Corner Grounded Delta 3P


Senior Member
Turn of Century building has Corner Grounded Delta 3P. 240 vt / 240 vt / 0 vt. A disconnect for a 3P a/c unit has a 2 pole type disconnect. 240 vt fused. 240 vt fused. The 0 vt is just running straight in without fuse.

I know it is not code, but what issues might this cause?


Staff member
There is no reason for a disconnect to disconnect the grounded conductor of a corner grounded system. Fuses are not permitted in the grounded conductor of any system, except where used for overload protection, which is not very common. There are also a number of single phase breaker panels that are marked as suitable for use with two pole breakers on a corner grounded system. The only thing you have to watch is that the breaker must have a single voltage rating and not a slash rating like 120/240.


Master Electrician Electric Contractor Richmond VA
Henrico County, VA
Electrical Contractor
The grounded conductor of a corner-grounded delta is normally treated like a neutral when it comes to switching and coloring.

A switch is allowed to open a grounded conductor if it also simultaneously opens the line conductors . . . but it doesn't have to.


Electron manager
NE Nebraska
So is this up to code as it is?
What you have described so far is.

People can be easily confused with grounding something other than a "neutral" sometimes. There is a reason the NEC calls it a "grounded conductor. any conductor of any system can be grounded, NEC requires the neutral when present to be the one that is grounded in most cases though. This system has no neutral, therefore you can ground any conductor of the system and it is treated just like the neutral on more conventional systems. You bond it at service or first disonnect and then keep current carrying sections separated from Equipment grounding conductor section after that main grounding/bonding point.