Overview
The Cutler-Hammer C306DN3B is a thermal overload relay engineered to protect motors and motor-branch circuit conductors against excessive heating caused by motor overloads and failure to start. This NEMA Freedom Series relay combines reliable trip-free operation with bimetal ambient temperature compensation, delivering consistent protection across varying environmental conditions. The Series B construction accepts interchangeable heater packs for field flexibility and precise current matching.
Key Features
- Bimetal ambient temperature compensation ensures accurate trip settings regardless of ambient conditions
- Trip-free mechanism prevents bypass of overload protection during manual reset or contactor holding coil failure
- Adjustable current range of 20–39 amps matches diverse motor sizes and applications
- Three-pole (3P) configuration for three-phase motor protection
- Series B heater pack compatibility allows quick field replacement without relay base swap
- Auxiliary contact block: 1NO/1NC for additional control logic integration
- UL Listed and CSA Certified for safe, compliant industrial deployment
Technical Specifications
- Part Number: C306DN3B
- Manufacturer: Eaton Cutler-Hammer
- Series: NEMA Freedom, Series B
- Poles: 3 (Three-phase)
- Current Rating: 20–39A (adjustable)
- Supply Voltage: 600VAC
- Trip Unit Type: Thermal, Trip-Free Mechanism
- Trip Class: 10 & 20 (Bimetallic)
- Mounting: DIN Rail, Panel Mount, or Direct to Contactor (Starter Replacement)
- Auxiliary Contact: 1NO-1NC
- Dimensions: 1.77 in W × 3.69 in L × 4.13 in H (45 mm W × 93.7 mm L × 104.9 mm H)
- Heater Packs: Series B required (sold separately)
- Wire Gauge: 14–6 AWG
- Ambient Compensation: Bimetal, temperature-compensated
- Certifications: UL Listed, CSA Certified
- NEMA Size: 00, 0
- IEC Size: A–F
Typical Applications
Cutler-Hammer C306DN3B relays are standard in motor control circuits requiring reliable overload and stall protection:
- Three-phase induction motor starter circuits (pump drives, fan motors, conveyor systems)
- HVAC and refrigeration compressor protection
- Machine tool and industrial equipment motor branches
- Direct mounting to Freedom Series non-reversing contactors
- DIN rail or panel-mount standalone protection in motor control centers
- Retrofit and upgrade applications where NEMA Freedom compatibility is required
Compatibility & Replacements
Compatible With
- Eaton Cutler-Hammer Freedom Series non-reversing contactors (NEMA Size 00, 0)
- IEC Size A–F starters and motor control components
- Series B heater packs (H2018-3, H2019-3, H2020-3, H2021-3, H2022-3, H2023-3, H2024-3)
- DIN rail and panel-mount infrastructure
- Standard three-phase 600VAC power distribution systems
Replaces / Drop-In Replacement For
- Previous-generation C306DN3 models (Series A heater designs)
- Equivalent thermal overload relays in NEMA Freedom startups requiring 20–39A protection
- Verify contactor and heater pack compatibility before ordering; Series B designation ensures forward compatibility with current Freedom hardware
Works With
- Eaton Cutler-Hammer Freedom Series software and configuration tools
- Standard motor control center (MCC) wiring and auxiliary contact integration
- Automatic/manual reset control circuits
- Trip indicators and alarm contacts for remote annunciation
- IEC 60947 thermal overload protection standards and motor branch circuit guidelines
