Comparison of Heat Recovery Ventilator Frost Control Techniques in the Canadian Arctic: Preheat and Recirculation

Abstract

Air-to-air heat/energy recovery ventilators can effectively reduce the cost associated with ventilating a home. However, high indoor moisture levels, in conjunction with extreme temperature differences between the outdoor and indoor air can cause frost accumulation in the mechanical equipment, leading to performance degradation or failure. In this research, a demonstration house using a heat recovery ventilation system in Iqaluit, Nunavut, Canada was used to compare the performance of two frost control techniques: recirculation and electrical preheat. The advantages and disadvantages of each method are outlined to highlight the need to adapt southern strategies to ensure system functionality in the Arctic. The system was equipped with a heat recovery ventilator (HRV) with built-in recirculation technology to defrost the HRV, as well as two electric preheaters that can be used instead of recirculation and prevent frost formation. Between December 2018 and April 2019 the ventilation system’s performance was monitored for seven weeks while using either recirculation or electrical preheat. The experiments showed the ventilation system equipment consumed more absolute energy with electrical preheat than with recirculation as the frost control technique. However, when using recirculation, the ventilation system experienced more losses throughout the ventilation system, causing the whole building to consume more energy due to an increase in energy consumption by the home’s heating system. Moreover, the quantity of outdoor air that was restricted while using recirculation made electrical preheat the superior option for this ventilation system design. The energy use of the ventilation system with electric preheat enabled was 35% lower on a per volume of outdoor air basis. Contrary to some belief that preheating is a poor approach for frost control in heat/energy recovery ventilators, this research finds that preheating can be a more energy efficient method to provide ventilation if controlled well.

Experimental study of a heat recovery ventilator preheated by a Building Integrated Photovoltaic system in a cold climate

“…This issue can be addressed by preheating the outside air before entering the HRV unit to reduce the frost risk of the heat exchanger core. Some studies [1][2][3] have been conducted regarding HRV preheating. The adoption of an electrical preheater can reduce the recirculation defrost of HRV at the cost of 1.5 to 2.3 times the ventilation energy increase depending on the cold climate locations of the HRV [1].…”

“…The adoption of an electrical preheater can reduce the recirculation defrost of HRV at the cost of 1.5 to 2.3 times the ventilation energy increase depending on the cold climate locations of the HRV [1]. Overall, the energy use of the HRV is greatly reduced when HRV preheating is not employed [4]. As reviewed by Rounis [5], building integrated photovoltaic/thermal collectors (BIPV/T) can serve multiple purposes.…”