Ice Bridge Grounding: Which combination of gauges is specified for grounding and bonding the ice bridge respectively?

• A. Supports #2 AWG; Bridge #6 AWG
• B. Supports #6 AWG; Bridge #2 AWG
• C. Supports #4 AWG; Bridge #8 AWG
• D. Supports #2 AWG; Bridge #4 AWG

Answer: (A)

Grounding a structure like an ice bridge needs a low-impedance path to earth to safely carry fault currents, while bonding is about keeping all metal parts at the same electrical potential without needing to handle large fault currents. That means the grounding path for the supports should be larger (more robust) to handle any fault current, and the bonding path on the bridge can be smaller since its job is to equalize potential rather than carry heavy fault current. Therefore, using a heavier conductor for the supports and a lighter conductor for bonding the bridge is the intended approach: a #2 AWG grounding conductor on the supports and a #6 AWG bonding conductor on the bridge. Other combinations would either under-size the grounding path or use unnecessarily large bonding conductors.