Does the Slash rating on a breaker (120/240 480Y/277) only apply when the load is connected to a neutral?

You really never use the neutral to B phase (208 v) so the 120/240 breakers are only used on A and C along with the neutral. The 3 phase brakers that use A, B, and C are straight 240v rated
Julio Chadrone said:
so the 120/240 breaker is that specifically for the. I forget the term but "single phase hi leg" wher there's a neutral stuck in the middle of a winding to provide 120 power. I dont know how common that is but it seems like a really specific scenario to build a breaker around
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Julio Chadrone said:
dont know how common that is but it seems like a really specific scenario to build a breaker around
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High leg, Wild leg, Center tapped delta are all names for a delta configuration, typically open, that provides 3 phase 4 wire where the B phase is 1.732X the L-N voltage because the A-C transformer winding has a center tapped winding.

These are actually very common in non-urban settings with many POCOs still offering them for new services. Nowadays their primary application is when a small amount of 3 phase power is required in what would otherwise typically be a single phase service.

The only time special breakers are required is when non 3-pole breakers are connected to the B-phase.
 
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jim dungar said:
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These are actually very common in non-urban settings with many POCOs still offering them for new services. Nowadays their primary application is when a small amount of 3 phase power is required in what would otherwise typically be a single phase service.
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Still very common around here as legacy services in de-industrializing urban settings. Often the high-leg is no longer used. Last one I worked on it was used, but only a tiny bit as the former small industrial site had been converted to a live-work setup.
 
Julio Chadrone said:
Open wye? is that just delta? Im guessing when they say open it means ungrounded?
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I call a 3-wire 208Y/120-volt service derived from a 3-phase, 4-wire, wye network transformer a 'open wye' service.
also a feeder from 208Y/120-volt, 3-phase system that only include two ungrounded conductors one neutral conductor is a open wye feeder.
This communicates that the neutral will carry more current than a conventional split phase system where the neutral can balance to 0.

More than a few places in the code have sentences like "single-phase feeder conductors consisting of 2 ungrounded conductors and the neutral conductor from a 208Y/120 volt system shall " ...
or
"Feeders from 208Y/120-volt, 3-phase systems shall be permitted to include two ungrounded
conductors and shall include one grounded conductor and one
equipment grounding conductor" ...

If the NEC simply defined 'open wye' (and 'open delta') it would make those sentences more readable and 'open wye' an easier topic to understand.
 
tortuga said:
If the NEC simply defined 'open wye' (and 'open delta') it would make those sentences more readable and 'open wye' an easier topic to understand.
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Yeah, makes communication muddy in the field like troubleshooting over the phone. Makes it hard to teach kids too
 
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