What is your current ducting? Do you plan to use this range or is it primarily for show? If the former then you'll likely need to replace your ducts. If they're not sufficient for a 900 cfm VAH then they'll not be properly sufficient for a proper hood.

@Kaseki will likely jump in with some accurate calcs but you need to think about how you'll use this range and how important it is to you that you exhaust heat, grease and odors (effluent). If your ducting is insufficient then no hood will overcome that. Not fun to get a nice range and then have a poor hood choice, insufficient ducting or lack of makeup air leave you with odors and other problems.

10" is minimal but likely OK. What does the run look like? How many of what degree bends?

The hoods you've spec'd appear to be 48"? You should have a minimum of 54" width by 27" depth (and ideally 30-32" deep). The Zephyr appears to have zero containment area and the Best very minimal so both of these could have a lot of effluent rolling out from underneath and in to your room.

I wasn't expecting all these technical questions! Here is a picture of the duct:

It's a 4' run, straight out the side. Unfortunately, I have to stay at 48" because the liner will be contained within stone and that's the biggest I can go. [Here's[(https://www.houzz.com/photos/leathered-antique-brown-granite-and-river-valley-granite-in-vienna-va-traditional-kitchen-dc-metro-phvw-vp~2473529) my inspiration photo.

This is a technical issue and so requires technical questions. :-) Somewhere along the way hoods became decorative rather than functional and increasingly people found that the functional was actually important and loosing it was a bit of a problem.

Your inspirational photo is a 36" range with a 54-60" hood which is actually quite appropriate. Reducing the hood to 48" and increasing the range to 48" will create problems for you if you intend to actually use your 48" range. Effluent from cooking will overwhelm your hood and spread odors, grease and heat throughout your kitchen.

There's a bit of a cart before the horse with someone planning cabinets and installing duct before they knew what was needed. If, as you said, the range is functional rather than show then you'll need a proper hood with a proper duct. You really should re-evaluate your cabinets so that you can fit a minimum 54" hood. The existing duct looks like it is off-center of the range? Maybe they can rotate it a bit so that a hood can work.

... coming out of hibernation to put his oar in, says:

This forum has a large wealth of technical information on this topic that should be reviewed by anyone new to the subject who is planning to achieve actual kitchen ventilation. Here are some tidbits, boiled down from various attempts here to provide practical rules of thumb.

We will start with opaone's suggestion. Hood function depends on successful capture and containment. Capture depends on hood aperture overlaping the rising and expanding cooking plumes. 54 inches by 27 inches would be considered the minimum for adequate capture of a 48-inch high power cooktop.

Hood containment depends on flow velocity at the capture aperture. For this size hood (assuming inside aperture is nearly 54 x 27) I would argue for around 1000 CFM of actual flow rate. To get this flow rate with a real blower, you will need a blower that is characterized (at zero pressure loss) as capable of 1500 CFM. Similarly, if one is constrained at 48 inches hood width (please cook greasy things on the middle burners), the values are 800 and 1200 CFM, actual and rated.

Either size blower can easily operate through a 10-inch duct.

Hoods with single duct interfaces are widely available from Modernaire, Captiveaire, Wolf, and many others.

The actual flow rates noted above are based on a 1.5:1 ratio of nominal to actual, and this assumes some generalities about the fan curves of reputable fans and pressure losses of baffles, ducts, and most importantly -- the make-up air system. (Please review relevant threads on MUA in this forum.) No air flows out the duct that didn't get into the house somehow. At the higher actual CFM levels, house leakage is not adequate for providing this air flow rate.

To answer the OP's question just above, higher flow rate through an undersized hood has only a slight to modest effect on increasing the effective size of the hood. The reason is that hoods do not suck cooking effluent from the cooktop, but intercept it and keep it in the hood. The rising plume velocity can exceed a meter per second for gas cooking, and this is what gets the plume to the hood. Air flow velocity for the flow rates I suggest is only half of this at the hood aperture, and rapidly drops off more than a few inches away from it. For actual flow effect at the source of the plume, one would have to use fume hood rules of engagement, where high flow at the effluent generator (welding, grinding, whatever) is achieved. You would need ear protection with such a system, and a huge heating capability for the make up air, perhaps augmented by structures intended to restrict the effluent from escaping the flow.

kas