Hi,
We are planning to buy Fridgidaire Slide In model # CGDS3065KF Gallery collection SS; which hood you would recommend. I want least noise and powerful; I'm ready to spend between $ 600 to $ 900 for the benefits of the range hood which will come under the cabinet.

If you can suggest.

Thanks

DJ

Disclaimer, I am not a vent expert. :)

I wanted CFMs, decent cost and a pro look. I bought before spending much time on GW so my hood is 30" wide and 24" deep. My highest burner is in the center so this hasn't been an issue, but if you regularly sear steaks and stir fry on your right front burner it would behoove you to go wide, deep and powerful in your choice of hood. As for ductwork, we put in whatever was required for the hood. Noise was unimportant because I don't entertain while I cook, if you do, then sones might be more important. Heat lamps were a nifty option and I use them a lot.

I ended up with a floor model VAH Nouveau Pro and I am very pleased with it.

The functions of a ventilation hood system are capture and containment of the rising effluent plume from a cooking surface and (where applicable) combustion products. Easily said but often ideal capture and containment are in conflict with available space, sight lines, tolerable noise, acceptable appearance, and affordable cost.

So the OP's question might be rephrased as: How much of each of A - H is enough to achieve the OP's maximum tolerance for odor and grease. Unfortunately, we can't know that tolerance, and hence can't apply it to establishing a balanced system.

Another approach is to start from basics.

1) Establish the cook top configuration and the sizes of pans that would be used on the cooktop.

2) Sketch from a side view and a front view the rising effluent plumes from these pans. Assume that the expansion is in the 20 - 25 degree half angle range from the edges of the pans cooking surface or edges if gas fired. Effluent hitting cabinet sides or the back wall is assumed to be directed at the hood.

3) In concert with choosing a hood depth and width that encompasses the effluent, establish a hood height that doesn't block one's view of the pans or provide a (one-time only, one poster noted) skull impact when bending over. Higher generally requires deeper, but also improves the view and safety. Note that in flat bottomed hood configurations (filters flush with the base) only the filter size counts as the hood size. Otherwise, the inside aperture of the hood counts as the hood size.

4) Choose an aesthetically tolerable design.

5) Determine the filter area (square feet) of the hood and multiply by 3 ft/second for effluent rate of rise and by 60 seconds per minute. The result will be the minimum full power air flow (cubic feet per minute) needed at the filters. (This is all approximate). Achieving this may require an exhaust blower rated 1.5X larger due to various pressure losses.

6) Given this flow rate (cfm), divide by 1000 ft/min, and also divide the cfm by 2000 ft/min. This is the duct cross-section area min-max range to strive for to keep unfiltered grease particulates from condensing on the duct. As always, a given duct diameter relates to duct cross section by A = (pi*D^2)/4. where the diameter D has to be in feet.

(Those who are metrically oriented can make the appropriate transformations.)

(There are many rules of thumb for required flow rate, but they often presume certain hood characteristics, such as conventional commercial design. The Wolf design guide has suggested fans to use with their hoods based on their estimate of what is adequate.)

Second order effects may come into play as one decides whether the result of the above is affordable or installable. For example, over specifying the fan may allow the hood to appear slightly larger, improving capture. Or a conscious decision to cook the greasiest most odoriferous food only under the center of the hood might be made to reduce effluent escape from a hood that is otherwise too small.

kas

Wow Kas, that is certainly a techncially excellent approach, unfortunately there are only so many hoods out there. The perfect one never seems to exist. It is about picking what's critical and compromising on the rest.

For me I have a 30" undermount area, and the height of the cabinet locked me into a certain product with a narrow height so that it is not too low. That left me looking for a 30" wide, 5-7" high hood. Next I looked for quiet ratings since I don't have a giant 20,000 btu gas cooktop to worry about, then CFM, then looks.

I choose the Kobe CH-27 with baffle filters. Once I had ot installed it worked like crap. On the quiet speed which is rated at 280 cfm it wouldn't even suck up a klennex held right on the surface of the filters. Plus is was loud. Kobe rates this hood as 1 sone in this mode but I measured with my radio shack sound meter at 65db. definately not 1 sone. With the filters removed the sound was below the lower limit of the meter which was 50db and honestly standing almost next to it you could hardly hear it. Bottom line is that Kobe rates these hood without the baffle filter. The baffle filters look nice but slow down the air flow and thus make noise. On a high setting it was fairly loud. So the almost $1,000 hood was louder and moved less air then the $150 Whirlpool it replaced. To be fair with Kobe they offered to send out a service rep to look at it but I didn't trust some A&E or whoever that would say it was working fine. Kobe instead set me a whole new hood. This time though I asked for the cheaper CH-22 which does not have the baffle filters. I took down the CH-27 and installed the CH-22. It drew much better air and was much more quiet. I have not measured it but I'd say it is probably 50db or less on quiet setting. Problem is the CH-22's workmanship was poor. One side of the hood has defects but I didn't want to ask for a replacement of a basically free hood.

This weekend I spent a few hours in my attic replacing the 5" pipe with 6" pipe. This improved the airflow more. I'm using the 7" round opening on the hood, goes down to 6" into the attic.

So.... not sure if that helped. Definately check the diameter of your vent pipe up to the roof. If this is small no hood is going to perform well. The ballle filter look nice but they work by making the incoming air so a sort of U-turn to fling the grease to the filter. This slows down the air and produces noise. I thought I wanted them but no longer so.

If the Ch-27 came in a non-baffle filter version it would be perfect for me. The CH-22 performs better, is cheaper, but is not as well made or stylish. Underneath they use the same guts.

Not sure if that helps.

5) Determine the filter area (square feet) of the hood and multiply by 3 ft/second for effluent rate of rise and by 60 seconds per minute. The result will be the minimum full power air flow (cubic feet per minute) needed at the filters. (This is all approximate). Achieving this may require an exhaust blower rated 1.5X larger due to various pressure losses.

6) Given this flow rate (cfm), divide by 1000 ft/min, and also divide the cfm by 2000 ft/min. This is the duct cross-section area min-max range to strive for to keep unfiltered grease particulates from condensing on the duct. As always, a given duct diameter relates to duct cross section by A = (pi*D^2)/4. where the diameter D has to be in feet.

So I need a degree from Cal Tech,MIT,or Harvey Mudd in order to corectly choose a Range Hood?

Just wanted to say thank you to Kas for a thorough and helpful guide.

Reading this I realized I could install the hood a little higher if we go 27 inches deep. Very good to know.

Thanks again

texaskitchentoo: My guess is that between the baffles and the duct diameter, the CH-27 fan was working against a pressure drop that degraded its flow to near zero. I didn't include a step for looking at the fan's pressure curve, because it is rarely available for fans packaged with hoods, even if mounted externally. One exception is Broan fans.

The pressure curve relates actual fan flow to the pressure across the fan (pressure loss). Pressure loss is due to friction in the duct, turbulence in the baffles, losses where there are duct transitions causing turbulence, and, if the house is closed without a make-up air system, the loss pulling air through cracks in the walls.

Fans are typically rated for flow rate at ZERO pressure loss, a nearly impossible condition to actually achieve in any real configuration. For every fan there is a pressure loss, perhaps only a few tenths of an inch of water, where the flow rate equals zero. In between these limits is a trade-off between pressure drop and flow rate. It is important to have a fan with good flow at significant pressure loss to overcome filters and ducting.

deeageaux: To put it Presidentially, it depends on your definition of "correctly." Due to lack of perfect information about all the components under consideration, one is unlikely to be able to determine the exact pressure loss of the system as a function of flow, and thus where on the fan curve one is operating, even if one has a fan curve. As a result, calculating flow rate for some particular combination of parts will yield a result that falls between an estimate and a guess.

The best approach, if affordable, etc., is to use a seemingly over-sized fan and when full flow is not needed, run it at a lower setting. It will also be quieter in that mode. Over-sized fans are generally only an option for remote mounting, as upgrading a fan built into a hood can be expected to be impractical in most cases.

kas