One of the key aspects of any air cooled heat pump is the defrost cycle. The defrost cycle for an air cooled unit is the state when ice forms on the outside coils and the air cooled unit reverses the mode from heating to cooling. As a result, the hot gas melts the ice away. For the purpose of this blog, we are going to focus on Aermec's air to water heat pumps.
The defrost cycle typically happens when the outside air temperature is between the range of 25°F to 40°F. Above this temperature range the air is not cold enough for ice to form and below this temperature range there is not enough humidity in the air for frost on the coils to be of concern.
Being a European manufacturer, Aermec is required to declare the penalty in heating output due to the defrost cycle. This penalty is automatically included in every selection and data sheet Aermec provides and is often around 20% when the outside air temperature is between 25°F to 40°F.
In order to ensure the defrost penalty is as low as possible, Aermec has come up with a defrost logic called Intelligent Defrost to ensure the unit goes into defrost only when it is needed and stays in defrost just long enough for the all of the ice on the coil to melt.
How Does Intelligent Defrost Work?
Aermec air source heat pumps are constantly monitoring the outside air temperature and the suction pressure on the outside coil. These factors are the best way to tell when ice has formed on the outside coil. Essentially, the absolute suction pressure and the relative (rate of decay) suction pressure is being monitored. At a certain point, the unit realizes ice has formed on the condenser coil and the unit will start the defrost cycle. During the defrost cycle, the unit produces cold water, there is hot gas in the coils, and the fans will be off to ensure maximum heat in the coil. The defrost cycle will end based on the liquid line temperature and typically lasts 2-6 minutes.
Aermec's Intelligent Defrost has revolutionized the North American industry. For more information on Intelligent Defrost please contact your dedicated Aermec Sales Representative or email@example.com.