Bonding of other systems, Intersystem bonding what you need to know.

Bonding of other systems, Intersystem bonding what you need to know. Wenatchee Home Inspection

Proper bonding is one of the most crucial mechanisms when it come to safer electrical installations.  By bonding all systems together this will help reduce potential induced electrical ( knows as voltage ) differences between the homes power and communication equipment, such as phone, cable and satellite. These differences can come from lightning, accidental energizing and even static energy.

Intersystem Bonding Terminal

So in the 2008 electrical code it became a requirement to install what is called an intersystem bonding termination.

From the 2008 NEC Handbook- “The code requires that separate systems be bonded together to reduce the difference of potential between them due to lightning or accidental contact with power lines. Lightning protection systems, communications, radio and TV, and CATV systems must be bonded together to minimize the potential differences between the systems. Lack of interconnection can result in a severe shock and fire hazard.”

( IBT on new Construction)

From the 2014 NEC-                      

250.94 Bonding for Other Systems

An intersystem bonding termination for connecting intersystem bonding conductors required for other systems shall be provided external to enclosures at the service equipment or metering equipment enclosure and at the disconnecting means for any additional buildings or structures.

The intersystem bonding termination shall comply with the following:

• Be accessible for connection and inspection.

• Consist of a set of terminals with the capacity for connection of not less than three intersystem bonding conductors.

• Not interfere with opening the enclosure for a service, building or structure disconnecting means, or metering equipment.

  
  

In homes built prior to the  Intersystem Bonding Termination requirement. The grounding conductor and any antenna discharge unit must terminate to the nearest accessible location in the following locations:

• Building or structure grounding electrode system [250.50].

• Interior metal water piping system, within 5 ft from its point of entrance [250.52(A)(1)].

• Accessible means external to the building, as covered in 250.94.

• Metallic service raceway.

• Service equipment enclosure.

• Grounding electrode conductor or the grounding electrode conductor metal enclosure.

Bonding requirements for other systems does go back a ways, in 1981 NEC 250.71 (b) was the first occurrence of this specific code provision.

When doing home inspection I am always evaluating these bonding areas to see if they are performed correctly. It does not really matter if these systems where installed prior to these requirements the danger is still there and should be corrected.

Here is an example of of communication system going to an independent ground rod. Well this one is very independent since the grounding conductor has come loose. These independent ground rods need to be bonded to the main grounding electrode system even if they were installed before these requirements to prevent potential electrical differences.

“If you think it's expensive to hire a professional to do the job, wait until you hire an amateur.”

Red Adair

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

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