400 Amp Safety Switch Tripping

[kwired]

A BPS is often fused, making it a "fused switch", or like I said, the ITE / Siemens Vacu-Break switches with fuses are "fused disconnect switches" to the untrained eye, and both can be fitted with trip coils. If the OP would be so kind as to post a brand name and model, or even a picture, this can likely be cleared up quicker. If there is a Ground Fault relay somewhere connected to that trip coil, it would open the switch MUCH faster than it would take for the fuses to clear. That's actually the point of it. Same on a phase monitor relay; loss of a utility phase or low voltage, for even a second, may cause the relay to change state and trip the coil, which would move the handle to a center position. The original installer may have known there were supply problems there and used the BPS because it could be fitted with a trip coil, unlike a basic "one-armed-bandit" safety switch.

I am now somewhat educated on this possibility, maybe unlikely at 400 amps, so we really need more information to verify, thanks.

 

[texie]

Could be a Bolted Pressure (aka "Pringle") Switch, they can have Shut Trip or Under Voltage Trip coils installed in them and when activated, the handle will go to a center position. The same is true of the old ITE "Vacu-Break" switches. The trip coils are usually used in conjuntion with a GF relay or a power monitor relay. It could very well be that the entire system is doing EXACTLY what it was designed to do, prevent further damage to the equipment down stream because of a ground fault or a phase loss, surge or sag.

Generally, BP switches are used for higher amperages, but they do make them in 400A. As a general rule, a BPS will have a long lever handle on the front door, as opposed to a side mounted handle like on a slot machine. but without knowing what you have, that would be my first guess.

When the OP said that the safety switch was "tripping" I considered the possibilty of a BPS but then I thought, well, this is likely a garden variety application and a BPS would not be likely so I didn't mention it. And as you say, especially as small as 400 amp. Until you mentioned it, I was not even sure they made one this small.