Bulletin 50-4-1 Wiring methods for Solar Photovoltaic Systems Rules 50-018 and 50-020, Tables 11 and 19 Issued December 2012 Supersedes Bulletin 50-4-0 (1) (2) (3) (4) (5) Scope Introduction New cable types RPV & RPVU Wiring methods within photovoltaic array (a) Acceptable wiring methods within an array (b) Combiner box (c) Cable support (d) Attachment plugs (e) Wiring method within an array for ungrounded PV systems Color coding of PV (dc) source and output circuit conductors Accessibility to public & guarding of ground-mounted PV installations (1) Introduction The intent of this bulletin is to clarify some of the wiring method requirements as per Section 50 Rules. In addition to this Bulletin, the following documents provide additional information on the installation of solar photovoltaic systems: Bulletin 50-1-* Installation of Solar Photovoltaic Systems Bulletin 50-2-* Grounding and Bonding of Solar Photovoltaic Systems Bulletin 50-3-* Voltage rating of a photovoltaic source circuit (2) New cable types RPV & RPVU New cable types RPV and RPVU, approved to CSA C22.2 No 271, have been introduced into the code. The following table shows different usages of RPV and RPVU type cables as permitted by Rule 50-018 and listed in Table 19: Table B1 Usage of RPV & RPVU conductors Installation RPV RPVU Raceway (except cable tray) in dry/damp location Table 19 Table 19 (note 5) Raceway (except cable tray) in wet location Table 19 Table 19 Inside building or structure in a raceway 50-018(8) 50-018(8) Cable tray for interconnection of PV system* - 50-018(5) Exposed to weather for interconnection of panels within an array without raceway** - 50-018(4) Direct earth burial - Table 19 (*) conductors type RPV are not permitted for cable tray installation, unless marked (TC) or equivalent (**) provided that conductors are mechanically protected, serviced by qualified person, and inaccessible to public Electrical Safety Authority Page 1 of 6
(3) Wiring methods within photovoltaic array (a) Acceptable wiring methods within an array In addition to conductors type RPVU, the following are also permitted for wiring within an array: Flexible cords for extra-hard usage as listed in Table 11, as per Rule 50-018(1); Conductors approved for exposed installations, where subject to the weather, as listed in Table 19 and marked for sunlight resistance. Although not listed in Table 19, type RWU conductors shall also be permitted, provided that they are marked for sunlight resistance and the installation satisfies all conditions listed in Rule 50-018(4); Conductors approved as part of an approved panel assembly, as per Rule 50-018(3); and PV wire or cables approved to UL standard UL 4703, with all conditions listed in Rule 50-018(4) satisfied The permission for using PV cables approved to UL standards will expire on January 1 st, 2013. Where an application for inspection or plan review are submitted after January 1st, 2013, all wiring used for photovoltaic system installations is required to be approved to Canadian Standards. (b) Combiner box The Appendix B note to Rule 50-002 shows the diagram of a typical solar photovoltaic system and a device referenced as a combiner box. ESA SPEC 004 defines a combiner box as a box used in solar installations to combine the multiple photovoltaic arrays to produce one circuit. It often contains generator overcurrent devices. The combiner box is permitted to be installed on the roof and it is preferred to be as close as possible to the PV modules forming the array. The purpose of the combiner box is to group the wiring from the array into one cable run to the inverter, which reflects the logic of having the combiner box as close as possible to the array (on the roof), as per the Photo B1. Direction 1 Wiring methods specified above (subject (3)(a) of this bulletin) are acceptable for interconnecting PV modules within an array. If the combiner box is located outside of a building or a structure and within 1 m from the physical edge of the PV modules, acceptable wiring methods permitted within the array are allowed to be extended to the combiner box, provided that they are mechanically protected from damage. Where a combiner box is not located within 1 m of PV modules or where conductors are run inside the building or a structure, wiring methods specified in Section 12 are required. Photo B1 Combiner box Electrical Safety Authority Page 2 of 6
(c) Cable support Cables and conduit shall be kept clear of sharp metals, be properly supported and shall not lie loosely on the roofing material. Notwithstanding Rule 12-206 requirements for open wiring support, acceptable supporting means are considered to be straps or other devices located within 300 mm of every box or fitting and at intervals of not more than 1.5 m throughout the run. This requirement is similar to the supporting requirements for non-metallicsheathed cable as defined by Rule 12-510(1). Conductors are also required to be kept clear of sharp metal edges. Photo B2 is an example of unacceptable cable support. Photo B2 Unacceptable cable support (d) Attachment plugs As per Rule 50-020, the plug-in connectors used to connect cables between PV modules are required to be of the locking type and be rated for the voltage and current of the circuit in which they are installed. Photo B3 shows an example of a connector that meets Rule 50-020(d) requirement. Photo B3 Example of a PV wire connector Attachment plugs may not be rated for interrupting the current and must be marked with a warning indicating that disconnection under no load is necessary. In this case, the modules must be disabled before disconnecting the connectors. Also, attachment plugs and connectors are required to be of a type that requires a tool to open, when: Readily accessible; and Used in circuits operating at over 30 V (e) Electrical Safety Authority Page 3 of 6
Wiring method within an array for ungrounded PV systems PV solar systems are permitted to be ungrounded as per Rule 50-026. Rule 50-026(2) refers to requirements in Section 64 (Rule 64-018) for ungrounded systems. Rule 64-018(1)(b) requires source and supply conductors to consist of either metal-sheathed (jacketed) multiconductor cables, in accordance with Rule 4-008(1), or to have the conductors installed in metallic raceways. Notwithstanding the above requirements, for the interconnection of PV modules, wiring methods permitted within an array as per Rule 50-018 (subject (3)(a) of this bulletin) are allowed for ungrounded systems provided that a transition junction box is provided within 1 m from the edge of PV modules to change the wiring method used for the PV modules interconnection to metal sheathed cable or conductors in a metallic raceway. Note If the combiner box is within 1 m of the edge of the PV modules, no additional transition junction box is required as it is permitted to extend the same wiring method used within the array (see Direction 1 of this bulletin). The requirement in the Rule 64-018(1)(b) above will be applied from the transition box or the combiner box to the inverter input. Background (4) Color coding of PV (dc) source and output circuit conductors ESA has been involved in several fire investigations that have resulted when polarity of PV (dc) source and/or output circuit wiring has been accidentally reversed during installation. It has been found that field marking of conductors presents many opportunities for errors and consequently, dangerous failures. Unlike traditional ac systems where connection of incorrectly identified conductors will cause reversal of motors or an overcurrent device to operate, reversal of dc sources can create series circuits that will produce voltages well in excess of the rated system voltage. Diagram B1 Reversed polarity of dc sources Electrical Safety Authority Page 4 of 6
Recently, a new rule has been approved by the Canadian Electrical Code, Part I Committee to address this issue. The new rule will mandate the dc photovoltaic output circuit conductors, and photovoltaic source circuit conductors installed between a module and the power conditioning unit of the dc system to be colored, coded, or both. This new rule requirement will be mandatory when the 26 th Edition of the OESC is introduced (anticipated in 2015) Recommendation In recognition of this new Section 50 requirement and for the added safety value to electrical installations in Ontario, ESA recommends complying with this new requirement regarding colour coding of PV conductors for PV installations, in the interim, until mandated with the introduction of the 26th Edition of the OESC, DC photovoltaic output circuit conductors and photovoltaic source circuit conductors installed between a module and the power conditioning unit of the dc system are to be colored, coded, or both, as follows: (a) for a 2-wire circuit (i) red for positive and black for negative; or (ii) black conductors manufactured with permanent surface printing indicating the polarity on the conductor; and (b) for a 3-wire circuit (bipolar circuit) (i) white ** for mid-wire (identified as centre tap), red for positive, and black for negative; or (ii) black conductors manufactured with permanent surface printing indicating the polarity on the conductor(*). The above requirement will not be permitted to be met by field marking or labelling, unless for multi-conductor cables through suitable field labelling or marking in a permanent manner as follows: (i) be made at every point where the separate conductors are rendered accessible and visible by removal of the outer covering of the cable; (ii) be made by painting or other suitable means; and (ii) not render the manufacturer s numbering of the conductors illegible. Notes: (*) CSA Standard C22.2 No 271 Photovoltaic Cables requires the positive or negative identification on RPV or RPVU multi-conductor cables to be +/, pos/neg, or positive/negative. Single conductor cables are allowed to be marked in the same manner (**) Grey or white with coloured stripe are also permitted (5) Accessibility to public & guarding of ground-mounted PV installations With the restrictions on some of the wiring methods within an array described in Rule 50-018, and attachment plugs (which do not need a tool to open) to be inaccessible to public, the following direction has been developed based on the clarification in the Appendix B note to Rule 50-018. Direction 2 The wiring for a solar PV installation is deemed inaccessible to public and not readily accessible if it satisfies one of the following conditions: (1) It runs in a raceway; (2) By the usage of physical barrier such as wire screening or guarding; (3) Isolated by elevation, such that no open wiring below 2.5 m (from finished grade)*; or (4) Enclosing the ground mount PV installation inside a fence**. (*) On sun tracker units the 2.5m shall be measured when the array is oriented in its lowest plane. (**) Fences complying with Rules 26-304, 26-312 and 26-314 are deemed acceptable to enclose ground mounted PV installations. No barb wire is required. Electrical Safety Authority Page 5 of 6
Photo B4 example of non-compliant installation Photo B5 example of using physical barrier around wiring Electrical Safety Authority Page 6 of 6