Thank you for your question on the model 611CM. We would not recommend using a 7" round duct size with an 1100 cfm blower. For an 1100 cfm blower, we would recommend using a 10" duct size. Our model 437, 10" round roof cap would be the appropriate roof cap for your application and pitch. Please contact Technical Support should you have further questions at 800-637-1453.
Date published: 2016-09-22