Flex Duct Size Calculator

While this may be true in most cases for a metal supply air duct it is not for a metal return nor a 6 flexible duct on supply or return.

Flex duct size calculator.

Use insulated duct or duct board in unheated spaces. Flexible duct work must be stretched tightly for maximum air flow. Always stagger take off ducts by 12 to maintain pressure. Include fittings in the duct tel enter either.

Input the required cfm in the box below that. For example if the vents are 5 by 10 inches the total cmf for the vents is 50 cmf per vent. Never locate ducts at the end of the trunk line run. Click calculate and you will see the size of flex duct you need for that room.

Use the online duct calculator see references and calculate the needed flex duct size. The duct vent size will depend on the size of the furnace and the size of your home so you know how many vents you need in each room. Calculations are for 60 f dry air at sea level from 5 to 3000 cfm approximately standard air which is 0 075lb da ft. Calculate the size of your ducts vents by multiplying the length by the width.

Friction loss inches water duct airflow cfm duct length feet 90 bends quantity 45 bends quantity 180 bends. If ashrae 2013 is selected flexible roughness is 0 003 ft when straight and fully stretched tight at 0 compression adjusted at other compressions otherwise the. In order to maintain velocity reduce duct size. Flex duct 05 on most metal duct calculator round metal pipe 06 on most metal duct calculators field duct sizing chart rectangular sheet metal duct 07 on most metal duct calculators.

Metal ductboard flex size by. Friction rate velocity friction rate. Rectangular duct is rounded up to the nearest 1 4 inch. While a duct sizing calculator built for a specific type of ductwork is the best possible method for sizing ducts the attached chart can be used in most single story homes with a centrally located.

The flex duct size may be different than the hard duct that runs to that room. Read duct diameter inches and duct velocity fpm. In wg duct tel. Select the duct type on the pull down menu.

Enter friction loss per 100 of duct inches of water duct airflow cfm duct length and the number of bends. Flexible duct friction loss calculator.