The practice of proper electrically bonding and grounding equipment is a topic that often confuses techs in the field. For more than 15 years we have been instructed to electrically bond separated systems together, but absent was better guidance on just how to accomplish that.

This practice is important mainly for the safety of technical personnel, users and system equipment. So in addition to looking at developing better bonding and grounding strategies, we’ll note some of the relevant changes that have taken place in the National Electrical Code (NEC, also known as NFPA 70). Even experienced techs can benefit from reviewing techniques that make for smooth, compliant and successful installations.

High Priority Even for Low Voltage

When inspectors place emphasis on bonding and grounding, it’s typically for high voltage or “line voltage” electrical equipment of 120-240VAC. On the other hand, the security industry deals primarily with low-voltage equipment, and there is often the misconception that bonding and grounding and the NEC have nothing to do with low-voltage equipment.

This can cause a rude awakening for a tech when it results in an electrical inspector rejecting an installation. The fact is bonding and grounding affects the overall integrity of any system and ensures it is electrically safe.

Since the NEC mostly emphasizes rules pertaining to line and high voltage, low voltage can mean anything below 30 or 50 volts. Unfortunately, this is often not very clearly explained. As a point of reference, articles covering low-voltage and power-limited devices, wiring, and systems are generally contained in Chapters 7 and 8 of the NEC. However, Chapters 4 and 5 contain the requirements for Low-Voltage Lighting (Article 411), Intrinsically Safe Systems (Article 504) and Sound Systems (Article 640).

Definitions and Methods

Let’s now define what is meant by the terminology of bonding and grounding, and the differences between the two.

Grounding refers to connecting the noncurrent-carrying, accessible parts of electrical circuits to ground (earth) as protection from hazards such as electrical voltages, static charges, voltage spikes, or inadequate insulation. Bonding refers to the connection of various ground circuits to a common grounding electrode system to avoid voltage potentials between them.

When grounding a system, even low voltage, you must have a good earth ground. This is typically a grounding rod of at least five feet in length. The most common place for this is the system demarcation point at the perimeter of the building. That is also a good spot to attempt to deflect lightning surges on the system.

Security system manufacturers take great effort to provide equipment with lightning surge suppression. However, these protection devices will not work properly without a good earth ground. Even if you think your AC line voltage outlet is a good ground you had better double check to make sure.

Do you always have to drive your own ground rod? Not really; you alternatively electrically bond your equipment to another local system that has a good ground. In turn, all systems will then have reference to a good earth ground. Remember, according to the NEC, the distance of that bonding connection cannot be longer than 20 feet, there must be a common ground point (see photo) and the correct gauge conductor (not smaller than 14 AWG) must be used.

Also, don’t forget that most exterior cold water and utility pipes, such as gas service, cannot be considered a reliable earth ground. Many of those conduits, such as that connected to water faucets, use insulated PVC piping below ground.

(NOTE: The term grounding conductor previously used in Article 800, NEC has been replaced in NEC 2011 by either bonding conductor or grounding electrode conductor (GEC) where applicable to more accurately reflect the application and function of the conductor.)

Tips for Passing Inspections

Many of us have learned to use the NEC book as the bible for meeting electrical code applications for our installations. However, you may run into situations where the selection and/or application of a particular UL product is questioned. The electrical inspector (AHJ) may declare that a listed device in your bonding and grounding application does not meet code.

A good FREE reference source to help avoid this situation is the UL White Book (download at www.ul.com/global/eng/pages/offerings/perspectives/regulator/electrical/newsletters). Version 2011 is the latest, but older versions are available as most likely these are being used by your AHJ.

Additionally, don’t forget to check UL University for its latest 90-minute online “Understanding the UL White Book” training session. It is a free self-paced, hands-on interactive course that is an invaluable resource for electrical inspectors, installers, electrical designers and counter staff at the local electrical supply house. It will walk you through the steps to achieve a code-compliant installation using UL Certified products.

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