Multiply the tonnage, 3.5, by the total BTU per ton and this will give you the total BTU rating. Multiply 6 x 42 to determine the duct size of 252 square inches The clear are of the duct must be at least 252 square inches This measurement also includes the opening in the floor at the bottom of the return.Jun 9, 2004
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.Jul 1, 2015
How is HVAC duct measured?
To do this, measure one side from top to bottom and measure across the top from edge to edge. For example, if the duct measures 12 inches by 24 inches, the contractor can determine the capacity of the primary duct using a standard calculation table.
How do I know what size ductwork I need?
To calculate the required equipment size, divide the HVAC load for the entire building by 12,000. One ton equals 12,000 BTUs, so if a house or office needs 24,000 BTUs, it will take a 2-ton HVAC unit.
To calculate the required equipment size, divide the HVAC load for the entire building by 12,000. One ton equals 12,000 BTUs, so if a house or office needs 24,000 BTUs, it will take a 2-ton HVAC unit. If you get an uneven number, such as 2.33 for a 28,000 BTU load capacity, round up to a 2.5-ton unit.
How do you calculate CFM for duct size?
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.
What size air duct do I need?
The size of the HVAC unit you'll need for the whole house can be found using the unit's average output and the square footage of your home. As a rule of thumb, you'll need 400 CFM of airflow per ton of air conditioning; it takes about 1 CFM of air to heat or cool 1 to 1.25 square feet of floor area.Nov 7, 2021
How many AC vents do I need?
Generally, the size of your home determines how many vents you will need per room. If your room is larger than 100 square feet, you will need more than one vent (at least two) to really get adequate airflow to the room. If the room is smaller, you only need one.
How many supply vents should a house have?
Having several return vents (ideally one in every room, but even two or three is better than just one) creates consistent air pressure. If you have one return vent, your home is fine. Keep the doors to each room open so air can properly circulate.Feb 16, 2017
Where should AC vents be placed?
Registers should be placed in the middle of the external wall (in the floor or low on the wall); if there are two external walls, both need registers in the middle. (If the room is tiny, one duct may work, even if there are two external walls.)Jul 4, 1992