How big does return air vent need to be?


How big does return air vent need to be?

A typical supply vent is 4 by 10 to 12 inches and a typical return vent is 16 by 20 inches or larger. Houses often have two or more return collecting points, each with a filter, which join before re-entering the heating unit.

How do you size a return air grille?

In order to determine the size of the tonnage you have, simply divide 980 by 400 CFM per ton. Doing this for this space will yield a tonnage of 2.45. Always round up and we have a tonnage value of 2.5. A return air grill should be sized for an air speed of 300-500 FPM(feet per minute).

How many CFM do I need for a 4 ton unit?

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 return duct do I need for a 3 ton?

If the actual airflow is unknown, use 400 CFM for each ton of cooling. A 3-ton heat pump has approximately 1200 CFM of air flow.

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 can a 14 duct handle?

CFM Sizing Chart For Metal Round Ducts (50-2,000 CFM)

How many CFM is a ton of return?

Air quantities (cfm): 400 cfm per ton of cooling is needed for normal comfort applications, 500 cfm per ton of cooling for heat pump and high sensible heat applications, and 350 cfm per ton of cooling for high latent heat applications. Example: You determine a return grille pressure zone required 340 CFM of return.

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How many CFM do I need for a 12×12 room?

The rule of thumb is that you need at least 1 CFM per square foot of room area.

How many CFM is a 3 ton?

350 to 400 CFM per ton of cooling is required for proper air conditioning system operation. For example, if you are checking a 3 ton system, the airflow required is between 1050 and 1200 CFM.

How many square feet does a 3 ton unit cover?

How many CFM do I need for 1000 square feet?

Heat and energy recovery ventilators

What size should the return air grill be for a 5 ton AC unit?

x 25-in.

What size air conditioner do I need for a 2000 square foot home?

If your home is 2000 square feet, you can calculate your HVAC needs the same as you would for a 1600 square foot home. Assuming one ton of cooling capacity can cool 400 square feet of your home, you’ll need about 5.0 tons of air conditioning capacity. Multiply this by 12,000 BTUs, and you’ll get 60,000 BTUs.

Can you have too much return air?

You really cannot have too much return air. Too little return air is a problem, but not too much. If you restrict the return air, it could cause problems with short-cycling of the furnace.

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.

Do bedrooms need return air?

Does Every Room Need Air Return Grilles? 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. The most important place to have these would be the bedroom.

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What happens if return air is undersized?

If the return duct is too small, there are an inadequate number of return grilles or they are undersized, it can’t return enough air to recirculate back into the system. This poor airflow not only makes your system run longer than necessary to provide comfort, but increases your energy bill as well.

Can flex duct be used for return air?

Flex duct doesn’t come in an R12 version, so you will have to wrap it. Its fine to use for a return.

Should flex duct be pulled tight?

Flex duct should pulled tight to reduce inner air resistance. It should be supported with straps that are a minimum 1.5″ wide. The straps need to be spaced no further than 5 feet apart, but closer is better. Local codes or manufacturers instructions may specify shorter intervals.

Is flex duct better than hard duct?

If flexible ductwork is installed correctly, the airflow will be the same or better than a metal ductwork. It’s all in the installation. The advantage of metal ductwork is that you are taking less of a chance of the ductwork being installed wrong than with flexible ductwork.

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