What size return duct do I need for a 3 ton?
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.
How big should my return grill be?
Quote from the video:
Quote from Youtube video: We got 200 square inches x 1.5 equals 300 it's okay to go over. It's not okay to go under.
What size ducts should my return air be?
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 size a return air conditioning grill?
To calculate return air grille size, take the CFM of the HVAC unit and divide it by 350 to get the grille area in square feet. Next, multiply the grille area by 144 to convert it into square inches. Finally, choose your preferred grille size that matches the required grille area.
How do you calculate duct size?
To calculate the required equipment size, divide the HVAC load for the entire building by 12,000. One ton equals 12,000 BTUs, so if a house or office needs 24,000 BTUs, it will take a 2-ton HVAC unit. If you get an uneven number, such as 2.33 for a 28,000 BTU load capacity, round up to a 2.5-ton unit.
Can ductwork 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.
What happens if return air is undersized?
If you can hear air moving at your return, chances are you have an undersized return duct. This leads to high bills, annoying noise and pre-mature blower motor burnout– meaning decreased system durability.
How much return air do I need per ton?
2: Sizing return grilles is easy; just use the 1 sq. ft. per ton or 100 sq.in. per ton rule of thumb.
How do I know what size cold air return I need?
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 duct should I use?
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.
Can air return too big?
No such thing as too much return. It will not take in any more air than it pushes out, thus no such thing as too big. Its hard to imagine a return that is too big ,but you want the return to have some draw to evacuate an area.
How much space does a cold air return need?
6-12 inches
So how much space does an air return vent need to work properly? Home Inspection Insider explains that an air return vent needs 6-12 inches of space in front of it, and recommends that you do not put large, bulky furniture like couches and bookshelves in front of an air return vent.
How do you increase return air flow?
5 Ways to Improve Airflow in Your Home
- 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. …
- Turn on Ceiling Fans. …
- Schedule HVAC Maintenance. …
- Consider Duct Cleaning. …
- Invest in a Ventilator.
Should cold air returns be high or low?
To ensure efficiency during the cooling season, your home should have high registers. High return registers draw hot air that rises to the ceiling back into the system to repeat the cooling cycle.
Where should a return air vent be located?
Return air vents are generally located near the center of the homes. Older and newer homes often have one register per floor, but homes built from 1960-1990 may have a cold return air vent in each room.
How many return air ducts do I need?
Your Home Might Not Have Enough Return Vents
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.
How do you calculate return air vents?
You can identify return vents by turning on the system fan and holding your hand or a piece of paper up. If the paper is pulled toward the vent or you feel a suction effect, it’s a return vent.
