Basic parameter for domestic fan selection

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NKV series (round)

NKV series (round)

Duct water heaters are designed for heating of supply air in round ventilation systems.

Products in this series (14)

Series   Flange diameter [mm]   Number of water coil rows
  100; 125; 150; 160; 200; 250; 315   2;4

Duct water heaters are designed for heating of supply air in round ventilation systems. They can be also applied in supply or supply and exhaust ventilating units.


The heater casing is made of galvanized steel, the tubular coils are of copper tubes and the heat exchange surface is made of aluminium plates. The heaters are equipped with rubber seals for airtight connection to the air ducts. The heaters are ailable in 2 and 4 rows modifications and are designed for maximum operating pressure 1.6 MPa (16 bar) and maximum water operating temperature +100°С. The outlet manifold has a branch pipe for installation of submersible temperature probe or icing protecting device. The heater is equipped with a nipple for the system deaeration.


The heater design ensures its mounting on the round ducts in any position by means of clamps. The water heating coils can be installed in any position that enables the heater deaeration. The air flow direction shall match the pointer designation on the heater.

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

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

The heater can be installed at the fan inlet ot outlet. If the heater is located at the filter outlet the air duct between the heater and the filter shall have the length of at least two connecting diameters to ensure the air flow stabilization as well as permissible air temperature level inside the fan.

The heater shall be connected on the counterflow principle, otherwise its efficiency can drop by 5-15%. All the nomographic charts in the catalogue are valid for such connection.

If water serves as a heat medium the heaters are suitable for indoor installation only. For outdoor installation use antifreeze mixture, i.e. ethylene glycol solution.

To ensure the correct and safe heater operation use the automation system that provides complex control and freezing protection:

  • automatic control of heating elements capacity and air heating temperature;
  • switching ventilating system on after preliminary heating with the heater;
  • use of air curtains equipped with spring-loaded actuator;
  • filter checking by means of differential pressure sensor;
  • fan shutdown in case of the heater freezing danger.


Connection against air flow Connection along air flow

Air pressure loss for water heaters

NKV round series


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