What is the difference between supply and return air?
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.