[. . . ] ® Microwave Hood Combination OVERALL DIMENSIONS PRODUCT MODEL NUMBERS MH1160XS MH1170XS MH2175XS Electrical: A 120-volt, 60 Hz, AC-only, 15 or 20 amp electrical supply located in the upper cabinet as close as possible to the microwave oven hood. [. . . ] To calculate the length of system you need, add the equivalent feet for each vent piece used in the system. (1. 8 m) B Recommended standard fittings 3-1/4" x 10" to 6" = 5 ft. 3-1/4" x 10" roof cap = 24 ft. 3-1/4" x 10" 90° elbow = 25 ft. 90° elbow 6" = 10 ft. 3-1/4" x 10" wall cap = 40 ft. 45° elbow 6" = 5 ft. 3-1/4" x 10" flat elbow = 10 ft. For wall or roof venting methods: If the wall exhaust method is chosen, be sure that there is proper clearance within the wall for the exhaust vent. that length of vent and number of elbows should be kept to a minimum to provide efficient performance. using caulking compound to seal exterior wall or roof opening around cap. NOTE: If flexible metal vent must be used, calculate each foot of flexible metal vent as two feet of rigid metal vent. Flexible metal elbows count twice as much as standard elbows. 2 ft. [. . . ] For complete details, see Installation Instructions packed with product. [. . . ]