NEC 2026, Move concept from 310.10(G)(1), Ex. No. 1 to 240.21(B)(1), new (I) section.

[James Williams]

Text Deletion New Text

Public input

Article 310 Conductors for General Wiring, Part III. Installation. 310.10 Uses Permitted. (G) Conductors in Parallel. (1) General.
Exception No. 1: Conductors in sizes smaller than 1/0 AWG shall be permitted to be run in parallel to supply control power to indicating instruments, contactors, relays, solenoids, and similar control devices or for frequencies of 360 Hz and higher, provided all of the following apply:

(1) …

Article 240 Overcurrent Protection.

240.21 Location in Circuit. Overcurrent protection shall be provided in each ungrounded circuit conductor and shall be located at the point where the conductors receive their supply except as specified in 240.21(A) through (H) (I). Conductors supplied under 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.

…

(I) Control Tap Conductors. Conductors of any size and length meeting the ampacity of the load served shall be permitted to supply signal or control power to indicating instruments, contactors, relays, solenoids, and similar control devices. Control tap conductors can be tapped from branch-circuit, feeder, and tap conductors.

Informational Note: Conductors larger than required for the ampacity of the load may be required for the correct functioning of indicating instruments and relays.

Substantiation: (1) The text removed from 310.10(G)(1) Ex. 1. does not describe paralleled conductors, it describes tap conductors. Moving it to 240.21 makes sense because that is the part of the Code dealing with tap conductors. The second reference to "(H)" is intentionally unchanged.

 

[don_resqcapt19]

Your substantiation is not correct. The exeption only applies where the control conductors are installed in parallel. It has nothing to do with tap conductors. The exception addresses the issue of skin effect for higher frequency circuits.

 

[James Williams]

Your substantiation is not correct. The exeption only applies where the control conductors are installed in parallel. It has nothing to do with tap conductors. The exception addresses the issue of skin effect for higher frequency circuits.

Please cite a plausible circuit in which control conductors are run in parallel with the current-carrying conductors of the circuit. I could not come up with such a scenario.

 

[James Williams]

Your substantiation is not correct. The exeption only applies where the control conductors are installed in parallel. It has nothing to do with tap conductors. The exception addresses the issue of skin effect for higher frequency circuits.

Prior to 2008 NEC the control exception and the high Hz exemption were separate. The two different situations were munged together in 2008 to use the same numbered list I guess. But they are separate concepts.

 

[don_resqcapt19]

Please cite a plausible circuit in which control conductors are run in parallel with the current-carrying conductors of the circuit. I could not come up with such a scenario.

This has nothing to do with the control conductors being installed electrically in parallel with the current carrying power conductors. This only has to do with the control conductors themselves being connected in parallel. These conductors are much smaller than 1/0 and the exception is needed to permit the control conductors to be connected in parallel.

Below are a couple of examples that I have installed over the years.

I worked on a couple of projects where engineered documents required parallel 14 AWG from a CT to the instrument to reduce the burden. Have also seen it used on long control circuits where multiconductor cables were run from the control system to a field junction box, and from that box to things like solenoids, where the voltage drop was too high on a single set of conductors, so two conductors were connected in parallel.

While the control circuits and high frequency circuits are totally different types of circuits, as the high frequency circuits can be power circuits, the concept covered by the exception is the same for both types of circuits...that concept being the installation of conductors smaller than 1/0 in parallel.

 

[James Williams]

This has nothing to do with the control conductors being installed electrically in parallel with the current carrying power conductors. This only has to do with the control conductors themselves being connected in parallel. These conductors are much smaller than 1/0 and the exception is needed to permit the control conductors to be connected in parallel.

Below are a couple of examples that I have installed over the years.

I worked on a couple of projects where engineered documents required parallel 14 AWG from a CT to the instrument to reduce the burden. Have also seen it used on long control circuits where multiconductor cables were run from the control system to a field junction box, and from that box to things like solenoids, where the voltage drop was too high on a single set of conductors, so two conductors were connected in parallel.

While the control circuits and high frequency circuits are totally different types of circuits, as the high frequency circuits can be power circuits, the concept covered by the exception is the same for both types of circuits...that concept being the installation of conductors smaller than 1/0 in parallel.

Thank you, that was very informative. When I reread the section with your example in mind, I now understand that it is the control conductors in parallel.

 

[James Williams]

Suggestion withdrawn and replaced with a newer suggestion for 240.21(I)