Iam installing a kitchen in the basement,just purchased a under cabinet range hood to be vented outside it calls for a 7inch ducting.It will be going straight up through cabinet tahn through the dropped ceiling,than going between ceiling and upstairs floor than out.It would help if we could take this to a 6 inch vent is this possible?
If the manufacturer's specifications call for a 7" round duct then you lose venting efficiency when you reduce the duct size. The installation manual will usually specify the maximum length of the run and number of change of direction you can make. e.g. it may specify a maximum run of 18' and deduct 5' for each 90 degree bend. If you have a long run or changes of direction you would not want to also reduce the duct. You can get an adapter to go from round to rectagular if that helps you keep the proper flow. e.g. 6" round equals 3 1/4" X 10" rectangular. I hope this has been of some help. good luck.
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