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A 3-ton heat pump has approximately 1200 CFM of air flow. To calculate the filter grill size, divide the airflow, (CFM), by 2. One filter grill or the total area of all grills must equal at least 600 square inches of area to adequately supply the system with the air needed to operate.
How much return air do I need per ton?
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 big should my return air be?
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.
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.
How many returns do I need for a 4 ton unit?
(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 return air 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.
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 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.
Do you need return air in every room?
While it is a myth that air return grilles are required in each and every room in the house, it is definitely necessary to have more than one of these grilles installed at strategic places in the house. Likewise, you can also install these in rooms that have a high footfall or usage in the house.
How many CFM is a 2.5 ton unit?
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.
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 do I know if I have enough return air?
Try this simple test when your HVAC system is running: get a piece of tissue paper and dangle it about six inches from one of the return vents. You should be able to see it being gently pulled towards the vent. Next, place it up against return vent and see if the air suction holds it in place.
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.
Should return duct be same size as supply?
Yes, return ducts are usually larger than supply ducts to ensure that air within the home is balanced. There are generally more supply vents in the system creating the need for return vents to be larger.
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.
What happens if ductwork is undersized?
Ducts that are undersized will increase the static pressure, which will result in excessive noise as air moves through the system. It is often loud enough to be distracting, so it will not be difficult to overlook and should be addressed, as undersized ducts overwork the heating unit.
How many CFM’s does a 4 ton AC unit put out?
1 ton of cooling is equal to 400 cubic feet of air per minute. 2 ton of cooling is 800 cfm and so on. So a 4 ton unit will have 1600 cubic feet of air passing through the system every minute.
What size should my ductwork be?
The size of your duct work depends not just on the size of your entire house but also on the size of each individual room. Thus, one needs to gauge the square footage of the entire house as well as that of all the different rooms in order to decide duct work sizing.
