Can a lower gauge duct make a range hood louder?

3 years ago

last modified: 3 years ago

(Update) Solved

Just in case any one finds this, the problem was the electrician wired the outlet wrong and the hood was getting 240V instead of 120V. Nothing to do with the ducting.

My range hood got 30db louder since moving it.

Have a Broan BWP1 30" ducted range hood. Advertised noise volume on mid setting is 3 sones (43db).

Installed it and ran for 3 months and it achieved about that sound rating.

Redid the kitchen, so took it down, installed it again, and now it runs at around 75db at the mid setting.

Tested the hood before mounting and it ran at the appropriate noise level.

Both installs have the same arrangement: one 6" 90 degree elbow and a 10" long run of 30 gauge duct to vent to outside

The biggest difference between installs is the new install uses a 24 gauge 90 degree elbow and the old install used a 30 gauge 90 degree elbow.

Could this be leading to the increase in volume?

The other difference is the new install is raised 6" from stove top when the original install was only 18" from the stove top. (ed. actually raised 8" to manufactured specified minimum of 26" from stove top - thank you commenters)

Is there anything else about my setup that could cause such a dramatic increase in noise level?

Attached is a picture of the original install

Featured Answer

3onthetree

3 years ago

24ga sheetmetal is thicker than 30ga, so I would also expect the opposite. You probably have a bad connection or a slight gap or dimple somewhere which is causing turbulence or pulling air from somewhere not intended.

Sort by:Oldest

Comments (10)

M Miller
3 years ago
"the new install is raised 6" from stove top"

Been on this forum for many years, and never have seen that! Even the previous 18" height is bad. SMH, the height should be 30-36" above the cooktop. Maybe you meant something else than 6"?
wdccruise
3 years ago
Broan BWP1 SERIES Specification:

"Mounting height: 24-in. from cooktop to bottom of hood"

Broan BWP1 SERIES Installation:

"The minimum hood distance above cooktop MUST NOT BE LESS than 26”. A maximum of 36” above cooktop is highly recommended for best capture of cooking impurities."

Hmmm.
Related Professionals
New London General Contractors · La Crosse Home Remodeling · Tampa Bathroom Remodelers · Los Angeles Bathroom Remodelers · Spokane Bathroom Remodelers · Tampa Kitchen & Bathroom Designers · Martinsburg Kitchen & Bathroom Designers · Little Rock Kitchen Remodelers · Savannah Kitchen & Bathroom Designers · Lawrence Kitchen & Bathroom Designers · Green Bay Kitchen & Bathroom Designers · Bartlesville Kitchen Remodelers · Grand Island Kitchen Remodelers · Denver Kitchen Remodelers · Oshkosh Custom Countertops
foodonastump
3 years ago
last modified: 3 years ago
I'm assuming he went from 18" to 24". Thank goodness.

OP, I highly doubt the lower guage increased the noise. If anything, intuitively I'd expect the opposite, but even that would seem a stretch. Have you introduced screws to the install? Are you measuring the db from the same spot relative to the hood? I could imagine the new hood "appearing" louder because your ear is closer to the motor and turbulence.
kitchenrenoguy
Original Author
3 years ago
My mistake. Double checked and the new install is indeed 26" from the stovetop
mcarroll16
3 years ago
Why was it installed at that height? Were you repurposing a vintage wall vent?
kitchenrenoguy
Original Author
3 years ago
@mcarroll16 yes
kitchenrenoguy
Original Author
3 years ago
@foodonastump thanks.

Screws are the same across installs. We have screws in the mounting bracket only.

Measuring sound from the same distance above the hood using the same device. The difference is big, less than 50db before to over 70db now.
kaseki
3 years ago
Is the image of the elbow on the stove top that of the old duct? If so, it appears to be smaller in diameter than the new duct elbow. A new larger diameter duct would be expected to have lower air resistance. Turbulence and turbulence noise could be less, but the motor is doing more work with a less restricted path and may be louder as a result, or noise at the baffles/mesh filters would be louder.

In both cases is the sound meter frequency weighting (none, A, C, Z) the same?

Put your hand on the elbow when the unit is running. Does the noise level seem to decrease?
PRO
Charles Ross Homes
3 years ago
Is the spring-loaded damper operating freely? If it's not fully open when the hood is operating I would expect an increase in the sound level.