480 VAC Service to Industrial Equipment Breaker Specification

[SteveAtx]

Our client is asking why we need 480 VAC breakers for an industrial control panel when any one pole will ever see 240 VAC, help with explaining this please. I need to explain that the breaker must match the electrical service... Any code or standards i could call out.

 

[infinity]

If you had a 1Ø, 480 volt circuit from a 2-pole circuit breaker what voltage would the breaker see?

 

[SteveAtx]

If you had a 1Ø, 480 volt circuit from a 2-pole circuit breaker what voltage would the breaker see?

If you had a single pole breaker, and measured from the load side to neutral you would have 240 VAC

 

[infinity]

If you had a single pole breaker, and measured from the load side to neutral you would have 240 VAC

There is no neutral in my example so the 1Ø voltage is 480 volts. Are you using a 1Ø, 240 volt circuit with a neutral and a single pole circuit breaker? If so I apologize I misread the question.

 

[augie47]

Clarify for me, please. Is your equipment designed for 480v or 240v single phase or 3 phase ??

 

[jim dungar]

If you had a single pole breaker, and measured from the load side to neutral you would have 240 VAC

No. You would have 277V, except for a few places that use 240/480V single phase for stuff like irrigation systems.

 

[SteveAtx]

There is no neutral in my example so the 1Ø voltage is 480 volts. Are you using a 1Ø, 240 volt circuit with a neutral and a single pole circuit breaker? If so I apologize I misread the question.

I might be asking the question wrong or giving the wrong answer, we have a panel that is Volts: 400Y/230 AC

 

[SteveAtx]

Our client is asking why we need 480 VAC breakers for an industrial control panel when any one pole will ever see 240 VAC, help with explaining this please. I need to explain that the breaker must match the electrical service... Any code or standards i could call out.

update to Volts: 400Y/230 AC

 

[augie47]

Your breaker would need to be rated for the phase to phase voltage

 

[jim dungar]

Your breaker would need to be rated for the phase to phase voltage

Correct.

A multi-pole breaker must be rated for the line to line as well as the line to neutral/ground voltage.

 

[Jraef]

update to Volts: 400Y/230 AC

The line-to-line voltage is still 400V, so even if all of the loads are fed from single pole breakers to feed 230V loads, the L-L separation of phase busbars in the panel is over 240V. Breaker voltage ratings jump from 240 to 480V for UL listed breakers, 400V rated breakers exist for worldwide use, but because 400V is not a standard voltage used here in North America, UL sticks to the ratings used here.