To bond or not to bond....Delta corner grounded 240v.

RICK G

Member
Location
WI
Replacing an old fussed sub panel, fed from a 200 amp disconnect, fed from a larger service. This is a 240v. three phase corner grounded delta. The panel being installed is a two bus using the N for the grounded B phase. Should the N bus be bonded or would it just be redundant. The entire system is metal.
 

Buck Parrish

Senior Member
Location
NC & IN
The neutral should be bonded at the first disconnect. Then isolated at the new panel. You should have a bonding bushing on the metal pipe and or a grounding conductor to bond all metal parts.
 

kwired

Electron manager
Location
NE Nebraska
It is a grounded conductor just like the neutral would be if it were a system that uses a grounded neutral.

Bond it to service enclosures, or at either transformer or first disconnect of a separately derived system. Everything else separate the current carrying portions of it from the equipment grounding portions of it.

This is the rule for grounded conductors no matter what phase, voltage, or type of system is.
 

RICK G

Member
Location
WI
I know it's bonded @ service , that's a newer install, but I'll have to check that disconnect between service & sub pan. It's older than ----. The sub's N bar wasn't bonded @ install & will remain so. The grounded B has a way of getting everyone second guessing what's even obvious sometimes.

Thank You for the info. R.
 

kwired

Electron manager
Location
NE Nebraska
I know it's bonded @ service , that's a newer install, but I'll have to check that disconnect between service & sub pan. It's older than ----. The sub's N bar wasn't bonded @ install & will remain so. The grounded B has a way of getting everyone second guessing what's even obvious sometimes.

Thank You for the info. R.
If you ever had someone that did not really understand what they have work on it, you never know what they may have messed up. Mis application of using grounded conductor for equipment grounding seems to be pretty popular with corner grounded systems, which results in current flowing on non intended paths during normal operation.
 
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