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 100 A, 240V, 2-pole, NEMA 3R, 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 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. On the 185 platform the lugs take one conductor per pole from #8 AWG to 2/0 AWG, and the whole switch is a compact wall-mount box one person can hang: this is the size that sits beside a residential panel or in a small mechanical closet and never gets a second thought. 100 A is the standard North American dwelling service and the point where a whole house transfers at once, so the contacts and the neutral plate are sized for the full load rather than for a selected circuit. 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 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 19 kW of load (100 A Γ 240V Γ 0.8 = 19.2 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.
