Automatic Changeover Switches are vital in situations where an uninterrupted power supply is critical to maintain the continuity of essential processes. In this regard, Protek’s SCO Automatic Changeover Switches are equipped with a contactor changeover system that can operate in either 2 pole or 4 pole. These changeover switches are rated at 230V or 400V AC and feature electromechanical interlocked AC1 / AC3 rated contactors that meet the essential requirements necessary for switching to a replacement power supply.

The SCO range of Automatic Changeover Switches are managed by a door-mounted front panel controller, which provides options for automatic or manual switching of the load from a MAIN LINE to a stand-by or emergency SECONDARY LINE or vice versa. The controller monitors two three-phase voltage inputs coming from two sources and connects to the output line that is within the limits. This controller is designed for use in both three-phase and neutral or two-phase systems and controls the contactors to perform the transfer between the lines.

The front panel controller is user-friendly and shows all the necessary information with LEDs, which provide a clear visualization of the Automatic Transfer System’s status. The push buttons on the controller allow you to select the operating mode, automatic or manual, and change the operating mode to manual switching of the load in position 1 (Line 1), position 0 (Neutral position), or position 2 (Line 2) as required, without needing to program any settings on the controller.    


Features and Benefits


  • Designed and built in the UK to BS EN 60947-6-1
  • IP40 Sheet steel enclosure
  • RAL 7035W Powder coating
  • Galvanized steel mounting plate
  • Fully welded construction
  • Foamed-in door PU sealing gasket
  • Solid top and bottom gland plates with PE gasket
  • 5mm Double-bit insert polyamide lock
  • Wall mountable
  • Easy install


  • Single and Three Phase ATS
  • Mains to Mains and Mains to Generator
  • Programmable using NFC App
  • Manual mode switchable on door or remotely
  • Automatic switching of the load from main line to standby / secondary line
  • Front panel controller with LED visualization showing status of ATS
  • Two potentiometers allow manual setting of line presence or tripping delays for the protection threshold

Front Panel Mounted Controller Overview & Self-Seeking Power Supply

The power supply accomplishes this without requiring any external circuitry or dual power supply module for selecting the auxiliary supply. 

The self-seeking power supply enables automatic selection of the most optimal available line for internal supply. This selection is based on the two measuring inputs with a rated voltage range of 110 to 240VAC L-N.


The controller is provided with two potentiometers on the back, one for each line (LINE 1 and LINE 2), which can be used for the following functions:

  • Setting of the line presence delays (default setting)
  • Setting of the tripping delays of the protection thresholds

The delays can be adjusted between 0 and 60 seconds. The function of the potentiometers can be modified with the NFC App.

Control Functions of Lines 1 & 2

For each line, the controller monitors the status of the voltage and the frequency to detect if the line is available and all the parameters are within the correct limits. The following controls are performed:

  • Phase sequence and phase loss
  • Minimum and maximum voltage
  • Voltage asymmetry
  • Minimum and maximum frequency

The tripping thresholds and delays of controller already have default settings. If necessary, it is possible to adjust these values using the NFC App.

Part Numbers

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