What size should a return air duct be?
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. Multiply the tonnage, 3.5, by the total BTU per ton and this will give you the total BTU rating.
Are cold air return vents necessary?
Cold air return vents aren’t the most elegant feature in your home, but they exist for reason. These vents, commonly found in hallways or on ceilings, are absolutely essential to an air conditioner’s well-being. Cold air returns take in warm air from your home’s indoor spaces for use in your air conditioning system.
How many cold air return vents do you need?
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.
Does every room need a return duct?
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.
Can I add a return vent?
A second return duct can lower static pressure if the airflow bottleneck is on the return side. If the static is on the supply side, adding a second return will do nothing. So it’s usually a good idea.
Can you have too much cold air return?
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 happens if my 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.
Can flex duct be used for return air?
Yes! You can use flex ducts for your return ducts. However, you have to make sure it fulfills all the necessary criteria. These include pressure checks, proper wrapping, and marking, airflow control, etc.
Can flexible duct be used for return air?
How do cold air return vents work?
Cold air return vents work by allowing cool air to be suctioned into a furnace or heating/air conditioning system. The cool air is then heated or cooled, depending on the system setting, and forced back out into the home or building.
How much return air duct needed?
To keep air speed down to 600 feet/min (Chapter 3 of Manual D), on a 5-ton system with 2000 cfm airflow you need one 24-inch return duct or two 18-inch. This is 450-500 square inches of duct cross section area. Possibly your system design will call for 350 cfm/ton and the total airflow will be lower.
What materials can be used to create cold air returns?
A cold-air return duct connects to a floor or wall return register and circulates air from each room back to a furnace for reheating. You can run a return made out of duct board instead of sheet metal to provide less leakage and loss of heat.
Should cold air returns be near the ceiling or on the floor?
In an air conditioning climate the return duct goes near the ceiling to draw off the hot air and cool it down. In a heating climate, the return duct goes near the floor to draw off the cold air and heat it up. The problem comes when you use both heating and air conditioning.