Product Overview
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, 240V, 3-pole, NEMA 3R, open transition. Typical loads are a main-tie-main arrangement, a large central utility plant, a data hall or an industrial process bus β 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 3R enclosure is rain-tight and rated for outdoor mounting against a wall or on a pad, so the switch can sit next to an exterior generator without an additional weather shelter. 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. Three-pole on a 240 V delta system: three ungrounded conductors with no usable neutral for line-to-neutral loads, still common in older industrial plants, farms, grain elevators and water districts where the service was built around motor loads. A delta service may be corner-grounded, so confirm the bonding jumper arrangement before dropping this switch into an existing service β it is the one voltage in this range where the neutral question is not academic. Neutral configuration. The neutral is switched β it opens and closes with the phase poles as one more pole. You need this when the generator is wired as a separately derived source with its own grounding electrode and its own main bonding jumper: leaving the neutral solid would tie the two grounding systems together through the neutral, put objectionable current on the grounding conductor and leave the generator frame at a potential above earth during a fault. It costs one more pole and one more set of contacts to maintain, but on a separately derived system it is not optional, and an inspector will look for it. Enclosure. The Type 3R cabinet is rain-tight, not watertight: it is built for outdoor mounting against a wall or on a pad, with a hooded or sloped top that sheds water and a gasketed door that keeps driven rain out. What it does not do is keep out dust or hose spray, and the installation still has to do its part β conduit entries need drip loops or sealing hubs so water running down the conduit cannot track into the enclosure, and the mounting surface has to drain. A 3R unit on a north wall in a coastal yard will outlast three indoor units in the same spot, which is why it is the default for anything not under a roof. Matching generator. At 240V with an 0.8 power factor this switch carries approximately 230 kW of load (1200 A Γ 240V Γ 0.8 = 230.4 kW, single-phase two-wire). 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 Γ 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 9,600β115,200 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.
