OA Mixing distance
OA Mixing distance
(OP)
I am looking for a general rule for "thorough" mixing of outside air and return air prior to entering an air handler. The air handler in consideration has no mixing plenum, so this needs to happen upstream. To keep cost down, I would prefer to accomplish mixing without addition of an "air blender" device. What is a minimum or safe distance between the OA branch and the intake on the air handler to accomplish this?
For this example, I have ~25% outside air in a constant volume system.
TIA.
For this example, I have ~25% outside air in a constant volume system.
TIA.





RE: OA Mixing distance
RE: OA Mixing distance
Non-uniform air flow, or stratified air flow entering your coil can have a significant effect on the coil performance.
An air blender is a cheap, simple static device. Will pay for itself the first time you don't have to go investigate why the unit is no performing as expected
RE: OA Mixing distance
RE: OA Mixing distance
It would be better for the air stream to blow against each other using opposed blade damper. Another way would be to put a fan powered unit heater in the plenum to stir up the air. Put the thermostat low & set for 40°F.