Square D 9999ST2 Starter Transient Suppressor

Product Description

The SQUARE D 9999ST2 is a transient suppressor accessory designed for use with Type S enclosed motor starters. It clamps voltage spikes generated when inductive loads such as motor starter coils are de-energized, protecting sensitive control circuits from transient overvoltage events. Measuring 4.5 inches long, 3 inches wide, and 1.5 inches tall, the 9999ST2 is a compact, purpose-built component installed by licensed electricians during starter assembly or field service. At 0.15 pounds, it adds minimal weight to the enclosure assembly.

This transient suppressor is used in industrial and commercial electrical installations where Type S enclosed motor starters are deployed. It mounts directly within the Type S enclosure to provide inline transient protection at the starter coil. Typical applications include motor control panels, mechanical equipment rooms, and industrial control cabinets where coil-switching transients can cause nuisance tripping or damage to downstream control devices.

Key Features

• Suppresses inductive transients generated by motor starter coil switching
• Purpose-built fit for Type S enclosure starters
• Compact form factor: 4.5 x 3 x 1.5 inches
• Lightweight at 0.15 pounds for easy in-panel handling
• OEM-style starter accessory for direct replacement or new installation

Compatibility

Designed for use with SQUARE D Type S enclosure motor starters as a direct-fit starter accessory.

Installation Notes

Installation should be performed by a qualified electrician in accordance with the NEC and applicable local codes. De-energize and lock out the starter panel before installing or replacing this suppressor. Verify that the enclosure type matches the Type S designation before installing. Do not energize the starter until the suppressor is fully seated and all connections are secure.