What is the difference between supply and return air?

Asked By: Pantaleona Aylon | Last Updated: 29th June, 2020
Category: home and garden indoor environmental quality
4.8/5 (204 Views . 14 Votes)
The biggest difference between supply and return vents is the direction in which the air flows. In a supply vent, the air flows out of the ductwork. In a return vent, the air flows into the ductwork. A second difference is the size of the vents.

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Similarly, you may ask, how does supply and return air work?

The supply vents in your home blow conditioned air out into your rooms. This air travels from your heating and cooling system, through your ductwork and out of the supply vents. The return vents in your home suck the air from your rooms into your return ducts and back to your heating and cooling system.

Secondly, does every room need return air? 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.

Also asked, what should the temperature difference be between supply and return?

The temperature your AC puts out is relative to the temperature you set on your thermostat. So even though there's no single ideal temperature, you do want a 16°–22° F difference from the supply air and return air. Professionals call this temperature difference the evaporator Delta T.

What is supply air?

Supply Air. Supply Air. Supply air containing at least the minimum volume of outside air is filtered and conditioned to the required temperature and humidity. It is then delivered by the AHU to an underfloor plenum, traveling through a shorter distance of ductwork than for ceiling-based systems.

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How do you increase return air flow?

3 Simple Ways to Improve Your Furnace's Airflow for More Comfort
  1. Unblock and clean your vents. Here's a super easy way to increase air flow.
  2. Change your filters and clean your return grill. A dirty air filter impedes air movement and makes it hard for your furnace to work efficiently.
  3. Seal leaky ductwork. Snap on some goggles and a dust mask, it's time to check out your air ducts.

Is it OK to cover a return air vent?

Avoid covering your cold air return vents with curtains, drapes or rugs. Always check your air filters and replace them when needed. Clogged air filters can also cause cold air return blockages.

How do I increase the airflow in a room?

How to Increase Airflow to One Room
  1. Change your air filter – A dirty air filter restricts the flow of air throughout the system by forcing it along an alternate path.
  2. Clear your vents – Supply and return vents should remain open and unencumbered by furniture, drapery, or other large objects.

Can you have too much return air?

While there is no such thing as too much return air for the equipment (actually, there is, and it causes fan cavitation, but very rare), this CAN be an issue for the house. It has the potential to throw off pressures in different areas of the house.

What is the purpose of return air ducts?


Return air ducts balance airflow in your HVAC system — The primary role of return ducts is to bring air that has been warmed or cooled back to your furnace or air conditioner. This air is returned so that it can be heated or cooled again, filtered of particulates and contaminants, and redistributed inside your home.

Should I put filters in my return vents?

Do not put filters in your supply vents. Your AC system should have a proper fitting filter on the return side. By placing a good fitting, high quality filter on the return vent, you will remove particles from the air before they can enter the AC system.

How many registers should a room have?

AC Registers per Room. Under basic guidelines, HVAC experts recommend at least one AC register or duct per room. But number this isn't set in stone, as some owners may prefer more than one register for better airflow.

Do all return vents need filters?

I recommend filters at the return air vents especially if they are at floor level or the client has pets. They sure catch a lot of hair and debris. Much better to catch it there than have it gunk up the return air ducts. Much better to catch it there than have it gunk up the return air ducts.

What temperature air conditioner should be set to?

The Best Temperature Settings When You're at Home
To stay comfortable and save money this summer, the U.S. Department of Energy recommends setting your thermostat to 78F (26C) when you are home. Setting your air conditioner to this level will allow you to stay cool and avoid an unusually high electricity bill.

Should thermostat be near return air?


Mounting a thermostat near a return won't cause any issues because the air returning to the furnace is at room temperature. The return duct should be positioned near the floor or ceiling, which will provide several feet between the thermostat and the moving air.

How do I know if my return air is working?

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.

Which return vents should be open?

Some say that the upper returns should be closed when the heat is running (to circulate out the cold air), and the lower returns should be closed when the A/C is running (to circulate out the warm air). Others say that they should always be open (so the HVAC unit doesn't have trouble pulling in air).

How low can I set my thermostat in the summer?

When your home will be empty for 8 hours or longer, set your thermostat 5°-8° higher in the summer and 10°-15° lower in the winter. When you get home, set the thermostat back to your comfortable setting.

How cold should my AC be at the vent?

If the AC system is operating correctly, then the air coming out of your vent should be about twenty degrees cooler than the regular temperature inside. So, if you're cooling it and the house is 80 degrees, then you would ideally want the air to be about 60 degrees.

Where should the return vent be located?


Place your cold air return vents on the inside walls of buildings at the lowest point. The return vent pulls cold air from the bottom of the room and returns it to the furnace to be reheated and returned as warm air. Unlike supply vents, return vents do not need to be cased in metal.

Does outside temperature affect air conditioner?

Outside Temperature. The lower the temperature of the outside air, the more cooling is done by the heat exchanger, instead of the compressor. When the outside air temperature increases, the air-conditioner works harder to cool the home because the compressor works more.

How can I increase the airflow in my room?

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. Another simple solution for improving airflow is to turn on your ceiling fans.
  3. Schedule HVAC Maintenance.
  4. Consider Duct Cleaning.
  5. Invest in a Ventilator.