Flex duct has a higher pressure drop and as such may require the size shown on this guide be increased by 1 round size for up to 800 cfm and 2 round sizes.
Round hvac duct sizing chart.
The table below can be used to compare equivalent diameters for rectangular and round circular ducts.
Enter duct airflow cfm duct velocity fpm duct length and the number of bends.
Sheet metal duct friction loss calculator.
The rectangular dimensions and the air flow volume are adapted to the equal friction loss.
Round duct is by far the most energy efficient type and that s what we ll use in our worked example later on.
Larger volumes or higher static pressures should be dealt with on an individual.
Residential duct sizing guide the following duct sizes are based on a fraction drop of 10 inches per 100 feet of lineal duct.
Ductwork comes in round rectangular and flat oval shape.
Read round duct diameter inches and friction loss per 100 of duct inches of water.
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 step one identify the volume of air that will be passing through the duct step two select the duct size from the table that can carry that volume of.
The table is based on the ducts friction loss formula.
The chart should not be used to design complete duct systems.
To insure proper distribution of air volume dampers must be used for all branch runs.
The furnace s british thermal units btus will help calculate the size it needs.
In order for your forced air furnace to work properly you have to have the right sizes of duct vents in each room expelling air.
Duct system sizes and airflow quick chart created date.
Round duct and rectangular duct comparison.
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 duct size duct height net inside dimension in inches round duct size estimate.
This equal friction method of duct sizing should be adequate for normal residential furnace heating and air conditioning applications.
If we compare round duct to rectangular duct we see that.
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.
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 unit and reasonable length duct runs.
