Grounding different voltage systems

[patpappas]

If conductors with different voltages are mixed 208v and 480v in the same conduit should they have their own separate ground for carrying fault current? Does it matter.

 

[Dennis Alwon]

If conductors with different voltages are mixed 208v and 480v in the same conduit should they have their own separate ground for carrying fault current? Does it matter.

To tell you the truth I don't think it matters for ground fault however, art 300.3 (B) may come into play. Thus if thwere is an egc from both conduits to a jb and then one is spliced to them both then I don't see an issue as long as it is sized to the largest breaker being used.

 

[JohnJ0906]

If conductors with different voltages are mixed 208v and 480v in the same conduit should they have their own separate ground for carrying fault current? Does it matter.

The EGC will need to have a path back to source on both systems. If this is done, I can't see a problem with 1 conductor serving as EGC for both circuits.

 

[tryinghard]

If conductors with different voltages are mixed 208v and 480v in the same conduit should they have their own separate ground for carrying fault current? Does it matter.

It?s not necessary especially if you splice or route through pull boxes, see 250.122(C), just run one and size it from Table 250.122 according to the largest OCPD (breaker). If you want to you can run separate but any bonding to enclosures needs to be sized from Table 250.122 and the largest circuit.

What?s most important is an effective ground fault path to all sources sized to handle the greatest fault current.