Cummins OTEC Spec C Automatic Transfer Switch 208V 3-Phase / 225A

This 225-amp, 208-volt three-phase automatic transfer switch is built for installations that need weatherproof protection — the NEMA 3R enclosure handles rain, sleet, and external ice formation, making it equally at home mounted outdoors on a building exterior or inside in a wet or dusty environment. It's a practical choice for rooftop mechanical rooms, outdoor generator pads, parking structures, and similar locations where a standard indoor enclosure won't cut it.

Like the rest of the Spec C family, it operates electrically and latches mechanically in both the normal and standby positions — so a control power loss won't cause it to drop out of position. Break-before-make switching is enforced at both the mechanical and electrical level, eliminating any possibility of paralleling the utility and generator, even momentarily.

Features & Benefits

Three upgrades define this generation. The PC40-11 controller replaces the previous platform with a more capable interface and broader communication support. Voltage imbalance sensing is now built in, catching unbalanced three-phase conditions that older units would miss. And phase rotation monitoring is standard — useful at commissioning and after any generator service work.

The PC40-11 Controller

A microprocessor-based controller with a backlit LCD and soft-touch navigation handles all programming and monitoring functions. Setup can be done at the door or from a connected PC. Standard communication includes Modbus RTU and TCP. The I/O is configurable for application-specific needs, and a built-in exercise scheduler keeps maintenance testing on track. When more output contacts are needed, expansion modules can be added in the field — 8 contacts per module, up to 16 with two modules. An Ethernet communication module, remote annunciator, and RS-485 Modbus are available as field-installed options.

Built for the Elements and Long-Term Duty

Silver alloy main contacts under high closing pressure hold resistance low and stand up to repeated switching without significant wear. Dedicated arcing contacts absorb the damage from each operation so the main contacts don't have to. A layered arc chute assembly extinguishes arcs quickly after each transfer. The whole mechanism carries UL 1008 certification — contacts included — confirming it's rated for high-endurance switching over the full service life of the unit, not just break-in conditions.

A removable protective cover allows visual inspection of internal components without exposing anyone to live parts.

Updated Breaker Ratings — September 2025:

 Cummins released revised Withstand Closing Breaker Ratings for the Spec C family effective immediately upon announcement. Full UL and CUL listing was completed the prior month. AHJ submittal documentation is available in the PDF section below.

Specs