Coaxial Cable (CATV) — Shield Grounding

The coax shield gets bonded to the building's grounding electrode system as close to the point of entrance as practical, using a grounding block. It is the same one-ground philosophy as the rest of Chapter 8.

Cable installers are notorious for grounding to a random water pipe or nothing at all. I always run that shield ground back to the real electrode system so a surge does not go looking through the TV.

When it applies

Where the cable company's coax enters a building, its metal shield has to be grounded at the point of entrance. That bond gives surges, lightning energy, and static a low-impedance path to the grounding electrode system instead of finding its way through your equipment or you.

Common mistakes

• Leaving the coax shield ungrounded or bonded to a separate, isolated ground rod.
• Running an overly long grounding conductor that adds impedance and defeats the purpose.
• Not bonding to the same grounding electrode system as the power service.

In the field

I land the coax ground block right at the entry and bond it back to the building's grounding electrode. Tying it to its own rod, separate from the power ground, is a classic error that can put a dangerous difference between systems.