How should the amount of supply air relate to the amount of return and exhaust air?

The amount of supply air should be approximately equal to the amount of return and exhaust air in a balanced HVAC system. This balance is crucial for maintaining proper indoor air quality, temperature control, and energy efficiency.

When the supply air matches the return and exhaust air, it ensures that the space is neither pressurized nor depressurized. An equal balance allows for effective circulation of air, which helps in managing pollutants and maintaining optimal humidity levels. Additionally, it minimizes strain on the HVAC system, which can lead to reduced energy consumption and lower operational costs.

If the supply air were significantly less than the return and exhaust air, it could create negative pressure in the space, leading to issues such as drafts, infiltration of unconditioned outside air, and difficulty in achieving desired temperatures. Conversely, if the supply air were greater than the exhaust and return air, it might create positive pressure, resulting in poor air exchange and insufficient removal of indoor contaminants.

Therefore, for effective air management and overall system performance, maintaining a balance where the supply air is approximately equal to the return and exhaust air is essential.