Grounding Electrode System and Grounding Electrode Conductor
250.54 Supplementary Grounding Electrodes
This section was revised to read:
Supplementary grounding electrodes can be installed and they can be connected to the equipment grounding conductors. Supplementary grounding electrodes and their conductors are not required to comply with the bonding requirements of 250.50 and 250.53(C) or the 25 ohm resistance requirement of 250.56. However, the earth cannot be used as the sole equipment grounding conductor [250.4(A)(5)].
Intent: The changes to this section make clarify that a supplementary electrode is (1) not required to be bonded to the grounding electrode system [250.50], (2) the bonding jumper to the supplemental electrode can be any size [250.53(C)], and (3) the 25 ohm resistance requirement of 250.56 does not apply. Figure 250–13
The supplementary electrode is sometimes called a “signal reference ground” for sensitive electronic equipment. We must be careful not to confuse the “supplementary” grounding electrodes with the “supplemental” grounding electrodes required in 250.53(D) for the water pipe electrode.
Some manufacturers of digital-based equipment require that a supplementary electrode (typically a ground rod) be connected to the machine.
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