# How do you size a return air conditioning grill?

## How do you size a return air conditioning grill?

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).

## What size return grill do I need for a 3 ton system?

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 do you measure air return duct size?

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 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.

### How do I know my HVAC return size?

How big is a return air conditioner Grill?

(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 big should a grill return duct be?

The square root of 576 is 24. Therefore, your return air duct and grill size will be 24 by 24 inches.) Always place return ducts as far away from the supply air vents as possible.

## What should the air speed be on a return Grill?

A return air grill should be sized for an air speed of 300-500 FPM(feet per minute). 400 FPM is the median air speed for this calculation. We are after the ability to move 980CFM so you now divide this number by 400 FPM yielding 2.45 or 2.5.

How big of an area do you need for a filter Grill?

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. ton of cooling = 12,000 BTU ton of cooling = 400 CFM (approximate)