1. Leak Prevention: The primary condensate pan of an air handler is designed to collect water that forms as a result of condensation from the cooling process. If this primary pan becomes blocked or damaged, water can overflow, potentially causing damage to ceilings, walls, and other structures below. The secondary drain pan acts as a backup, capturing any overflow and preventing it from causing damage.
2. Protection: In locations like attics where an air handler is commonly installed, leaks from the primary condensate pan can go unnoticed for extended periods, leading to significant water damage. The secondary drain pan provides an additional layer of protection, reducing the risk of damage to the building and its contents.
3. Code Compliance: Many building codes and regulations require the installation of secondary drain pans for air handlers in certain locations, such as attics or above ceilings. Compliance with these codes helps ensure the safety and integrity of the building.
4. Early Warning System: If water accumulates in the secondary drain pan, it can serve as an early warning sign that there is a problem with the primary condensate pan or the HVAC system. This allows for timely inspection and maintenance to prevent potential issues from escalating.

In summary, a secondary drain pan for an attic air handler is a crucial component of the HVAC system, providing backup protection against condensate overflow and helping to prevent water damage in the event of primary pan failure.