Unravelling mystery of FT marking for conductors and cables

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Photo 1. Examples of buildings required to be non-combustible construction in downtown Toronto. Photo, Steve Douglas
Photo 1. Examples of buildings required to be non-combustible construction in downtown Toronto. Photo, Steve Douglas

By this time, the subject of FT marking for combustible insulation and jackets of conductors and cables should be well understood by the Canadian Electrical Code (CE Code, Part I) users. However, reality appears to be quite different, and confusion still exists. Let’s try to re-visit this subject and to answer 5 basic questions related to it.

Question 1. What does FT marking mean?

Answer 1.  A specific FT marking on a combustible jacket of a conductor or cable is a manifestation that that particular conductor or cable was subjected to a vertical flame test FT1 or to a vertical flame test FT 4 in accordance with provisions of the CSA standard C22.2 No. 0.3 or CSA standard C22.2 No. 2556, or was subjected to a flame and smoke density test FT6, conforming to ULC standard CAN/ULC S102.4.

Question 2. Is compliance with FT marking mandated by the CE Code, Part I?

Answer 2.  Yes, it is. Rule 2-130 of the CE Code mandates the following:

“2-130 Flame spread requirements for electrical wiring and cables (see Appendices B and G)

Electrical wiring and cables installed in buildings shall meet the flame spread requirements of the National Building Code of Canada or local building legislation. “

Appendix B Note on this Rule provides a detailed explanation on use of specific flame spread marking (FT1, FT4 or FT6) for such exposed combustible insulation or jackets of the conductors and cables, depending whether such conductors and cables are located in building of combustible construction or in buildings required to be of non-combustible construction by the National Building Code of Canada. Appendix B Note also offers additional clarification on FT marking requirements for conductors and cables located in plenums with exposed combustible insulation. Appendix G of the CE Code provides a relevant cross-reference between the CE Code requirements and the NBCC requirements in this regard.

Question 3. What does “exposed combustible jacket or exposed combustible insulation” mean for the purpose of Rule 2-130 of the CE Code, Part I?

Answer 3.  Rule 12-504 of the CE Code allows use of non-metallic-sheathed cable only in a building of combustible construction, and allows such use in buildings required to be of non-combustible construction, only where such installation is accepted by an AHJ (see below):

“12-504 Use of non-metallic-sheathed cable (see Appendix B)

Non-metallic-sheathed cable shall be permitted in or on buildings of combustible construction and in or on other types of construction where acceptable. “

This means, that in a building required to be of non-combustible construction – wiring methods for installations covered by the scope of Section 12 of the CE Code must be done by means of metal sheathed cables or by means of conductors installed in raceways. This also means that if conductors and cables are installed in raceways, their combustible insulation and combustible jackets are no longer exposed, and flame spread requirements mandated by Rule 2-130 of the CE Code, are not applicable for such installations. It should be noted that some armoured cables might be constructed, tested and certified with the outer combustible jackets, and removal of such combustible jackets in order to prevent a need to comply with Rule 2-130 of the CE Code, may void certification of the cable. Thus, in each such case, a confirmation from the cable manufacturers must be obtained – to ascertain that such removal will not void original certification of a cable.

It should be also noted that some wiring methods are exempt from the scope of Section 12 (see below), and under these (exempted) wiring methods, non-metallic-sheathed cables or conductors in raceways – may be installed in buildings required to be of non-combustible construction.

“12-000 Scope (see Appendix B)

(1) The provisions of Section 12 apply to all wiring installations operating at 750 V or less, except for

(a) Class 2 circuits unless otherwise specified in Section 16;

(b) community antenna distribution and radio and television circuits unless otherwise specified in Section 54;

(c) optical fiber cables unless otherwise specified in Section 56;

(d) communication circuit conductors unless otherwise specified in Section 60; and

(e) conductors that form an integral part of factory-built equipment.”

So, if armoured cables with exposed outer combustible jackets are installed in a building, or any non-metallic-sheathed cables allowed for installation by  Section 12 of the CE Code, or any conductors and cables for communication circuits, Class 2 circuits, optical fiber circuits or community antenna distribution and radio communication circuits allowed for installation in a building with exposed outer combustible jackets, such conductors and cables are subjected to compliance with Rule 2-130 of the CE Code.

Photo 2. TECK with FT4 marking on outer combustible jacket.   Photo  by  Steve Douglas
Photo 2. TECK with FT4 marking on outer combustible jacket. Photo by Steve Douglas

Question 4. What does “combustible” or “noncombustible” construction mean, and where the requirements for building construction could be found?

Answer 4. The National Building Code of Canada (NBCC) provides the following definitions of “combustible” and “noncombustible” construction of buildings. Note: 2015 edition of the NBCC is used for all relevant quotes and references provided in this article.

“Combustible construction means that type of construction that does not meet the requirements for noncombustible construction.”

“Noncombustible construction means that type of construction in which a degree of fire safety is attained by the use of noncombustible materials for structural members and other building assemblies”

Specific provisions in Subsection 3.2.2. of the NBCC determine a type of construction for each building, and application of Subsection 3.2.2. states the following:

“3.2.2. Building Size and Construction Relative to Occupancy

3.2.2.1. Application

1) Except as permitted by Article 3.2.2.3., a building shall be constructed in conformance with this Subsection to prevent fire spread and collapse caused by the effects of fire.”

Thus, it is up to the building code experts – to advise the electrical designers and electrical contractors, whether a specific building is required to be of noncombustible construction, and the electrical designers and electrical contractors would have to select conductors and cables with the appropriate flame spread rating (with the appropriate FT marking), if conductors and cables are installed in buildings with exposed outer combustible jackets.

Question 5. Why are the flame spread requirements (FT marking) for conductors and cables with exposed outer jackets different when such conductors and cables are installed in buildings of combustible construction in comparison with their installation in buildings of noncombustible construction?

Answer 5. The NBCC requirements for construction materials used in buildings of combustible construction are less restrictive that the requirements for the construction materials allowed for use in buildings required to be of noncombustible construction.

The Subsection 3.1.4. of the NBCC applies to the buildings of combustible construction, and Subsection 3.1.5. of the NBCC applies to the buildings required to be of non-combustibles construction.

Article 3.1.4.1 of the NBCC mandates the following generic flame spread rating in buildings of combustible construction:

“3.1.4.1. Combustible Materials Permitted

1) A building permitted to be of combustible construction is permitted to be constructed of combustible materials, with or without noncombustible components.

2) The flame-spread rating on any exposed surface of foamed plastic insulation, and on any surface that would be exposed by cutting through the insulation in any direction, shall be not more than 500.”

When non-metallic sheathed cables or conductors not enclosed in raceways are installed in buildings of combustible construction (as allowed by the CE Code), exposed outer combustible jackets of such conductors and cables must be marked FT1. Where such conductors and cables are located in a plenum in a building of combustible construction, only conductors and cables with FT6 marking are allowed by Article 3.1.4.3. of the NBCC (see below):

It should be noted that such restrictive requirement – for FT 6 marking of conductors and cables in plenums of combustible construction buildings has been introduced only in 2015 edition of the NBCC, and hopefully, 2018 edition of the CE Code will reflect these changes. It should be also noted that Article 3.1.4.3. of the NBCC allows the exception that permits up to 9 m of such conductors and cables extended from non-combustible raceways in plenums to be FT 4 rated (and not FT 6 rated).

“3.1.4.3. Wires and Cables

1) Except as required by Sentence (2), optical fibre cables and electrical wires and cables with combustible insulation, jackets or sheathes that are installed in a building permitted to be of combustible construction shall

  1. a) not convey flame or continue to burn for more than 1 min when tested in conformance with the Vertical Flame Test (FT1 rating) in CSA C22.2 No. 0.3,

“Test Methods for Electrical Wires and Cables,” or

  1. b) be located in
  2. i) totally enclosed noncombustible raceways (see

Note A-3.1.4.3.(1)(b)(i)),

  1. ii) masonry walls,

iii) concrete slabs, or

  1. iv) totally enclosed non-metallic raceways conforming to

Clause 3.1.5.23.(1)(b).

(See Note A-3.1.4.3.(1).)

(See also Sentence 3.6.4.3.(1).)

2) Except as permitted in Sentences (3) and (4), optical fibre cables and electrical wires and cables with combustible insulation, jackets or sheathes that are used for the transmission of voice, sound or data and are installed in a plenum in a building permitted to be of combustible construction shall exhibit the following characteristics when tested in conformance with CAN/ULC-S102.4, “Test for Fire and Smoke Characteristics of Electrical Wiring, Cables and Non-Metallic Raceways,” (FT6 rating):

  1. a) a horizontal flame distance of not more than 1.5 m,
  2. b) an average optical smoke density of not more than 0.15, and
  3. c) a peak optical smoke density of not more than 0.5.

 

3) Except as permitted in Sentence (4), where totally enclosed noncombustible raceways are used in a plenum,   exposed components of wiring systems with combustible insulation, jackets or sheathes, including optical fibre cables and electrical wires and cables that are used for the transmission of voice, sound or data, that are installed in the plenum or that extend not more than 9 m from the plenum, including drop down to the floor level, are permitted, provided they exhibit a vertical char of not more than 1.5 m when tested in conformance with the Vertical Flame Test – Cables in Cable Trays (FT4 rating) in CSA C22.2 No. 0.3, “Test Methods for Electrical Wires and Cables. “  

 Article 3.1.5.1. of the NBCC in general mandates use of only noncombustible materials in a building required to be of noncombustible construction (see below):

“3.1.5.1. Noncombustible Materials

1)  Except as permitted by Sentences (2) to (4) and Articles 3.1.5.2. to 3.1.5.24., 3.1.13.4. and 3.2.2.16., a building or part of a building required to be of noncombustible construction shall be constructed with noncombustible materials.”

When conductors and cables with exposed outer combustible jackets are installed in accordance with the CE Code in buildings required to be of noncombustible construction, exposed outer combustible jackets of such conductors and cables must be marked FT4. Where such conductors and cables are located in a plenum in a building required to be of noncombustible construction, only conductors and cables with FT6 marking are allowed by Article 3.1.5.21. of the NBCC (see below):

It should be noted that Article 3.1.5.21. of the NBCC allows the exception that permits up to 9 m of such conductors and cables extended from non-combustible raceways in plenums to be FT 4 rated (and not FT 6 rated).

“3.1.5.21. Wires and Cables

1) Except as required by Sentence (2) and Article 3.1.5.22., optical fibre cables and electrical wires and cables with combustible insulation, jackets or sheathes are permitted in a building required to be of noncombustible construction, provided

 

  1. a) the wires and cables exhibit a vertical char of not more than 1.5 m when tested in conformance with the Vertical Flame Test – Cables in Cable Trays (FT4 rating) in CSA C22.2 No. 0.3, “Test Methods for Electrical Wires and Cables,”

 

  1. b) the wires and cables are located in
  2. i) totally enclosed noncombustible raceways (see

Note A-3.1.4.3.(1)(b)(i)),

  1. ii) masonry walls,

iii) concrete slabs,

  1. iv) a service room separated from the remainder of the building by a fire separation having a fire-resistance rating not less than 1 h, or
  2. v) totally enclosed non-metallic raceways conforming to

Clause 3.1.5.23.(1)(b), or (c) the wires and cables are communication cables used at the service entry to a building and are not more than 3 m long.

(See Note A-3.1.5.21.(1).)

2) Except as permitted in Sentences (3) and (4), optical fibre cables and electrical wires and cables with combustible insulation, jackets or sheathes that are used for the transmission of voice, sound or data and are not located in totally enclosed noncombustible raceways are permitted to be installed in a plenum in a building required to be of noncombustible construction, provided the wires and cables exhibit a horizontal flame distance of not more than 1.5 m, an average optical smoke density of not more than 0.15, and a peak optical smoke density of not more than 0.5 when tested in conformance with CAN/ULC-S102.4, “Test for Fire and Smoke Characteristics of Electrical Wiring, Cables and Non-Metallic Raceways,” (FT6 rating).

3) Except as permitted in Sentence (4), where totally enclosed noncombustible raceways are used in a plenum, exposed components of wiring systems with combustible insulation, jackets or sheathes, including optical fibre cables and electrical wires and cables that are used for the transmission of voice, sound or data, that are installed in the plenum or that extend not more than 9 m from the plenum including drop down to the floor level, are permitted provided they exhibit a vertical char of not more than 1.5 m when tested in conformance with the Vertical Flame Test – Cables in Cable Trays (FT4 rating) in CSA C22.2 No. 0.3, “Test Methods for Electrical Wires and Cables”

Hopefully, the answers to the questions posted above, are sufficient to address the background and logic behind FT marking of conductors and cables.

However, as usual, local AHJs must be consulted for each specific installation project

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Ark Tsisserev is president of EFS Engineering Solutions, Ltd., an electrical and fire safety consulting company, and is a registered professional engineer with a master’s degree in Electrical Engineering. Prior to becoming a consultant, Ark was an electrical safety regulator for the city of Vancouver. He is currently the chair of the Technical Committee for the Canadian Electrical Code and represents the CE Code Committee on the CMP-1 of the National Electrical Code. Ark can be reached by e-mail at: ark.tsisserev@efsengineering.ca His company web site is: http://www.efsengineering.ca

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