Product Description
The Allen-Bradley W21 is a precision-engineered W-Type thermal overload heater element designed to provide reliable motor protection for industrial applications. Utilizing a sophisticated eutectic alloy design, this element ensures your motor is shielded from overheating by tripping the overload relay with extreme accuracy when an overcurrent condition is detected.
As a Class 20 protection device, the W21 is built for heavy-duty cycles, ensuring the relay trips within 20 seconds or less at 600% of its rating, making it ideal for motors with longer starting times.
Technical Specifications
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Manufacturer: Allen-Bradley (Rockwell Automation)
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Part Number: W21
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Heater Type: W-Series (Type W)
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Trip Class: Class 20 (Standard Industrial Trip)
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Full Load Current (FLA): 0.53 to 0.6 Amps (Varies by Starter Size)
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Technology: Eutectic Alloy (Melting Alloy)
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Compatible Starter Sizes: NEMA Size 00, 0, and 1
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Ambient Temperature: Rated for standard 40°C (104°F) environments
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Compatibility: Bulletin 100, 500, 609, and 1200 Series
Key Features & Benefits
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Reliable Eutectic Design: The "melting alloy" technology provides consistent trip points that are not affected by aging or environmental vibration, unlike bimetallic strips.
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Class 20 Protection: Offers superior protection for motors that require a slightly longer start-up period without nuisance tripping.
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Broad Compatibility: Designed for seamless integration with Allen-Bradley Bulletin 100, 500, 609, and 1200 motor starters and contactors.
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Accurate Overload Detection: Precisely calibrated to protect small-fractional horsepower motors within the 0.53–0.6A range.
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Simple Field Installation: The modular design allows for quick installation and easy current-range adjustments by swapping elements.
Applications
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Industrial Motor Control: Essential for protecting small pump, fan, and conveyor motors.
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NEMA Starter Maintenance: A standard replacement part for Allen-Bradley NEMA-rated starters in factory environments.
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Control Panel Engineering: Used where precise thermal protection is required to prevent costly motor burnout.
