While conducting technical training classes for field technicians, we often debate the need to provide an earth-ground for our intrusion control panels. The common misconception is that the earth-ground is primarily used for protection against lightning strikes. In fact, many of the dealers I deal with do not ground their panels because they believe adding an earth ground attracts lightning, resulting in damaged equipment. As far as lightning protection goes, there are products on the market designed to trap and route lighting strikes away from our equipment if that is the desired protection.
In my experience, grounding the control panel provides a way for any foreign AC noise riding back through the peripheral wired devices to bleed off safely and effectively. This AC noise, depending on the intensity and duration, can slow down system responses, or result in an unstable condition of the intrusion control panel. I have also seen a high AC induction send an intrusion control panel into a “Ground Fault” condition.
A proper earth ground does provide the intrusion control panel with some protection from current surges and voltage spikes. Our intrusion control panels are equipped with built-in noise and limited surge protection that is not used when an earth ground is not provided. Therefore, our documentation requires the addition of an earth-ground in our commercial intrusion systems for its lightning transient protection devices.
The real issue with providing an effective earth-ground is where to find one. Back in the day, the installer was instructed to locate the ground clamp (ground straps tend to build resistance between the pipe and the strap) on the closest cold-water pipe. Of course, today the plumbing practice is to use PVC or other plastic materials from the tap to the source, so cold-water pipes are not always a reliable ground. Some technicians have been locating the ground clamp on gas lines. This is not an effective ground source due to inconsistencies of a proper ground path. A 16 gauge (minimum), solid copper wire needs to be routed from the alarm control panel to the main location of the site where other utilities get their ground. In residential applications, this is where the telephone or cable service terminates at the home. Please note that using the ground from a nearby receptacle is not always the answer to a proper earth ground source. AC noise from the receptacle can ride up into the intrusion control panel and create problems instead of correcting them. Proper testing of this ground source may need to be conducted by a trained electrical technician.
If the location does not have a proper earth ground source nearby, a ground rod may be the answer. Ground rods are typically 3/4” to 5/8” diameter by 10’ length, and are driven straight into the ground. Of course, the type of soil the ground rod is set in plays an important part in its effectiveness. Many Florida locations, for example, have more sand than soil in the ground, rendering a ground rod ineffective.
If you would like more information on the proper way to install our products, reach out to your Regional Technical Manager for training and support.