Product Overview
The ASCO Series 185 is a UL 1008-listed automatic transfer switch intended for optional standby systems under NEC/NFPA 70 Article 702, in residential and light-commercial installations. It is designed to work with two-wire automatic-start generators and is the entry point of the ASCO transfer switch range. This unit is rated 400 A, 240V, 2-pole, NEMA 1, open transition. Typical loads are a whole-building distribution panel, a rooftop packaged unit group, a small data or telecom room, a clinic or a restaurant β installations where the transfer switch is sized to the full service and must coordinate with the upstream overcurrent protection. 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. Two conductors per pole from 1/0 AWG to 250 kcmil, or one from #4 AWG to 600 kcmil, in the same 24 in by 56 in by 14 in cabinet at 250 to 270 lb. 400 A is the largest rating that still shares that enclosure with the 260 A unit, and it is the practical ceiling for a wall-adjacent installation: beyond this the switch is a floor-standing assembly with a different footprint and a different rigging plan. Service arrangement. Two-pole 120/240 V single-phase: two ungrounded conductors and a grounded neutral, the arrangement behind nearly every North American dwelling and behind small shops on a split-phase service. Only two poles switch, so a solid-neutral unit carries the grounded conductor straight through while a switched-neutral unit opens it β which is what you want when the generator is treated as a separately derived source and the neutral must be broken to keep the two grounding electrodes apart. 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 77 kW of load (400 A Γ 240V Γ 0.8 = 76.8 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. The 185 platform uses a DIP-switch controller with factory-set pickup and dropout thresholds (198 V pickup, 187 V dropout on the normal source by default), a approximately 10-second transfer delay, a 5-minute return-to-utility stability window and a 2-minute unloaded cool-down before the generator is signalled to stop. Two-pole configuration. Both the hot and the neutral are switched, which is the normal choice for 120/240 V single-phase residential and light-commercial services and for any circuit derived from a separately derived source. 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.
