Range hoods, need some advice!
I'm going to be getting a lovely Viking gas range with about 15,000 BTUs per burner. It's a 30" range, so theres 4 elements. We had the Ventahood all picked out as a range hood, but unfortunately we can't install it since our ducting is only 6", and the Ventahood requires a 6". The smaller 6" Ventahood is only 300cfm, and I was told that it's not enough for my range. I need some help getting a good range hood that would be adequate for my range, with only a 6" duct!
300 CFM is adequate for some of the less powerful electric ranges but is not appropriate for any gas range. 300 CFM is not enough air flow for the heat generated by the gas range. 15,000 BTU x 4 = 60,000 BTU. You require a range hood in the 600 CFM range.. The Windster line of range hoods includes an adapter for 6 or 7 inch ducting. You can find them here: www.vent4less.com
Check if there are any warranty issues concerning the actual vent diameter as well as hood CFM requirements.
The Viking dealers and installers in NYC and NJ will sometimes decline to warranty equipment unless a minimum diameter of actual vent per/ft run is not maintained.
I am not sure what the formula is but my SIL had to pull out her 6 inch ducting and install 10 inch because there was a15 ft run with an elbow to vent outside before the dealer would install and warranty her 30 inch Viking and 900 cfm hood. Also air feed to replace the vented heated air has to be addressed especially in the winter months.
I'm a little confused about your ducting situation, since all your references are to a 6" duct. Does the Vent-a-hood require a larger duct? How much? I have a terrific KitchenAid 30" hood, 600CFM, with a 7" duct system. If I only had a 6" duct it would be hindered, but it would still be better than any 300CFM hood. And its over a five burner Viking, 50,000 BTU total.