480/3W Feed 480/277 Panel

[quantum]

Is it permissible to use a 480/277 panel with a feeder that is straight 480V? I believe the answer is no, based on NEC 240.85, but I'm looking for any additional information that I may be over looking. I'm working on an availability issue.

 

[electrofelon]

Hmmmm there was just a thread on the same topic.

https://forums.mikeholt.com/showthread.php?t=196150

 

[augie47]

Is the service (or SDS) 480/277 or is the supply actually 480 ungrounded or corner grounded?

 

[ron]

What 240.85 refers to is that individual-pole testing of molded-case circuit breakers (MCCBs) may be inadequate for some corner-grounded delta systems.

You are fine running a 480V 3 wire feeder from a 4 wire panelboard.

 

[quantum]

...

 

[quantum]

Is the service (or SDS) 480/277 or is the supply actually 480 ungrounded or corner grounded?

I'm awaiting specifics from the field, but it should be a feeder from an existing 480V MCC.

 

[augie47]

It still falls back to the premises voltage (assuming its not fed by a customer transformer). If the service is 480/277, you are fine using a 480/277 panel-board and breakers as the voltage to ground will not exceed 277.
(You do not have to have a neutral present at the panel to give you 277v).

 

[electrofelon]

What 240.85 refers to is that individual-pole testing of molded-case circuit breakers (MCCBs) may be inadequate for some corner-grounded delta systems.

You are fine running a 480V 3 wire feeder from a 4 wire panelboard.

I think he may be supplying a 277/480 panel with a 480 feed, not sure though.

 

[quantum]

It still falls back to the premises voltage (assuming its not fed by a customer transformer). If the service is 480/277, you are fine using a 480/277 panel-board and breakers as the voltage to ground will not exceed 277.
(You do not have to have a neutral present at the panel to give you 277v).

10-4. Are there any other code references to this that I can read up on besides the one listed above?

 

[masterinbama]

Is it permissible to use a 480/277 panel with a feeder that is straight 480V? I believe the answer is no, based on NEC 240.85, but I'm looking for any additional information that I may be over looking. I'm working on an availability issue.

I've done this with the inspectors blessing. I removed the neutral bus and clearly labeled the panel "480 volts only, no neutral present"

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