To move the 1000 CFM required by a 2.5 ton system (approximately 400 CFM per ton), two 14″ flexible return ducts or one very short flexible 18″ duct would be required for the 2.5 ton system to move the 1000 CFM.
How big should my return air grill be?
A return air grill should be designed for air speeds ranging from 300 to 500 feet per minute (FPM) (feet per minute). For the sake of this computation, the median air speed is 400 FPM. We are looking for the ability to transfer 980CFM, therefore divide this figure by 400 FPM, which gives us a result of 2.45 or 2.5. Convert this measurement from centimeters to inches.
What size return is needed for a 2 ton AC unit?
According to this rule of thumb technique, a 20 x 20 return filter grille would be required for a 2 ton unit with an airflow rating of 800 CFM.
How much return air do I need per ton?
There is no such thing as too much return air; as an HVAC contractor, you should aim for no less than 144 square inches per ton of air. In regards to the 3.5 TON vs. 4 TON comparison, Given that the average square foot per ton is 400, if the house is 1600 SQFT, a 4 TON unit should provide adequate cooling.
How many vents should a 2.5 ton AC unit have?
To move the 1000 CFM required for a 2.5 ton system (about 400 CFM per ton), two 14″ flexible return ducts or one extremely short flexible 18″ duct would be required for the 2.5 ton system to carry the 1000 CFM.
What size return do I need for a 3.5 ton?
Electric heat pumps must be tested in line with UL 559 or UL 1995 standards before being installed. As an illustration, consider a 3.5 ton heat pump. The ductwork for this system must be sized in accordance with the rule of six square inches of clear duct space per 1000 BTU of cooling. 12,000 BTUs are contained in each ton of cooling fluid.
What is a return grill?
It is connected to ductwork and allows air to be returned to any cooling or heating system through this connection. Grillwork is typically used to cover the openings that connect to ductwork and other spaces where returning air is distributed. In such cases, a return air grill will protect the ducts and can also be used to regulate the flow of air.
What size filter grill do I need?
Expect 2 CFM per square inch of filter grille area to be required for optimum performance. As a result, if your furnace produces 800 CFM, you will want 400 square inches of filter grille space.
What happens if there is not enough return air?
If your HVAC system does not have enough return air available, it will not be able to heat or cool correctly. Your HVAC system will not be able to keep up with temperature demands if not enough air is carried back into the building. In rare instances, two returns may be required in order to supply sufficient return air.
Can you have too much return air?
It is impossible for your HVAC system to heat or cool adequately if there is insufficient return air. If your HVAC system is unable to keep up with temperature demands because not enough air is returned, it will fail. Depending on the situation, it may be essential to install two returns to ensure adequate return air.
Can you have too many return air vents?
Having many return vents (preferably one in each room, but even two or three are preferable to one) helps to maintain consistent air pressure throughout the house. If your home only has one return vent, everything is OK. Keep the doors to each room open to ensure that air may flow correctly.
How do you calculate return on supply and air?
As an example, 200 CFM of outside air divided by 2000 CFM of supply air equals 10% outside air in the system. Afterwards, subtract the percent of outside air from the airflow of each return air grille in the system (as determined above) to obtain the needed adjusted return airflow.
How big does a return air plenum need to be?
The length of a single plenum should not exceed 24 feet in total. The entire length of a double plenum should not exceed 48 feet in total.
What size should the return air grill be for a 5 ton AC unit?
25-in. x 30-in. When designing a five-ton system, return grilles are the best option for delivering 2,000 cubic feet per minute (cfm) back to the blower without causing the return to bleed.