Overview#
The ASCO 185 Series is ASCO's residential and light-commercial automatic transfer switch, covering 100A through 400A at 240V single-phase. It brings ASCO's commercial switching heritage to the home standby market — true double-throw contacts with mechanical interlocking, the same fundamental switching mechanism used in ASCO's 300 and 7000 Series commercial lines.
The 185 uses standard 2-wire start control, making it compatible with any generator brand. When utility power is absent for 1 second or more, the ATS signals the generator to start. Transfer occurs automatically once the generator reaches rated voltage and frequency. An integrated exercise circuit tests the generator weekly under load or no-load, selectable by the installer.
Sizing for residential#
| Home size | Typical service | ASCO 185 size |
|---|---|---|
| Small home / cottage | 100A | 100A |
| Standard home | 200A | 200A |
| Large home (heavy-use) | 200A+ | 230A or 260A |
| Estate / custom home | 400A | 400A |
The ATS amperage must match or exceed the main service panel amperage. Most Northern California residential installations use the 200A variant. The service-entrance rated 185SE version can serve as the main disconnect, simplifying the installation when the ATS is positioned at the utility service point.
NEMA 1 vs 3R enclosure#
- NEMA 1 (indoor): Steel enclosure for utility rooms, garages, or basements
- NEMA 3R (outdoor): Aluminum alloy enclosure rated for rain, sleet, and ice. Standard for residential generator installations where the ATS mounts outdoors near the meter and generator
Our service experience#
The ASCO 185 is less common in our residential service territory than Kohler and Generac bundled switches, but when we encounter them, the quality is evident. The mechanical switching components are more robust than the residential switches from generator OEMs. The most common service call is exercise timer misconfiguration — installers sometimes set the weekly exercise without confirming the homeowner's preferred day and time. We also see occasional LED indicator board failures on units over 10 years old, which don't affect switching function but eliminate visual status feedback.