Overview
The Allen-Bradley W27 thermal overload heater element is a precision-engineered component designed to provide thermal protection in motor control systems. Constructed from eutectic alloy, the W27 heater element integrates with standard Bulletin 500 and 509 motor starters and overload relay blocks. It delivers Class 20 trip-time operation, making it the industry-standard choice for general motor control applications where reliable, predictable thermal protection is essential.
Key Features
- Eutectic alloy construction for consistent thermal response and long service life
- Class 20 operation—trips in 20 seconds or less at 600% rated current
- Compatible with Bulletin 500/509 motor starters and overload relay blocks
- Rated for 0.88–1.00 full load amps (Type W, Size 00–0)
- Compact, plug-in design for fast field replacement
- UL and CSA listed for industrial motor control applications
Technical Specifications
- Full Load Amperes (FLA): 0.88–1.00 amps (Size 00–0)
- Heater Type: Type W, eutectic alloy
- Trip Class: Class 20
- Compatible Relay Blocks: Bulletin 500, 509 line
- Trip Time at 600% FLA: 20 seconds or less
- Material: Eutectic alloy thermal element
- Mounting: Plug-in cartridge design
- Operating Environment: Standard industrial ambient
- Certifications: UL, CSA
Typical Applications
- General-purpose AC induction motors (fractional to small integral horsepower)
- Soft-starter and contactor-based motor control circuits
- HVAC fan and pump motor protection
- Machine tool and industrial automation systems
- OEM equipment with Bulletin 500/509 motor starters
Compatibility & Replacements
Compatible With
- Allen-Bradley Bulletin 500 motor starters
- Allen-Bradley Bulletin 509 motor starters
- IEC-style overload relay blocks with Type W heater sockets
- Standard three-phase AC motor control circuits
Replaces / Drop-In Replacement For
The W27 is a direct replacement for any motor control system originally specified with an Allen-Bradley W27 heater element. For systems using older Type N heater elements (Bulletin 709), verify motor starter compatibility with your system integrator before ordering.
Works With
- Allen-Bradley motor starter overload relay blocks
- Manual and magnetic motor starters
- Contactor-based motor control assemblies
- Industrial control panels and distribution equipment
- EtherNet/IP and ControlLogix-enabled motor control centers (as thermal sensing component)
