Having proper duct size is vital to having a Portland air conditioning system that functions appropriately. If the air ducts are too small not enough cooled air will reach the intended rooms, if the ducts are too large the air will not have enough force to make its way from the AC to the room vents. As such there are some AC industry standards for duct sizing which should be followed by any Portland air conditioning professional.
Air Duct Sizing for Central AC Systems
While there are many misused rules of thumb in the AC industry, there are also some newer standards which have been put into place such as “Manual D” methods of design that have already begun to improve performance of AC systems in homes and offices.
There is a difference between what is needed for an AC system supply ducts and return ducts. Supply ducts tend to need smaller ducts while return ducts will often need to be larger.
Proper air duct sizing greatly depends on the square footage of the building being cooled, the air conditioner capacity or BTUs, how many ducts will be utilized, where they are positioned, and how many vents there are. Additionally, the entire system will need to be properly balanced so that the AC works efficiently.
Duct sizing is based on the air volume that will be produced and the velocity at which it will be flowing through the ducts. Determining the proper combination of these factors with the AC that will be used is essential to having a duct system that works efficiently. A good rule of thumb for proper air flow is to have anywhere from 600 to 900 feet per minute of air flow flowing through the ducts. To reach this, the cubic feet per minute will be determined, which will then be compared with a standard friction rate of 0.1 inches of water per 100 feet. This calculation will result in an appropriate duct size for either rectangular or round ducts based on the size of the building and how powerful the AC is.
Air ducts should be properly sized prior to being installed. Call The Clean Air Act, Inc. today to learn more about AC installation!