Can you cut ducting to size?

Ducts also have to be cut when sizes change, from a large central duct to a smaller one running to a room vent. Metal ducts can be either round or rectangular; flex duct is round, consisting of coiled wires inside an insulated metallic jacket.

How do you calculate CFM for ductwork?

To calculate CFM, you need to know the size of your heating or cooling unit in tons. Multiply this number by 400, which is the average output of an HVAC unit. Then divide by the total square footage of your home. This will give you the multiplier for all your rooms’ CFM.

How many CFM is a 12 inch round duct?

2000 cfm (0.94 m3/s) of air flows through a 10 x 12 inches rectangular duct. The friction loss according the table above is 0.81 inches water gauge per 100 ft duct (aprox. 6.6 Pa/m). The velocity in the the equivalent 12 inch circular duct according the table above is 2589 ft/min (13.2 m/s).

How big is a 100 ft HVAC duct?

The friction loss according the table above is 0.81 inches water gauge per 100 ft duct (aprox. 6.6 Pa/m). The velocity in the rectangular duct is v = (2000 cfm) / (((10 inches) (1/12 ft/inches) ((12 inches) (1/12 ft/inches))) = 2400 ft/min (12.2 m/s)

What is the diameter of an equivalent duct?

The equivalent diameter is the diameter of a circular duct or pipe that gives the same pressure loss as an equivalent rectangular duct or pipe. The table below can be used to compare equivalent diameters for rectangular and round circular ducts. The table is based on the ducts friction loss formula.

What is the velocity of a rectangular duct?

The velocity in the rectangular duct is v = (2000 cfm) / (((10 inches) (1/12 ft/inches) ((12 inches) (1/12 ft/inches))) = 2400 ft/min (12.2 m/s) The velocity in the the equivalent 12 inch circular duct according the table above is 2589 ft/min (13.2 m/s).