Preventing condensation and frosting in an energy recovery ventilator using a preheat coil

One of the problems presented by energy recovery ventilators (ERV) is the condensation/frosting problem that occurs during winter time. In order to prevent this problem, preheating outdoor air is the most common method used nowadays. The aim of this research is to evaluate preheat coil capacities according to different indoor/outdoor inlet air conditions (temperatures and humidities) and sensible/latent effectiveness of ERV (εS, εL). Considering all these factors, formulas for calculating a frost threshold temperature (TFrost)are suggested, Tfrost being the minimum inlet outdoor temperature at which condensation/frosting occurs under specific conditions. As a result, a control strategy for operating preheat coils for preventing condensation/frosting problems in ERVs is presented. For an ERV operating under outdoor inlet air conditions of -15 ˚C and 70% indoor inlet air conditions of 22˚C and 50% humidity, and sensible effectiveness is 80%, latent effectiveness is 70%, the capacity needed for the preheat coil is 227 W. In addition, preheat coil capacities were calculated for the operation of an ERV in a few cities of AIVC countries.