Overview
The Siemens 3UA5800-8W overload relay is a solid state protection device designed for motor overload and phase-failure detection in AC and DC motor applications. Part of the established 3UA series, the 8W variant is rated for 70–88A and integrates directly into motor starter circuits using standard IEC contactor platforms.
Key Features
- Solid state design ensures reliable, repeatable performance without mechanical wear
- Temperature compensation maintains accuracy across changing ambient conditions
- ON/OFF indication for visual status and diagnostic feedback
- Manual or automatic reset options to suit circuit requirements
- Plug-in mount compatible with 3TF and 3TE series contactors
- Phase-failure detection for three-phase motor protection
Technical Specifications
- Current Rating: 70–88A adjustable range
- Supply Voltage: 250V AC (typical for 3UA5800 series)
- Thermal Class: 10s trip time per IEC 60947-4-1
- Contact Type: Normally open (NO)
- Mounting: Plug-in, fits 3TF46–3TE47 contactors
- Operating Temperature Range: –5°C to +55°C
- Reset Mode: Manual or automatic (model-dependent)
- Protection Functions: Overload, phase failure, phase reversal
- Standards: IEC 60947-4-1, EN 60947-4-1
- Weight: Approximately 0.4 kg
Typical Applications
The 3UA5800-8W is widely used in:
- Three-phase and single-phase motor starter circuits
- Pump, compressor, and fan motor protection
- Machine tool control and automation systems
- HVAC and refrigeration motor protection
- Industrial process equipment requiring IEC-compliant motor safeguards
Compatibility & Replacements
The 3UA5800-8W is designed as a plug-in relay for 3TF46, 3TF47, 3TE46, and 3TE47 contactors rated for 160–250A. Older installations may use 3UA5500 or 3UA5200 series variants. Direct mechanical and electrical interchangeability should be verified with your contactor base and control schematic before substitution. OEM replacements and modern alternatives from Schneider Electric (Tesys variants) or ABB are available for systems requiring updated solid state protection.
