The HRXE-HERA models have been designed with 100% automatic bypass, as listed on the SAP Products Characteristics Database (PCDB). The HRXE-HERA range operate by continuously extracting moisture laden air from wet rooms within the property whilst simultaneously drawing in fresh, filtered supply air from outside. The heat from the extracted stale air is recovered via a heat exchanger inside the heat recovery unit which becomes tempered and filtered before supplied into the habitable rooms, creating comfortable and well ventilated homes.