Code users often ask whether Section 46 of the CE Code governs only the requirements foremergency systemsthat are mandated by the National Building Code of Canada (NBCC) to provide alternate source of power when the normal power fails.
Some of the Code users feel that Section 46 also covers wiring to the emergency systems that must function in a high building upon interruption of a normal power. Emergency systems mandated by the NBCC to perform the intended functions under a power failure conditions are considered to be life safety systems. The NBCC mandates that such life safety systems (i.e., fire alarm system, emergency lighting, fire pumps, elevators, smoke control and smoke venting equipment) must be provided with an emergency power supply in the event that the regular power supply to the building is interrupted.
Photo 1. Emergency Gen Set
However, by analyzing the scope of Section 46 the Code users might deduce that the Subrule 46-000(1) is quite clear on the extent of the scope in this regard, and life safety systems are not covered by the current scope.
The Code users also question whether current Rule 46-108(3) requires to prevent conductors supplying life safety systems from co-occupying raceways, boxes, cabinets with otherconductors that supply equipment not specifically mandated by the NBCC (but which is also connected to the emergency generator).
These questions usually are presented by the designers of institutional and health care building electrical systems who design building systems to comply with the CEC, the NBCC and requirements of other CSA and NFPA codes and standards for life and fire safety. These designers understand that combination of the codes and standards attempt to reduce the risk of failure of building life safety systems, and they are looking for a consistency in application of this requirement.
Based on their experience with both new and existing buildings, they appreciate that there can be risk reduction to building life and fire safety systems if their emergency wiring is separated from all other building wiring systems. These Code users are aware of buildings that have suffered the loss of power to NBCC-mandated life safety systems as a result of a fault to non-mandated equipment wiring being installed in the same cabinet, raceway or a box.
It is interesting to note that the question regarding requirement of Rule 46-108(3) has been interpreted differently by the Code users, including the electrical safety regulators.
Analyzing the Rule
If this is done, then a conclusion could be made thatconductors of emergency systems referenced in Rule 46-108(3) are the conductors from generators or batteries that are mandated by the NBCC, and these conductors must be “”kept entirely independent of all other conductors”” (i.e., of conductors from normal power supply).
Therefore, in accordance with the current wording of Rule 46-108(3), it appears to be clear that the conductors supplying equipment (other than life safety systems mandated by the NBCC) from an emergency generator could share the same distribution panel and a raceway as the conductors feeding life safety systems.
In light of the concerns by the Code users, a proposal was submitted to revise Section 46 so as to expand and clarify its scope and to prevent conductors supplied from an emergency generator to the equipment other than the NBCC-mandated life safety systems from sharing the same cabinet, box or a raceway with conductors feeding the life safety systems from the same generator.
The Technical Committee responsible for the development of the Canadian Electrical Code supported recommendation by the S/C on Section 46 for revision of the scope of Section 46 and for clarification of the conductors’ separation requirements in Rule 46-108.
The Technical Committee felt that Section 46 should be modified in order to harmonize requirements for the wiring methods between the emergency power supply and the NBCC-mandated life safety systems with similar provisions ofNEC700.1 and 700.9B.
It was agreed by the Technical Committee members that the following should be clarified in Section 46:
1. The Scope of Section 46 in light of the NBCC provisions for specific types of emergency power supply to the mandated life safety systems;
2. Terminology used in Section 46 in conjunction with the terminology used in Subsection 3.2.7. of the NBCC; and
3. Wiring methods requirements between the emergency power supply and life safety systems.
Thus, Technical Committee formally approved changes made by the S/C of Section 46 for the inclusion to the 2009 edition of the CE Code.
The readers may find that the most significant changes relate to the scope of Section 46 and to the requirements for wiring between the emergency power supply and the life safety systems.
The readers will also see that Section 46 of the 2009 CE Code incorporates new terminology that defines emergency power supply and life safety systems.
Sneak Preview of Significant Changes
Below is a sneak preview of the most significant changes to Section 46 in respect to the scope, terminology and wiring methods:
“Section 46 – Emergency Power Supply, Unit Equipment,Exit Signs and Life Safety Systems
“46-000 Scope (See Appendix B)
(1) This Section applies to the installation, operation, and maintenance of:
(a) emergency power supply and unit equipment intended to provide power to life safety systems, and
(b) emergency power supply and unit equipment intended to provide illumination of exit signs,
in the event of failure of the normal supply, where the emergency power supply is required by the National Building Code of Canada
(2) This Section applies to the wiring between the emergency power supply and life safety systems that are required by the National Building Code of Canada to be provided with an emergency power supply.
(3)This Section applies to the wiring of exit signs.
(4)The requirements of this Section supplement or amend the general requirements of this Code.
“46-002 Special Terminology (See Appendix B)
In this section the following definitions apply:
Emergency Power Supply– emergency power supplied by a generator, batteries or a combination thereof required bythe National Building Code of Canada.
Life Safety Systems– emergency lighting and fire alarm system that are required to be provided with an emergency power supply from batteries, generators or combination thereof, and electrical equipment for building services such as fire pumps, elevators, smoke venting fans, smoke control fans and dampers that are required to be provided with an emergency power supply by an emergency generator in conformance with the National Building Code of Canada.
Unit Equipment– unit equipment for emergency lighting conforming to CSA standard C22.2 No. 141.
“46-108 Method of Wiring (see Appendices B and G)
(1) Except as permitted by Subrule (3), Rule 46-304(3)and Rule 46-400(2), the following conductors shall be installed in accordance with Subrule (2):
(a) conductorsrequired for operation of life safety systems and installedbetween an emergency power supply and life safety systems;
(b) conductors between an emergency power supply and exit signs; and
(c) conductors between unit equipment and remote lamps.
(2) Conductors described in Subrule (1) shall be
(a) installed in metal raceway of the totally enclosed type;
(b) incorporated in a cable having a metal armour or sheath;
(c)installed in rigid non-metallic conduit where embedded in at least 50 mm of masonry or poured concrete or installed underground; or
(d) installed in electrical non-metallic tubing where embedded in at least 50 mm of masonry or poured concrete.
(3)Notwithstanding Subrule (2), conductors installed in buildings of combustible construction in accordance with Rules 12-506 to 12-520 shall be permitted to be incorporated in a non-metallic-sheathed cable.
(4) Conductors installed in accordance withSubrule (1) shall be kept entirely independent of all other conductors and equipmentand shall not enter a fixture, raceway, box, or cabinet occupied by other conductors except where necessary
(a) in transfer switches; and
(b)in exit signs and emergency lights supplied from two sources.
(5) Conductorsbetween an emergency power supply andany electrical equipment that is not defined aslife safety systems in accordance with this Section shallnot enter afixture, raceway, box, or cabinet occupied byconductors installedas described inSubrule (1) except where necessary in busways, splitters and other similar enclosures provided for connection to the overcurrent device for an emergency power supply described in Rule 46-206(1)”
The Technical Committee has also adopted new Appendix B Notes and a Diagram on Subrule 46-108(5) to explain the intent of the changes as follows:
“Appendix B Note on Rule 46-000
This Section is intended to apply to the installation, operation and maintenance of the emergency power supply such as batteries or generators that are required in conformance with the National Building Code of Canada (NBCC) to provide the emergency power for operation of the life safety systems.
This Section is also intended to govern wiring methods between the emergency power supply and emergency lights, exits signs or life safety systems where such emergency power supply and exit signs or life safety systems are mandated by the National Building Code of Canada.
It is not intended by this Section to prohibit connection of loads other than the NBCC required emergency lights, exit signs or life safety systems to the emergency power system mandated by the NBCC provided that all applicable requirements for wiring methods described in this section are met.
“Appendix B Note on Rule 46-002
It is intended by this Section to correlate special terminology with the NBCC description of an emergency power supply and life safety systems (see Subsection 3.2.7 of the NBCC).
“Appendix B Note on Rule 46-108(4)
It is intended by this rule that the wiring between the NBCC required emergency power supply and the NBCC required electrically connected exits signs or life safety systems is kept entirely independent of all other wiring including wiring to other loads that are connected to the emergency power supply.
“Appendix B Note on Rule 46-108(5)
It is intended by this rule that the wiring between the NBCC required emergency power supply and life safety systems is kept entirely independent of all wiring to other loads that are connected to the emergency power supply, except where necessary in the enclosures for splitters that are provided for connection between the emergency power supply overcurrent device and:
(a) a separate disconnecting means and O/C device for a feeder supplying a transfer switch for equipment that is not defined as life safety systems in this section,
(b) a separate circuit breaker circuit for a feeder supplying a fire pump transfer switch in conformance with Rules 32-206(4) and 32-208, and
(c) except for a fire pump circuit breaker, a separate disconnecting means and the O/C device for a feeder supplying a transfer switch for the equipment that is defined as life safety systems in this section.”
The Code users should be aware that the information of this article is of a preliminary nature, and it is intended only to advise the readers what could be expected in the 2009 edition of the CE Code in respect to installation of the emergency power supply and life safety systems under Section 46.
Although this article allows the readers to take a look into a very near future, it should be clearly understood that this sneak preview cannot be used asthe interpretation of the current Code. In order to apply amended provisions of Section 46, the Code users should wait until the new edition of the Code is formally published, and the 2009 CE Code is adopted in a jurisdiction for a regulatory purpose.
When the 2009 CE Code is adopted for enforcement, then the answer to a question whether Rule 46-108 requires to prevent conductors supplying defined life safety systems from co-occupying raceways, boxes, cabinets with conductors supplying other equipment (not specifically mandated by the NBCC but also connected to the emergency generator), would be unequivocal YES. And new Subrules 46-108(4) and (5) clearly substantiate this answer.
Hopefully, Appendix B Notes and the diagram (figure 1) on Rule 46-108(5) make this substantiation very transparent.