What can impact capacity and lead to evaporator coil freezing according to ACCA Manual D?

The impact of undersized ducts on capacity and the potential for evaporator coil freezing is significant, as described in ACCA Manual D. When ducts are too small to accommodate the required airflow for the system, the air velocity increases, but the volume of air delivered decreases, causing the system to struggle to maintain the designed temperature. This reduces the capacity of the air conditioning unit to effectively cool the space.

As a result of insufficient airflow, the evaporator coil may not receive enough warm air to transfer heat away effectively. When the air does not circulate properly over the coil, it can lead to a drop in temperature on the coil's surface. If the surface temperature of the evaporator coil drops below the freezing point of water, moisture can condense on the coil and eventually freeze, causing ice buildup. This ice not only restricts airflow even further but also diminishes the overall efficiency of the HVAC system, leading to potential operational failures.

In contrast, the other options—such as improper insulation, oversized ducts, and dirty filters—can affect system performance but do not directly cause the same mechanism of freezing in the evaporator coil as undersized ducts do. While these factors may contribute to inefficiencies and other operational issues, it is the duct sizing that