Bonding & Grounding

Everybody understands Grounding.  Drive a stake in the ground and attach a wire to it, pretty simple -- conceptually anyway. Bonding is a little harder.  Bonding requires you to tie all the utility grounds together.  The equipment, the cable shield and the other utilities in the area should all share the same ground potential with less than 4 ohms difference. If you Ground but fail to Bond you may put yourself in danger and you can put the ADSL Loop Extender in the best ground path for a nearby lightning strike.

When lightning hits a nearby tree, it will create an electric field that radiates through the ground in all directions. If the telephone ground rod is closer to the strike than the other utilities' ground rods, you can have big problems.  In this situation there will be a large voltage between the ground and the service pairs because of the common ground point at the customer premise.  The lightning's electric field may pass through the telephone ground rod and into the loop extender & service pairs until it can find a better path to the other utility grounds. 

The best solution is to install the loop extender where the other utilities share a ground rod.  If you can't do that, then at least be sure that you have good shield bonds between the loop extender and ALL the other NEARBY utility grounds.  Whatever you do, make sure that the best path to that utility ground isn't through the loop extender.

 Whenever you have repeat service calls, please be sure to check your grounding AND bonding.


Getting Technical

What happens when you ground but fail to bond.


Breaking It Down

The above image shows an UNBONDED Loop Extender install and how that can lead a lightning hit to surge through the Loop Extender:

  • Lightning hits a tree or other nearby structure(1)
  • The surge reaches the Loop Extender Ground(2)
  • Seeking the path of least resistance to the Power Company Ground(4), the lightning will travel their via the Customer NID(3)
  • The surge has traveled through the Loop Extender to the Customer NID(3) via the service pair, damaging the Loop Extender in the process
  • The surge is dissipated via the Power Companies Ground(4).

Why does this happen?

By grounding the Loop Extender but not bonding it, it is being exposed as a possible conduit for the surge. This happens because there is often LESS resistance from the Loop Extender to the CPE ground than there is to ANY OTHER nearby ground. In this case it would actually be better to NOT GROUND the Loop Extender at all! But as we know, there is an even better solution.



Tying it all together


In this image we see a properly bonded Loop Extender Installation. When lightning strikes this setup the following will happen:

  • Lightning hits a nearby tree or structure(1)
  • The surge reaches the Loop Extender Ground(2)
  • Because of the cable shield bond the path of least resistance is now straight to the Power Company Ground(3)
  • The surge is safely dissipated having never passed through the Loop Extender(4)


ADSL Loop Extender Improvements

We've been hard at work analyzing units sent back for lightning damage and we've made several improvements in the product line.

Our analysis of RMA units concluded that because of extremely dry weather conditions, the ground resistance was increased over the summer months. This lead the lightning impulse discharge channel to be impaired and resulted in more strikes surging through the Extender. We've gone with a two-fold solution to help combat this in the future.

  • We have replaced the surge supressors on the ADSL Loop Extender with units that have a much higher protection capacity.
  • We have added an advanced protection circuit which can better handle the residual voltage from nearby lightning strikes.

The improvements have been implemented on all units manufactured after August 2012