Home Inspection State Practice Exam

What might indicate a dirty filter while inspecting a heat pump in cooling mode?

1. High interior humidity levels

2. Low temperature differential

3. 28°F temperature differential between supply and return air

4. Running unit with loud noise

The correct answer is: 28°F temperature differential between supply and return air

A 28°F temperature differential between supply and return air in a heat pump while in cooling mode can indicate a dirty filter. In an efficiently operating system, the expected temperature difference is typically between 14°F to 22°F. When the filter is dirty, it restricts airflow to the system, leading to a larger temperature differential because the air is not circulating properly. This can cause the unit to struggle to cool the space, resulting in an increase in the temperature differential beyond the normal range. High humidity levels could also suggest that the system is not functioning properly, but this does not directly point to a dirty filter as the primary issue. Likewise, a low temperature differential indicates the system is not effectively cooling the space, which may suggest other faults rather than solely pointing to the filter condition. Excessive noise from the unit while running can arise from various mechanical issues or problems unrelated to the cleanliness of the filter itself, such as wear or damage to other components. Thus, the temperature differential emergingly shows a direct correlation to airflow issues likely caused by a dirty filter.