Table of Contents
Electric heat pumps shall be tested in accordance with UL 559 or UL 1995. Example: 3.5 ton heat pump. The duct for this system must be sized by using 6 square inches of clear duct area for each 1000 BTU of cooling. Each ton of cooling contains 12,000 BTU.
How big of a return does a 4 ton unit need?
You can never have to much return air, as a HVAC contractor you want no less than 144 square inches per ton. Regarding the 3.5 TON VS 4 TON The average square foot per Ton is 400 so say the house is 1600 SQFT a 4 TON unit should work great.
How large should return air duct be?
A typical return vent is 16 inches by 20 inches, according to Hunker.
What size duct do I need for a 4 ton unit?
Calculate the square root of the total. (Example: 4 (ton unit) x 144 square inches = 576 squared. The square root of 576 is 24. Therefore, your return air duct and grill size will be 24 by 24 inches.).
How many CFM is a 3.5 ton?
How many cfm for 1 – 5 ton ac unit ? Cooling Capacity CFM (Airflow) How many CFM is a 2 ton ac unit? 700 – 800 CFM How many CFM is a 2.5 ton ac unit? 875 – 1000 CFM How many CFM is a 3 ton ac unit? 1050 – 1200 CFM How many CFM is a 3.5 ton ac unit? 1225 – 1400 CFM.
What size ductwork do I need for a 3 ton unit?
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.
What size return do I need?
Generally, if you are using a Duct Sizing Chart or calculator (such as the Trane Ductulator), size the re- turn ducts for 0.05 inches/100 ft (0.40 Pa/m) based on the expected airflow through that return air duct. The total sum of air from all the returns should be at least 250 CFM/nominal ton (33 l/s per-kW).
Can a return air duct be too big?
Can an air return be too big? No, an air return cannot be too big, except in extreme cases where a closed room is temporarily under negative air pressure. Return vents maintain air pressure, filter out debris, and are critical to the efficient operation of any HVAC system.
Can you have too many return air vents?
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.
What happens if there is not enough return air?
If there is not enough return air available, your HVAC system will not heat or cool properly. If not enough air is brought back, your HVAC system will not be able to keep up with temperature demands. In some cases, two returns may be necessary to provide enough return air.
What size duct do I need for a 12×12 room?
A 12×12 foot room will need a 4×8 inch supply duct to get an adequate CFM rate, which is about 144 CFM.
How many CFM is a ton of return?
The airflow is measured in cubic feet per minute (CFM). 350 to 400 CFM per ton of cooling is required for proper air conditioning system operation.
How many CFM do I need for 600 square feet?
160 CFM Room Size: CFM (At 2 ACH) How many CFM for a 500 sq ft room? 133 CFM How many CFM for a 600 sq ft room? 160 CFM.
What size ductwork do I need for a 5 ton unit?
Using this approach, two 20-in. x 25-in. return grilles will be the right choice for a five-ton HVAC system in order to actually deliver 2,000 cfm back to the blower without causing the return to hemorrhage.
How do you calculate return on supply and air?
Example: 200 CFM outside air divided by 2000 CFM of supply air equals 10% outside air. Then subtract the percent of outside air from each return air grille airflow in the system (as calculated above) to find the required adjusted return airflow.
Can flex duct be used for return air?
Flex duct is widely used for return air in commercial air conditioning systems. Flex duct is able to withstand a certain negative pressure of return air. When installed properly, a flex duct is a reliable and convenient ductwork solution. Flex duct often gets a bad rep because of airflow issues.
Does register size matter?
Unless you are severely undersizing your register, the noise is really the only issue. So a bigger register will not help cool or heat your room better. Putting the register in a better location and making sure the air is shooting out in an efficient manner and at an efficient angle is key.
How do I know what size flex duct I need?
Measure the length and width of the room where the flex duct will be supplying the air. Multiply the length and width together to get the square footage of the room. For example, a 10-by-10 room will be 100 square feet.
What size should the return air grill be for a 5 ton AC unit?
x 25-in. Return grilles are the best choice for a five-ton system in order to deliver 2,000 cfm back to the blower without causing the return to hemorrhage.
How many vents should a 2.5 ton AC unit have?
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.
