The NFPA Standards Council has issued a tentative interim amendment (TIA) Number 1688 for the 2023 National Electrical Code to correct an oversight that occurred during the process of revising Article 725, which previously covered Class 1, Class 2 and Class 3 remote-control, signaling and power-limited circuits.

Panel 3, which has had jurisdiction over Article 725 since the 2002 NEC, did a total rewrite of Article 725 for the 2023 edition. In it, Panel 3 limited newly revised Article 725 to Class 2 and Class 3 power-limited circuits. There is a new Article 722 that provides requirements for cables for power­-limited circuits, such as Class 2 and Class 3, as well as cables for the new Class 4 fault-managed power circuits, which are covered in new Article 726. New Article 724 now covers Class 1 power-limited and Class 1 power-limited remote control and signaling circuits.

With all of these substantial changes and rewrites, Panel 3 missed addressing the requirements for one of the most important parts of old Article 725—the requirements for Class 1 nonpower-limited installations. Panel 3 provided a new Section 300.26 that did not adequately cover Class 1 remote-control and signaling circuits classification.

Now that I have thoroughly mixed you up, let’s discuss the reason for the TIA and provide the remainder of the information for accessing the proper information on nonpower-limited Class 1 circuits.

Class 1 circuits

First, an explanation on Class 1 circuits. There are two types: power-limited and nonpower-limited. They are often used for motor control, signaling and other important control applications. Class 1 power-limited circuits (formerly covered in parts I and II of old Article 725) are now covered in new Article 724, with the same basic information in the old article, but only for power-­limited circuits. New Article 724 covers Class 1 circuits that are not an integral part of a device or utilization equipment (as also applied in previous Article 725).

Class 1 power-limited circuits are supplied from a source with a rated output of not more than 30V and 1,000 volt-amperes.

Class 1 power-limited circuits are supplied from a source with a rated output of not more than 30V and 1,000 volt-amperes (VA). Section 724.40(A) permits transformers to supply Class 1 circuits and 724.40(B) permits other types of power sources, such as solid-state power supplies. While these Class 1 power sources are power-limited, the voltage level of 30V and 1,000 VA can develop up to 33A, which is a shock and fire hazard. Due to the hazards, these circuits are required to be dealt with as power circuits, with insulation on the circuit conductors to be rated for the system voltage and not less than 600V. Conductors larger than 16 AWG must comply with Article 310 requirements.

Panel 3 and old wording

Panel 3 established a new section to read, “300.26. Remote-Control and Signaling Circuits Classification. Remote-control and signaling circuits shall be classified as either power-limited or non-power-limited and comply with the following: Class 1 power­-limited remote-control and signaling circuits shall comply with 724.3. Class 2 and Class 3 power-limited remote-control and signaling circuits shall comply with 725.3. Non-­power-limited remote-control and signaling circuits shall be installed in accordance with 300.2 through 300.25.”

The reference to 300.2–300.25 in the 2023 NEC did not provide any information on how to specifically install Class 1 nonpower-limited circuits. None of the former text related to these circuits was transferred from the old Article 725. 

The purpose of TIA 1688 is to restore that text to the 2023 edition by adding it to 300.26. This will further divide this section into three subsections: 300.26(A) covering Class 1 power-limited remote-control and signaling circuits and (B) covering Class 2 and Class 3 power-limited remote-control and signaling circuits. 

New subsection (C) covers nonpower-­limited remote-control and signaling circuits and states the following: “Non-power-­limited remote-control and signaling circuits shall be installed in accordance with 300.2 through 300.25 and comply with 300.26(C)(1) through (C)(3).”

These three new subsections restore the former text from Part II of the 2020 NEC version of Article 725 into 300.26 and provide the missing pieces of the puzzle. Section 300.26(C)(1) now provides the requirements for sizing and use of conductors, 300.26(C)(2) provides the types of conductor insulation and 300.26(C)(3) provides the requirements for the types of overcurrent protection required.

If you purchased the first printing of the 2023 NEC, none of the text in the paragraphs above will be in the soft- or spiral-bound versions of the 2023 NEC Handbook. It can be found in the electronic version. If your municipality, county or state has adopted the first printing of the NEC, you should also get them to adopt this TIA.