Single phase or Three Phase Breaker?

[ramsy]

In most cases they will not trip the other pole(s).

If we can't expect one breaker to trip the other two, can two breakers overcome the third?

Are handles listed to tie 3 single-phase breakers anywhere? If a bolted L-L fault --tripping two breakers-- can overcome the third, are we shure a L-L connected ground fault also trips both poles, or just one, which may not overcome the other two handle-tied breakers?

 

[don_resqcapt19]

Roger,
In cases where the code permits the use of handle ties, there is no need for a fault on one phase to trip the other phases. The handle ties are only to provide a common means of disconnect for the circuit. If you need to have all of the conductors open on a fault, you need a mulitpole breaker. Multipole breakers have common trip.
The reason that the handle tie often does not trip the other breakers is because breakers are required to be of the "trip free" design. This means that the breaker will still open the circuit with the handle restrained in the on position. When the breaker trips, most of the energy stored in the internal trip spring is used to open the contacts, and very little is applied to the external handle.
Don

 

[ramsy]

The handle ties are only to provide a common means of disconnect for the circuit. If you need to have all of the conductors open on a fault, you need a mulitpole breaker.

That does make more sense. Don, many thanks for the clarification.