How large should return air duct 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).

How many cold air returns do I need?





How many cold air returns do I need? Ideally you want a cold air return register in every major room in your home. This would not include bathrooms and closets, but bedrooms, living rooms, etc. Older homes might only have just one or two on each floor.

Is return duct bigger than supply?

The return vents in your home suck the air from your rooms into your return ducts and back to your heating and cooling system. Your return vents are typically larger than supply vents, and you will not feel air being blown out of them.

Where should I put my return and supply ducts?

They must be correctly placed and unobstructed —Return ducts are usually placed in hallways, under stairwells, or in larger open areas of your home. This placement ensures that they will be able to pull in enough air to take back to the HVAC equipment.

Can you have too much return air ducts?

This isn’t the most efficient system. 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.

Can you have too many air returns?





To answer your question, no, you normally cannot supply too much return air. If installed in a certain fashion, with bedroom doors closed, it is possible to put a single room or two under negative pressure but that won’t affect the amount of heat entering the room substantially.

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.

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.

How do you increase return air flow?

5 Ways to Improve Airflow in Your Home

  1. Check Vents and Registers. One of the simplest things you can do to increase airflow in your home is to check the vents and registers in each room. …
  2. Turn on Ceiling Fans. …
  3. Schedule HVAC Maintenance. …
  4. Consider Duct Cleaning. …
  5. Invest in a Ventilator.



How far away should a return vent be from a supply vent?

Return vent on wall adjacent to wall of supply vent. The return vent would be approximately five feet away from the supply vent.

What is the disadvantage in having ducts in the ceiling?

Cons of ceiling vents



Exposes HVAC system to unconditioned spaces – Attics tend to be dusty and prone to extreme temperatures, which can add wear-and-tear on the equipment and increase heat transfer loss.

How many heat vents should be in a room?



Generally, the size of your home determines how many vents you will need per room. If your room is larger than 100 square feet, you will need more than one vent (at least two) to really get adequate airflow to the room. If the room is smaller, you only need one.

Why does my house have 2 air return vents?

Having two air return vents allows you to seasonally control which air is returning to the HVAC system. In older homes, this may not be an option. The theory is that in the Summer cooling season, you want to be circulating warmer air back through the HVAC system to be cooled.

Why does my house have so many return vents?

Your return vents are an indispensable part of the HVAC system in your house. They function to keep your interior pressurized as well as the interior air clean as they feed air to the air handler.

What size return do I need for a 3 ton AC unit?

Recommended airflow is typically 400 cfm per ton of AC. A 3 ton AC would therefore need 1200 cfm airflow. With only 423 sq in of return your air velocity through the grille would be just over 400 ft/min, a good number as far as noise is concerned.

Can duct work be too big?



Too big – Oversized ducts will give the heated or cooled air they carry more time to come to room temperature before they get through the vents and into the room, so you’ll end up with less heating or cooling where you want it, and the system being overworked to meet demand.

How big should supply duct be?

The size of the HVAC unit you’ll need for the whole house can be found using the unit’s average output and the square footage of your home. As a rule of thumb, you’ll need 400 CFM of airflow per ton of air conditioning; it takes about 1 CFM of air to heat or cool 1 to 1.25 square feet of floor area.

How do I know if I have enough return air?

If you were to put a wet finger close to the vent that is generating airflow, you should be able to tell if there is a lot of airflow or not enough airflow. This is the simplest way to tell if you are getting enough return air. If you lick your finger and put it close to the return vents, you will feel the airflow.

How do you design a return air duct?

Quote from the video:
Quote from Youtube video: With one ton of air you need 400 CFM worth of space which is cubic feet per minute worth of space in order to fit all of that airflow into the duct.

Do you need a cold air return 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. The most important place to have these would be the bedroom.

What size return do I need for a 3 ton AC unit?

Recommended airflow is typically 400 cfm per ton of AC. A 3 ton AC would therefore need 1200 cfm airflow. With only 423 sq in of return your air velocity through the grille would be just over 400 ft/min, a good number as far as noise is concerned.

What is the most efficient ductwork?

For instance, round duct is the more efficient shape in terms of material use, resistance to airflow, and air leakage. “The tradeoff is that round duct will not always fit in the space provided. In these cases the duct is converted to rectangular or flat-oval so that it can fit the available space.

Is round ductwork better than rectangular?

In many ways, round metal duct work is more economical than rectangular metal duct work as a means of conveying air. 1) Size: For a given pressure loss, the surface area of rectangular duct can be double the comparable round duct surface area. Round duct, therefore, requires less metal than rectangular equivalents.

What is the most energy efficient shape of duct?

Round Round ducts

Round. Round ducts are the most efficient in transporting air. They use less material than rectangular ducts to handle the same amount of air.