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1200cfm oversized hood...Overkill for 30" BlueStar range?

Posted by ILoveCookie (My Page) on
Tue, Mar 25, 14 at 13:43

I am getting a 30" BlueStar RNB range for my kitchen remodel. The sales person says a 600cfm vent will be sufficient, even if all four burners are on at the same time.

The hood is going to be installed on an interior wall, and the duct is going to run sideways (inside the wall cabinets) for about 6', straight out through an exterior wall. So there is going to be one 90 degree turn.

I read in an old thread that 900+cfm is recommended for such a powerful range. However, the Prizer / BlueStar hoods I am considering seem to be only available in either 600cfm or 1200cfm. Would 1200cfm be overkill?

I do plan to oversize the hood, so it's going to be 36" wide. I also want to have the 27" depth (larger capture area), but the sales person says that's probably unnecessary... and she doesn't see a 27" option in her BlueStar / Prizer pricing book.

Here are the three hoods I am considering:

Prizer Incline Wall Mount
BlueStar Pro-Line
Vent A Hood Professional

The sales person suggested Vent A Hood because: 1) their 600cfm is equivalent to 900cfm, and 2) it's the quietest vent on the market. But I read that VAH filter is harder to clean than the baffle filter.

What do you think? I'd really appreciate your input. Thank you!

This post was edited by ILoveCookie on Tue, Mar 25, 14 at 14:54


Follow-Up Postings:

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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

You won't regret getting a bigger/more powerful hood if you have the space for it, and proper makeup air.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range

Yes, I have the space for a bigger hood.

Speaking of make up air, the sales person suggested an inexpensive approach -- install a 10" BEST universal automatic air damper somewhere inside the house, rather than tie the make up air system to the HVAC system.

Does the air damper approach make sense? I am in NJ.

I am replacing the air handler as part of the kitchen remodel, so maybe it makes sense to tie the make up air system to the HVAC system... I am not exactly sure what's involved in doing that. Say if replacing the air handler costs $5K total. Approximately how much more would it be to add a proper make up air system?

Thank you very much.

Edit to add:

I just read a bit more on the forum about makeup air system. It seems the passive approach (i.e. install an automatic air damper) is acceptable.

This post was edited by ILoveCookie on Tue, Mar 25, 14 at 15:34


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

One advantage of having a large vent is that you can run it on lower speeds a lot of the time which will be quieter. IE, a 1200cfm running at half speed will be quieter than a 600cfm at full speed.

The other thing you need to consider with the barometric damper is some kind of inline filter and heater. The HVAC guys should be able to bend some tin to make up a filter holder. Larger is better (less pressure drop). Thermostatic heaters are available in various duct sizes and BTUs for a few to several hundred dollars.

Replacing the blower is one thing. Adding ductwork is something else and would need to be discussed with the HVAC guys. Doing the outside stuff (cutting a hole for the intake) might be done by GC (carpentry).


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

I'd go for the larger vent too. I don't think it's overkill. I'm going to get a 36" BS RNB and I'm looking for a similar hood to what you're looking at, 1200 cfm, 27" deep (though I want a 42" wide). The point weedmeister made about running a more powerful hood at lower speeds is good. I had a salesperson make that same point to me. I'm still figuring out which hood to get. Ventahood's filter is pretty easy to clean I believe. The same salesperson showed me how easy it is to take off, and then you can wash it in your sink or put it in the dishwasher. One thing I didn't like about VAH is it only has two speeds. I like the idea of having multiple speed options depending on the type of cooking you're doing at the time. I haven't ruled out VAH yet, but hoods are really challenging to decide on imo. I've got all my other appliances figured out, but the hood is not easy. I'd love to know what you end up getting and why once you decide.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

Been there, did that. :) I have a three element Induction and a two burner gas under one large hood and had the same dilemma. They stopped making the intermediate speed and 600 cfm, like my old hood, didn't seem like enough for all guns blazing. I got the 1200, with continuous speed control (which you can probably add if it doesn't come with it). I don't regret it at all. It's not quieter on low because the low is higher, but it's worth it. Low is good enough for small stuff: a little steam, a little saute, a simmer, Somewhere in the middle for a quick sear. High when every burner is blazing away! On low to medium I don't need make-up air. There's a sufficient volume of air in the house, and sufficient cracks for refilling it, that there's no problem. I'm in a temperate climate where it doesn't affect the HVAC. For higher speeds, I crack a window in the kitchen. At that point, there's enough heat coming from the stove that the fresh air moving through is quite pleasant. ;)


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

I would go with 1200cfm. People, including many sales staff tend to be fixated on the size of the stove or btu to dictate cfm. I have a 1200 cfm 54"x27" vah over my 48" bs, and when woking I couldn't imagine a lower cfm. Since you can wok as easily on your 30" as I can on my 48 I would highly recommend 1200.

As for the the claims by vah having an "equivalent" rating higher than actual cfm I think its a bunch of bolagna. And as for vah being quiet? No way. Ive had two, first one was either 300 or 600 cfm (cant recall) and current is 1200 and they are anything but quiet. If I was to buy a hood today I would look around at others. Not saying I wouldn't buy vah again, but I would take closer looks at competition.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

Well, I'll disagree. I have a 600 CFM hood over a 30" DCS range and I rarely run it on high even when wokking. Depending on the code in your area, you may not need make-up air with a 600 CFM hood and for me that would be the deciding factor. My hood is only 30" wide and with flanking cabinets that is not a problem, but I do wish my hood was deeper - I do get some grease on the outside front of the hood.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

A plug for 27" deep hood which quite frankly, isn't even deep enough. I was worried about standing underneath it and the hood being in the way: no problem at all.

I don't remember how many bazillions of cfms we got but it's a lot, with an inline blower placed high up in the attic. It's still noisy. The variable fan is way-nice; I would not, personally, install a system without it. I use the whole shebang dull to take-off roar.

I can't speak to the necessity of the monster suck. What bad thing happens if you don't have enough suck? I presume a smaller version of what happens when you have, say, no hood at all, which I lived with for the first 50 years of my life. It wasn't the end of the world, but like everyone says here, once you experience a good hood, you kinda never want to look back. It is really nice to live and work in a kitchen that's not coated with weird nasty sticky ick. I think that's the bad thing that happens when you don't suck enough, the surfaces suck instead.

If you can afford it, I'd go for the massive one with a variable speed dampener that will give you the best of all worlds, less noise at more moderate speeds, and the ability to wick it all away when needed. It is a purchase I have never once regretted, fwiw.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range

I have the 30" RNB with a crummy hood that goes 320-560 CFM. I think a 36" hood up to 600-800 CFM will be adequate for my needs, but I want one a lot quieter than what I have.

I've been having a really tough time finding a hood. I got some good advice here in my thread "super-quiet 600+ cfm range hood for condo - mission impossible??"

My top pick would so far be

Kobe CH9136SQB-1
QuietMode™ 300 CFM (1.0 sone)
Speed 1 370 CFM (1.4 sones)
Speed 2 440 CFM (2.8 sones)
Speed 3 540 CFM (3.5 sones)
Speed 4 640 CFM (4.2 sones)
Speed 5 760 CFM (4.5 sones)

22" deep (I would consider building out from wall to improve capture area)

suitable for 6" duct

underside is somewhat concave which should improve performance

I also have a very similar duct setup to yours so I'll be interested to know what you choose!

This post was edited by feisty68 on Wed, Mar 26, 14 at 1:55


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

I did a little geometry and it looks like I'd have to put a 27" deep hood super high due to my 6'2" husband to avoid head-bumping - high enough to undermine the suck factor of the hood. That leaves the dilemma of whether to have a shallower hood/lower CFM, or deeper hood/higher CFM (and more $$$). Also, the higher the hood the more noise.

I think the OP might be in the same situation as me where the external exhaust is too close to make a remote blower feasible.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range

Just to correct some miss-impressions by sales people: The air flow rate (CFM) required is proportional to the aperture area of the hood and to the uprising effluent velocity from the HOTTEST pan. It does not matter how many burners are on if the aperture is large enough and the required velocity in the aperture is met.

A VAH hood will not move its rated CFM unless the hood is standing alone in a field. There are pressure-loss restrictions from the ducting to the outside, and make-up air (MUA) pressure-loss restrictions, even from replacing air through a window screen.

However, giving VAH the benefit of the doubt that their reported CFM is for the hood with blower, then baffle pressure loss in conventional hoods, along with some internal transition losses, will make the ratio of real-world CFM to zero static pressure CFM for conventional blower hood duct and MUA systems a little lower than for a comparable VAH hood with duct and MUA systems.

For conventional systems I always assume a 2/3 factor unless analysis suggests otherwise, and analysis requires not only calculations of losses through all the pieces including the rarely specified hoods and baffles, but also the fan curve. Thus, barely educated guesses are likely to be the best one can have before installation and the opportunity for measurement occurs.

The second mis-impression I'd like to correct is that hoods suck effluent from the pans, or even from the area between pans and hood. Hoods do have an input air velocity, and this air comes from the area around the cooking zone, (albeit rapidly decreasing with distance) and this velocity helps pull effluent into the hood, but hot pans can emit effluent at 3 ft/s upward, and this velocity gets the effluent to the hood without much help from the hood doing any sucking. What the hood has to do is have enough air velocity that when the rising hot effluent hits the hood parts, the momentum change tending to reflect the effluent out of the hood (visible in Schlieren photos as a curling out) is overcome by the hood's own air velocity.

If, for some unimaginable reason, you wanted to remove odor from the kitchen emitted from a bunch of cilantro set on a cold cooktop, then all you would have to work with is the hood removing air from the kitchen, which is certainly suction at the aperture, and by extention there has to be some airflow to the hood at the cooktop, if not suction.

In any case, people bend over to get their heads under hoods, so a stick figure cartoon will help reveal what hood height is sufficient to avoid bumps. The higher the height the hood is placed at, the larger the hood aperture has to be to capture the rising and expanding effluent, and the larger the CFM capability has to be to meet the rule of the first paragraph.

kas

This post was edited by kaseki on Thu, Mar 27, 14 at 11:25


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

feisty68 you might want to have your husband go to a store and see what hood height he needs. My husband is 6'1" and this was my concern also with a 27" depth hood. The salesperson I referred to in my original post was 6'. I asked him about mounting hoods higher then the rec of 30" above the cooktop b/c of my husband's height. He demonstrated with himself that he didn't hit his head on a 27" b/c you do bend a bit when you cook. I do think I would want to mount it 32-33" higher than the cooktop to be safe, but my husband will be going in to "test" this issue, as I'd like to mount it as close to 30" as possible, though I think 30" will be a bit too low.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range

Thank you so much for your inputs!!

I am inclined to go with 1200 cfm, 27" depth (if Prizer / BlueStar makes it). The main goal of my kitchen remodel is to significantly improve the cooking power and ventilation. If I don't go with 1200cfm, I think I might regret down the road, which will defeat the purpose of this remodel. I am sure any hood will be better than what I currently have (downdraft)...I just don't want to regret my decision.

weedmeister -- I am going to need to look up what a barometric damper is, and try to educate myself before talking to an HVAC guy about inline filter, thermostatic heater, etc.

plllog -- I read on the forum that some people put their make up air thingy under their fridge, so the cold air could get heated by the fridge somewhat. Very clear. :)

Regarding the continuous speed control, I think Prizer / BlueStar hoods only come with a fixed speed control. ctycdm posted a while ago that they don't recommend using a variable speed control with their hood. I never used a continuous speed control before, so I guess I won't miss it?

Converting a 3 speed hood blower to continuous control

``I was informed by my hood mfg. (Prizer) that their 3 speed motors are not compatible with variable speed controls, and advised against it. They stated shorter motor life, and humming were two possibilities, besides voiding the warranty... "

feisty68 -- My husband is 5'8". In the store, he tried standing next to a 24" deep hood mounted at 29" high, with his shoes on. His fluffy hair touched the hood when he bent forward. So we decide that if we mount the hood at 30" high, he should definitely be fine.

Now, if we can get the 27" deep hood, we might need to mount it slightly higher than 30". I will try using kaseki's method to find out. :)

``People bend over to get their heads under hoods, so a stick figure cartoon will help reveal what hood height is sufficient to avoid bumps."'

This post was edited by ILoveCookie on Wed, Mar 26, 14 at 12:22


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range

ILoveCookie, I know that Sone ratings need to be taken with a grain of salt, but does it concern you that Blue Star hoods don't have published Sone ratings? I have a hood that does a pretty good job of ventilating at 320-560 CFM - but I hate using it because of the noise (4.5-9.5 Sones).

And the Pfizer hood that you linked to - the fans that they make for that hood shroud only go up to CFM600 in the 36". Unless I am missing something?

This post was edited by feisty68 on Wed, Mar 26, 14 at 12:48


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

While making your decisions about hood height, do remember to pretend cook beneath it. There's a big difference in the way one stands to cook and the way one stands when a looming presence is threatening! In real life, one is used to the hood and not intimidated, so doesn't square up to it, and no one is looking the top of the backsplash in the eye except while scouring splatter spots. I don't hear about tall guys bumping their heads until they're at least 6'5". :) Not that it can't happen--just be sure what you need, rather than being intimidated.

Oh, and if you're worried about just walking by, my sincerely too low garage door put the bent down part of my new tailgate into the headbopping range, and it only took getting bopped a couple of times to learn to duck without thinking about it. :)

I know enough physics to follow Kas most of the time, but I know more about IRL cooking than the science. I have been chopping an onion on the island about six feet away from the draw zone of my 1200 cfm hood, with nothing cooking, and used the hood to suck the onion fumes out of the air. It works. Maybe not 100%, but enough to take it from tear gas to smells like good dinner.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

I don't think that chef height is too much of an issue for the OP. Here's a drawing using 30" Bluestar RNB dimensions, with the range trim adjusted to the recommended 11/18" height over the counter surface (36" above floor in this case). I don't want to threadjack so I will be taking further commentary about chef height/hood depth to my thread.


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

feisty68, thank you for the drawing! It's very helpful.

``The Pfizer hood that you linked to - the fans that they make for that hood shroud only go up to CFM600 in the 36". Unless I am missing something?"

Hmmm. The 1200cfm fan option is indeed only listed under 48"+ Prizer hood. However, my sales person was able to quote 42" Prizer hood with 1200cfm internal blower for the 36" RNB that I was originally considering. I am going to double check.

I prefer the rounded front bottom edge of the Prizer hood, over the square edge of BlueStar. But if turns out Prizer doesn't do 1200cfm for the 36", then I will probably just go with BlueStar.

RE: noise level -- I haven't read much noise related complaint about Prizer / BlueStar hoods, so I guess it's on the reasonably loud side? Or maybe all the owners are so happy with the performance that the noise issue is negligible?

I haven't lived with a quiet vent, and don't really expect my new vent to be quiet either. I guess there is a difference between reasonably loud and intolerably loud, but as long as I can still hear my phone ring (inside the kitchen), I think it will be good enough. If husband needs to tell me something when I am attending the stove, he could always come closer...


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

pillog:

The onion chopping ten feet away from the hood can be expected to fill the kitchen air volume with fumes that the 1200 cfm hood removes at a rate that roughly depends on the actual air flow rate and the volume of the kitchen, or house, depending on how open the kitchen is. Sixty seconds of chopping may represent a few air-change periods by itself, thereby significantly diluting the onion odor by temporal exponential decay without us having to deal with any near-field hood flow patterns and their capture and containment interactions with hot rising effluent.

kas


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range

RE: fan options for 36" Prizer Incline Wall Mount hood

``The Pfizer hood that you linked to - the fans that they make for that hood shroud only go up to CFM600 in the 36". Unless I am missing something?"

I contacted Prizer, and found out that the 36" is compatible with 1200CFM internal blower. This combination is not listed in their spec because most people don't need such a powerful vent.

I also found out that Prizer can build the Incline Wall Mount hood that I want at 27" depth. :)

This post was edited by ILoveCookie on Thu, Mar 27, 14 at 13:20


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

Okay, Kas, I usually follow you, but I'm totally lost in that last paragraph. My overall feeling is that you meant the fumes might dissipate by themselves in the volume of air in the kitchen. I don't know enough about the physics, nor the distribution properties of onion fumes to follow.

What I know is (not for the first time) I chopped half an onion on the island, about 6 feet from the center of under the hood, with myself between the two. I could barely get through the half from tearing up. So I turned on the hood (which I needed to for the saute, anyway). When I went back to do the other half of the onion, unlike when I don't turn on the hood, there was no tearing, and I was able to chop the second half, with the hood drawing, without tearing up again. Since it was the same onion, and the tearing only gets worse as the onion warms up, I'm going to continue to believe that the hood makes the difference. Maybe it's just circulating the air to make the fumes dissipate faster--maybe that's what you were saying!--but whatever it is that it does, the onion smell and tear fumes were gone, and the landscaper was commenting about smelling it outside, but not when he came into the kitchen. So however it works, it's a good thing, and I'm satisfied. :)


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

No no, I wasn't saying that, nor was I saying that the hood wasn't removing the onion fumes. I was saying that it removes those fumes pretty much as it removes any fumes that are introduced into the kitchen air, by removing the kitchen air at.X cubic feet per minute. When enough kitchen air has been replaced, the onion is hard to smell. During the cutting, depending on the flow paths of the air (rarely uniform), heavy onion oils may be swept out faster near the hood than if they had the dilution rate (molecular velocity) into the kitchen air that, say, gasoline, would have.

kas


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range?

Oh! Thanks for the explanation, Kas. I was totally lost, but I understand the translation. :) And I was thinking that the onion didn't disperse that much, and totally get the "heavy" and lower dilution rate. That makes a lot of sense if one knows onions. :)

And another endorsement for the powerful hood. :) Because we use far more onions in the kitchen than gasoline. :D


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RE: 1200cfm oversized hood...Overkill for 30" BlueStar range

  • Posted by ctycdm 10b/Sunset 24 (My Page) on
    Thu, Mar 27, 14 at 22:36

I don't think one can have too much ventilation. I went with 1000 cfm over my 36" RNB with griddle, thinking it would be more then enough. Turns out, it is adequate, but I often wonder what 1400 cfm would have been like?
BTW, my 36"x27" is mounted 36" above my range and works just fine with no head knocking, or sight problems...

This post was edited by ctycdm on Thu, Mar 27, 14 at 22:44


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