I was once touring the back spaces of one of Reno's better casinos, when I saw 250 rated disconnects on 480 v equipment.
There are two areas where the non-rated disconnects are most likely to fail:
- In time of need, the disconnect will fail to interrupt the current, as the current will arc across the gap; and,
- A small amount of dirt, or damage, will lead to an internal line-to-line arc.
There's areason the 600 v. ones are physically larger!
