CQD Spotlight features questions and answers from NECA and ELECTRICAL CONTRACTOR’s Code Question of the Day program.
Whether you’re a seasoned contractor, an apprentice or simply a National Electrical Code enthusiast, you’ll gain knowledge with a nod to the legacy of Charles M. “Charlie” Trout, a true NEC legend.
From the archives—April 12, 2013
In reference to NEC 250.122(B) as it applies to increasing conductor sizing to compensate for voltage drop, it states that the grounding conductor shall be increased in size proportionately to the increase in area of the ungrounded conductors. For example, the copper ungrounded and grounded conductor in a 120V, 20A circuit are increased from No. 12 to No. 6 to compensate for voltage drop, since the required equipment grounding conductor (EGC) for a 20A OCPD is a No. 12 copper conductor, would the EGC also need to be increased to No. 6 AWG?
Your example is correct, the equipment grounding conductor would also need to be increased to a No. 6. The ungrounded and grounded neutral conductor are both being increased from a No. 12 to a No. 6. In your example, the required copper EGC for a 20A OCPD is No. 12 per Table 250.122. This happens to be the same size as the ungrounded copper conductor (before the increase), which makes the increase the same for both conductors.
From the archives—Dec. 14, 2021
In reference to NEC 250.122(B) as it applies to increasing conductor sizing to compensate for voltage drop, it states that the grounding conductor shall be increased in size proportionately to the increase in circular mil area of the ungrounded conductors. The ratio from ungrounded and grounded conductors to the grounding conductor is one to one for 15A, 20A and 30A circuits. For example the ungrounded and grounded conductors in a 120V, 20A circuit are increased from No. 12 to No. 6 to compensate for voltage drop. Would the one-to-one ratio No. 12 grounding conductor also have to be increased to a No. 6?
The equipment grounding conductor has to be adjusted in size proportionately to the adjustment in size of the ungrounded conductors when addressing voltage drop situations. In long runs, current that goes out must be able to return on an effective ground-fault current path, without the impedance due to undersizing.
Get more out of this discussion through the CQD Spotlight podcast.
Post sponsored by Eaton Corp.
Section 250.122(B), and now (D) of the NEC 2026 is frequently misunderstood, particularly when conductors are increased in size for reasons such as voltage drop. The common assumption is that when ungrounded conductors are upsized, the equipment grounding conductor (EGC) must be increased proportionately. This is sometimes true. It is not universally required.
Section 250.122(B) and (D) requires increasing the EGC in size proportionately only when the ungrounded conductors are increased in size and the resulting ground-fault current would otherwise be insufficient to operate the OCPD.
The NEC does not require the OCPD to trip instantaneously or operate in the short-time delay region. The ground-fault current is required to be sufficient to trip the OCPD. The long-time pickup value is the gateway to meeting this requirement. For a 200A circuit breaker or 200A fuse, the ground-fault current would have to be less than 200A to require upsizing the EGC. Adding GFPE to this circuit breaker set to trip at a lower value than 200A, i.e., 30 mA, would eliminate the need to increase the EGC, as the ground-fault current would need to be less than 30 mA to require it.
This distinction is critical. If the ground-fault current available on the EGC is greater than the handle rating of the OCPD, the code objective has been met. In that case, there is no requirement to increase the size of the EGC, even if the phase conductors have been upsized for voltage drop.
When determining an EGC size increase under 250.122(B), follow these two simple steps:
Step 1: Determine the available ground-fault current.
Step 2: Compare the calculated ground-fault current to the handle rating of the OCPD protecting the circuit. If it exceeds the handle rating, the OCPD will open and the EGC size does not need to be increased. If it does not, the EGC must be increased, or an alternative method must be employed.
An alternative method: Protect the circuit with GFPE. The EGC will never be subjected to current greater than the GFPE pickup value.
At no point does the NEC require that the EGC be sized to survive the fault—only that it clears it. Understanding this distinction prevents unnecessary conductor upsizing, avoids material waste and ensures compliance with the actual language of the code.
