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

11 years ago

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):

http://www.imperialhoods.com/m8/WH2000PS-K--imperial-wh2000ps-k-wall-range-hood-1000-cfm.html

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:
Vent-A-Hood CWLH9-242 42" 600 CFM Sensa Source
http://www.ventingdirect.com/vent-a-hood-cwlh9-242-42-600-cfm-sensa-source-wall-mounted-range-hood-with-dual-blowers-and-halogen-lights/p1035944

Modernaire:
PS-19
http://www.modernaire.com/PS-19.html

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?

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Comments (7)

armada
11 years ago
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 :)
kaseki
11 years ago
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.

kas
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Eandhl, are you buying direct from Modern Aire, or from a Dealer? I will say that a friend got quotes from dealers in her area (CA) for a MA hood nearly identical to mine, and the price came in a lot higher. (and Modern Aire wouldn't sell directly to her because there were local dealers in her area). I really think I just got lucky on the pricing of my hood. Probably MA hadn't really thought out their pricing policies for direct sales. I have been happy enough with the performance, but to be fair the hoods in my past have been pretty pathetic, so I don't have much to compare it to. On the Modern Aire hoods, both the fan speed and the lights are on variable setting dials, so you aren't limited to just High or Low options (a nice feature). It certainly isn't silent at the highest fan speed, but I don't find it to be bothersome. The 30" width seems fine for me--I'm sure its better to have a few extra inches on either side (ie wider hood than range) but I just didn't have the space for that. When I stir fry, I do still have to shut the door between the kitchen and hallway or else the smoke detector goes off--so I can't say my hood is sucking ALL the smoke out. But not bad. In my case, I think the issue has more to do with the depth of my range--the hottest burner is in the front and since the range is particularly deep, the hood doesn't fully cover that front burner. With a normal depth range this probably wouldn't be an issue. The Modern AIre hood is 24" deep, which is pretty standard (although Vent A Hood has some 27" deep models, I think) One sort of gross thing about the hood, though--I seem to get a 'grease bead' on the back corner of one of the baffle filters, that eventually drips onto my countertop if I don't dab it once every day or so. (I know, I know, the solution to this problem is probably to clean the filters more often!) I don't know if this is a Modern Aire issue or a general issue with baffle filters (or just a slothenly housekeeper issue !) All in all I'm happy with the hood, and wouldn't hesitate to buy from them again--but honestly I was more concerned about the aesthetics than about having the very highest quality or quietest ventilation available. I'm sure there are quieter, better-sucking (and probably cheaper, too) options out there, depending on your priorities! Hope you can find a solution that works for you!
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Correct. If you (as I'd strongly recommend) use an infinitely variable speed control for your blower, you can adjust it from the lowest possible setting (great if you're just simmering something on the back burner) to high. Since a 1200 cfm motor and fan are designed to move larger volumes of air, they typically are "working" less hard to move an equal volume of air versus a smaller blower, thus the notion that they are quieter at the same airflow volume. And yes again, there is no difference in the need for makeup air between a 600 cfm fan running at full, and a 1200 cfm fan that has been throttled down to 600 cfm. The difference again, is that the 1200 cfm fan still gives you the option to run full out at twice the volume, thus eliminating the "I set off the fire alarm" scenario if you do occasionally do some really smoky cooking. weissman is right about overkill in general, but in this specific case, the "price" of using the larger fan is very small--a few hundred dollars of initial cost. Otherwise, the electricity consumption of either running at the same flow rates is not markedly different. As others have suggested, I think there is a very good chance that once you have a high powered range, and a great ventilation system, you'll find yourself cooking in ways you never have, because you can. So I think building in some seemingly excess capacity may turn out to be something you're glad you did.
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marthavila: sounds like a good decision based on good advice. All the cfm junkies on GW are nodding their heads. Both changes will reduce noise: the duct upsizing reduces the airflow turbulence, and as you note, the larger blower may run at a lower speed with same cfm output as a smaller unit running harder. The latter is particularly true if you do have a continuously variable fan speed control so you can "fine tune" the blower to what you're cooking. I have a somewhat different take than trailrunner however, on the issue of airflow speed and grease handling. In general, the concept of a well-designed hood is to trap the grease before it enters the ductwork. Once it's in the ductwork, all is pretty well lost, especially if the duct run is at all long. Much of the grease will end up on the duct walls, never to be removed again. As a result, different hoods use different systems to trap grease. There is the Ventahood "squirrel cage" system, which uses a centrifugal fan that theoretically flings the grease particles into the fan housing, where it is trapped, while the air continues up into the ductwork. There is the mesh filter system, which is similar to what is used in most (barely useful) recirculating hoods and UC MW/hood units. The air flows through a metal mesh that is supposed to trap the grease particles. Then there are the baffle systems. These use a system of alternating U-shaped baffles that force the air to make two abrupt 180 degree turns before heading out the duct. At each turn, the grease particles that fail to negotiate the tight turn are trapped by the baffles (and shameless bias--the polished stainless steel baffles on our new MA hood are gorgeous! Almost too pretty to hide under a hood). High airflow speeds likely do not increase grease trapping efficiency: I could imagine that overly high airflow might even facilitate more grease making it past whatever filter system is being used. The reason that high cfm are desirable is not so much to whisk grease out the ductwork, which is unlikely, but to exhaust as much of the fumes/smoke/odor/grease from the temporary confinement in the body of the hood before it can spill back out of the hood into the kitchen. The combination of large capture area, a deep hood, and a high cfm blower should give maximum f/s/o/g evacuation. But totally concur with trailrunner's advice about starting the hood early and letting it run afterwards. Definitely will help.
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dljmth
Original Author
11 years ago
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.
kaseki
11 years ago
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.

kas
sleepydrj
11 years ago
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!!
mata
11 years ago
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.
gerardjerry
11 years ago
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.

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

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

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