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 70 A, 240V, 3-pole, NEMA 1, open transition. Typical loads are a residential service panel, a small retail or office panelboard, a well pump, a sump pump or a light commercial kitchen β circuits where the entire load can be picked up at once and where a compact wall-mounted enclosure is an advantage. 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. Same #14 AWG to 4/0 AWG lug on every pole and the same 35 in by 17.5 in by 11.6 in cabinet, 84 lb. 70 A is the rating that covers a whole dwelling on a 100 A service with a modest generator: the contactor is still small, but the poles now carry the total load rather than a single circuit. It is the most common size we ship for residential retrofit work in North America. 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 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 β 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 β a mechanical room, an electrical closet, a plant room β 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 240V with an 0.8 power factor this switch carries approximately 13 kW of load (70 A Γ 240V Γ 0.8 = 13.4 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.
