Freezing condensation in exhaust air on the exhaust coil
prevented with a freeze pretection bypass.
Konvekta high performance energy recovery coils provide very high heat transfer with very low approach temperatures. This means that in very cold climates, the fluid circuit is potentially cooled as low as -10°F/-23°C or even colder. If fluid at -10°F/-23°C enters the exhaust coils, it will cool the exhaust air below the dew point and condense the moisture, which creates frost and ice on the exhaust coils. This causes air flow and eventually permanent damage to the coils. To prevent this, Konvekta installs a bypass line on the Hydronic Module to allow warm fluid coming from the exhaust coils to mix with the cold fluid from the supply coils until the fluid going to the exhaust coils is at least 28.4°F/-2°C. At this temperature the condensation in the exhaust air will never freeze.
Free supplemental heat or free-cooling
Data centers and other high-occupancy building areas generate waste heat that can be used as a source to heat the fluid circuit when necessary. A plate and frame heat exchanger can be installed on the hydronic module to transfer this waste heat to the fluid circuit. If this addition of waste heat to the fluid circuit doesn't heat the return fluid to 28.4°F/-2°C, the bypass will still open to achieve this minimum fluid temperature.
This will reduce the performance of the heat recovery system, but since sub-zero temperatures only occur very few hours per year, the overall impact is very minor.
See also: Free-cooling