Industrial control panels and assemblies

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A new safety standard in Canada for industrial control panels and assemblies has been developed known as CSA Standard C22. 2 No 286 Industrial Control Panels and Assemblies. This new standard was published in March 2015.

The scope of this new standard will cover control panels and assemblies that are intended for use in an ambient temperature of 0 to 40°C, with a maximum supply voltage of 1500 volts, for installation in non-hazardous locations under provisions of the Canadian Electrical Code, Part I (CE Code).

Examples of control panels covered by this standard include but are not limited to motor control panels, process control equipment panels, heating panels, programmable control panels, controls for cranes and hoists, and heating and cooling control panels.

Photo 1
Photo 1. A picture of a control panel enclosure and a picture of typical marking inside the enclosure. Photograph courtesy of Roberts Onsite Inc.

It should be noted that the scope of this standard does not include industrial control devices covered by the CSA standard C22. 2 No. 14 such as manual and magnetic starters and controllers, thermal and magnetic overload relays, selector switches and pilot lights, control circuit switches and relay, resistors and rheostats, time-delay relays, switches, and control devices. Examples of equipment covered by other CSA standards that are not part of the scope of this new standard are power supplies, automatic transfer switches, elevator equipment, enclosed switches, switchgear, line isolation monitors, panelboards and custom panelboards, hazardous location equipment, hydro-massage equipment, power factor correction capacitor banks, fire pump controllers, assemblies of equipment intended solely for the distribution of power, and motor control centre sections.

As with all CSA Part II standards, control panels certified to this new safety standard are to be in accordance with the general requirements of CSA Standard C22. 2 No 0 General requirements—Canadian Electrical Code, Part II.  In addition, electrical components that are part of the control panel are required to be certified for the specific use, examples of such are disconnect switches, transformers, fuses, circuit breakers, controllers, terminal strips conductors, etc.

Photo 2
Photo 2. A typical terminal strip used for termination of bonding conductors that is not approved to be used to bond the control panel enclosure

Enclosures used for control panels are required to be approved enclosure or can be evaluated as part of the certification to the requirements in CSA Standard C22. 2 No. 94. 1 Enclosures for Electrical Equipment, Non-environmental Considerations or C22. 2 No. 14 Industrial Control Equipment. In addition, this standard contains specific requirements regarding the size of opening in the enclosure and acceptable material that can be used for observation windows and barriers. Enclosure thermal insulation can also be included in the control panel; like the recently published edition of the SPE-1000 Model Code for the Field Evaluation of Electrical Equipment, this standard provided direction on clearance and creepage distances and  acceptable means to secure thermal insulation to the enclosure walls.

Photo 3
Photo 3. The inside of a control panel near the final stage of manufacturing. Photograph courtesy of Prime Engineering

Bonding provisions in the control panel are required to meet the general bonding requirements in CSA Standard C22. 2 No 0. 4 Bonding of Electrical Equipment. Also the size of bonding conductors, maximum number of bond conductors allowed on each termination, and the minimum number of bonding termination points are detailed. In addition, a clause has been included detailing limitation of DIN rail-mounted terminations used for bonding. Typically DIN rail-mounted terminations used in Canada are not tested or approved to be used to bond an enclosure.

 

System grounding provisions have been included aligning with the requirements and limitation in the CE Code. These requirements include which systems are required to be grounded, and the minimum size of grounding conductors. Where two or more systems require grounding, the standard allows the installation of a common tie point for all system grounding conductors. The standard also reflects the permission by Rule 10-206(3) of the CE Code to ground systems rated 1000 VA or less by use of the control panel incoming bond as the system grounding connection. It should be noted that Rule 10-206  of the CE Code does not allow a bond conductor in a branch circuit or feeder supplying power to a control panel to be used as the system grounding conductor for systems over 1000 VA. To assist installers and inspectors in the identification of control panels that require the installation of a system ground conductor the following caution notice is required to be located adjacent to the designated grounding tie point: “The secondary system(s) must be connected to a grounding electrode in compliance with the Canadian Electrical Code”.

Photo 4
Photo 4. A terminal strip used to allow termination of field-installed conductors. Photograph courtesy of Robertson Bright Inc.

Internal wiring used in control panels is required to have a minimum insulation temperature rating of 90°C.  The allowable ampacities for internal 90°C and 105°C insulated conductors is provided in Table 7 covering both ventilated and non-ventilated enclosures. As an alternative to the allowable ampacity tables, temperature testing is allowed to verify conductor sizing. The ampacity of conductors leaving the control panel are not covered by this new standard, for these allowable ampacities refer to the appropriate standard for the equipment the control panel is used for, or the CE Code for conductors feeding motors, heating loads, transformers, capacitors, etc. When selecting internal conductors, consideration needs to be given to the ambient temperature grouping of conductors, voltage ratings, flexibility, and clearances from moving parts, heat generating components or bare live parts. Colour coding of the conductor insulation is required to be in compliance with the CE Code including the requirement for ground and bonding conductors to be bare copper, green coloured, or green with a yellow stripe.

Photo 5
Photo 5. The four devices on the left are supplementary protectors that are not acceptable to be used as an overcurrent device for branch circuits. The two devices on the right are approved circuit breakers that can be used as an overcurrent device for branch circuits.

 

For field-installed conductors the standard details the required wiring space and wire bending space recognizing the largest conductor that could be installed with an allowable ampacity based on 60°C.  Internal conductor requirements cover minimum size, minimum 90°C conductor insulation, allowable ampacities, termination temperatures, voltage ratings, and insulation colouring.

Photo 6
Photo 6. An example of a DIN rail-mounted breaker that is acceptable to be used for branch circuit overcurrent protection.

The installation of components section of the standard has requirements to securely mount components to a supporting surface including additional provisions that would prevent panel-mounted devices like switches and rheostats from rotating during normal operations. Another clause addresses enclosures required to be opened during normal operation that expose the operator to bare live parts. In these latter cases, the enclosure must have a hinged door that will not be dislodged inadvertently, and barriers installed to prevent contact with the bare live parts. Single throw knife switches are required to be mounted in a manner that gravity will not tend to close the switch, and installed such that the blades are not energised when the switch is in the open position complying with CE Code Rule 14-506. Manual motor controllers marked “Suitable for Motor Disconnect” may be used as local motor or controller disconnecting means only when connected on the load side of the branch circuit disconnect and overcurrent device. Manual motor controllers with external operating mechanisms and not marked as “Suitable for Motor Disconnect” may only be used where identified as not for use as an isolating means for maintenance functions.

Photo 7
Photo 7. Typical tap conductors in a control panel. Photograph courtesy of Roberts Onsite Inc.

Branch circuit protection within the control panel is required to meet the requirements in Sections 14, 26, and 28 of the CE Code, and the standard indicates what types of protection are allowed and are not allowed. Approved fuses, circuit breakers and combination motor controllers can be used for motor branch circuit protection.  Examples of devices that cannot be used for branch circuit protection are supplementary protectors, supplementary fuses, semi-conductor fuses, magnetic only breakers, molded case switches, and manual starters.

This new standard provides limitation on the use of supplementary protectors. A supplementary protector is a manually resettable component that may look like a circuit breaker but has only been certified to the less stringent CSA Standard C22.2 No. 235 Supplementary protectors. Supplementary protector ratings consist of the following seven application codes C1, C1a, C2, U1, U1a, U2, and U3. Supplementary protectors are not allowed to be used as a substitute for branch circuit overcurrent devices, and cannot be used for short circuit or motor branch circuit protection. Supplementary protectors installed in accordance with the manufacturer’s literature can be used for control circuit protection provided the supplementary protector has a minimum short circuit current rating of 5 kA and an application code of U3. To assist users of this standard Annex D provides information on the limitation of supplementary protectors.

Photo 8
Photo 8. A 150 VA 480V to 120V control transformer installed in a control panel. Photograph courtesy of Robertson Bright Inc.

The standard also covers requirement for the size and maximum length of tap conductors within the control panel, and it mandates compliance with Rule 14-100 of the CE Code. In addition where group installation motor controllers are used, the ratings of the overcurrent protection installed on the line side of the group installation motor controllers, and the size and maximum length of the conductors are required to be in accordance with Section 28 of the CE Code in respect to the size and maximum length of tap conductors.

 Photo 9

Photo 9. A picture of a main disconnecting means in a control panel.

Transformer overcurrent protection is mandated to meet the requirements of Section 26 of the CE Code with the protection rated at not greater than 125% of the transformer primary full load current; of not greater than 300% of the primary with secondary protection not higher than 125% of the secondary full load current rating of the transformer. The standard provides options for control transformer overcurrent protection similar to what is presently allowed in CSA Standard C22. 2 No 14 Industrial Control Equipment, with a table allowing primary only protection set at not more than 500% where the primary full load ampacity is 2 Amp or less, and up to 167%  where the primary full load ampacity is between 2 and 9 Amps.

 

The standard emphasises that disconnecting means are required for all control panels with fuses or more than one supply circuit. The disconnecting means for multiple circuits are required to be integral with or adjacent to the control panel and grouped together, and warning labels are required to identify multiple circuits and to warn users that all of the disconnecting means must be opened to ensure that the circuits are de-energized. The intent of the disconnecting means is to allow maintenance and fuse replacement without exposure to any live part. Where the control panel is a floor mounted control panel, the maximum height for the disconnecting means is 2 m above the surface on which the operator is intended to stand.

Photo 10
Photo 10. A 120V 400W heater used in the control panel where the external ambient temperature may be below 0°C. Photograph courtesy of Eclipse Automation

Where the disconnecting means is used for a motor circuit, the standard states that the rating is required to be in accordance with Section 28 of the CE Code, and in addition all disconnecting means that are required to have a continuous rating such as a fused switch, molded case switch, and circuit breaker, must have the loading limited to the continuous rating of the disconnecting means.

Ambient temperature and the temperature within the control panel must be considered ensuring manufacturer’s installation instructions are followed with power electronic devices such as adjustable speed drives, variable frequency drives, contactors or other components that may generate heat within the control panel.

Where a control panel is intended to be installed where the external ambient temperature may be below 0°C, humidistat or thermostat controlled anti-condensation heaters, or space heaters that will not negatively affect the operation or life expectancy of any components or wiring, are required. In addition, the allowable ambient temperature range is required to be marked on a label attached to the panel where the control panel is intended to be installed in environments beyond the normal limits of 0 to 40°C.

The marking section of the standard includes the normal nameplate information to satisfy CE Code Rule 2-100 such as the manufacturer’s identification, serial number or date code, electrical information including voltage, frequency, full load ampacity, number of conductor, and the short-circuit current rating (SCCR). In addition, the nameplate of a control panel must state either “Industrial Control Panel” or “Industrial Control Panel Assembly” this is intended to avoid confusing control panel identification. The SCCR for a control panel is determined by the individual component directly connected to the primary circuit(s) of the control panel with the lowest interrupting rating or withstand rating. A table known as “Table 10 Short Circuit Current Ratings” has been provided to determine the ratings of components not marked with interrupting rating or withstand rating. Table A in this article details the typical minimum component ratings.

Photo 11
Photo 11 . An example of warning label for a control panel that has components that can only be connected to a solidly grounded wye system.

The overall control panel SCCR can be greater than the rating of the lowest rated component directly connected to the primary circuit when the component is part of a series rated combination that has been tested with a specific upstream overcurrent device. If the specific upstream overcurrent device is not part of the control panel, a label is required to be applied to the panel to notify installers that a specific overcurrent device must be installed in the supply circuit to the control panel in order to maintain the required SCCR. The standard requires the wording to read:   “SUITABLE FOR USE ON A CIRCUIT CAPABLE OF DELIVERING NOT MORE THAN ____ RMS SYMMETRICAL AMPERES, ____ V MAXIMUM, WHEN PROTECTED BY ___ (B) ___ WITH A MAXIMUM RATING OF ___ (C) ___” and “PEUT ÊTRE UTILISÉ DANS UN CIRCUIT PRODUISANT UN COURANT RMS SYMÉTRIQUE D’AU PLUS ____ A, À UNE TENSION MAXIMALE DE ____ V, À CONDITION QUE LE CIRCUIT SOIT PROTÉGÉ PAR ___ (B) ___ DONT LA CAPACITÉ NOMINALE EST DE ___ (C) ___”, where (B) represents the type of overcurrent protective devices, (fuses or circuit breaker) and (C) represents the maximum ampere rating of the overcurrent protective device specified by the manufacturer.

Components connected to secondary circuits as part of the control panel must be suitable for the calculated fault current available. Annex C of the standard provides calculation methods and tables that can be used to calculate the fault current for the secondary circuits.

The marking section of this standard also has a list of warning labels that must be used where applicable, including a label for control panel not intended to be mounted over a combustible surface. The standard mandates instructions for the conditions where current elements are used, and where control panels are used suitable for resistance heating loads. It also mandates, instructions for intrinsically safe circuits, control panels intended for burner control only, control panels intended to be connected to a solidly grounded wye system to comply with CE Code Rule 2-104(2), where field-installed overload and overheating protection is required to be installed, and more than one live circuit with instruction to refer to the circuit diagram. The standard also requires a label to indicate that after an interrupter has tripped the current carrying components of the motor controller should be examined and replaced if damaged.

Table 1
Table A

Caution markings are required to indicate the control panel has been evaluated with regards to electrical safety and shock hazards only, labels to replace fuses with the same type and rating for all fuseholders, a label to indicate the minimum size and maximum length of field-installed conductors allowed to comply with CE Code Rule 28-106(3), and a label adjacent to the designated grounding tie point to indicate that the secondary systems larger than 1000 VA must be connected to a ground electrode to comply with CE Code Rule 10-206 (3).

Another marking not identified and as a caution or warning label is required adjacent to bonding terminals to indicate the acceptable range for conductors to be terminated and that the conductors must be twisted together before inserting in the terminal where more than one bonding conductor of No. 6 AWG or smaller is to be terminated in a single- or multiple-conductor terminal.

Photo 12
Photo 12. An example of a caution label used to notify installers that the control panel includes a secondary system that the CE Code requires a connection to a ground electrode.

Service equipment: The standard includes a section for control panels intended to be used as a service box as defined by the CE Code, requirements for labelling, a separate compartment for the service disconnecting means, barriers to allow access for maintenance with access to live parts, ability to connect the line side of the main switch or circuit breaker without passing through compartments or raceways containing conductors connected to the load side of the main switch or circuit breaker, provisions to lock and seal the service disconnecting means, and provision for system grounding.

The standard also includes a section for control panels intended for electric heating control, oil and gas burning control panels, compressor control panels, and a section for control panels with intrinsic safety barriers; this section also includes specific component and marking requirements.

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Steve Douglas is an IAEI International Past President. He is also the Senior Technical Codes Specialist for QPS Evaluation Services. As the International Association of Electrical Inspectors Representative on Part I and Part II of the Canadian Electrical Code, Steve is the Vice Chair of the CE Code Part I, Chair of CE Code Part I Subcommittees for Section 2, and 12, and a member on Sections 40, 64, 68, 76 and Appendix D. In addition Steve is the Chair of the CSA Standards C22.2 No. 273 Cablebus, C22.6 No. 1, Electrical Inspection Code for Existing Residential Occupancies committee the Chair of the SPE-1000 Working Group, and a member on committees for the Objective Based Industrial Electrical Code, Safety Management Systems, Solar Photovoltaic Modules, Industrial control panels and assemblies, Photovoltaic Cable, Fuel Cells, Wind Turbines, Distribution transformers, Outlet Boxes, and Wiring Fittings Hardware and Positioning Devices.