Communications Circuits — Grounding and Bonding

The key is bonding to a single point: the communications ground ties to the same electrode system as the power service. If the phone or data ground and the power ground are at different potentials, a surge finds its way through your equipment.

Chapter 8 stands mostly on its own, but this grounding rule is where it shakes hands with the rest of the Code. One building, one ground reference.

When it applies

This applies where communications cabling — phone, some broadband and similar circuits — enters a building. A listed primary protector goes at the entrance and its bonding conductor and any cable shields tie back to the building's grounding electrode system so a surge has a low-impedance path to earth instead of through the equipment.

Common mistakes

• Bonding the protector to a random ground rod separate from the power grounding electrode, creating a difference in potential.
• Running an overly long, sharply bent bonding conductor that fights fast surge currents.
• Leaving the shield floating and hoping the equipment survives the next lightning event.

In the field

I always bond the comms protector to the same grounding electrode system as the electrical service, short and straight. When everything shares one ground reference, a surge lifts the whole system together instead of arcing across your gear looking for a path.