Siemens 3UA55 00-2B Motor Starter Overload Relay 12.5-20A 600V Class 10

Siemens 3UA55 00-2B Motor Starter Overload Relay 12.5-20A 600V Class 10

The Siemens 3UA55 00-2B is a thermal motor starter overload relay with an adjustable current range of 12.5 to 20 amps, rated for 600V AC service. It is designed to mount directly onto compatible Siemens contactors and provides thermal overload protection for three-phase motor circuits. A front-panel rotary dial lets the installer set the trip current to match the motor's full-load amperage, and both manual and automatic reset modes are supported.

Specifications & What's Included

• Model: Siemens 3UA55 00-2B
• Current setting range: 12.5–20 A
• Voltage rating: 600V AC
• Trip class: Class 10
• Tripping current: 125% of dial setting
• Auxiliary contact: 1 NO + 1 NC (B600/R300)
• Reset modes: Hand / Automatic
• Short-circuit coordination fuse: 8A gG / 10A Dz flink
• Type 1 coordination: 100 gG / 100 A T BS88
• Type 2 coordination: 50 gG / 50 A T BS88
• Rated insulation voltage (Ui): 690V
• Operational voltages (Ue): 24V, 230V, 400V, 690V AC
• Torque: 22–28.5 lb·in (2.5–3 Nm)
• Standards: IEC 847, VDE 0880, UL Listed 185C IND CONT EQ
• Country of manufacture: Germany
• Front panel: rotary current-setting dial, red trip/reset button, blue manual reset button
• Auxiliary contact terminals: 95 (NC), 96 (NC), 97 (NO), 98 (NO)
• Main terminals: 1/L1, 2/T1, 3/L2, 4/T2, 5/L3, 6/T3
• Includes: relay only — no contactor, cables, or accessories

Applications

The Siemens 3UA55 series are bimetallic thermal overload relays designed for use in motor starter assemblies, typically paired with Siemens 3TB or 3TF series contactors. They protect three-phase induction motors from damage caused by sustained overload currents, single-phasing, and phase imbalance by tripping the control circuit when the thermal element reaches its set threshold. In a motor starter combination, the overload relay clips directly onto the bottom of the matching contactor, making it a compact and wiring-efficient solution for panels and MCC (motor control center) buckets. The 3UA55 series dates from the 1980s and 1990s era of Siemens IEC motor control hardware and remains compatible with many still-operating legacy motor control panels. Maintenance departments servicing older industrial machinery, packaging lines, HVAC systems, and pump stations continue to source these relays as direct replacements.