Square D cc156.0 Thermal Unit Trip Class 20 Nema 3 4

Product Description

The SQUARE D cc156.0 is a melting alloy thermal unit designed for use in thermal-type overload relays. When line current exceeds a set threshold, the internal alloy solder liquefies, tripping the overload relay and breaking the contactor's power contacts to protect downstream motors and loads from damage caused by sustained overcurrent. Once the alloy cools and solidifies, the unit can be reset automatically or manually. This thermal unit is rated for Trip Class 20 and covers a full load current range from 70.4 to 86 amps, depending on the motor starter frame and configuration. Licensed electricians and industrial maintenance technicians are the primary installers.

The cc156.0 is used in thermal overload relay assemblies installed in motor starter panels serving commercial and industrial applications. It is compatible with NEMA Size 3 and Size 4 motor starters using CC or S frame sizes. Typical applications include three-phase motor protection in HVAC, pump, compressor, and conveyor systems where sustained overload protection is required. Selection should be based on the full load current rating of the connected motor and the operating conditions of the motor starter assembly.

Key Features

• Melting alloy construction trips reliably at sustained overcurrent conditions
• Trip Class 20 timing characteristic for motor protection applications
• Full load current coverage spanning 70.4 to 86 amps across multiple ranges
• Compatible with NEMA Size 3 and Size 4 motor starters
• Fits CC and S compatible frame sizes for broad relay fitment
• Supports both automatic and manual reset after trip and cooldown

Compatibility

Designed for use with thermal-type overload relays in NEMA Size 3 and Size 4 motor starters with compatible CC or S frame sizes, as stated by the manufacturer.

Installation Notes

Installation should be performed by a licensed electrician following applicable NEC requirements. De-energize and lock out the motor starter panel before removing the existing thermal unit or inserting the replacement. Verify the full load current rating of the connected motor against the thermal unit range before installing. Do not force the unit into an incompatible relay frame, as improper seating will result in unreliable overload protection.