Product Overview
Thermal Overload Heater for Bulletin 709/712 Motor Starters – Class 20
Condition
Unused, New Old Stock (NOS). Visual inspection completed with no issues noted. Acquired during a warehouse cleanout by a government contractor. No signs of prior installation or heat stress.
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Product Overview
Allen-Bradley N7 is a Type N thermal overload heater element engineered for use in compatible Allen-Bradley magnetic motor starters and overload relays. It functions as the calibrated sensing component that converts motor current into heat, providing inverse-time overload protection rather than instantaneous tripping. The N7 is part of the legacy N-Series family used in Bulletin 709, 712, 713, and 809 starters.
This heater utilizes a eutectic alloy ratchet mechanism. Under sustained overcurrent conditions, the alloy melts at a calibrated temperature, releasing the spring-loaded trip mechanism and opening the control circuit. The N7 is typically applied to motors with a full-load current in the 0.60A to 0.85A range, depending on starter size and service factor.
Key Features
- Allen-Bradley Type N thermal overload heater element
- Designed for Bulletin 709, 712, 713, and 809 starters
- Inverse-time protection, typically Class 20 trip
- Calibrated for approximately 0.60A–0.85A motor FLA (verify with heater table)
- Eutectic alloy solder-pot trip mechanism
- One-piece integrated heater and mechanical interface design
- Non-ambient compensated element
- Precision factory calibration by heater number
Applications
- Motor overload protection in NEMA magnetic starters
- Maintenance of legacy Allen-Bradley motor control centers
- Industrial pump and fan motor circuits
- Small single-phase and three-phase induction motors
- Brownfield equipment upgrades without replacing starter assemblies
- UL 508A compliant panel repairs requiring original heater types
Frequently Asked Questions
What does the N7 designation mean?
The N7 number identifies a specific thermal calibration matched to a defined motor full-load amp range. Selection must be based on the motor nameplate FLA and Allen-Bradley heater tables.
Are Type N heaters interchangeable if they physically fit?
No. While Type N heaters share a mounting format, each heater number has a different calibrated trip curve. Installing the wrong number can result in nuisance trips or inadequate protection.
Is this heater ambient compensated?
No. The N7 is a non-compensated element, meaning ambient enclosure temperature can influence trip timing. This provides a conservative safety margin in warmer environments.
How long does it take to reset after a trip?
Because it uses a thermal eutectic mechanism, it must cool before reset. Typical cool-down time is 1 to 3 minutes depending on ambient conditions.
What starters is this compatible with?
It is designed specifically for Allen-Bradley Bulletin 709, 712, 713, and 809 overload relay assemblies that accept Type N heater elements.
In a legacy motor control center, the heater is the quiet part that decides when to step in. If you are maintaining an original Allen-Bradley starter and matching the nameplate amps correctly, this N7 keeps the protection exactly as designed.
