480/3W Feed 480/277 Panel

Status
Not open for further replies.
Q

quantum

Senior Member
Location
LA
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.
 
Is the service (or SDS) 480/277 or is the supply actually 480 ungrounded or corner grounded?
 
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.
 
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).
 
ron said:
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.
Click to expand...

I think he may be supplying a 277/480 panel with a 480 feed, not sure though.
 
augie47 said:
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).
Click to expand...

10-4. Are there any other code references to this that I can read up on besides the one listed above?
 
quantum said:
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.
Click to expand...
I've done this with the inspectors blessing. I removed the neutral bus and clearly labeled the panel "480 volts only, no neutral present"

Sent from my LGL157BL using Tapatalk
 
Status
Not open for further replies.
Top