I have a 160' run between my meter pedestal and my 100a subpanel. The table for sizing the conductors accounts for the length of run, but NEC 250.122 for sizing ground wires doesn't say anything about length of run. It just shows number 8 (cu). Does length of run effect the ground wire size? The meter is grounded with 2 ground rods and the subpanel is grounded to the rebar in the footers per code in my area.
Electrical – Ground wire size for meter pedestal to subpanel
electrical
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Best Answer
The grounding conductor is sized based on the largest ungrounded (hot) conductor. So if you have to use a larger ungrounded conductor due to distance, the grounding conductor will scale up as well.
8 AWG CU ground is good for up to 2 AWG CU ungrounded (hot) conductors (If I'm not mistaken).
250.122 is for sizing equipment grounding conductors. The ground wire running from the meter to the panel is not actually an equipment grounding conductor, it's actually serving as a grounding electrode conductor. Which means it should be sized based on 250.66.
You might want to ask your local building department, as they might allow you to use 8 AWG. After all, I'm not a professional, so I could be interpreting the code incorrectly.