Noise difference between inline and local blowers

5 years ago

last modified: 5 years ago

I want a quiet vent hood, and would like to hear from someone who has personal experience. I've read a lot of opinions, people say "it should be quieter", etc. but I haven't seen any posts from someone who has said they've compared the noise level between a hood with a local blower vs. an inline or remote blower.

I'll have a 36" Kitchenaid 90K BTU total, often cook a seafood stock for 4 hours or so, like to sear my steaks pretty hard, and cook some a lot of gumbos, curries, etc. I'll never have all burners on at same time, but I do want to be able to clear the air quickly and well.

Another question is, do I need 900 cfm, or can I get by with less?

Thanks!

Featured Answer

kaseki

5 years ago

last modified: 5 years ago

The logic is valid; the life experience may reveal what are not actual equalities in the two conditions. For the remote blower, we have potential ducting of sound back to the hood. Also blower assembly vibration can be transmitted by the duct skin back to the hood if care is not taken to attenuate this. Most importantly, the dominant noise from a blower is blade tip (and edge) induced air turbulence. It is unlikely that the hood blower and an inline blower will have the same blade contour, and they will also have different dimensions and blade tip clearances. So your noise may vary (YNMV).

On the plus side, the in-line blower for various reasons might be expected to have a better balanced and aerodynamic blade design, and this will make it quieter than some hood blowers for the same CFM vs pressure loss operating point.

In summary, I would expect comparative performance blowers to result in less noise at the cook's ear from the inline blower, but this is not guaranteed.

Conversely, in my experience and that of others here, what is nearly guaranteed is that a silencer in the duct path between hood and blower will greatly attenuate the blade tip turbulence noise, leaving baffle hiss as dominant noise at the cook.

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Comments (6)

kaseki
5 years ago
You can start by reading the many hood related threads here, followed by the slightly fewer make-up air (MUA) related threads. The CFM requirement depends on what you cook (or more exactly, the temperature you cook at) and the entry area of your hood, and the blower that will supply it will be rated higher by an amount that depends on its 'fan curve' versus the pressure losses in your hood and MUA systems.

Very few people have had both styles of hood ventilation and the means to measure sound pressure level for each in a relatively equivalent way. I think the only case here that I recall was by @clinresga about a decade ago, and that was a VaH with its internal blower vs. some other hood with a roof blower.

Whether roof or in-line blower, the use of a silencer will be needed between hood and blower if significant noise reduction is to be obtained.

After reviewing this forum's 'literature,' please supply the size of your hood to start.
barryv_gw
5 years ago
Kaseki is the expert here on hoods. I had a hood with a local blower, then bought a replacement hood that was way too weak, and a bit loud, gutted the hood of everything but the baffles and installed a remote inline blower with exhaust and found it to be much quieter. I did not take sound level readings before and after, but it seems logical to me that if you use a remote blower, of the same size and power as a local blower, there should be less noise at the kitchen because the remote blower is further away.
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opaone
5 years ago
You do not need high CFM's if you have proper containment area in your hood. You'll need to get a commercial hood for that though. Slightly more expensive but worth it IMO as you get much better exhaust of effluent, less energy usage, and quiet (on the low setting (540 actual measured CFM = maybe 900 CFM on a consumer hood) that we use most of the time you cannot hear our hood (though it will still suck a 40 page manual up against the bottom of the baffle).

More: https://www.gardenweb.com/discussions/5161173/hood-faq

Search 'commercial hood install' on here.
Chris
Original Author
5 years ago
Thanks, y’all. I checked the hood cabinet size can be up to 48-50”, based on the span between two windows. That’ll get me good capture area, and I could go with 40” insert.
Opaone, which inline motor did you go with? Thanks
opaone
5 years ago
Accurex XID-VG IIRC. More: https://www.houzz.com/discussions/5745986/commercial-range-hood-install

You should have at least a 42" (x 27" or 30") wide hood for a 36" range.