What operational requirement must the HVAC system fan meet in HRVs and ERVs?

In heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs), the operational requirement for the HVAC system fan is that it must be set to run continuously or on a timed basis. This requirement is crucial because continuous or timed operation ensures that adequate ventilation is provided in the building, enhancing indoor air quality by consistently exchanging stale indoor air with fresh outdoor air.

By maintaining this level of airflow, HRVs and ERVs can effectively perform their function of transferring heat or energy between the incoming and outgoing airstreams, thus improving energy efficiency while ensuring comfort. Additionally, specific timed operations can be programmed to match user patterns, ensuring that ventilation needs are met when they are most likely needed.

In contrast, continuously operating modes or timed options help to balance efficiency and air quality, making the system more effective in residential or commercial applications. This operational requirement supports building codes and health standards aimed at minimizing harmful pollutants indoors.