Mine is Modern-Aire, 1200 cfm, which is actually tandem 600s. The exhaust is through the wall, so the blowers are inside the hood, and the air makes one 90" turn then out. A sheet of 20 lb. copy paper, balanced horizontally on the flat of my hand, gets sucked up at about 6" below the baffles on high, and about 3" on low.

More to the point, is steam. Try getting a pan a little too hot and pour a little water in it to make a big, visible plume of steam. How much escapes the hood? How much gets sucked back in?

Thanks plllog,
My range is not installed yet, so I can't do the steam test yet. Even though it is very quiet, I do feel air exiting the vent on both high and low. Unfortunately, my venthave 3 turns before a 10 ft run and then exiting on the side of the house. My paper test is about 2 inches away on low, and about 4 on high.

Is it true that you should turn the vent on 10 minutes before you cook to start the air flow?

You might ask on the Appliances Forum. Do a search there for the 10 minutes thing. There was a recent discussion about this, with engineers and wannabees discussing air mass movement and which forces are at play.

I'm no engineer. I can tell you that I find a difference in use between turning it on one minute ahead of time, and ten. The one minute is turn on hood, turn on stove, heat pan. The ten minutes is turn on hood, think up some missing ingredient and prep it or answer the phone. Either way, if you've got good suckage you've got good suckage.

My hood is overpowered. By the numbers, I figured I needed 900 cfm, they offered 1000 cfm so I planned for that, then they changed to 1200 cfm, so that's what I ended up with. Once in awhile, when I'm cooking by the tens of gallons, I'm glad for the extra suck. For most daily cooking, I use the lowest setting. Every once in awhile I fry something and crank it closer to the high end.

I don't know about ducting or how that affects the suckage, but I'd guess that with all those bends and the length of the duct, from everything that I've read which says that those things will reduce the suckage, it sounds like you're doing fine.

If you're really worried, try an electric tea kettle or coffee pot underneath and watch the steam.

Reading this I had to try the experiment. Mine is a Prestige 1200 CFM (double 600 fans). I held a heavyweight paper napkin and it got sucked up at about 8 - 10 inches below the fan.

More important, it works really well when I stir fry and the baffles are really easy to take out and wash in the dishwasher.

Sayde...is your vent loud or quiet on high?

I just did the steam test. I placed 4 steaming mugs around the perimeter of the stove, counter height. On low, the steam went straight up. As I increased the speed, the steam was drawn to the vent. On close to high, all of the steam was captured. I hope that this will be sufficient. Pllog, how does this sound?

Your vent will work better if you compensate for "make up air". Opening the kitchen window 2-3" when running your vent should make it run more efficiently.

I think it sounds fine. These were where the stove will actually be, right? Not on the counter next to it? If the latter, it's not fair to your poor hood, your hood sucks a treat and you need to stop worrying. :) You'll know for sure in practice, of course.

Is your hood the same size as the stove, or is it one size bigger? If it's the same size, I don't think you have any concern at all. You've proven that your hood is powerful enough to capture from the very edges of your cooking area. What it tells you either way is something that is true of all hoods. They draw best in the center. So...if you have something big/smelly/smoky/steamy/greasy, put it as close to the middle as you can. If you're simmering something that's not doing much, on a small flame, put it in the front, on the side.

Most of all, unless you have really bad issues with asthma or something similar with your family members, you have a heck of a lot better venting than most people and your new kitchen is going to be great!

I agree with Aloha, however. Did you account for make-up air? You seem so well informed about your vent, I didn't think to ask. If you're in an extreme climate with cold, heat or humidity, or if you have a well sealed, modern house, you might want to put in a "conditioned" make-up air system while you're still not finished. That means air that enters the area where it's being sucked out, that's heated, cooled or dehumidified as needed. If you live in a temperate area, however, the open window is just fine if you're not getting enough make-up air from cracks and drafts. 1200 cfm is a lot of suck, and the air it's sucking has to come from somewhere. :)

tangent but somewhat on topic...this test is a wonderful idea--watching a piece of paper get sucked by a vent unit. I tried it with my humble 30 inch undercab Broan Allure III on "Boost" mode (430 cfm) -- a piece of notebook paper independently rode upward about 5-4 inches from the unit.

More interesting to me was a faint black imprint of the filter grid on the paper that first time the paper hit the filter. As I played this game over and over again the paper got dirty on both sides with grease and goo. It proves to me how well the greasy vapor goes to the vent. It was also a reminder to me to take out the filters and wash them. The unit is doing its job!

We bought this unit because it's so low in sound on the first two settings; third setting is problematical and boost setting quenches conversation. We use the two low settings most of the time. Allows us to listen to radio or talk while we cook.

REading this I just had to try the paper test too. I have Broan E64E30SS with an 1100 CFM inline blower. But the way our kitchen is designed, I had to have the duct go down into the basement before venting to the outside, so a lot of duct lenths and bends. Sounds like breadandsuch but with 1 less turn and maybe 8' instead of 10. But even with that, the paper was sucked up 6" on high and 2" on low. So maybe that 1 extra bend cost breadandsuch 2". But ultimately it's how well the hood functions when cooking.