5

According to my understanding, if a supplementary ground rod is installed, it must be bonded to the existing rod via a buried 6 AWG cable (NFPA 70).

However, because virtually every side of my house is paved, I have no access to the soil around the ground rods. Could I use a 4- or 6-gauge wire running above ground through a PVC conduit via the basement to bond the two ground rods?

The new ground rod is for a TV antenna, and I have been told it is very unwise to ground it to the meter, which is just several feet away.

Note: The house needs to pass inspection, so please keep that in mind.


This question regards code compliance, which is not specifically requested in this post: Bonding Ground Rod for Rooftop Antenna.


3

I can find nowhere in the NEC that says that you must bury inter-electrode bonding jumpers. In fact, 250.64(B) explicitly allows for running grounding electrode conductors (such as inter-electrode bonding jumpers) along construction or otherwise aboveground when suitably protected against physical damage, etc.:

Securing and Protection Against Physical Damage. Where exposed, a grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried. Grounding electrode conductors shall be permitted to be installed on or through framing members. A 4 AWG or larger copper or aluminum grounding electrode conductor shall be protected if exposed to physical damage. A 6 AWG grounding electrode conductor that is free from exposure to physical damage shall be permitted to be run along the surface of the building construction without metal covering or protection if it is securely fastened to the construction; otherwise, it shall be protected in rigid metal conduit (RMC), intermediate metal conduit (IMC), rigid polyvinyl chloride conduit (PVC), reinforced thermosetting resin conduit (RTRC), electrical metallic tubing (EMT), or cable armor. Grounding electrode conductors smaller than 6 AWG shall be protected in RMC, IMC, PVC, RTRC, EMT, or cable armor. Grounding electrode conductors and grounding electrode bonding jumpers shall not be required to comply with 300.5.

Of course, you'll have to double-check with your local inspectors, though -- they may have some local requirement for burial of bonding jumpers.

-1

We're talking about noise issues on the common bus. Two scenarios: high voltage and its for life safety, or high sensitivity and its for unbalanced audio or RF signal fidelity.

It was my understanding that the usual practice is to stake diametrically opposite sides within the concrete formwork for the foundation pad, at 3 o'clock and 9 o'clock position with your grounding electrodes, then lay a loop of bare grounding wire within the footprint of the pad formwork, and go around the clock with that loop, and bond it to both the electrodes on the way by, so that theres a current path possible either way around the ring, and you end up with the two ends of the bare ground wire to cary current shorted to ground. All this cable gets encased in concrete when the pad is poured, probably could be encased in rubble that'll protect it, the point is lots of contact with earth on the ground bus, and the buried cable adds to that, and as for the PVC, as for the NEC, as if dual electrodes alone were not enough, there is a need for a highly reliable ground, i believe when there is significant unbalance between high voltage poles resulting in significant common current which is shorted to your grounding rods, so they had better be the path of least resistance. Related: Faraday Cage.

Yes it is the unbalance between the current on the poles that leads to current on common, if your common bus is tied to the "ground" bus, but ground bus is not really in fact well bonded to earth, that is if you "lift ground" you may be able to detect current between common and ground, which i have felt jolts of electricity, and detected by illuminating an LED with the energy between common and earth from an unbalanced, and poorly grounded installation of an electric fence generator, long story. So yes, if you "ground to the meter" you might pick up some nasty transients on ground that are going to bias your radio frequency signal with the clicker or 60 hz harmonic noise, so in theory having a separate ground network for your RF circuits is going to be quieter, but if everything was actually well bonded to earth per code and on that one good ground bus you have your meter common and your tv ground, it should be really quiet, an EQUIPOTENTIAL SURFACE BONDED TO EARTH but there are high frequency harmonics and noise is complex and unpredictable.

In PA audio, you may sometimes encounter a noisy ground and elect to lift the ground with a switch on the mixer or by disconnecting the ground pin at the power plug, or by plugging all PA gear into the same outlet on the same phase, thus your PA ground reference voltage is no longer sensing the noise due to unbalance on the common bus as mixed in noise and can form its own equilibrium assume some quiet unperturbed value, that all the mic's and generators and pre-amplifiers can agree upon, to achieve a higher signal to noise ratio, that factor of fidelity that crackles into analog RF signals. Of course you have to shield your signal wires or they become aerials, too, and there you may/may not want to be earth bonded or ground lifted, I'd have to experiment to say. Related: Direct Inject Box and Ground Lift.

DTV, FM-HQ, FHSS and other Digital RF systems seem to be robustly tolerant of noise, but if its DTV you're picking up, i'd say there is a small chance that NEC proper earth bonding could play a determining factor in your ability to tune into a particular station. The combinations of ground, aerial antenna, cabling, signal attenuators, and tuner, could be tricky to buzz out, and you might find performance differences between makes of tuners to be more hit an miss than your ground quality.

  • I really don't see this answering the question. A supplemental ground rod is all that was asked about and the connection and 3 phase answered this with code references. - – Ed Beal Jan 25 at 15:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.