An integrated Defrost Mode control sequence is designed to maximize heat pump runtime and maintain system capacity during cold, humid conditions when frost accumulation on the outdoor coil is most likely. Instead of relying solely on outdoor dry-bulb temperature as a trigger, Greenheck’s control strategy monitors outdoor air dew point to more accurately predict frost formation potential.

Because frost development is directly influenced by moisture content in the air, using dew point as the initiating parameter allows the system to enter Defrost Mode only when conditions truly warrant it. This approach reduces unnecessary defrost cycles in dry-cold climates, improves overall system efficiency, and minimizes disruptions to heating performance.

By aligning defrost initiation with psychrometric conditions rather than temperature alone, the unit can operate longer in heating mode, maintain more stable supply air temperatures, and reduce energy penalties associated with excessive defrost operation. The result is optimized cold weather performance, improved reliability, and greater seasonal efficiency in climates where humidity and temperature fluctuate.

Air-source heat pumps (ASHPs) can experience reduced capacity and efficiency when operating in extreme ambient conditions, particularly during very cold winters or hot, humid summers. Integrating energy recovery into the system design helps mitigate these challenges by preconditioning the incoming outdoor air before it reaches the heating or cooling coils. By tempering ventilation air with recovered energy from the exhaust airstream, the system reduces the load imposed on the ASHP and improves overall system stability and performance.

In heating mode, energy recovery devices transfer sensible (and, when applicable, latent) energy from the warmer exhaust air to the colder incoming outdoor air, effectively raising the entering air temperature at the coil. This reduces compressor lift, decreases defrost frequency, and helps maintain heating capacity in low-ambient conditions. In cooling mode, recovered energy lowers the entering dry-bulb temperature and can reduce moisture content, decreasing the latent load on the cooling system and improving overall efficiency.

Greenheck Models RVE and RVC are available with multiple energy recovery configurations, including total energy wheels and total enthalpy cores, allowing engineers to select the appropriate solution based on climate zone, ventilation requirements, building occupancy, and performance objectives. This flexibility supports compliance with energy codes, enhances part-load efficiency, and helps stabilize ASHP operation across a wide range of design conditions. The result is a more resilient, efficient HVAC system capable of maintaining comfort while reducing energy consumption and supporting electrification and decarbonization strategies.