Freezing characteristics

Due to the narrow construction depth and the good axial temperature conductivity, rotor-systems do not freeze tight in central European climates and normal operational conditions.

There is a risk of freezing when employed in countries with outdoor temperatures of below -25 °C.

In case of longer operation at such cold outdoor temperatures a layer of ice can form inside the rotor heat storing mass channels. This ice layer increases the pressure drop on the air side.

Solutions are also available for such operational conditions in order to ensure a fault-free operation of the rotorsystem.

Freezing characteristics 1

Valid as a rule of thumb under the condition of equal air flow rates:
If tm = (t11+t21) / 2 = 0°C
no freeze problems exists..

Solution 1:

Connecting a difference pressure switch to the rotortronic variable speed drive system. To thaw the ice layer the rotor is briefly run at low speed until the normal pressure drop has been reattained.

Solution 2:

A further possibility is the brief reduction of the outdoor air flow that flows over the rotor. At pressure increase a partial outdoor air flow is fed past the rotor until the pressure drop has dropped to the normal level.

Solution 3:

Temporary mixing of the circulating air into the outdoor air side before entering the rotor.

Solution 4:

Special device with ring chamber heating for especially extreme conditions.


In Scandinavia and Eastern Europe rotorsystems are reliably run with the methods mentioned above at outside temperatures of down to -50 °C.
Please give us a call. We would be glad to consult you on the methods available.

Freezing characteristics 2