Square D A.71 Contactor Thermal Unit

Product Description

The SQUARE D A.71 is a thermal unit designed as an accessory for compatible Square D contactors and motor starters. Thermal units function as the sensing element inside an overload relay, responding to heat generated by motor current to provide overload protection. When current exceeds the rated threshold over time, the thermal unit trips the relay and disconnects the load, protecting motors from damage caused by sustained overloads or locked-rotor conditions. Weighing just 0.04 pounds and measuring 2.4 inches in length, 1.2 inches in width, and 0.8 inches in height, this compact unit is a direct replacement for worn or incorrectly sized thermal elements in the field.

Thermal units like the A.71 are used in residential and light commercial motor control applications where an overload relay protects a compressor, pump, fan, or other motor load. The unit snaps into the overload relay block mounted on or near the contactor. Selecting the correct thermal unit number is critical and is determined by the full-load amperage of the motor being protected, the ambient temperature at the installation site, and the service factor of the motor.

Key Features

• Serves as a sensing element for overload relay assemblies on Square D contactors and motor starters
• Provides thermal overload protection by tripping on sustained overcurrent conditions
• Compact form factor: 2.4 inches long, 1.2 inches wide, 0.8 inches tall
• Lightweight at 0.04 pounds for easy handling and field replacement
• Sold individually, allowing precise selection of the correct trip class for the application

Compatibility

Designed as an OEM-style replacement thermal unit for Square D overload relay assemblies used with compatible contactors and motor starters. Confirm the correct thermal unit designation against the motor full-load amperage, ambient correction factors, and the overload relay selection table before installation.

Installation Notes

Thermal units are installed and replaced by licensed electricians or qualified HVAC technicians. Disconnect and lock out all power to the motor control panel before removing or installing any thermal unit. Select the unit number using the manufacturer ampere selection table based on motor FLA and ambient temperature. Do not substitute thermal unit numbers without completing the full selection procedure, as an incorrectly rated unit will not provide proper motor protection.