Grounding wires inside boxes

[bobinyelm]

I am running #6 wire for a welder using 6-2 w/gnd NMC.

Obviously I will connect the ground wire to the grounding terminal of the 50a receptacle, but what gauge minimum do I have to run to the metal box itself?

It would seem that the box wire doesn't carry current, but is there for "short protection" to blow the breaker, so a lesser gauge would suffice.

Same question for my 30a 220v #10 wire for my compressor...

Thanks

Bob

 

[mm08822]

The overcurrent protection for the circuit determines the minimum size of the egc.
The size of the grd wire jumps at various breaker sizes. See table 250.122.

The 6-2 nmb will have a #10 grd wire. Use #10 to pickup the box. A pigtail will work best here.

10-2 nmb will come with a #10 grd wire. Use #10 to pickup the box. A pigtail will work best here.

 

[wyliesdiesels]

u need #10 for both circuits.

 

[bobinyelm]

The overcurrent protection for the circuit determines the minimum size of the egc.
The size of the grd wire jumps at various breaker sizes. See table 250.122.

The 6-2 nmb will have a #10 grd wire. Use #10 to pickup the box. A pigtail will work best here.

10-2 nmb will come with a #10 grd wire. Use #10 to pickup the box. A pigtail will work best here.

Thanks for the table.

I noticed that the #6 had #10 ground wire, so I guess that they automatically size the ground wire inside cable according to that table, so you're safe using the same for grounding. Makes sense!