July 2, 2024

By William (Bill) Burr^{^[i]}

The Code is a comprehensive document. Sometimes, it can seem daunting to quickly find the information you need. This series of articles provides a guide to help users find their way through this critical document. This is not intended to replace the notes in Appendix B, or the explanations of individual requirements contained in the CEC Handbook but will hopefully provide some help in navigating the Code.

Section 16 Class 1 and Class 2 Circuits

(The 26th Edition of the Canadian Electrical Code, Part 1 (CSA C21-1:24) is now available. To order a copy go to https://www.csagroup.org/store/ This discussion of Section 16 is based on the 26th edition)

Although Section 16 is a general section of the Code, the Scope applies specifically to remote control, signal circuits, Class 2 power and data communication circuits connecting power sourcing equipment and powered devices, and voltage or energy limited circuits installed in accordance with the requirements of the Code, unless amended or modified by other sections.

Excluded from Section 16 are communications circuits included in Section 60 and circuits internally integral to an otherwise approved device. The premise of these requirements is that voltages less than 30 volts do not constitute a shock hazard and power levels less than 100 volt/amps do not constitute a fire hazard.

Section 16 is divided into four main parts covering General requirements, Class 1 Circuits, Class 2 Circuits and Class 2 Power and Data Communication Circuits

General

Rules 16-000 to 16-012 outline that this section applies to Class 1 and Class 2 remote control circuits; Class 1 and Class 2 signal circuits; Class 1 extra-low-voltage power circuits; Class 2 low-energy power circuits; and Class 2 power and data communication circuits connecting power sourcing equipment and powered devices

Rules 16-002, 16-004 and 16-006 outline that this section applies to the wiring between the load side of the overcurrent device or the power-limited supply and all connected equipment, the classification of circuits into Class 1 or Class 2 circuits and the definition of Class 1 extra-low voltage power circuits (limited to 30 volts) and Class 2 low-energy power circuits (current limited per 16-200).

Rule 16-008 notes that Class 1 or Class 2 circuits installed in Hazardous locations are also subject to the rules of Section 18.

Rule 16-010 specifies that remote control circuits to safety control devices where failure could cause a fire, or a life hazard are to be considered and installed as Class 1 circuits.

Rule 16-012 deals with circuits in communication cables and Class 2 power and data communication circuits shall be in accordance with Rule 16-300. It specifies that a Class I circuit cannot be run in the same cable as communication circuits, and Class 2 control and signal circuits that can be, are deemed communication circuits and need to conform to Section 60.

Class 1 circuits

Rules 16-100 to 16-118 outline the requirements for installation of Class 1 circuits.

Rule 16-100 describes the limitations of a Class 1 circuit:

for an extra-low-voltage power circuit it must be supplied by a source limited to a rated output of 30 volts and 1000 volt/amps, and
for a remote control or signal circuit it is limited to a source not exceeding 600 volts.

Rule 16-102 specifies that Class 1 circuits are to be installed as per other sections of the Code except as provided by rules 16-104 to 16-118.

Rule 16-104 designates that the overcurrent protection of Class 1 circuits must be in accordance with Section 14 or other specific sections of the Code with the following exceptions:

where No 18 or 16 AWG copper insulated conductors extend beyond the equipment enclosure, they must be protected by overcurrent devices rated at 5 for 10 amps respectively, and
to exempt overcurrent protection on the primary side of a secondary-side-protected enclosed transformer, other than the normal overcurrent protection for the branch circuit.

Rule 16-106 requires that the overcurrent device for Class 1 conductors be located where the conductor receives its supply, and may be integral to the power supply.

Rule 16-108 limits the maximum power output of Class 1 extra-low-voltage power circuit sources, including transformers.

Rule 16-110 specifies conductor material and sizes for various installations of Class 1 circuits.

Rule 16-112 indicates selecting conductor insulation types for Class 1 circuits from:

Table 19 for conductors larger than No. 19 AWG, and from
Table 11 for conductors No. 16 and 18 AWG for Class 1 circuits.

Rule 16-114 permits insulated conductors of different Class 1 circuits, which are insulated to the maximum voltage of any of the conductors, to be installed in the same enclosure raceway or cable. Power supply conductors are not permitted to be in the same enclosure, raceway or enclosure of Class I circuit conductors except when connected to the same equipment and all conductors are insulated for the maximum voltage of any conductor.

Rule 16-116 requires mechanical, moisture, excessive heat or corrosive action protection for a remote-control circuit where damage would result in a fire or life hazard as per Rule 16-010.

Rule 16-118 reiterates that Class 1 circuits extending aerially beyond a building shall comply with Rules 12-300 to 12-318.

Class 2 Circuits

Rules 16-200 to 16-226 outline the requirements for installation of Class 2 circuits.

Rule 16-200 describes the limitations of a Class 2 circuit to prevent a shock or fire hazard under normal circumstances by:

limiting the current of Class 2 circuits by various methods depending on the voltage:
1. 0 to 20 V — with an overcurrent protection rating of 5 A, except that overcurrent protection shall not be required where the current is supplied from
  1. primary batteries that under short-circuit will not supply a current exceeding 7.5 A after 1 min;
  1. a transformer or other power supply device having a Class 2 output; or
  1. a device having characteristics that, under normal operating conditions or under fault conditions, limits the output current to a value not exceeding 5 A and the output volt amperes to a value not exceeding 5 A multiplied by the open-circuit voltage.
1. 20 V to 30 V — with an overcurrent protection rating in amperes not exceeding 100 V•A, except that the overcurrent protection shall not be required where the current is supplied from
  1. primary batteries that under short-circuit will not supply a current exceeding 5 A after 1 min;
  1. a transformer or other power supply device having a Class 2 output; or
  1. a device having characteristics that, under normal operating conditions or under fault conditions, limit the output current to a value in amperes not exceeding 100 V•A divided by the open-circuit voltage;
1. 30 V to 60 V with an overcurrent protection rating in amperes not exceeding 100 V•A, except that the overcurrent protection shall not be required where the current is supplied from
  1. a transformer or other power supply device having a Class 2 output; or
  1. a device having characteristics that, under normal operating conditions or under fault conditions, limit the output current to a value in amperes not exceeding 100 V•A divided by the open-circuit voltage; and
1. 60 V to 150 V — with an overcurrent protection rating in amperes not exceeding 100 V•A, and in addition
  1. must be equipped with current-limiting means other than overcurrent protection that,
  1. under normal operating conditions or under fault conditions, limit the output current to a value in amperes not exceeding 100 V•A divided by the open-circuit voltage.

energy limiting through use of suitable rated series resistors or similar devices, and
preventing a transformer or other power supply device having a Class 2 output to be connected in series or parallel with another Class 2 power source.

Rule 16-202 accords that insulated conductors and equipment on the supply side of overcurrent protection, transformers or current-limiting devices of a power supply having Class 2 outputs

must comply with the appropriate other sections of the Code, and
devices be protected on the supply side by an overcurrent device rated at not more than 20A.

Rule 16-204 states that the rating of a Class 2 power supply and suitability for wet locations when intended for wet locations be permanently marked and be readily visible after installation.

Rule 16-206 permits overcurrent protection to be an integral part of a Class 2 power supply but prohibits interchangeable type overcurrent devices with different ratings being used.

Rule 16-208 requires the overcurrent device to be located where the Class 2 insulated conductors receive their supply.

Rule 16-210 provides specifications for:

selection of insulated conductors and cables in accordance with Rule 4-008 (Table 19) with some exceptions,
use of ELC cables with limitations as noted,
size of insulated conductors for various installation conditions, and
maximum allowable current.

Rule 16-212 requires the separation of Class 2 circuits from various other circuits like electric power, Class 1, and electric lighting through appropriate minimum separations or barriers of raceway, cable or other metal or non-metal material. This also applies to a compartment, outlet box, junction box, or similar fitting with the insulated conductors of electric lighting, power, or Class 1 circuits unless where the power circuit conductors are supplying power for the Class 2 power supply and all conductors are insulated for the maximum voltage of any conductor in the enclosure.

Rule 16-214 permits more than one Class 2 circuits within the same cable, enclosure or raceway providing they are insulated for the maximum voltage of any conductor.

Rule 16-216 requires that any Class 2 insulated conductors and cables penetrating through a fire separation be installed in accordance with Rule 2-128.

Rule 16-218 and 16-220 cover insulated conductors and cables in vertical shafts or hoistways in accordance with Rules 2-128 and 2-130 or ducts and plenum chambers in accordance with Rules 2-130 and 12-010.

Rule 16-222 requires that all lighting products, medical electrical equipment, equipment for hazardous locations, thermostats incorporating heat anticipators and the field installed insulated conductors and cables connected to these products shall comply with Rule 2-024(1). However, it allows that equipment located on the load side of overcurrent devices, transformers or current-limiting devices for Class 2 circuits operating at not more than 42.4 volts peak or dc be only acceptable for the application and not necessarily approved. For circuits operating at more than 42.4 volts peak or dc the equipment must be arranged so that no live parts are accessible to unauthorized persons.

Rule 16-224 requires that Class 2 circuits extending beyond a building and run in such a manner as to be subject to accidental contact with lighting or power conductors or cables operating at a voltage exceeding 300 V between conductors, shall also meet the requirements of Section 60.

Rule 16-226 specifies conditions to be observed when installing Class 2 circuits underground.

Class 2 power and data communication circuits

Rules 16-300 to 16-350 apply the requirements for Class 2 power and data communication circuits

Rule 16-310 provides some Special terminology used in this subsection such as Cable bundle, Class 2 power and data communication circuit, Power sourcing equipment, and Powered device

Rule 16-320 specifies that A Class 2 power and data communication circuit shall be supplied from power sourcing equipment with an output limited to 100 VA and 60 V dc.

Rule 16-330 outlines the applicable suitability, size, bundling, ampacity, voltage, temperature and power limitations for Class 2 power and communication circuits.

Rule16-340 provides Wiring methods to be followed for Class 2 power and data communication circuits.

Rule 16-350 requires markings to indicate the Class 2 power and data communications circuits power supply and the electrical rating of power sourcing equipment be permanent and readily visible for inspection after installation.

In the next installment we will be discussing Section 18 – Hazardous locations.

[i] William (Bill) Burr is an associate member of the Canadian Electrical Code, Part 1, Technical Committee and formerly Chair of the Canadian Advisory Council on Electrical Safety (CACES), Chief Electrical and Elevator Inspector for the Province of BC & the Northwest Territories, Director of Electrical and Gas Standards Development and Director of Conformity Assessment at CSA Group. Bill can be reached at Burr and Associates Consulting billburr@gmail.com..

[i] Source: CSA C22.1:24, Canadian Electrical Code, Part 1 – Safety Standard for Electrical Installations. © 2021 Canadian Standards Association. Please visit Store – CSA Group or call 1-800-463-6727. With the permission of CSA Group, the material is reproduced from CSA Group standard CSA C22.1:21, Canadian Electrical Code, Part 1 – Safety Standard for Electrical Installations. This material is not the complete and official position of CSA Group on the referenced subject, which is represented solely by the Standard in its entirety. While use of the material has been authorized, CSA Group is not responsible for the manner in which the data are presented, nor for any representations and interpretations. No further reproduction is permitted. For more information or to purchase standard(s) from CSA Group, please visit Store – CSA Group or call 1-800-463-6727.