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Modern Aire, Vent-a-Hood: Does 600=900? or Imperial?

Posted by laurat88 (My Page) on
Tue, Jan 29, 13 at 20:47

I have a Wolf AG range with a griddle. Not a heavy duty cook. Lots of breakfast fare like pancakes, french toast, etc. Some stir frying and some garlic dishes. Loads of baking.

After reading all the forums and postings I finally concluded that I want a min 900 CFM hood and I was set on the Imperial WH2000PS-K with 1000CFM (7" duct):

Double checking before I place the order, I realized that this hood is shallow with only a 20 1/8" depth. I measured and at that depth the hood reaches to the mid point of the front burners. There are posts here that say the hood may not be as effective being so shallow.

So, back to the appliance store and a call to Modernaire. BOTH say that their 600 CFM units are at least as good if not better than any other vendors 900 CFM unit. A similar model Vent-a-Hood with a CFM of 600 has a depth of 21" while the Modernaire has a depth of 24".

Vent-A-Hood CWLH9-242 42" 600 CFM Sensa Source


Price wise, the Imperial 1000 CFM and Moderaire 600 CFM are about the same price. But the model that has the same styling as the Imperial is more. The Vent-a-hood is definitely pricier.

So I am wondering, is it worth the extra $$ to get a deeper hood (if even 7/8") but that has less CFM? Can Ventahood and Modernaire 600 blowers really be as good as an Imperial 1000 CFM blower?

Follow-Up Postings:

RE: Modern Aire, Vent-a-Hood: Does 600=900? or Imperial?

no clue on an answer for you, but i'll be at this decision in a couple months, so free bump so someone else can :)

RE: Modern Aire, Vent-a-Hood: Does 600=900? or Imperial?

To be brief, because this has been covered in various ways in myriad other messages:

Fans have a relationship between flow rate (cfm) and the pressure difference across the fan. The rated flow rate of a fan at zero static pressure is measured in open air with, as one might guess, the same pressure on both sides.

As the flow is restricted by one means or another, (e.g., the hood aperture transition, baffle losses or mesh losses, duct friction, etc.) the flow rate goes down. Some suppliers will rate their fan hood assemblies, accounting for some of the losses. In this manner they can claim that a 600 cfm assembly equals a 900 cfm fan, but that assumes that the fans have the same fan curve (flow rate vs. pressure drop). Fans are all different, so the only way to really guess what will happen is obtain the fan curve, estimate the losses through the entire system, including the pressure loss from imperfect make-up air, and then see what flow rate is achieved.


RE: Modern Aire, Vent-a-Hood: Does 600=900? or Imperial?

Thanks kaseki - I appreciate the explanation and did read as much as possible of the previous posts and sorry I may have missed the detail. From a simple end consumer point of view, it would be nice if there were some sort of reliable standard but I guess that's asking for too much. It is the way the hood vendors differentiate themselves I presume.

For my application, I think I will stick with the Imperial brand for several reasons. Given our cooking style, I think their 900cfm unit should suffice. It has lower sones ratings at the higher speed than the vent-a-hood (even though I know that is somewhat subjective as well), it is aesthetically more appealing for our design and they have a 7year warranty whereas Modernaire is 2 and Vent-a-hood is 5. Price wise, there is not too much of a difference between VAH and Imperial, but MA is pricier.

Hoping this all works out and I am not wasting my $$ :)

Thanks again for your help. I appreciate it.

RE: Modern Aire, Vent-a-Hood: Does 600=900? or Imperial?

The biggest obstruction to calculating this stuff is that residential hoods are not specified for pressure loss versus flow rate. The best one can do is scale commercial baffle hoods if the residential model is baffle type.

More fan is always better than less fan, just like in commercial sports spectacles.


RE: Modern Aire, Vent-a-Hood: Does 600=900? or Imperial?

Here's the empirical answer to that question. We got a 36" wolf range with grill- which calls for 900 cfm. We installed the 600cfm vent-a-hood, on top of that, we raised it higher than the recommended height (tall cook!).
We did that 6 years ago, and have heavily used the grill (on average 2-3 x per week all those years). In our experience, when we cook healthy foods- non greasy and so not much smoke- the hood is perfect. (Examples: fish, chicken, chicken sausages, filet mignon/ not marbled beef ). When we cook less healthy foods (beef with a lot of marbling, or fatty cuts of meat, really oily salmon, pork sausages) then it is quite possible that the smoke alarm is going to chime in. A quick run to open a window or swoosh the back door is needed. If I had it to do over again, I'd do it exactly the same, but might decide to install it at the recommended height. I think ours is 6" higher- and this has a big impact. Good luck, and cook healthy!!

RE: Modern Aire, Vent-a-Hood: Does 600=900? or Imperial?

I would avoid such a shallow hood. All the experts say the hood should cover the cooking surface. I can't offer any technical data but it seems like common sense. Most hoods are 24" or 27" deep.

RE: Modern Aire, Vent-a-Hood: Does 600=900? or Imperial?

The Imperial hood you mentioned requires a 10" duct to get 1000 cfm, NOT a 7" duct. Also, deeper is always going to perform better. The Vent A Hood is quieter.

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