COS Panel

A COS Panel (Change Over Switch), often also called an OHM Switch Panel or Manual Transfer Switch (MTS), is an electrical panel with a manual changeover switch that mechanically transfers the power supply from one source to another (for example, from the utility grid (PLN) to a generator set, or vice versa).

Unlike an ATS panel, which works automatically, a COS panel is operated manually by an operator or technician by turning the switch handle.

Main Functions of a COS Panel

1. Manual Power Source Changeover: Switches the power path from the main source (utility) to the backup source (generator) during an outage.
2. Backfeed Prevention (Interlocking): Ensures that both power sources are never connected at the same time (backfeeding), which could cause a short circuit or an explosion.
3. System Isolation for Maintenance: Allows the power supply to be completely disconnected (OFF position) during repair or maintenance of the internal installation.

Advantages of a COS Panel

1. Highly Reliable & Durable: Has a simple mechanical construction without complex electronic components, so the risk of failure or glitches is minimal.
2. Affordable Price: The initial investment and maintenance costs are much lower than those of an automatic transfer panel (ATS).
3. Full Control in the Operator’s Hands: Power transfer is entirely under human control, preventing the generator from connecting to the network if a utility outage lasts only a few seconds.
4. Easy Maintenance: The main component is usually just the COS lever switch, which is easy to inspect and replace when worn.