Section 16 – Class 1 and Class 2 Circuits
The CE 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.
(The 24th Edition of the CEC, Part I, (C22.1-18) * is now available from CSA Group. This discussion of Section 16 is based on the new edition.)
Section 16, although a general section of the Code, applies specifically to remote control circuits, 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 subsections: general requirements, Class 1 Circuits, Class 2 Circuits, and Class 2 power and data communication circuits.
The General requirements subsection 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; 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 covers: 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 where failure to operate of remote control circuits to safety control devices could cause a fire or a life hazard, circuits 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 shall conform to Section 60.
Class 1 circuits
This subsection outlines 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 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 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 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 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 an integral part of 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
- 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. 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
This subsection outlines 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;
- 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. (Note: a device having a Class 2 output must be marked as having energy-limiting characteristics and as suitable for the purpose).
Rule 16-202 reiterates that conductors and equipment on the supply side of overcurrent protection, transformers or devices having Class 2 outputs of a power supply having Class 2 outputs shall comply with the appropriate other sections of the Code.
Rule 16-16-204 requires that a Class 2 power supply unit have permanent markings, readily visible after installation, indicating the class of supply, electrical rating and suitability for wet locations if intended for wet locations.
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 conductor receives its supply.
Rule 16-210 provides specifications for:
- selection of conductors in accordance with rule 4-008 (Table 19,) with some exceptions (Table 60 for Class 2 power and data communication circuits);
- use of ELC conductors with limitations as noted;
- size of conductors for various installation conditions; and
- 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 raceway, cable or other metal or non-metal material. This also applies to a compartment, outlet box, junction box, or similar fitting with the 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 circuit 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.
Rules 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 equipment located on the load side of overcurrent devices, transformers, or devices having Class 2 outputs for Class 2 circuits shall:
- (for all lighting products, electromedical equipment, equipment for hazardous locations, and thermostats incorporating heat anticipators) comply with Rule 2-024(1) (be approved);
- (for other equipment operating at not more than 42.4 volts peak or dc) be acceptable for the application and not necessarily approved as per Rule 2-024(2);
- be suitable for dry or damp locations when the voltage characteristics are:
- 30 V rms for sinusoidal ac,
- 42.4 V peak for other waveforms (non-sinusoidal ac),
- 60 V continuous dc, and
- 24.8 V peak for interrupted dc (square wave dc at a rate of 10 to 200 Hz); and
- Be suitable for wet locations (not including immersion) when the voltage characteristics are:
- 15 V rms for sinusoidal ac,
- 21.2 V peak for non-sinusoidal ac,
- 30 V for continuous dc, and
- 12.4 V peak for interrupted dc (square wave dc at a rate of 10 to 200 Hz).
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, 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 to Class 2 power and data communication circuits (see Appendix B for important notes).
Rule 16-310 outlines special terminology to be used with this subsection.
Rule 16-320 requires that power supply for Class 2 power and data communication circuits be limited to 100 V•A and 60 V dc outputs.
Rule 16-330 provides an outline for determining the ampacity of cables and conductors for this subsection and notes that:
- conductors must be suitable for the application in accordance with Rule 12-102 3);
- the maximum current that each insulated conductor be as per Table 60, and based on the size of the conductor and the cable temperature rating, the number of cables in the bundle, and the smallest conductor and lowest temperature rating of any cable in the bundle;
- where not more than four conductors in each cable are used to transmit power, the maximum ampacity for each conductor is calculated by multiplying the values listed in Table 60 multiplied by 1.4;
- not more than 192 cables shall be permitted to be bundled together except for communication cables marked with the suffix “-LP” where the maximum current for each insulated conductor is limited to the current rating marked on the cable, and for conductors smaller than No. 26 AWG, or in cable bundles of more than 192 cables, is determined by a qualified person, with permission as per Rule 2-030;
- the maximum current permitted in a Class 2 power and data communication circuit is limited to the rating of the connectors or components used in the circuit;
- where the maximum conductor termination temperature for equipment is not marked use 60°C;
- where cables are installed in an ambient temperature exceeding 30°C use Table 5A correction factors;
- the length of a circuit, in addition to Rule 8-102(1), must be limited to ensure that voltage at the connected utilization device is within its rated voltage tolerance;
- multiple cables installed in a ventilated and ladder-type cable tray must be spaced at least 25 mm; and
- communication equipment rated at 60 W or less supplied by a cable having a minimum conductor size of No. 24 AWG, can be exempted from bundling requirements.
Rule 16-340 requires conductors for Class 2 power and data communication circuits to be:
- used only as part of a common cable assembly marked as being suitable for the application;
- installed in accordance with Rule 16-224 where extending beyond a building;
- installed in accordance with Rule 12-012 where installed underground; and
- not connected in series or parallel with other conductors for Class 2 power and data communication circuits.
Rule 16-350 requires permanent and readily visible marking indicating class of supply and rating of the power source to be visible for inspection after installation.
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 firstname.lastname@example.org.