Supplementary protectors have been recognised in Canada since the publication of the standard in 1989, CAN/CSA C22.2 No.235 Supplementary Protectors. Twenty-eight years later, misapplication of supplementary protectors continues to be a problem.

The reason for the confusion regarding their application misapplication could relate to the following:

  • product similarity,
  • price,
  • incomplete product application knowledge,
  • the marketing of supplementary protectors, or
  • misunderstanding of the difference in testing and approval requirements between a certified product and a recognised component.

This article is intended to explain the difference between a certified circuit breaker and recognised supplementary protectors.

First, we should start by exploring the difference between a “certified” piece of equipment and a “recognised” component. Accredited certification bodies can use two types of product markings: full certification, and recognition. Let’s begin with explaining the difference between the marks of conformity for certified, and recognised products.

Certification Marks

The two most commons accredited certification bodies that have both “certification” and “recognition” marking are Canadian Standards Association (CSA) and Underwriters Laboratory (UL). The certification marking is well known and is shown in photos 1 and 2. Products with this marking (with a certification monogram) are intended to be installed in accordance with the Canadian Electrical Code Part I (CE Code) and meet all of the Canadian Electrical Code Part II requirements for their specific product type.

Photo 1. A Canadian Standards Association certification mark
Photo 1. A Canadian Standards Association certification mark
Photo 2. An Underwriters Laboratory certification mark
Photo 2. An Underwriters Laboratory certification mark

Recognition Marks

The recognition marking is not as well known and is shown in photos 3 and 4. Products with recognition marking are intended to be part of an electrical product that is either certified by an accredited certification body or approved under a Field Evaluation (FE) program by an accredited inspection body. FE can include (but does not normally involve) abnormal or destructive testing typical of a certification project, so acceptability of recognized components under field evaluations greatly depends on the intended use and what testing was done by a certification body in order to recognize the component. Products with only recognition markings are not intended to be installed in accordance with the CE Code and are not intended to be installed as stand-alone components. These products (components) are intended to be part of an approved assembly.

Photo 3. A Canadian Standards Association recognition mark
Photo 3. A Canadian Standards Association recognition mark
Photo 4. An Underwriters Laboratory recognition mark
Photo 4. An Underwriters Laboratory recognition mark

Supplementary Protectors and Circuit Breakers

Now, let’s look at supplementary protectors and circuit breakers. There are two North American product standards for supplementary protectors: CSA C22.2 No 235 Supplementary Protectors, and UL 1077 Supplementary Protectors for Use in Electrical Equipment. Although these two standards are not harmonised, the requirements within them are very similar. CSA Standard C22.2 No 235 defines a supplementary protector as follows: — a manually resettable device designed to open the circuit automatically on a predetermined value(s) of time versus current or voltage within an appliance or other electrical equipment.

CSA Standard C22.2 No 5 Molded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures and the CE Code Part I defines a circuit breaker as  — a device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its ratings.

The main difference between these definitions is that a circuit breaker must be capable of being operated without damage to itself when properly applied within its ratings, and the standard for supplementary protectors allows them to be damaged when applied within their ratings. The misunderstanding of this crucial difference and misapplication of supplementary protectors can contribute to a shock or fire hazard.

This also explains why circuit breakers have an interrupting rating and supplementary protectors only have a withstand rating, as supplementary protectors are only tested to withstand a short-circuit, and not tested to interrupt current.

Photo 5. Four supplementary protectors
Photo 5. Four supplementary protectors

There is an old saying that what looks like a duck, walks like a duck, and quacks like a duck, is probably a duck. Although to an undiscerning eye, supplementary protectors may appear like circuit breakers, there are significant differences, and as has been noted above, misapplication can result in a shock or fire hazard. The intended use of supplementary protectors is to provide additional protection for components inside an appliance or piece of electrical equipment where a certified overcurrent protection device already exists for the circuit. It should be noted that supplementary protectors are not approved as a disconnecting means, nor for the protection of wiring or devices located outside of the enclosure in which they are mounted. The acceptability of supplementary protectors is intended to be determined in their final application

In acknowledgement of the serious shock and fire hazard, Rule 14-114 and an Appendix B note were added to the 2006 Edition of the CE Code that reads:

14-114 Application of supplementary protectors (see Appendix B). Supplementary overcurrent protection shall not be used as a substitute for branch circuit overcurrent devices or in place of branch circuit protective devices specified in this Section.

 

Appendix B Rule 14-114

Supplementary overcurrent protectors used as components of some appliances and equipment are not suitable for the protection of branch circuit conductors.

In addition, CSA Standards C22.2 No 235 Clause 1.5 reads:

Protectors covered by this Standard are not to be used for overcurrent protection of circuits defined as “branch circuits” by the Canadian Electrical Code, Part I.

Adding to the confusion, there are seven types of supplementary protectors, differentiated by application codes. These application codes include U3, U2, U1, U1a, C2, C1, and C1a. During the short-circuit testing detailed in CSA Standard C22.2 No 235 and UL Standard UL1077, the supplementary protectors with an Application Code of C2, C1, and C1a – are allowed to be tested with a fuse ahead of the supplementary protector. Unfortunately, the type of fuse that can be used in the circuit during the testing is not specified, and unless a copy of the testing report is available, it is impossible to know what type of fuse was used. This makes it very difficult to accept supplementary protectors with an Application Code of C2, C1, or C1a without additional testing.

Supplementary protectors with an Application Code of U3, U2, U1, and U1a are not allowed to have a fuse in the circuit during the short-circuit testing.

After the short-circuit testing supplementary protectors with an Application Code of C1, C1a U1 and U1a are deemed to meet the standard even if they are no longer able to trip the circuit, are unable to be reset, and no longer indicate whether the circuit is open or closed. The standard allows welding or the complete destruction of the contacts when the supplementary protector operates.

After the short-circuit testing the U3 supplementary protectors are the only supplementary protectors that must have the ability to trip the circuit, the ability to be reset, the ability to indicate whether the circuit is open or closed, pass the voltage withstand test between the line and load, and can not have welding of the contacts, or destruction of the contacts. This is why CSA Standard C22.2 No 286 Industrial Control Panels, and Annex A of CSA Standard C22.2 No 235 only allow supplementary protectors with an Application Code of U3 to be used for protection of control circuits within a control panel. Note: supplementary protectors with an Application Code of U3 are not common.

How can a supplementary protector be identified?

This is another problem! Neither CSA Standard C22.2 No 235 nor UL Standard UL1077 requires a supplementary protector to be marked as a supplementary protector (this marking is optional). Following are general guidelines to identify a supplementary protector, any of these can be used to identify a supplementary protector:

1)  The device has a recognition mark (as shown in photos 3 and 4)

2)  The device has a withstand rating (not and interrupting rating)

3)  The device has an Application Code U3, U2, U1, U1a, C2, C1, and C1a

4)  The device has small spacings between the line terminals and the between the load terminals. (see photo 10)

Photo 6. A Schneider Electric supplementary protector, note the location of the recognition mark on the end of the device. The marking on the side indicated an Application Code of U1
Photo 6. A Schneider Electric supplementary protector, note the location of the recognition mark on the end of the device. The marking on the side indicated an Application Code of U1
Photo 7. An ABB supplementary protector, note the two recognition marks on the side of the device. The markings do not indicate the application code for this supplementary protector. Looking at the certification record on line the Application code is U1
Photo 7. An ABB supplementary protector, note the two recognition marks on the side of the device. The markings do not indicate the application code for this supplementary protector. Looking at the certification record on line the Application code is U1
Photo 8. An Allen-Bradley supplementary protector, note the marking includes an ac application code of U2 and a dc Application Code of U1.
Photo 8. An Allen-Bradley supplementary protector, note the marking includes an ac application code of U2 and a dc Application Code of U1.
Photo 9. A Siemens supplementary protector, with one recognition mark on the side of the device. The markings do not indicate the application code for this supplementary protector. Looking at the certification record on line the Application Code is U2
Photo 9. A Siemens supplementary protector, with one recognition mark on the side of the device. The markings do not indicate the application code for this supplementary protector. Looking at the certification record on line the Application Code is U2
Photo 10. An example of a Siemens supplementary protector (on the left), and a Siemens circuit breaker (on the right). Note the extra spacing between the line terminals and the between the load terminals.
Photo 10. An example of a Siemens supplementary protector (on the left), and a Siemens circuit breaker (on the right). Note the extra spacing between the line terminals and the between the load terminals.
Photo 11. A Tyco Electronics supplementary protector, with two recognition marks on the side of the device. The markings do not indicate the application code for this supplementary protector. Looking at the certification record on line the Application Code is C1.
Photo 11. A Tyco Electronics supplementary protector, with two recognition marks on the side of the device. The markings do not indicate the application code for this supplementary protector. Looking at the certification record on line the Application Code is C1.

Supplementary protectors are marketed by some manufacturers as “mini circuit breakers”, “circuit breakers”, “overcurrent protection” etc., that can be very misleading. This is also the reason it is so important to be able to identify supplementary protectors to ensure they are not used in place of overcurrent protection. An overcurrent device is not considered a circuit breaker in North America and acceptable for branch circuit overcurrent and short-circuit protection unless it is certified to UL489 or C22.2 No.5 and so marked.

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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.

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