Canadian Electrical Code users have no doubt noticed the reminder (see Appendix B) next to the headings of many code rules. Appendix B is there to help us understand and correctly interpret the requirements of the code. It provides supplementary information including explanations, interpretations, other standards and sources of information to assist users in applying the rules so identified. It also gives us a better idea of what an inspector will expect. It’s a very good idea, in particular when applying a rule for the first time, to take a look at what Appendix B has to say.
In order to expand on the above, this article will identify a few of the rules that include this notation, with some examples of the types of important information provided, that can help us meet the requirements of these rules.
Rule 2-126 simply specifies that the minimum flame spread requirements for wire and cable must meet the specifications of the building code. But if you go to Appendix B, you will find a great deal more useful information including:
- The relevant building code paragraph numbers that provide minimum flame spread ratings for different types of construction
- The required wire and cable identification markings
- Acceptable installation methods for wire and cable that are unmarked and may not have the necessary flame spread ratings
Rule 2-128 requires that nonmetallic conduit run exposed in buildings of noncombustible construction must meet the requirements of the building code. Appendix B provides added information on the maximum trade size and required marking for conduit so installed.
Rule 4-004(1) and (2) permit wiring ampacities other than provided in Tables 1 to 4 of the electrical code through the use of IEEE Standard 835. To the chagrin of anyone who has contemplated using this method of calculation, Appendix B provides almost two pages of direction on minimum data that must be submitted to electrical inspection to justify using the IEEE Standard 835 as an alternative to the electrical code tables.
Rule 10-500 requires that the ground faults must have a low impedance return path so that they may be safely interrupted. Appendix B provides further essential information, requiring that the impedance be sufficiently low so as to permit 5 times rated current to flow during a ground fault, so that fuses or circuit-breakers can do their jobs effectively, without harm to persons or damage to property.
Rule 10-814(1) requires that the data specified in Table 16 be used to select minimum bonding conductor sizes. However, the rule is silent on minimum requirements when metallic cable sheaths or metallic conduit are used for bonding electrical equipment. Appendix B takes on this task, spelling out that when cables or conduits are correctly sized for other purposes, the metallic sheaths or conduit will automatically be correctly sized for the intention of bonding.
Rule 12-1104(1) tells us that rigid PVC conduit must not be exposed to temperatures in excess of 75°C. But Appendix B clarifies this requirement by advising that wiring having 90°C temperature ratings, when continuously loaded under conditions of 50 percent conduit fill, in a 30°C ambient will not result in temperatures above 75°C. Therefore, 90°C rated conductors in PVC conduit may be loaded up to their 90°C ratings and conductors having insulation temperature ratings above 90°C may also be installed in PVC conduit when their allowable ampacities are derated to 90°C.
Rule 12-2200 requires that cable trays be supported in accordance with support spacings provided by the cable tray manufacturer. But Appendix B adds some further conditions:
- The best support points are at the one quarter span points
- There must not be more that one joint between cable tray supports
- Some fittings (especially horizontal fittings) may need additional supports
Rule 26-256 stipulates that the primary overcurrent protection for dry type transformers must not exceed 125 percent of the rated primary current of the transformer. Appendix B offers additional valuable information — that fuses or circuit-breakers should be able to carry 12 times the primary load current for .1 second and 25 times the primary load current for .01 seconds so as to avoid unintended power outages due to inrush currents.
Rule 26-354 requires that transformer vaults meet the special construction, drainage, ventilation and lighting requirements of the building code for such facilities. Appendix B identifies the relevant building code paragraphs that provide this information.
Rule 30-322 specifies that a switch controlling bathroom lighting must be out of reach of a person in a tub or shower. Appendix B interprets “”out of reach”” as one metre.
As mentioned above, Appendix B contains an abundance of valuable and often critical information and it’s there for our use and convenience.
As with other articles, you should consult your local electrical inspection authority for a more precise interpretation of any of the above information.