Communications grounding for multi-family buildings

[Mvillines]

After reading Section 800.100 (A) (4) I have a question on grounding of communications circuits entering a multi-family dwelling entering the opposite end of the building that the electrical service equipment is mounted. In a one- and two-family dwelling the grounding conductor shall be as short as practicable, not to exceed 20 feet in length. Then we have the exception that could allow the conductor to exceed the 20 feet by following the exception. What about multi-family dwellings? Is the code silent for these buildings?

 

[raider1]

The code does not limit the length of the primary protector grounding conductor to 20 feet for other than one and 2 family dwellings.

Here is what the FPN to 800.100(A)(4) says

FPN: Similar grounding conductor length limitations applied at apartment buildings and commercial buildings help to reduce voltages that may be developed between the building's power and communications systems during lightning events.

As you may already know FPN's are not enforceable as code but just for informational purposes only.

Chris

 

[Mvillines]

Yes I did read the FPN. What concerns me is that it refers to ?similar conductor length limitations applied at apartment buildings and commercial buildings?. Where can these similar limitation rules be found?

 

[raider1]

Yes I did read the FPN. What concerns me is that it refers to ?similar conductor length limitations applied at apartment buildings and commercial buildings?. Where can these similar limitation rules be found?

There are no specific length limitations for apartment buildings and commercial buildings.

What the FPN is referring to is if you do limit the length to 20 feet it will help limit the voltages that may develop between the building power and communications systems during lightning events.

Chris