Under what circumstance is stratification desirable in an air handler unit mixed air plenum?

Stratification in an air handler unit mixed air plenum refers to the phenomenon where different layers of air are formed based on temperature or density differences, resulting in warmer air being at the top and cooler air at the bottom. Generally, this condition is not desirable because it can lead to inefficient mixing of air, causing comfort issues and uneven temperature distribution throughout the space being conditioned.

In an ideal air handler operation, the goal is to achieve a uniform distribution of conditioned air that is evenly mixed before it is introduced into the occupied space. When stratification occurs, the efficiency of the system can be compromised, since some areas may receive too much or too little heating or cooling, leading to increased energy consumption and potential complaints regarding thermal comfort.

While there might be specific scenarios in advanced designs where limited stratification could be beneficial under controlled conditions, these are exceptions rather than the rule within standard HVAC practices. Thus, it is generally accurate to state that stratification is not a desirable condition in typical operations of air handler units.