ST-21 Central Heating Pump Controllers with LED Display

The ST-21 controller is intended for controlling the circulation pump in the heating installation. The controller's job is to turn the pump on when the temperature exceeds the set value and turn it off when the oven cools down (by extinguishing). This prevents unnecessary work of the pump, which allows to save electricity (depending on the level of use of the oven) and extend the life of the pump.

Thanks to this, their reliability increases and usage costs decrease. The control unit also has a function that prevents the pump from being blocked by limescale deposits. Outside the heating period, the controller switches the pump on for several minutes every 10 days (AUTO STOP function).
The current oven temperature is shown on the LED display.

The device can work as a thermostat with a temperature display (controlled device works from switching on the control device until the set temperature is reached; re-activation occurs after a
Temperature reduction up to the specified temperature or after the set hysteresis)

Technical data

• Power supply: 230V/50Hz +/-10%
• Permissible power consumption of the control unit: 2W
• Ambient temperature: 5÷50°C
• Heating pump output load: 1A
• Temperature measurement range: 0÷85 °C
• Measuring accuracy: 1°C
• Hysteresis setting: 0-10°C
• Temperature adjustment range: 25÷85 °C
• Temperature sensor resistance: -25÷90 °C
• Fuse_ 1.6 A
• Dimensions: 13x8x4 cm
• Cable length: approx. 150 cm