May 7, 2020

By William (Bill) Burr

Since earlier articles were based on the 23rd Edition of the CEC, Part I, I have revised these articles to reflect any changes made pursuant to the 24th Edition. This edition of the CEC, Part I, (C22.1-18), is available from CSA Group. The Code is a comprehensive document. Sometimes it can seem quite 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. Here in this issue: Section 16 Class 1 and Class 2 circuits.

Section 16, although a general section of the Code, applies specifically to
• remote control, signal circuits, Class 2 power and data communication circuits connecting power sourcing equipment and powered devices
• 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 – Electrical Communication Systems
• 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.

General requirements

Rule 16-000 Scope outlines 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
• 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 covers
• wiring between the load side of the overcurrent device or the power-limited supply and all connected equipment
• classification of circuits into Class 1 or Class 2 circuits
• definitions 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:
• Class I circuit cannot be run in the same cable as communication circuits
• Class 2 remote control and signal circuits, that run in a cable assembly with other communication conductors, are deemed communication circuits and must conform to rules in Section 60
• Class 2 power and data communication circuits and requires that they be in accordance with 16-300 to 16-350

Class 1 circuits

Rule 16-100 describes the limitations of a Class 1 circuit:
• an extra-low-voltage power circuit must be supplied by a source, limited to a rated output of 30 volts and 1000 volt/amps
• a remote control or signal circuit must be 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 16-104 to 16-118.
Rule 16-104 designates that the overcurrent protection of Class 1 circuits be in accordance with Section 14, or other specific sections of the Code, with the following exceptions:
• where No 18 or 16 AWG copper conductors extend beyond the equipment enclosure, they must be protected by overcurrent devices rated at 5 or 10 amps respectively
• overcurrent protection on the primary side of a secondary-side-protected enclosed transformer is exempted, 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
• Table 11 for conductors No. 16 and 18 AWG for Class 1 circuits

Rule 16-114 permits 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. Note that 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 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

Rule 16-200 describes the limitations of a Class 2 circuit in order 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
• energy limiting through use of suitable rated series resistors or similar devices
• 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 specifies that 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.

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

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

Rule 16-208 requires the overcurrent device to be located where the Class 2 conductor receives its supply.

Rule 16-210 provides specifications for
• selection of conductors in accordance with Rule 4-008 (table 19), with some exceptions
• use of ELC conductors, with limitations as noted
• size of conductors for various installation conditions
• maximum allowable current

Rule 16-212 requires the separation of Class 2 conductors from various other circuits like electric power, Class 1, and electric lighting, through appropriate minimum separations or barriers of bonded-to-ground raceway, cable or other metal or non-metal material.

This also applies to a compartment, outlet box, junction box, or similar fitting, with the separation of conductors of electric lighting, power, or Class 1 circuits, except 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.
In addition, where Class 2 conductors are installed in a cable, it must be marked as suitable for Class 2 and conductors be insulated for the maximum voltage of any conductor in the cable.

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 conductors, penetrating through a fire separation, be installed in accordance with Rule 2-128.

Rule 16-218 and 16-220 cover conductors 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, electromedical equipment, equipment for hazardous locations, and thermostats, incorporating heat anticipators, must be approved,
• 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, may be only acceptable for the application and not necessarily approved,
• equipment on circuits operating at more than 42.4 volts peak or dc, 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, operating at a voltage exceeding 300 V between conductors, must also meet the requirements of Section 60.

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

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

* The source for this series of articles is the Canadian Electrical Code, Part I, published by CSA.

William (Bill) Burr is the former Chair of the Canadian Advisory Council on Electrical Safety (CACES), former Director of Electrical and Elevator Safety for the Province of BC, and former Director of Electrical and Gas Standards Development and former Director of Conformity Assessment at CSA Group. Bill can be reached at Burr and Associates Consulting billburr@gmail.com.