Common Mistakes With New Construction – Week 4 of October 2024

Published by Don Hester on October 28, 2024October 28, 2024

I think I am starting a new series on construction defects that are very common here in North Central Washington.

Let us start with one that is super simple to fix but is almost always missing.

Enter the “Intersystem Bonding Terminal” or IBT as required by NEC 250 94.

The intersystem bonding terminal has been a required element since 2008 on residential homes. The inner system bottom material will bond together different elements of the home such as a satellite dish cable TV phone and other auxiliary connections to the home. 

 The reason we want to do this is to eliminate voltage differentials between these different systems. This helps protects us and the home from electrical shock, fire and damages to these equipment. In addition the bonding terminal helps reduce potential arcing between metal surfaces from different electrical potentials.


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.”

Common is that I find just a grounding conductor stubbed out to the exterior but with no intersystem bonding terminal installed as the example below.

From the 2023 NEC-

250.94 Bonding for Communications Systems

Communications system bonding conductor terminations shall be connected in accordance with 250.94(A) or (B).

(A) The Intersystem Bonding Termination Device

An intersystem bonding termination (IBT) for connecting intersystem bonding conductors shall be provided external to enclosures at the service equipment or metering equipment enclosure and at the disconnecting means for any buildings or structures that are supplied by a feeder or branch circuit. If an IBT is used, it shall comply with the following:

• 1) Be accessible for connection and inspection
• 2) Consist of a set of terminals with the capacity for connection of not less than three intersystem bonding conductors
• 3) Not interfere with opening the enclosure for a service, building or structure disconnecting means, or metering equipment
• 4) Be securely mounted as follows:
  1. At the service equipment, to a metal enclosure for the service equipment, to a metal meter enclosure, or to an exposed nonflexible metal service raceway, or be connected to the metal enclosure for the grounding electrode conductor with a minimum 6 AWG copper conductor
  2. At the disconnecting means for a building or structure that is supplied by a feeder or branch circuit, be electrically connected to the metal enclosure for the building or structure disconnecting means, or be connected to the metal enclosure for the grounding electrode conductor with a minimum 6 AWG copper conductor
• Be listed as grounding and bonding equipment

So if you’re buying a new home this will be one of the elements you want to look for to see if it has been installed. Again this is a simple correction but it really should never be missed.

Quote of the Day

” A mistake repeated more than once is not a mistake. It is a decision, it is a behavior, it is who they are”

Edwin Matos

If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.

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…  

Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service

Coordinator & Instructor- Fundamentals of Home Inspection-  Bellingham Technical College

Former WA Home Inspector Advisory Licensing Board

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