Advice on Range Hood Ducting and Noise
pascalli
9 years ago
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HomeChef59
9 years agohvtech42
9 years agoRelated Discussions
Need the best range hood for a 6' duct and 60k BTU Range
Comments (9)I have your same problem but have no option to enlarge the vent duct due to the size of the space between the wall and ceiling studs. My previous vent hood was a 36" Cavaliere 900 cfm for a 36" Dacor Epicure cooktop. My new range is 36" DCS with 6 burners. Because I wanted a more substantial look, and after much searching and debating, I bought an AirPro 860 cfm (link below) The Cavaliere hood was more than what I needed for the 36" Dacor. I never turned it up past 1 or 2 while cooking. On 6, the highest speed, it was kinda loud but since I never used it on high it wasn't a problem. The AirPro has not been installed yet so I don't know what the actual noise level will be but it's rated at 35 / 0.7 to 67 / 6.5 (Lowest to Highest Speed). I just couldn't see paying thousands of dollars for a vent hood especially since my $400 Cavaliere had worked fine for 5 years. During my hood research one of the retailers did tell me there was a vent outlet adapter available online but because our contractor wasn't thrilled with that idea, I stayed with the 6" hood duct. Hope this helps. Good luck in your search for the right hood. Here is a link that might be useful: AirPro Hood...See More90 degree turn in duct over range hood? or move the range?
Comments (31)Ah! you missed one of the versions of a comment I have added to quite a few threads. Here it is again. Because we do not get to close off parts of the hood not receiving cooking plume impact, all of the hood has to flow the amount needed at the most stressing part of the effluent plume to be contained at the hood baffle space. How much do we need? Well the actual issue is what velocity of air has to be pulled past the baffles to ensure that the rising plume is pulled into the baffles and contained, versus reflecting off of the baffles and potentially curling back into the room, thereby escaping the capture area and hence removal by the hood. Hot cooking plumes over gas burners can rise at velocities of 1.2 m/s, or almost 4 ft/s. The baffle gap is roughly half the baffle assembly area, so to entrain the plume flow, it seems that some portion of 4 ft/s or 4 x 60 CFM per sq. ft. of baffle area is needed for good containment. Actually, there is usually space under the baffles larger than the baffles proper, so adequate flow is needed all across the hood capture aperture. I believe that I have about 900 actual CFM at home, pulled through a 10 sq. ft. Wolf Pro Island hood. This is equivalent to 90 ft/s. This works over induction hobs, including searing and wok cooking with a 3500W Cooktek wok hob. As it happens, Greenheck also looked into the requirements for CFM, perhaps like me doubting that 100 CFM per ft. of hood edge had a mathematical connection to the process of cooking plume containment. They have published a range of values, and I have taken the liberty of copying their relevant table below. So take your hood area, multiply by some value you believe in for actual needed flow, then multiply by another factor to account for blower ratings not actually applying to the conditions in which they are used. (Another topic written about here more than a few times.) http://www.greenheck.com/media/pdf/otherinfo/KVSApplDesign_catalog.pdf No one has complained here that aiming for 90 CFM/sq. ft. of hood aperture allowed smoke and steam to escape into the kitchen, so long as the hood overlapped the cooking area by enough to capture the expanding plumes....See MoreI'm trying to acquire a new pro range hood. How do I reduce noise?
Comments (48)@opaone: your numbers, while still higher than my estimates, are at least within an order of magnitude, which in this business probably is reasonable correlation. I agree that this could rise to a significant concern with 10 people really cranking away in a poorly ventilated room. So we're on the same wavelength. @spurpura: you are correct in that I've not invested in air quality monitoring devices or hired PhD's to test my house. But my calculations are grounded in simple physics. The only assumption I have made is in the estimate of CO2 production during exercise, and that was from an academic sports physiology laboratory, authored by a PhD and published in a peer-reviewed journal. If you have figures showing that CO2 production during exercise is roughly 10 times higher than my estimate (which is what would be needed to support your observations), I'll await the citation. There are really only three possible scenarios: You are measuring local concentrations of CO2, presumably close to where you are exhaling. Your PhD consultants and their equipment are wrong. There's an exogenous unidentified source of CO2 infiltrating your exercise room. Enough of that dead end discussion. But...as to your original question, I think you're on the right track. As noted upthread, our 1200 cfm hood runs through a straight run of 10" duct, about 25' upwards, with an attic-mounted Fantech LD10 silencer and FKD10XL blower. It measures 60db (LCS weighted, ear level, roughly 4' from baffles) on high. So we hit the mark you are shooting for and I expect your setup will too. Good luck!...See MoreWolf Range Hood Noise - Internal or In-line Blower?
Comments (9)A remote (as Wolf puts it) outside blower might be quieter than one in the hood, and could possibly be made larger (higher spec'd CFM) and run slower to keep down noise and still move the needed CFM (90 CFM/sq. ft. of hood entry aperture) at the pressure loss resulting from baffles, ducting, and make-up air path. As for in-line, it is probably intermediate in noise assuming one can actually fit one in the space. In-hood and outside locations should be easier for maintenance, if any is needed in the future, unless you panel the soffit for easy removal. Better is to use a silencer between blower and hood, as it will remove most blade tip turbulence noise and half the duct noise. From the image, you may not have room for a Fantech round silencer, but you can look up dimensions at their site based on what duct size you are using. Is there some impediment to using an outside blower?...See Morepascalli
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