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Why you need Primary Protectors on Outside Plant Cable Installations.

Thu, 23 Jul 2015

The underlying principal behind protection is simple: install a suitable protector unit into your telecommunications and networking equipment to protect both the equipment and human lives. The reason for this part of the code is to eliminate the possibility of stray currents following outside cable into buildings where it can seriously damage or destroy networking equipment, cause human injury and perhaps death.

Here is some relevant information you should be aware of when running outdoor cable. 

  • Article: 800.48
Unlisted Cables Entering Buildings. Unlisted outside plant communications cables shall be permitted to be installed in locations as described in 800.154(C) where the length of the cable within the building, measured from its point of entrance, does not exceed 15 m (50 ft) and the cable enters the building from the outside and is terminated in an enclosure or on a listed primary protector. FPN No. 1: Splice cases or terminal boxes, both metallic and plastic types, are typically used as enclosures for splicing or terminating telephone cables. FPN No. 2: This section limits the length of unlisted outside plant cable to 15 m (50 ft), while 800.90(B) requires that the primary protector be located as close as practicable to the point at which the cable enters the building. Therefore, in installations requiring a primary protector, the outside plant cable may not be permitted to extend 15 m (50 ft) into the building if it is practicable to place the primary protector closer than 15 m (50 ft) to the entrance point. FPN No. 3: See 800.2 for the definition of Point of Entrance. 
  • Point of Entrance. The point within a building at which the wire or cable emerges from an external wall, from a concrete floor slab, or from a rigid metal conduit (Type RMC) or an intermediate metal conduit (Type IMC) connected by a grounding conductor to an electrode in accordance with 800.100(B). 
  • ANSI/TIA-607-B: Commercial Building Grounding and Bonding requirements for Telecommunications ANSI/TIA-862A: Building Automation Systems Cabling, Standard for Commercial Buildings.
This standard specifies grounding and bonding design and distribution methods for commercial buildings. Proper earth grounding of the building structure and wiring is a requirement of the National Electric Code (NEC). Bonding all electrical and telecommunications equipment to the primary grounding electrode conductor (GEC) is essential for maximizing performance and safety. Note: Bonding to water pipes is now a code violation.Bonding telecommunications equipment, facilities, and cabling to the primary grounding electrode is accomplished using the following major elements:
  • Grounding Electrode Conductor (GEC)
  • Bonding Conductor (BC)
  • Telecommunications Main Grounding Busbar (TMGB)
  • Telecommunications Bonding Backbone (TBB)
  • Telecommunications Grounding Busbar (TGB) 
  • J-STD-607-A specifies the TMGB and TGB as a pre-drilled solid copper bar that extends the GEC for connecting the TBB. The TBB is typically a 6AWG stranded copper conductor that joins the copper TGBs on each floor of the building. A TGB is located in every TR and ER in the building. J-STD-607A also recommends surge protection devices for active telecommunications equipment. Note: The GEC is the largest grounding conductor and extends into the earth to a specified depth. The TBB should be continuous with no splices. Connections to the TBB must use listed compression fittings. 
  • The Entrance Facility (EF) is located where the access provider and inter-building network cables enter the building. Outside plant cables, typically from underground, are terminated inside the entrance facility. This location is known as the demarcation point – the transition from access provider to customer owned cable. A combination of electrical, fire, building, municipal, and FCC codes apply to the EF. The EF may share other functions, including fire and security alarms, CCTV, CATV, PBX, etc. Basic requirements:
  • Dry environment
  • Proper back-boarding for equipment
  • Secure location
  • Access to building electrical service ground
  • Circuit protection
  • According to the ANSI-J-STD-607-B Standard*, TBB Conductor size is directly related to the length of ground wire run. See the chart below for selecting the appropriate AWG size of wire.

*Reference ANSI-J-STD-607-B for more information.

Written by: Edgar Schuchardt

Account  Manager at Datcom Inc. 

For more information on the Primary Protectors call 1-800-427-2055. 

You can also visit the Primary Protector page to review the products.

 Disclaimer: Please note the author of this piece is not an electrician. For a wide scope and understanding of the 2015 Electric code please visit The CSA Group.

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