You don't really need a powerful hood at all. Depending on how you cook, 300 CFM or less will work to avoid the makeup air requirement. You can get away with this partially because the range will only be 30 inches (so there's only so much cooking that will be going on at one time), and partially because induction doesn't emit combustion products and it gives off much less waste heat than gas. If you want a bit of extra fan power, that's fine as well, but 600 is the highest I'd go.

This post was edited by hvtech42 on Sun, Nov 16, 14 at 17:36

Mine is 300 with a boost to 350. It has never gone into boost mode.
I wish I considered a higher CFM but the MUA issue scared me.
Also some lower CFM fans only have a single fan on one side.
I might replace it with something more powerful

The reason for considering something higher is the food smell permeates the house and I can still smell last nights dinner the next morning.

This post was edited by a2gemini on Mon, Nov 17, 14 at 13:57

HVtech42's phrase "Depending on how you cook" leaves a lot of maneuver room. Ultimately, the required flow rate of the hood follows from the air velocity needed across the hood aperture to capture and contain the rising effluent plume. For high temperature cooking, which induction is even more capable of achieving than gas or electric coil, the plume rises at a velocity that is best captured with around 90 cfm/sq. foot of hood aperture.

So this value times the hood aperture area is the actual desired flow, and this is to be achieved at the pressure losses from the hood to outdoors plus the pressure losses of the MUA (there is always make up air) getting to the hood. Hence, the fan curve for the blower used with the hood has to show that the blower can flow that much air at that pressure loss.

For lower temperature cooking, and/or greater tolerance for grease and odor, lower cfm capability will do. Lower tolerance for greater cost can also be a design factor.

kas

I gotta admit, I'm somewhat biased on this topic because I am also involved in the HVAC side of things, and I have seen some bad situations from people going with super powerful fans because it's the "in" thing to do. In most cases they do not actually need that power, and are prioritizing keeping up with the Jonses over what is actually good for their house. Makeup air can be a big pain. Simple dampers are relatively easy to set up, but then you need to figure out where to duct this air to avoid discomfort in cold climates. If you tie into the HVAC system you need to worry about not cracking the heat exchanger by dumping too much cold air over it. Then there's the whole set of issues with combustion appliances and fireplaces/chimneys. Or, you could avoid these issues by putting in a dedicated fan with electric strip reheat system that will not only empty your wallet from the initial cost, but will continue to on your electric bills.

Thank you all! That is all really very helpful information. Based on what you have said I think I am going to go with a 36 inch zephyr monsoon i at 600 CFM. The CFM rate is adjustable so most of the time I will probably use much less than 600. Our code will require make up air. I will just do a simple passive mua kit. I think any time I did any cooking that would require the high setting (smoky/ high temp stuff) I would very likely crack open a door or window anyway.
Can anyone comment on how close the make up air source needs to be to the hood?
Thanks!

Ideally, one wants the air to enter the kitchen as laminar as possible, so the point of entry should be an opposite wall, or from down the hall, etc. Or, one can insert the air so that it rises up to the cooktop from under the range or cabinet, but this may not be allowed by some ranges, and may frost the toes of the cook.

Essentially, what is to be avoided is cross drafts that decrease capture by deflecting the plume.

kas

Hi, kas thanks! So to make sure I understand, across a room or down a hall works, but another floor does not? Is 30' away down a hall too far if it's a straight shot?

Thirty feet is only modestly longer than I have. No distance is too far so long as it is not obstructed. Insertion into a basement will work if the basement is free of mold, dust, and chemical fumes and there is some low resistance path to the kitchen. Note that the farther away the insertion point is, the more air inertia that has to be overcome, so the time it takes from turning on the hood and having the house pressure(s) reach balance will lengthen. In most residential configurations, this is commensurate with the time it takes a large hood blower to spin up, so the transient is both slight and brief.

kas

Oh, so if our basement is completely open to the upstairs (We have turning stairs with no door) I could get away with putting the air intake in the basement? That would be terrific.

Oh, so if our basement is completely open to the upstairs (We have turning stairs with no door) I could get away with putting the air intake in the basement? That would be terrific.

I see no impediment.

kas