Can you clarify? The 30" Nutone model you cited is an undercabinet hood. So, are you saying you have a 30" undercabinet hood over a 48" range, so that there are cabinets on either side of the 30" hood? Not to mention the 30" wood enclosure over the 48" range? How did you get a building inspector to OK that? That is a serious fire hazard. I mean scary-serious. You cannot have combustible material like cabinetry over a range, nor a hood surround over a range that is narrower than the range.

Forget whether it's "reasonable to keep the 30" hood for now". The cfms you are so concerned with are completely secondary to the fire hazard that you have described. You need to rip out the surrounding upper cabinetry over the range, and the 30" wood surround. Install a 48" hood over your 48" range. When you bought the Capital range, didn't anyone mention exhaust requirements to you?

Here is a link that might be useful: Nutone NSP130SS

STOP using the range NOW! This is a major league fire hazard when you say you only have a 30" wood hood above a 48" pro style range and now have grease build up.

Your insurance company would probably NOT pay for a fire claim either as this so egregiously violates code as to defy belief and should have NEVER EVER been installed like this.

Hi,
The nutone is house within a 48" wood hood. We bought the house with the hood in place but it did not have a range so we got the culinarian. There is no cabinetry. The wood hood is similar to this :
http://www.kitchensource.com/range-hoods/na-r2636ouf1.htm#table_reviews
Any recommendations for 48" hoods? Why would anyone install a wood hood if it is as big of a fire hazard as you state?

Oh - I see now. You have a 48" hood, but a 30" insert in the hood. Correct? It's not the wood hood that is a fire danger per se, it's having the combustable materials (wood) directly over the range. Which you still have as 18" of the hood at the bottom of the hood is not completely protected by the insert itself.

Honestly, I'd scrap the insert you have and get a properly sized one to be installed in your existing hood. The hood will be fine if you pair it up with a proper insert. Increasing the CFMs you can move with the existing insert will not address the lack of protection your current set up now has.

Doc

The wood hood should be 6" wider and at least 27" deep to avoid any part of the wood being directly above any of the burners. I'd scrap it and look for a 54" professional stainless hood instead with some decent CFM, like at least 1200. And you need to look into makeup air for it as well, and possibly an ERV.

I have been VERY happy with a Modern Aire hood that I bought through Euro Stoves. One big enough for you (54'' wide at minimum and ideally 27''deep) would be very pricey, but if you want to use the grill, you must have a powerful hood. I don't know if 1200CFM is enough for such a large area. I am sure someone who does know will respond to your posting, though.

The 48'' wood housing you have is not going to work for this stove.