240 Volt Only Circuit Breakers

[infinity]

I saw this on another forum. Anyone want to take a crack at what the note on the bottom of the label means? Sound like slash rated circuit breakers are not permitted but that makes little sense. This panel is supposedly from the 60's.

 

[jim dungar]

It says for a 2wire supply, 240V to ground, you cannot use slash rated breakers.

These types of manufacturer instructions were ignored for decades, until equivalent language was added to the NEC.

 

[charlie b]

I think the phrase "additional rating" is the key to understanding this note. To me, it says that if you use a two-pole breaker for a circuit that needs no neutral, then the breaker you choose must be rated for 240 volts. That "additional rating" is in addition to the breaker rating of 120V required for single pole circuits.

 

[jim dungar]

I think the phrase "additional rating" is the key to

It is a rating for a 240V 2 wire source in addition to the normal rating for 120/240V 3 wire source.

 

[infinity]

It says for a 2wire supply, 240V to ground, you cannot use slash rated breakers.

These types of manufacturer instructions were ignored for decades, until equivalent language was added to the NEC.

I agree but I'm trying to think of a scenario where you would actually use that type of system to supply a panel. Two ungrounded legs of a corner grounded Delta?

 

[jim dungar]

Two ungrounded legs of a corner grounded Delta?

Yes. Or a single phase from a 2 phase system.

Nothing common.