600 cfm hood with Blue Star 36' RNB

12 years ago

In my remodel, I am planning to buy a Blue Star 36" RNB with four burners and a grill. Now, the question of the hood. I live in a Manhattan pre-war apartment building with thick plaster wallks, structural columns, ceiling beams, etc.

In looking at Blue Star and Modernaire hoods, it seems that once you go over 600 cfm, there is no choice but to have a duct larger than 6". I will not have the ability to run the ductwork in the walls. The ducts will have to run through my upper cabinet (what a waste of space!) and out through a window, which I will modify to accommodate the duct. (Alternatively, I might be able to break through to the adjacent maid's room and conceal the ducts through a soffit.

If I have to use a larger duct, I will either lose extra cabinet space or have to build a larger soffit.

The question is whether I cn use a 600 cfm hood and have it perform adequately. I will be unlikely to be running more than a couple of burners and the grill at the same time--at the most. I have read that the lower cfm will mean a noisier operation but I think I could live with that if I had to. My concern is the smoke and the smell. Will the lower cfm level work well enough?

TIA

Featured Answer

Armchairbuilder

12 years ago

600 CFM for your flat is probably more than plenty, but perhaps you should consider contacting a HVAC contractor to make sure you get exactly what you need for your home.

To give you a rough idea of calculating CFM for a commercial kitchen you take 200CFM per foot for medium heat equipment (griddles, ovens, and ranges,)and 300 CFM per foot for high heat equipment (char broilers, wok ranges etc.) But there is more to the equation than that, the vent hood needs to be balanced as well. Balanced means that the air you remove from the building needs to be replaced as well, such as with a make up system.

When you suck a large amount of air out of your home you are creating negative pressure inside. With a pressure differential the higher pressure outside will try to equalize with the lower pressure inside. This is where you can run into nasty problems. With not enough leaks around your doors or windows the air can be pulled in through your water heater vent, or through your fireplace flue effectively creating a back draft. This is a serious condition, as flue gases contain carbon monoxide.

This is something alot of people are not aware of as they set out to get a powerful new hood for their kitchen.

Comments (13)

weissman
12 years ago
Without a grill 600 CFMs would be more than adequate. Grills can generate a lot of smoke. Also, if you go over 600 CFMs code might require you to have makeup air. Personally, I'd skip the grill in an apartment and go for 6 burners or a 30" range. Are you sure you're allowed to duct outside through a window. Several people on this forum in NYC apartments have been forced to go with recirculating hoods.
GreenDesigns
12 years ago
The grill is the problem. It generates a LOT of smoke and heat. Enough to drive you out of the kitchen if you don't have a wide open window or enough suckage on the vent. 600CFM is no where near enough oomph with a grill. I'd do a plain 30" and use a grill pan and stay with the 600 CFM.
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antiquesilver
12 years ago
Is a 6" duct adequate for a 600 CFM vent?
nycbluedevil
Original Author
12 years ago
I am the president of the coop board! But even for those not so lucky to have that job, yes, we can vent to the outside. That's how we vent our gas dryers now. I can also vent through a window which is what I will probably do rather than expanding the small vent to the outside that is currently there.

30" out of the question completely. I really don't want to do a regular six burner if I don't have to so I am trying to make this work--it really is just a cosmetic question because I can do the 10" duct. It is just that it is SO big.

The specs for the 600 CFM hoods provide for 6" ducts which is what prompted my question. The ducts get bigger after that.

Regarding MUA, we do have the ability to open up windows in all rooms. Since this is an apartment building, there is no waterheater, flue or any of that.
kaseki
12 years ago
Whether 6-inch duct diameter is adequate for a 600 cfm flow is actually a question of what fan curve applies to the candidate fan and does it reach 600 cfm (or thereabouts) for the pressure losses that will occur in the ducting and through the hood, including whatever negative pressure the residence drops to with the fan running. This will depend on the fan motor and blade design.

Some guessing may be required unless measurements on the residence are made by a HVAC specialist. I would think 6-inch ducting will work for appropriate blowers and a leaky residence, but an 8-inch duct will provide more margin.

kas
willtv
12 years ago
600 CFM is about all you can push through a 6" duct.
You'll be better off with at least an 8" duct and a 10" would be best.
As for how many CFMs, because of the grill, I'd look into a 1200 CFM unit.
Also be sure to get a hood with a large capture area as that grill will generate a ton of smoke.
BTW, you're going to love your Bluestar,
daveliv
12 years ago
I have a 36", 6 burner BS with a 600 cfm hood in Manhattan. I vent through a common stack in my building (6" duct, one turn, and about 10 foot duct run), but that shouldn't make a difference.

600 cfm is more than plenty for me. I rarely even turn the blower up to full speed, even when broiling steaks or grilling on my griddle that spans two burners.
nycbluedevil
Original Author
12 years ago
Thanks Dave. So you don't have the open grill? That is what gives me pause with the 600 cfm. I can do a 1200--it will just mean a larger duct to build a box around in my adjoining maids room. I have a while to decide.

Thanks for all your responses.
User
12 years ago
A grill is just like an outdoor one. Open flame and grease create a TON of smoke. A grillpan is totally different in it's ventilation needs because it doesn't involve the grease contacting the flame. You can get a great sear with a grillpan, but you won't get that smoky flavor that is the hallmark of grilling. You need the grill for that. And the grill needs 1200 CFM in order for you to not set off every smoke alarm in your building.
guadalupe
12 years ago
do a kobe hood 800 cfm 7" duct
afineman
9 years ago
nycbluedevil,

I'm curious what hood you ended up getting for the 36" Blue Star with the grill and what your experience has been so far.

We live in lower manhattan and planning to order the 36" Nova with grill and are trying desperately to figure out the hood solution.

Thanks in advance,
nycbluedevil
Original Author
9 years ago
I answered on the kitchen forum post.