Overview
The Square D H-321-NRB safety switch is a heavy duty fusible disconnect designed for reliable circuit protection and isolation in three-phase electrical systems. This 30A, 240VAC unit combines robust construction with proven switching performance, making it ideal for machinery control, motor starter isolation, and industrial equipment protection.
Key Features
- Heavy duty fusible design with quick-make, quick-break operating mechanism
- Galvannealed steel enclosure with NEMA 3R protection rating
- Factory-installed neutral for four-wire, 3-pole switching
- Accepts Class H, J, K, L, and R fuse types for flexible protection coordination
- Dual cover interlock and color-coded indicator handle for safe operation
- Short circuit current rating from 10kA to 200kA
Technical Specifications
- Rated Current: 30 Amperes
- Voltage Rating: 240VAC / 250VDC
- Horsepower Rating: 7.5 HP
- Pole Configuration: 3-pole, 4-wire with neutral
- Enclosure Type: Galvannealed steel, NEMA 3R
- Switching Action: Single throw
- Short Circuit Rating: 10kA–200kA
- Fuse Types: Class H, J, K, L, R
- Mounting: Surface mount with bolt-on hub provision
- Wire Size: #14 to #8 AWG (aluminum or copper)
Typical Applications
Heavy duty safety switches are commonly used in:
- Three-phase motor isolation and control circuits
- Industrial machinery disconnect and lockout/tagout (LOTO) procedures
- HVAC compressor and pump protection
- Manufacturing equipment primary disconnects
- Standby generator transfer and protection
Compatibility & Replacements
Compatible With
- Class H, J, K, L, and R fused protection systems
- Three-phase 240VAC industrial control circuits
- Motor starter control schemes up to 7.5 HP
- Industrial lockout/tagout (LOTO) procedures
- Standard electrical panel and surface-mount enclosure installations
Replaces / Drop-In Replacement For
Verify compatibility with your system integrator before ordering. The Square D H-321-NRB is a heavy duty variant; confirm interchangeability with general duty models such as D321NRB or other variants in your application.
Works With
- Fused circuit protection (Class H, J, K, L, R)
- Industrial lockout/tagout systems and energy isolation procedures
- Three-phase power distribution and motor control systems
- Standard electrical installation and maintenance practices per NEC and NFPA guidelines
