NK...U series (rectangular)
Duct electrical heaters are designed for heating of intake air in rectangular ventilating system. The heaters are applied for air heating in ventilation and air conditioning systems in various premises.
The casing and the terminal box are made of galvanized steel plate and the heating elements are of stainless steel. The models with the size from 400x200 to 600x350 the electric heating elements are extra ribbed to increase heat exchange surface. NK duct heaters are equipped with two overheating protection thermostats:
Each standard size has several electric power capacity options. Higher capacity can be attained by means of installation of the heaters in series. In the heaters with heating capacity above 27 kW the tubular heating elements are grouped per 9 kW each. Each group consists of three Δ connected tubular elements.
|DUCT ELECTRIC HEATER WITH NK...U INTEGRATED TEMPERATURE CONTROLLER|
The NK heaters are available in modifications with a control unit for the heaters with power demand from 4.5 up to 54.0 kW to maintain set air temperature in the air duct.
The NK…U model with a control unit is equipped with a three phase triac power control unit.
Power control is effected by means of switching on/off the maximum load commutated by the semiconductor device that is free of any mechanical wear parts. The load commutation starts at zero current and load to disable any magnetic field interferences. The load commutation starts at zero current and load to disable any magnetic field interferences.
The NK…U heaters include two overheat protection thermostats:
Operation logic options for the NK…U heater with a control unit:
The temperature is set with the integrated potentiometer. Optionally, an external 0-10 V control signal from another control unit may be connected to the control unit, which corresponds to the temperature 0 up to +40 °C.
Offered temperature sensor options for the NK...U heater operation logic based on temperature sensor readings (not included into delivery set):
The heater design ensures its mounting by means of flange connection. 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 condensate penetration and wiring short circuit.
The mounting shall be performed in such a way as to enable the uniform air stream distribution along the entire cross section.
The air filter shall be installed at the heater inlet to protect the heating elements against pollution.
We recommend to keep such distance between the heater and other system elements which is no less than the heater diagonal, i.e. the distance from one angle to another in its air passage part.
The duct heaters are designed for the minimum air flow 1.5 m/s and the operating air temperature 40 °C. 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 the automation system can be applied to ensure the complex control and protection:
|Series||Flange dimensions (WxH) [mm]||Heater power [kW]||Phase||Options|
|NK||400х200; 500х250; 500х300; 600х300; 600х350; 700х400; 800х500; 900х500; 1000х500||4,5; 6; 7,5; 9; 10,5; 12; 18; 21; 24; 27; 36; 45; 54||3 - three phase||U - integrated temperature control|