Circuit Breaker Trip

[dinkelja]

Opinions needed: What does this mean to you?

MCC Incomming Line Disconnect
Circuit Breaker
Frame - 800A MC
Trip - Non-Auto

The first three lines are obvious. What is the reference to Non-Auto (Trip). I was told it was a thermal-magnetic breaker, without the overload ("thermal"). It would operate for a fault only then I suppose. Thoughts?

 

[davidbeach]

Sounds like a molded case switch rather than a circuit breaker.

 

[oldfieldguy]

I'll go along with davidbeach on this one: They look just like circuit breakers and have the same physical dimensions, but they lack internals to operate on overload or fault currents.

I have heard of some which have a high instantaneous element for tripping purposes, but you probably want to check the manufacturer's label. If it says "switch", then forget about expecting it to trip by itself for anything.

Some frames may have provision for installing and externally-operated shunt trip device.

old field guy

 

[dpc]

Ditto. "Non-auto" means there is no tripping mechanism. It is a molded-case switch. These used to be fairly common, but they can't be UL labeled so they are not used much anymore.

You should assume it will never trip for any kind of fault. It cannot provide any overcurrent protection.

 

[jraef]

I agree, this is essentially just a disconnect switch using a circuit breaker frame. If they said it didn't have thernmal trips but would trip on a short circuit, that would make it a Mag-only breaker, which is illegal to use as a main breaker on an MCC anyway. If, however, you have another SCPD upstream from this MCC that is properly sized and dedicated to the MCC feed, then you may not need a full circuit breaker anyway. Lots of special circumstances and pitfalls on that though, read the code very thoroughly before accepting it.

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