Overview
The Allen-Bradley W73 is a eutectic alloy thermal overload heater element designed for use with Bulletin 500 line starters and magnetic motor control systems. Class 20 trip classification makes it the industry standard choice for general industrial applications requiring precise and reliable overload protection. This heating element is part of Allen-Bradley’s proven Type W heater family, engineered to deliver consistent performance across motor starting and running conditions.
Key Features
- Eutectic Alloy Construction: Provides reliable thermal response for Class 20 operation
- Multiple Size Ratings: 58 AMP @ SIZE 2, 72 AMP @ SIZE 3, 77 AMP @ SIZE 4
- Bulletin 500 Compatible: Standard overload relay protection for 500 Line starters
- General Application Class: Class 20 recommended for general applications
- Type W Series: Industry-standard thermal heater design trusted by controls engineers and maintenance technicians
- Compact Form Factor: Minimal footprint for integration into existing starter packages
Technical Specifications
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Part Number | W73 |
| Type | Thermal Overload Heater Element, Type W |
| Trip Class | Class 20 |
| Construction | Eutectic Alloy |
| Current Rating – Size 2 | 58 Amps |
| Current Rating – Size 3 | 72–67 Amps |
| Current Rating – Size 4 | 77–74 Amps |
| Applicable Bulletin | Bulletin 500, 100, 609, 1200 Line Starters |
| Weight | 0.05 lbs |
| Condition | Used, tested and functional |
Typical Applications
The Allen-Bradley W73 is used for thermal overload relays, magnetic motor starters and motor controls. Common applications include:
- Three-phase AC motor protection in industrial facilities
- Conveyor systems and material handling equipment
- Pump and fan motor control circuits
- Compressor and HVAC motor protection
- General machinery and production line motor starts
- Replacement in existing Bulletin 500 starter cabinets
Compatibility & Replacements
Compatible With
- Allen-Bradley Bulletin 500 Line Starters
- Bulletin 100 motor starters
- Bulletin 609 magnetic starters
- Bulletin 1200 line starters
- Type W thermal overload relay packages
- Standard three-phase AC motor control systems
Replaces / Drop-In Replacement For
The W73 is a direct replacement for other W-series Type W heater elements in equivalent amp ratings. Verify current requirements match your application before ordering. Related models in the series include W72 (lower amp rating) and W74 (higher amp rating).
Works With
- Allen-Bradley Thermal Overload Relays
- Standard industrial magnetic motor starters
- AC motor control circuits (general purpose)
- Class 20 overload protection schemes
- No software or firmware required—hardwired protection device
