Current Flow

[DBoone]

You have a metal frame appliance, sitting directly on a concrete slab, with EGC attached. Would you have current flow from the supply neutral in the panel -- EGC--metal frame-- concrete -- dirt-- up the GEC to the transformer?

No because there isn't a difference in potential?

 

[charlie b]

Correct. The GEC lands on the neutral bar in the main panel, so there is no difference in potential that would drive current along the path you described.

 

[GoldDigger]

Correct. The GEC lands on the neutral bar in the main panel, so there is no difference in potential that would drive current along the path you described.

Or more accurately the only thing driving current through the earth would be the small voltage drop along the POCO neutral wire from the point where the transformer ground is connected to it to the point where it terminates in your service disconnect.

Since the resistance of the neutral wire will be tenths of ohms and the earth electrode resistance will be tens of ohms, at most 1/100 of the neutral current will flow through the parallel earth path. And most of that current will flow through the directly connected home ground electrodes (GES via GEC) while an even smaller amount might flow through the branch EGC back to the washer and into the concrete slab.

 

[DBoone]

Thanks guys