Basic parameter for domestic fan selection

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NK series (round)

NK series (round)

Duct electric heater.

Series   Air duct diameter, mm   Heater power [kW]   Phase
NK   100; 125; 150; 160; 200; 250; 315   0,6; 0,8; 1,2; 1,6; 1,7; 2,0; 1,8; 2,4; 3,0; 3,4; 3,6; 5,1; 6,0; 9,0   1 - single phase; 
3 - three phases

Duct electrical heaters are designed for supply air heating in round duct ventilating system. The heaters are applied in heating, ventilation and air conditioning systems for various premises.


The casing and the terminal box are made of galvanized steel and the heating elements are of stainless steel. The heaters are equipped with rubber seals for connection to the air ducts.

NK duct heaters are equipped with two overheating protection thermostats:

  • basic protection with automatic restart with +50 °С operating temperature. After cooling the thermostat closes the control circuit of the heater automatically.
  • emergency protection with manual restart (operating temperature +90 °С). In case of response the power supply to the heater is allowed after the manual emergency reset only.
  • the thermostat contacts are located in the terminal box for external connection.

Each standard size has several electric capacity options. The higher capacity can be attained by means of installation of the heaters in series. All the three phase heaters have star connection.


The heater design ensures its mounting on the round ducts in any position by means of clamps. The air flow direction shall match the pointer on the filter. The duct heaters can be installed in any position except for with the electric control unit below to prevent liquid penetration and wiring short circuit.

The mounting shall be performed in such a way as to enable uniform air distribution along the entire cross section.

The air filter shall be installed at heater inlet to protect the heating elements against pollution.

The minimum distance between the heater and other system elements is no less than two connecting diameters.

The duct heaters are designed for minimum air flow speed 1.5 m/s and the maximum operating outlet temperature 40 °С. In case of speed control option ensure the minimum air flow through the heater.

Power supply to the heater shall be disabled if the fan is not running.

To ensure the correct and safe heater operation he automation system can be applied to ensure the complex control and protection:

  • automatic control of heating elements capacity and air heating temperature;
  • checkingfilter condition by means of differential pressure sensor;
  • power supply disabling in case of supply fan shutdown or airflow speed decrease as well as in case of the built-in overheating thermostats operation;
  • shutoff of ventilating system with blowing of electrical heating elements.


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