[AIVC, Air infiltration and ventilation glossary, 1992]:(see heat exchanger (Air-to-Air); heat recovery effectiveness)[EN 14511-1:2022, 3.20]:recovery of heat rejected by the unit whose primary control is in the cooling mode by means of either an additional heat exchanger (e.g. a liquid chiller with an additional condenser) or by transferring the heat through the refrigerating system for use to unit whose primary control remains in the heating mode (e.g. variable refrigerant flow).[EN 12792-2003, 199]:heat utilized from a heating system, which would otherwise be wasted.