Pre-heating element for frost protection Ø125 - 1200W

If the unit has a high-efficiency counterflow heat exchanger (heat exchanger), ice may form in the exchanger during periods of cold weather. This will result in reduced heat recovery and potentially cause a draught in the dwelling at night. 

In order to prevent icing of the counterflow heat exchanger during cold periods, it is recommended that you install a pre-heating element for frost protection before the unit. The pre-heating element ensures that the outdoor temperature does not fall below -3 ºC. It regulates in steps to avoid unnecessary energy consumption. 

Duct connections Ø125 mm with rubber gasket
Output 1200W
Max. phase current 5,5A
Voltage 230V - 50 Hz
Airflow >1,5 m/s
Min. air volume 70 m3/h
Plate type Aluzinc steel plate
Tightness class IP44
Heating element Stainless steel ASI304
Max. thermostat Turns off if the temperature > 50 ºC (at vertical installation > 70 ºC)
Safety thermostat Turns off if the temperature > 100 ºC. Then reset manually


Calculation of correct pre-heating element​:

Δt * air density * air volume [m3/h]

e.g.: The pre-heating element must give frost protection down to -15°C and the air volume is m3/h.

15 * 0,34 * 100 = 510W

In the table below we have calculated the energy consumption when using a pre-heating element for frost protection. The calculations clearly show that it is worth using energy on frost protection because you achieve an overall reduction in energy consumption. 

Air volume 126 m3/h* 216 m3/h**
Frost protection at outdoor temperature -2 ºC -2 ºC
Hours per year *** 676 676
Energy for frost protection via pre-heating element 107 kWh/år 183 kWh/år
Energy loss when icing occurs 105 kWh/år 180 kWh/år
Energy loss when de-icing 200 kWh/år 343 kWh/år
Energy saved with frost protection​ 198 kWh/år 340 kWh/år

*Average for apartment
**Average for detached house
***Average calculated from Danish DRY weather data

It is important that the temperature sensor is placed at least 25 cm from the pre-heating element in order to achieve efficient regulation.

ATTENTION! The heating element must be insulated with a fire retardant insulation material. The cover of the connection box, however, must not be insulated.

Positioning options: