobody can hear it, why does it matter? Given that one has to live with their range hood in operation every time they cook, I would say perception is king. Put it this way: if blower X has a minimal SPL rating, but in my kitchen it drives me crazy vs. Y that has a higher SPL rating in identical test conditions, which blower does it make sense to buy?

I will concede that I don't know whether grease really gets into VAH motors or not. VAH cleaning instructions include the housing (easily removable) and the blower wheel (clean in place, or remove with a hex wrench). The warranty is five years for the motor, so I assume that not enough grease gets in to mess up the motor within five years. Given that the motors are enclosed in a different housing, it shouldn't be that difficult to proof most of it against grease - the trickiest part would be the motor shaft enters the housing, but most of that ought to be protected by the blower wheel itself. Grease is sneaky though.

I never claims that fan size / rpm / cfm follow a linear relationship, but you can make general claims about them with the proper assumptions. For example, for the same blade design and RPM, a bigger fan will move more air than a smaller fan. But the very fact that there are many complex variables and that they do not hold to a linear relationship means that you can very well have a smaller fan that is both quieter and moves more air than a bigger (poorly designed) fan. Just saying it's plausible, and shouldn't automagically be dismissed as 'smoke and mirrors'. (And I've never read or owned a fluid dynamics tome.)

Once more, I reiterate that I only compared internal blowers to internal blowers in the show room (the exception being a Viking external blower I saw at the distributor - different location altogether) - which happens to be a reasonable simulation of my particular environment.

The majority of them [external blowers] are... what? Easier or harder? Harder, if the blower is going somewhere other than the first floor (second floor, or roof application). But the original poster asked about 4' of ducting, so I assumed first floor - in which case, just mount the thing onto the brick veneer (more annoying) or siding (less annoying). Running the electricity 4' out isn't all that difficult either.

I agree you can't compare against a 1500 CFM external powerpak (unless it was specifically installed in a similar config - pretty unlikely), but a would also say that 1500 CFM (or external blowers) are not typical installations. The original poster did not specify the capacity they were looking at, so I made an assumption that it would be in the 900-1200 CFM range. VAH maxes out at 1200 CFM (or 1800 "equivalent" CFM).

Regarding the fire starting inside the hood, I don't have that concern, I didn't even say that, I was merely correcting the misinterpretation of a VAH claim. On the other hand, why say no to a bonus safety feature?

I realize that all companies, including VAH, will stretch the truth, massage the message, spin the numbers, in their favour. No problem. But I have yet to hear anyone point out anything really wrong with VAH performance claims (grease in the motors notwithstanding). They've been in business for 75 years - if there was something really wrong with their claims, I'm sure they would have a much worse reputation at this point (or been sued all to hell).

One thing I do like about some of the VAH models is that the halogen versions often have a heat sensor that automatically maxes out the fans when it gets too hot. The downsides is that the lights only have two settings (instead of being dimmable), and the fans have discrete settings (which is common, but I think I might like the flexibility of analog dials). Also, they don't have a delay timer stop feature.

Anyway, I would agree with your (antss) first post - it does depend on the specifics. I am in a similar situation as the original poster, and I decided against the external blower in favour of an internal blower, based on the assumption that good quality motors and blade/wheel designs are a lesser noise component compared to air movement, and I specifically went with VAH because a filterless design is, in general, quieter than a filtered design (backed up by my "anecdotes".

Sigh. I talk too much.

"On the other hand, why say no to a bonus safety feature? "

It's not a bonus really. That Wolf hood with external blower is just as likely to not have a fire start in their duct.

"I assume that not enough grease gets in to mess up the motor within five years"

"For example, for the same blade design and RPM, a bigger fan will move more air than a smaller fan. "

Yes, but the larger the blade the harder it is to keep up the RPM's.

" means that you can very well have a smaller fan that is both quieter and moves more air than a bigger (poorly designed) fan"

Yes, but those in the same industry don't design poorly made larger fans to compete with smaller more efficient ones or they'd quickly go out of business.

Correct , but this is a bit diff than their claim that nothing gets up there.

" Running the electricity 4' out isn't all that difficult either. "
No, not really , but it's an ADDITIONAL line because power is fed to one location first and then routed to the other spot. so most electricians charge another $125 or so new construction.

" 1800 "equivalent" CFM)"

Again, CRAP !

VAH has not found the better mouse trap, if they had everyone would be jumping on board to copy them like all the pro range for home use copycats did with Viking.

Glad you like yours, it's not a bad product. All I'm saying is their cool-aid is not fat free and 0 calorie like the label says.

I have a VAH in my primary residence and an abbaka liner with a broan external 1200 cfm blower with maybe 3 feet of 10" ducting on our vacation house. No question, the VAH is WAY louder and there is no comparison to air flow. I have checked all the ducting on the VAH and its all good/clean etc. Go external with a large fan (lower speed and low noise) if you can afford it - you will not regret it.