National Electrical Code Tips: Article 800, Communications Circuits, Part 3
- The title of Article 800, Part III is "Grounding Methods." It should be "Bonding and Grounding Methods" because we see this phrase used copiously throughout "The bonding conductor or grounding conductor...."
- Do you bond or do you ground? To avoid confusion, read the defintions in Article 100. Now here's an example. Suppose you have a one-family house. On one exterior wall, you see the electrical service meter, the gas meter, and the box that contains the splice for the Internet cable. The electrical service meter connects to a ground rod, the gas meter connects to a ground rod, and the cable system (covered by Article 800) connects to a ground rod. All of these must be bonded together. If you think about it, running a ground rod for the cable does not even make sense. Simply bond it to the existing grounding electrode system. I will use the phrase "bonding conductor" instead of "bonding conductor or grounding conductor" going forward, and now you know why. Look at Informational Note Figure 800.111(B)(1) to get an even better handle on this.
- The bonding conductor must be copper [800.100(A)(1)]. If you use aluminum, you'll create a battery that corrodes the whole system. In addition, you'll have a higher impedance than you should and that will cause differences of potential instead of eliminating them as a copper conductor would.
- Make your bonding conductor(s) as short as practicable [800.100(A)(4)] with as few bends as is practicable [800.100(A)(5)].
- You're required to use bonding conductors that are at least 14AWG [800.100(A)(3)]. Nothing stops you from using even bigger ones. Oversizing this conductor relative to the minimum won't necessarily increase the electrical protection, but it will mean a mechanically stronger, more durable bonding conductor.
- If the structure has an intersystem bonding termination, connect to that [800.100(N)(1)].
- If the structure lacks an intersystem bonding termination but does have a grounding means, connect to that [800.100(N)(2)].
- If the structure doesn't have an intersystem bonding termination or a grounding means, what do you do? Connect to one of the three items listed in 800.100(N)(3)(1) through (3). .
- Going back to point 2 for a moment, where separate electrodeds are used. Use a bonding jumper that's at least 6AWG to connect the communications grounding electrode (whatever that turns out to be) to the power system grounding electrode.
An easy way to do this is to use an ice scraper (the kind used for driveways) to make a narrow trench about 4 inches deep between electrodes. Then lay 4AWG bare copper into that trench and use the ice scraper to push it down. Use listed connectors at each end to attach to the grounding electrodes. Gently tap the conductor down with the ice scraper and use your foot to stomp the trench closed. You now have a horiztonal grounding electrode in addition to a big bonding jumper and you installed it in only a few minutes.
- Mobile homes have their own requirements. See 800.106.