Phoenix UT 6-HE SI Surge Protection Terminal Block

The Phoenix Contact UT 6-HE SI is a high-performance surge protection terminal block for 24V DC circuits, designed to protect sensitive electronic equipment from lightning-induced transients and switching overvoltages. With a maximum discharge current of 6kA (8/20 µs) and a protection level of<40V, it offers enhanced protection compared to the UT 4-HE SI model. The device fits into the standard 6.2 mm UT housing and is fully compatible with UT terminal block accessories.

Protection Circuit

The UT 6-HE SI combines a metal oxide varistor (MOV) and a gas discharge tube (GDT) with a thermal disconnect mechanism. Under normal conditions, the device is transparent to the circuit. When a surge occurs, the GDT breaks down to conduct the bulk current to ground, and the MOV clamps the remaining voltage to less than 40V. If the MOV degrades due to repeated surges or aging, the thermal disconnect opens the circuit and the optical indicator changes from green to red. The device is designed to fail in a safe mode (open circuit) to prevent fire or damage.

Integration into UT Terminal Strips

The UT 6-HE SI has the same width, height, and mounting footprint as standard UT 6 terminal blocks, allowing direct replacement or insertion into existing terminal strips. It can be jumpered with standard FBS jumpers to other UT blocks for common potential distribution. End covers and partition plates are available to separate protected circuits from unprotected ones.

Application Domains

This SPD is ideal for protecting 24V DC power supplies, PLC input/output modules, sensor power lines, and fieldbus segments in areas with high lightning exposure, such as telecommunications towers, wind turbines, and outdoor industrial plants. It is also suitable for use in building automation and traffic control systems where surge events are common.