Duct Sizes For Hvac Ducting

One six inch round duct is good for about 120 cfm a six inch duct carries about 150 cfm and eight inch carries about 200 cfm of cool air.

Duct sizes for hvac ducting.

For this reason homeowners may want to contact a certified hvac technician or contractor to determine the optimal size of ductwork throughout the home or business environment that also measures up to code standards. 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. So if you have a two ton system you need ductwork that will carry 800 cfm. Install the appropriate duct size connections.

Duct sizing how to size ductwork. How to determine duct size per room. Divide that number by 10 000 btus. Look at the plate on your furnace to figure out how many btus it produces.

Ducts that are too large will decrease the air flow velocity thereby allowing air to cool or warm before it reaches the registers. These charts hold a lot of information. Use insulated duct or duct board in unheated spaces. For instance a 2 5 ton system approximately 400 cfm per ton would require 2 14 flexible return ducts or 1 very short flexible 18 duct to move the 1000 cfm required by the 2 5 ton system.

Run the correct size from the furnace and be sure they are installed correctly. Some houses have ducts that are too large or too small. To size the ducts you re going to need a duct sizing chart. Once all the rooms are considered for duct size calculations increase the duct size accordingly.

Link 1 and link 2. Installing the duct incorrectly will affect the heating capacity of the system as much as improper sizing. To maintain a house s energy efficiency the correct heating duct sizes are crucial. If you don t have one you can find them in the following links.

Most cases the air in a duct is assumed to be incompressible an assumption that overlooks the change of air density that occurs as a result of pressure loss and flow in the ductwork. As systems increase in efficiency the tolerances of how we have always done it will no longer be adequate. For example if your furnace. The duct size must adequately handle air flow intake and return in order for an hvac system to operate at optimal levels.

In order to maintain velocity reduce duct size. Flexible duct work must be stretched tightly for maximum air flow. V 2 v 1 a 1 a 2. Also you want to make sure that the return ducts are the same size as the supply ducts.

You can obtain these from ductwork manufacturers or from industry bodies such as cibse and ashrae. Last take off run to be located 12 18 from end. Multiply that number by the amount of cubic feet of airflow per minute cfm your type of furnace.