Cool. Well I do like the 27”, I am 6’5” so it will make things interesting. I think the distance between hood and the external blower on the roof or outside wall isn’t enough anyway to compensate for it or the expense of putting it in. Maybe I’ll just make an internal 1200 cfm blower work and raise the height to 34” with a 27” depth hood. Figure since I can’t go with a 42”, best I can do is make it 27” deep. The front burners on the Blue Star gotta be taken care of.

How much do you actually cook? What kind of cooking? How much greasy residue do you want on those windows on either side?

Agree w/ @kaseki. You want at least 27" depth. And a minimum of 3" extra width on each side but 6-12" would be better with the adjacent windows. My concern w/ the Modern Aire is the lack of aperture and containment space. It's 27" deep but 5-6" of that is nearly useless as it has a flush to the bottom light bar. There is also very little containment space so you could get a lot of effluent rolling out from under it.

If you don't cook much then the Modern Aire would likely be OK. Otherwise I'd look at commercial hoods if you don't want to be constantly cleaning greasy residue off your windows.

I cook a lot and all types.

I can't go wider than a 36" because of the windows. I figured at least a 27" depth would make up some for that limitation.

Thanks for the notes on Modern Aire. I thought I had it all settled as of last night, but apparently I'm not done researching. But, what hood that is 27" deep doesn't have the light bar where Modern Aire has it? I'm surprised this is an issue as it is the first time I've heard of it for any hood that is 27" deep. And little containment space? I don't know, I'm having trouble finding other Modern Aire owners with similar problems.

What commercial hoods do you recommend? Are those different than the Best by Broan, Zephyr, and the like I've been looking at? You can't honestly be talking about restaurant hoods. That's ridiculous.

I did not look at the actual designs of the two candidate hoods -- my bad; my comment on maximizing depth was directed at aperture. I evidently assumed too much about ModernAire's hood design.

Generally, for reasons of efficiency in various respects, residential hoods that roughly approximate commercial hood architecture will be most effective. One commercial approach to aiding capture when hood width is limited is to use "side curtains," also called "side panels" or "end skirts." These could be provided with a custom residential hood.

The curtains do not need to drop all the way to the cooktop if drafts are minimal, rather they only have to intercept the main effluent plume -- nominally a 10-degree from vertical truncated inverted cone aligned with the pan edges.

If greasy cooking is expected to rarely occur, then removable skirts might provide both capture when needed and more open window view when not. Otherwise, greasy cooking may have to be limited to the central burners where the effluent cone is fully captured.

To be fair, it is difficult to fully analyze what a given hood can do. Normally, we depend on the velocity of the rising effluent plumes to bring them to the hood aperture where the flow (if adequate) will bring them to and through the baffles. Suppose that one significantly exceeded the 90 CFM/sq.ft. actual flow rate rule of thumb and evaluated, via computational fluid dynamics, the actual flow of the ventilation air rising to the hood versus that from the burners and hot cooking surfaces. The presence of the counter top will tend to align the ventilation flow inward near the burners, and this will provide some modest influence on the horizontal components of the plume elements' flow vectors as the two flows merge. This behavior will have the effect of slightly narrowing the plume below the hood edges. Using even a short hood side skirt could be helpful in such a case. The cost of depending on this is noisier ventilation.

Thanks Kaseki. I'm understanding what was being said now. There is no way I'll be putting in skirts though. That's not even my decision. My wife would not allow that. I'm not sure I like it either.

Someone else recommended a parametric hood. What would that look like? Google is not helping.

Use and expectations are all different. Some years ago I would have told you that we were quite happy with the 42" VentAHood over our 36" Wolf AG. What I didn't know then was that there were much better options that weren't as noisy and that didn't leave the lingering odors around. We also cook a lot more now and are more likely to pan fry and sauté which both produce more greasy effluent.

If you don't cook much or don't mind the odors and are OK cleaning those windows frequently then you'll be quite happy with a lessor hood.

As @Kaseki said, if you can't do a wider hood then you'll want to limit greasier stuff to the center and back. As effluent rises it spreads out. There is almost no amount of exhaust air that can overcome this. Even the most powerful commercial hoods rely on a wide and deep aperture or capture area to capture the effluent and then a large containment area is needed to contain it until the blower can exhaust it.

Personally there is no way that I would ever have windows that close unless the range was mostly decorative.

If I had a choice I wouldn’t have it between windows either but nothing I can do about it. Going to make it work. Still having trouble seeing a better option than the Modern Aire.

Re: parametric hood: This link showed up near the top of a duck-duck-go search: http://ths.gardenweb.com/discussions/2329631/parametric-vent-hood

The link in that thread doesn't work, so one might have to search for the hood that was noted in the question. I suspect my comment in that thread still applies to similar experiments in how to build a good looking, but perhaps non-performing hood. Maybe the hood was designed using parametric CAD software.

Commercial hoods are optimized for efficient capture and containment, but even they depend on a correct balance of aperture and flow rate. In the schlieren images below, the second shows adequate flow rate, the first slightly inadequate flow rate. Imagine attempting to capture that rising hot flow with an edge slotted "hood." Although the images are of hot air flow off of a commercial griddle, hot greasy pans behave with similar characteristics.

P.S. Kobe has a 2011 video on YouTube at:
http://ths.gardenweb.com/discussions/2329631/parametric-vent-hood

What's wrong with this video? Using steam generators near the vent hood is not representative of hot grease effluent from a hot pan 30+ inches below. The mesh filter is not optimal for most uses except (in my opinion) low specific flow rates used with low grease generating cooking conditions, and in this video the mesh filter doesn't seem to be on. If Kobe's approach were more efficient, commercial hood suppliers would use it. One of the highest costs of a restaurant is the electric bill for kitchen ventilation (including conditioned MUA).

From Kobe's web site:

What is Parametric Panel?

• A parametric panel increases static air pressure by limiting airflow
  space. Panel may be opened or removed to access the filters for cleaning
  purposes. Parametric panel apply to KOBE Brillia CHX30 Series only.

Other ways to increase (household) static air pressure are:

• Use no hood at all
• Use a recirculating hood
• Use an over-powered MUA system

I can't rid my mind of the image of taisho-san laughing every night as he is driven home from work at Tosho & Company, Ltd.

I’m wondering if they meant a parabolic hood. Like a shape that would capture effluent better.

All of this said, and thank you so much, is there a better alternative to the Modern Aire? Based on all of my research I can’t find a better suited hood.

This video does a pretty decent job of showing Modern Aire’s 27” hood at work. I know. It is smoke. Not super greasy effluent, but it certainly seems to work well, even with the light bar.

https://youtu.be/pMDTz7SaMnU

Clearly opaone has no idea about Modernaire hoods or how they work.

I have a Modern-Aire hood and I'm pleased with its performance. My pots are back from the counter edge quite a bit so there isn't a problem with the capture area. The light bar doesn't get very gunky. I thought part of the reason for the deeper hood was to pull that away from the pots. :) Recently, I've been doing some frying experiments, and I get all kinds of spatter and grease on the cooking surface, but the hood does a good job. There is some smell in the air, but no grease outside of the spatter skirt which is from me making a mess. Whereas the baffles get gunk. As they're supposed to.

Thanks plllog. Basically what I've been reading elsewhere.

This video needed to specify, unless I missed it, the nominal CFM of the blower being used. In any case, the assertion that no smoke missed the hood doesn't seem to be consistent with what I saw. Certainly the great bulk of the smoke was captured and contained, and that is perhaps the most that can be expected of a reasonable hood.

I think it would have been interesting if the smoke bomb were situated at the outer edge of the pan base where it and the rising combustion products from the burner would intermingle, and where the smoke source would have been farther from the center of the hood. This would represent an extreme component of the overall cooking plume.

(These tests are difficult to perform in a rigorous manner. Ideally, the wok would have heated oil at the smoke point, and schlieren imaging would be used to see the rising hot plume interaction with the hood. The smoke bomb demonstration may be the best that can be managed for visualization without schlieren imaging.)
https://en.wikipedia.org/wiki/Schlieren_photography

1200 cfm and the hood was 54” above the 48” cooktop with a depth of 27”. It’s a shame I can’t do a 42” hood, but apart from that, I think the Modern Aire at 27” depth with 1200 cfms is going to be best for me. I may upgrade the middle front Blue Star burner to 22k btus and then use that for wok cooking so I don’t have to worry as much about stuff escaping up the sides.

I had a BlueStar 36" Platinum range top paired with a 36" Vent-A-Hood. It wasn't optimal. Ideally, I should have had a 42" but I didn't want to trash a perfectly good hood that I already owned. I found that I had more "stuff" coming over the front than the sides. I suggest that the 27"D hood would be an improvement over the standard 24"D. At least, you will deal with part of the problem. It's a shame you can't install the 42". But, you have to do what you have to do.

FYI, I've had both internal and external blowers, they are all loud. I couldn't tell a bit of difference between the volume. It's going to be loud. Just accept it.

Yep. It’s too bad I can’t put in a 42” hood. I’d have to trim the window molding. That’s not happening. I’d trim it 1.5” in from the top down 14” and the hood would sit right inside.

Even operating on the fan curve at 2/3 or less of the blower rating due to pressure losses, a 1200 CFM rating will be more than enough for that size hood. You can probably operate at partial power, even with a wok in play. This should reduce the blade-tip turbulence noise relative to a lower flow rated blower running full speed. Baffle noise will be the same, as it is a function of the air flow rate. Let us know how it works.

Kaseki - what size hood? 36” or 42”?

asking because 42” came up in my previous post

With a goal of 90 CFM/sq.ft., a 36 x 27 inch aperture (I'm sure it is actually a bit less) is 972 square inches, or 6.75 square ft. This aperture area calls for an achieved flow rate of 6.75 x 90 = 608 CFM. Usually when I write here I just multiply by 1.5 to find a blower nominal flow rate to cover all sins, which would lead to a 900 CFM rated blower.

You have a short duct path, so the main exit pressure losses are the hood transitions, baffles, and outside cap. These are likely to be not more than a tenth of an inch or so of water column. On the other hand, the air return to the house interior (make-up air) losses are undefined at this point, so it is hard to estimate total loop pressure losses.

As it happens, I have a Wolf/Broan 804702 1200 CFM internal blower fan curve in my stockpile. It includes the [undefined] hood losses, as it crosses the abscissa at zero static pressure loss with a flow rate of 910 CFM. Your short duct and cap will have little additional loss; throw-in, say, 0.05 inches (guess). Now if the pressure loss of the MUA is only another tenth, then the blower will move about 860 CFM. To get down to the 608 CFM computed in the first paragraph, the loop air path pressure loss has to be about 0.75 inches exclusive of the hood for this blower, which would be a lot of MUA restriction.

Hence, my comment that the 1200 CFM blower could be run at a reduced
speed is very likely for the 36-inch hood, and this is probably also
true of a 42 inch hood.

(Safety Caution: House pressure should not fall below 0.03 inches if gas combustion appliances are used without a their own separate MUA path. Oil-fired burners may tolerate 0.06 inches for non condensing boilers. This avoids back-drafting of the combustion effluent, which contains carbon monoxide. Fireplace draft may not be much better, depending on fire level. Even without this safety issue, high house negative pressure causes moisture to be pulled into wall cavities in summer, and insulation dust pulled out of wall cavities and ceiling penetrations into the house.)

kas

Wow. Thank you kas. That was thorough. I feel totally confident in my hood choice now and everything else. I did the due diligence and contacted the local major HVAC company and the owner also assured me I won’t need to worry about MUA with my 1888 home. My tankless water heater (also how I heat my home) has its own MUA path so I think I’m all set. We do have a chimney but I don’t think that’ll be a problem as the HVAC guy, aitoro installer, and a general contractor all said it wouldn’t be.

Thank you so much for your help with all of this.

"Clearly opaone has no idea about Modernaire hoods or how they work."

Apparently not. But I do know a bit about fluid dynamics and the design of dust and fume collection systems. Is there something about Modernaire or the effluent from cooking that gets by the laws of physics that you can educate me on?

Firstly, lets deal with the smoke bomb marketing video. Smoke is not an indicator of how cooking effluent will react. It's great for marketing because it makes something seem like it can do something that it may not be able to, not so great for predicting reality. The plume from cooking is much hotter and likely much denser than that smoke. It creates a plume of much greater CFM than that smoke.

Cold smoke like that is much easier to control. You talked about it 'bending in' which is something that a smoke bomb plume will do much easier than the plume from cooking. That smoke is also of much less volume and velocity for the hood to deal with.

If, instead of a smoke bomb, you were pan frying something on that burner, then things would likely be a bit different. The plume would be hotter, denser, and of greater volume. Rather than bend in, it would simply continue to rise up (and spread out as it does so). A minimal amount might bend in slightly but it'd likely take a massively greater blower to get the cooking plume to act like the smoke. About half of the cooking plume will either hit the light bar or become spillage (fall outside the hood on the cooks side of the hood). Some of what hits the light bar may get pulled in to the hood but much of it will likely under roll out of the hood.

In that example, maybe 30% becomes spillage and directly bypasses the hood, 20% hits the light bar of which 5% gets pulled in to the hood and 15% rolls out as spillage. So overall about 45% of effluent begins to disperse in the room and on to surfaces while 55% is exhausted. The caveat is that these will all be different for different types of cooking that produce plumes of differing temps, densities and volumes.

(As @kaseki mentioned, a schlieren of an actual cooking plume would be a much better indicator of actual performance. But to be accurate it should include not just the effluent from a single pan but of several.)

Now, given the minimal containment area of the Modernaire hood, a large volume of very hot and dense cooking effluent (and that often rises in very variable amounts), even only 50% of it, will likely not be able to be contained until it is exhausted so some bit of the effluent that rises directly in to the hood area may roll out and in to the room.

This is all why commercial hoods in restaurants (and labs) are big giant boxes with nothing to obstruct the aperture. The large unobstructed aperture or opening is needed to catch as much of the initial plume as possible as it rises naturally because a cooking plume, unlike smoke, is very difficult to control. They have a large containment area to prevent under roll and because the rate of a cooking plume is quite variable.

All that said, Modernaire may very well be the best of all consumer hoods and the best choice for the vast majority of people. OP included. But it is likely not a good choice for people who cook a lot, produce a lot of grease laden effluent, use more than one pan at a time, or want to avoid cooking odors to the greatest extent possible.

On that last one, cooking odor can have a major impact on people's enjoyment of food. This is why most restaurants make sure to have as well designed of systems as possible so that these odors do not diminish the flavor and enjoyment of the food.

If you have anything that proves me incorrect then I would love to see it. I'd much prefer the cost of a Modernaire hood to the commercial system we're currently planning for.

Finally, my apologies for how long this bit of thinking out loud became... :-)

Opaone, firstly I know nothing about fluid dynamics. I am 100% sure that your good self and kaseki would have my head spinning and a blank look on my face within minutes of a conversation beginning in person. I will agree that a in general commercial hoods are better, but your numbers of smoke and grease missed by a Modernaire hood is so far off the make.

What I do know is the following.

1) You will not find one single compliant on this forum or any other that suggests that a MondernAire hoods performance is anything but excellent.

2) After selling MondernAire Hoods for 8 years mainly above Bluestar and Capital open burner ranges, the most powerful residential ranges and rangetops in the USA, which I also sell. I have never had a customer complain to me that it does not remove smoke and grease from said ranges, bearing in mind these units produce 25k btu per burner.

I am sure you would agree an extremely hot plume of smoke and heavy grease from multiple burners is created. Which is removed more than satisfactorily according to owners, further Bluestar and Capital ranges are renowned for the ability to wok cook, again producing more than the average plume of hot smoke and grease on a regular basis.

3) I had 7 MondernAire units in my cooking school (Eurostoves) in Boston for over 8 years, and in that time never had an issue with the removal of only 50%, 40% or 30% of smoke and grease, or a complaint from customer using the cooking school only compliments.

We had the cooking school running 13 years, in the school we only used residential ranges (Capital, & Bluestar for the main) and residential hood in the school, 4 x 48" ranges , 2 x 36" ranges and 1 x 60" range. We spent $$$$ on residential hoods, VaH, faber, zephyr, Independent, Broan and Best and so on that simply did not work for the amount of cooking we did.

It wasn't until we were sent a Modernaire hood to try that we found what worked extremely well in the school and was a unit I could confidently sell to customers across the US, within 4 months ALL the hoods were changed to MondernAire. they were more expensive than any of the failed hoods, further they are harder to sell due to price than cheaper hoods, yet it was the best thing I ever did for customers in the school and customer who purchase Modernaire hoods from us. That in itself tells a story.

With absolutely no disrespect to you at all, and your understanding of fluid dynamics, I feel the difference between this post and your post is real life experiences of the product in real situations.

It is perhaps an aspect of full disclosure to note that if I am not criticizing a hood's form, I have assumed that it has the general characteristics of a commercial hood as approximated by the usual manufacturers for residential applications. This means that I expect the aperture being analyzed to be relatively unblocked, and that unless otherwise noted, the filtration is by baffle filters.

Further, I didn't look up the ModernAire hood that the OP first listed. Having done so just now, I cannot determine from the spec sheet what the aperture plan view is, hence, I can't criticize it for any blockages I don't know about. Anyone having a photo or drawing of the aperture view of this hood, please feel free to include it in this thread.

I think the phrasing of opaone: " ... minimal containment area of the Modernaire hood ..." may be referring to the capture volume (volume before the baffles). If so, then I would argue that except in dynamic cases where a large volume of greasy effluent is released at once from some large cooking vessel, the static capture and containment rate of a hood depends much more on its flow rate relative the the effluent up velocity (up to 1.2 m/s for gas cooking) and not so much on capture volume, assuming that the hood aperture overlaps the cooking pans by enough to capture most of the expanding plumes.

In commercial hoods, one may see that the actual area of the baffles is often much less that that of the hood aperture, and that a tapering hood inner structure mates the hood entry aperture with the baffle section. (Also, the baffles are required to be steeper than 45 degrees to the horizontal.) In such cases, the effluent flow is being concentrated, and the specific flow rate (CFM/sq.ft.) has to be higher at the baffles to ensure containment. Plume reflections on the way to the baffles as well as at the top of the baffles can cause turbulence that the large capture volume helps constrain as opaone has noted.

Where the baffles mostly fill the aperture area and have nearly the same specific flow rate as the aperture, I don't believe the capture volume is as important. My hood captures and contains adequately operating at roughly the desirable 90 CFM/sq.ft. specific flow rate, when induction wok cooking at the edge of the hood, or searing more centrally.

If the ModernAire baffles are horizontal and flush with the aperture, then I will have to rely on Trevor's observations, because in such a case with no capture volume, there could be a tendency for the effluent to slide in the direction of the baffles toward the front edge without being completely contained by the baffle gaps. However, CFD by intuition is fraught with risk, so this is only a suspicion.

kas

This photo from kitchensource.com appears to be the 24-inch version of the PS1018. I guess we need to know what the aperture depth is from the light bar to the rear blockage for the 27-inch version. For the Wolf/Independent hood pictured in my message above, the clear aperture front to back is 26 inches.

With respect to the rear blockage at the wall, this is usually not a problem with cabinets, because the reflected plume components will be entrained in the main flow except at the edges where the cabinets perform the function of reflection back into the flow stream. With only window frames, there might be spillage. This is a case where small side curtains can help without being too obtrusive.

A to-scale side drawing of the hood and the range with a wok or such on it would allow calculation of the angle being captured inside the light bar. A desirable value is 10 degrees from vertical, pan edge (wok hot zone edge) to the inside of the light bar.

ModernAire is known for making custom variants of their hoods, so one can imagine a missed plume vs. missed money trade study.

It also appears* from the kitchensource photo that the baffle configuration is, er, atypical. Perhaps what we need to know is what the configuration is above the light bar.

Edit: Other photos I've since found show more conventional baffles; perhaps this photo is deceptive.