In a single zone system, what could be the cause of a customer feeling damp or sticky?

The feeling of dampness or stickiness in a single zone system is often related to issues with humidity levels in the air. When unconditioned air is pulled into the ductwork through holes in the duct, it introduces outside humidity into the conditioned space. This unconditioned air typically has a higher moisture content, especially in certain weather conditions.

As the system continues to operate, this influx of humid air can overwhelm the capacity of the air conditioning system to dehumidify effectively, leading to discomfort for the occupants. In contrast, the other options may contribute to issues but do not directly explain the sensation of stickiness in this context as effectively as unconditioned air infiltration does.

Excessive humidity settings on the thermostat might lead to high humidity levels, but typically a well-functioning thermostat should not create that scenario on its own. Improperly sized air ducts can lead to airflow issues, but not specifically to a feeling of dampness; rather, it typically leads to temperature inconsistencies. Faulty compressor operation may also affect the overall performance but would more likely cause issues like inadequate cooling rather than specifically producing humidity problems. Thus, the influx of unconditioned air is the most direct and clear cause for the damp or sticky sensation experienced by