Danger of resetting a 400 amp 480 volt breaker with a dead short

[Fulthrotl]

I have always had a very strict policy on personel protective grounds, controlling them is very important, I use additional tags on the LOTO point that says "Warning, PP Grounds installed" and include the assigned number for that ground set (The ground cluster is tagged with a number also).

the shorts and grounds i mentioned were not applied by the holder of the
work clearance. santa's little helper was hard at work. shorts and grounds
always have the owner's tag on them. these were untagged....:-? they were
in the middle of a bus, between positions, and tied back so they were out of
the way... i was always told to hang the grounds way out there where they
stuck out like a sore thumb, not tucked neatly out of the way....

 

[zog]

i was always told to hang the grounds way out there where they stuck out like a sore thumb, not tucked neatly out of the way....

Yep, me too, as obvious as possible.

 

[brian john]

Busway fault:

And it does not matter if it is midnight or 7:00AM,

Dress properly for the job (PPE)
Determine other components that could result in a trip, phase failure, remote EPO, blown fuse trip.

Check the GFP settings, low settings permit numerous smaller CBs to result in trip.

Ask if

There is any construction taking place (knuckle head electricians or possible demo).
Any water issues in the building.
Large frame motors or chillers on the line.
Larger transformers 500 kva and above (might cause tripping with a low setting on resetting the switch)

1. Visual inspection of switchboard interior, power off.
2. Open all busway switches. YES you have to walk the risers cause sure as heck someone else will miss a switch.
3. Check aux controls for connection to load of switch turn aux controls off.
4. Megger switch and busway.
5. Set GFP to minimum.
5. Secure all covers
6. Close switch.
7. Close busway disconnects.

If switch trips check all HVAC (or similar devices) units meggering compressors and fans.

8. Complete 1-7
9. Check current on neutral ground disconnect (bond).
10. Return GFP setting to original settings

 

[brian john]

Oh and I'll add (depending on the number of floors*) this will not take me more than an hour once I am on site.

*Typical DC office building 12 floors with penthouse at 56 I'll can still run the stairs THOUGH I DO NOT.