3ATSA31200NG0C Series 300 - ASCO | Automatic, 1200 AMP

The ASCO Series 300 is a UL 1008-listed automatic transfer switch built for commercial, institutional and light-industrial standby power. It monitors both the utility and the generator source and transfers the load automatically when the normal source falls outside acceptable limits, then returns it once the utility is restored and stable. This unit is rated 1200 A, 480V, 3-pole, NEMA 1, open transition. Typical loads are a main-tie-main arrangement, a large central utility plant, a data hall or an industrial process bus — installations where the transfer switch is engineered to order, coordinated with the service entrance equipment and frequently supplied with bypass isolation or delayed transition. The NEMA 1 enclosure is intended for indoor installation in a dry, protected space such as a mechanical room or an electrical closet. Terminations and footprint. Four conductors per pole from 1/0 AWG to 600 kcmil, in a 38 in by 87 in by 23 in enclosure weighing 581 to 639 lb. This is the top of the H frame and the last rating before the switch moves to the G frame with six and twelve conductors per pole. The cabinet is tall enough that the top lugs are above shoulder height, which is why front-accessible terminations and a proper working platform matter more here than at any smaller size. Service arrangement. This is a 480Y/277 V three-phase four-wire switch, the standard industrial and large-commercial service in North America: 480 V for motors, chillers and process equipment, 277 V for lighting, with the neutral bonded at the service and carried solid through the transfer switch. This is the voltage at which arc-flash energy climbs fastest, so the upstream coordination study matters more here than at 208 V. Neutral configuration. The grounded conductor is solid: it runs straight through on a bolted neutral plate and is never opened. That is the correct choice when the transfer switch is not a separately derived source — the generator neutral is bonded to the same grounding electrode system as the utility, so the neutral is one continuous current-carrying conductor end to end and breaking it would serve no purpose. It is also the cheaper of the two arrangements and has one fewer set of moving contacts to inspect, which is why it is the default on most commercial retrofits where the existing service neutral is already bonded. Enclosure. The Type 1 cabinet is for indoor use in a dry, protected space — a mechanical room, an electrical closet, a plant room — where the only thing it has to keep out is incidental dust and the occasional touch. It is not rain-tight and not watertight: mounting one on an exterior wall, even under a soffit, invites water in through the door seam and the conduit knockouts, and the first sign is usually a rusted mechanism rather than a tripped breaker. If the switch has to live outdoors, the 3R version of the same rating is the one to order. Matching generator. At 480V with an 0.8 power factor this switch carries approximately 798 kW of load (1200 A × 480V × √3 × 0.8 = 798 kW, three-phase). Size the standby generator so that its standby rating meets or exceeds that figure, and confirm the generator's two-wire automatic-start contacts are compatible with the transfer switch controller. Controller. This unit carries the ASCO Group G controller: a 128 × 64 graphical LCD with switch-position, source-availability, common-alarm and not-in-auto indication. Transfer and re-transfer delays, engine cool-down and the in-phase transfer timer are all set from the membrane keypad rather than from DIP switches, with ranges up to 60 min 59 s. The Group G controller supports both open transition and delayed transition, and accessory 11BE adds RS-485 communication at 9,600–115,200 bps, a seven-period programmable exerciser and a 300-event log. Three-pole configuration. The three phase conductors are switched with a solid neutral. This is the standard arrangement where the neutral is bonded at the service and must not be opened by the transfer switch. Supply. Supplied as a genuine ASCO Power Technologies (Schneider Electric) unit, brand new and factory original, packed for export from our Dongguan warehouse. Ask us for the outline drawing, wiring diagram and data sheet for this exact catalog number.