Sq D QED style switchboard ?

Davebones

Senior Member
We have a 2 section Sq D QED style switchboard . The first section has a 1600 amp main breaker that feeds the section section . We need to pull out some cable's and install larger feeders for a new air compressor in the second section . Both sections have a label that says " Prohibited " for the arc flash rating . Can we just isolate the main breaker and work inside the second section or would we need to isolate the feed to the main breaker too ???
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Engineer
Can we just isolate the main breaker and work inside the second section or would we need to isolate the feed to the main breaker too ???
Isolate the feed to the main breaker. That type of QED (non-drawout) has no internal barriers between sections. Something can easily fall from one section into the other.
 

wbdvt

Senior Member
Location
Rutland, VT, USA
Occupation
Electrical Engineer, PE
What is the justification on the energized work permit to do this work energized? Not sure what incident energy value is Prohibited but probably above 40 cal/cm2 and this may be the main switchboard so the protection is the utility fuse which results in a very long trip time for a fault on the switchboard.
 

Davebones

Senior Member
We are going to have the transformer isolated and shut down and grounds added . Yes this is above 40 cal/cm2 . I know there are still people that won't have the utility do this they would just lock out the main and work inside the other section. Thanks for the input . I put questions like this out there as it's easier to show management why we have to power down a whole switchgear section .
 

wbdvt

Senior Member
Location
Rutland, VT, USA
Occupation
Electrical Engineer, PE
How are you going to test for de-energized condition per NFPA 70E prior to installing the grounds as you will need the arc rated PPE to do that?
 
Top