Range hood capture area

11 years ago

With our kitchen remodel, we're putting in a Wolf 36" rangetop (with a grill and the updated higher BTU burners) and a Modernaire Hood Liner (Model PS10 with baffle filters). Due to various limitations, we could only go with a 36" x 24" hood (outside dimensions - the liner is a bit smaller). In order to make up for this smaller capture area, I specified a 1,500 CFM roof fan (it's a one story house, so the fan is nearby).

So I've always known that our hood setup wasn't going to be ideal, but I figured it would be sufficient for all but the smokiest applications. I was a bit surprised though, when I saw the actual hood liner. The opening on the liner is only about 13 1/2" deep. The rest of the depth is taken up by lights in the front and a metal strip in the back. Above the baffle filters, the area does get larger and then the smoke exits through a 10" duct.

Is this 13 1/2" deep capture area problematic, or will the smoke/grease hitting the solid metal surfaces naturally be drawn in to the baffles?

Thanks for your help.

Featured Answer

charon70

11 years ago

last modified: 11 years ago

I also have a 600 cfm Modern Aire hood that is 30 x 24 over a 30 inch Wolf range. I sear meat often and found the hood works best when I turn it on about 5 minutes prior to searing. This establishes the air flow and I get very good capture of the smoke. At times I do wish I had gone with a higher cfm and/or a 27 inch depth because I see smoke exit the hood at times. This may be due to a hvac vent in the kitchen ceiling that is very close to the hood. Based on my experience, I believe your setup will work just fine. I do not have any grease on the front of my hood where the lights are.

Sort by:Oldest

Comments (8)

cookncarpenter
11 years ago
last modified: 11 years ago
Here's my set up I've had almost three years now, this may help as a comparison;

Bluestar 36" RNB with griddle, 27"x36" Prizer Hood mounted 36" above grates. (Baffle opening is 20"x31"). 1000cfm roof mounted remote blower (three speed), about 6ft. away on 8" duct and two adjustable elbows to accommodate an offset.

Low or medium speeds are sufficient for all but the smokiest foods such as woking or searing a steak in cast iron, when I use high. Occasionally, I have seen a little smoke escape from the outside burners, but it's brief and usually related to cross drafts since mine is an island hood, and I have nearby windows, a dutch door and a skylight open almost year round. I would suggest having your grill in the middle where my griddle is, and I never have any escape from there.

Honestly, most of the time for general cooking, I don't even turn the blower on. (I know a big GW no no) but with the fact my windows are open all the time, I've rarely had an issue with lingering food smells.
greasetrap thanked cookncarpenter
greasetrap
Original Author
11 years ago
Thanks. My grill is in the middle, but I believe the hottest area is at the front. So I've been concerned that smoke might escape when searing meat. I'm not that concerned about the sides, as we don't do a lot of high heat cooking in pans.
Related Professionals
Ocala Kitchen & Bathroom Designers · Augusta Kitchen & Bathroom Designers · Jacksonville Kitchen & Bathroom Designers · Cherry Hill Kitchen & Bathroom Designers · Newport Kitchen & Bathroom Designers · Carlsbad Kitchen & Bathroom Designers · Aberdeen Bathroom Remodelers · Hagerstown Bathroom Remodelers · Concord Bathroom Remodelers · Marietta Bathroom Remodelers · Elgin Bathroom Remodelers · Saginaw Bathroom Remodelers · Plattsburgh Kitchen Remodelers · Superior Kitchen Remodelers · Salem Kitchen Remodelers
kaseki
11 years ago
In commercial hoods, the baffle area can be significantly smaller than the aperture area, but these hoods have a long approach path between aperture and baffles and high flow rates. In general, smaller baffle areas work only if either (a) the approach (throat) between the aperture and baffles has very steep angles allowing the rising effluent to reflect upwards (think mirrors and light beams), or (b) the air velocity is sufficiently high in the throat that the combined reflected effluent momentum vector and the air velocity vector sum (vectorially) to a net upward direction. (Some margin is needed to accommodate turbulence.)

While high flow rates can cause a slight widening of the effective aperture around the lip (region where the lights are), this is quite modest for normal flow rates. (See Figure 6, Section 30.4, 2003 ASHRAE Handbook: HVAC Applications.) Higher flow rates than normally used may gain you an inch or two.

1500 CFM (zero static pressure rating) is a lot for a less than six square foot aperture area. I expect flow rate will be significantly limited by baffle pressure loss (and, of course, make-up air pressure losses). You will probably see less than 900 actual CFM even with windows open. However, that is still a lot of flow over the aperture area, and I think it likely that condition (b) above will easily be met. Expect more than typical baffle noise for this flow rate.

What angle is the plate at the back relative to vertical or horizontal? Is this a wall or island/peninsula mount?

kas
User
11 years ago
OK, thank you for the scientific reasoning, but for the rest of us a bigger capture area is better....it's that simple. Of course you have to consider exit air options, horizontal/vertical etc. but the "optimum" capture area is what you should be concentrating on.
kaseki
11 years ago
kfunky_gw: Are you lecturing me or the OP on optimal capture area? The OP has already purchased an insert that, while non-ideal for capture area, met other constraints. The OP was raising the question of the insert's performance in the context of his blower's rated CFM. Lacking a computational fluid dynamics analysis, or schlieren photography, I can only suggest what might be expected from the geometry.

The OP did not ask what the optimal capture area would be if he could fit it. Had he done so I could have repeated the same formulation I have provided dozens of times on this forum. This formulation is for adequacy, as are almost all rules for effective capture and containment. Unless all the trades are specified, with their relative weightings, optimal capture area is indeterminable, like optimal anything else. For example, in a restaurant context, ventilation design will attempt to minimize HVAC operational costs while minimizing customer discomfort. Lower cost is more optimal than higher cost, but not if income is reduced.

kas
User
11 years ago
kas: It was a statement: not lecturing anyone, looks like your the one lecturing. Sorry if you got your feelings hurt ... just trying to state the obvious, a bigger capture area is best, and will give better performance than just "adequate". Not questioning your expertise just another perspective on the subject from the OP "Range hood capture area".
kaseki
11 years ago
You are welcome to question my expertise, such as it might be. Questioning assertions is fundamental to scientific progress (except for "climate science," which is exempt). However, you were informing me of what I should be concentrating on in my response. I thought that was a bit too forward to go without a response.

kas; feelings unhurt