Often, many a telecommunications person will proudly admire the bright cheerful telecommunications spaces, data centers, entrance facilities, and workspace locations. They’ll marvel at how well everything is organized, color-coded, and distributed to meet the needs for the site as well as for the users who function there. But did you know there resides dark and sinister forces behind the walls that can quickly erode that gleaming façade of high-tech gadgetry and well-groomed cable pathways?

They are loose connections! And they can hide in every ac outlet, panelboard, junction box, transformer, and many other locations within the ac electrical system. The International Association of Electrical Inspectors (IAEI) had an article several years ago talking about the impact of loose connection for personnel safety and fire hazards. The facts were sobering but so was the revelation that most people couldn’t tell you the torque specification of many of the electrical terminations, regardless of how simple it is to acquire it.

In this day and age of ‘install it and move on’, preventative maintenance (PM) has seemed to be a thing of the past; especially within the ac electrical system. With the exception of some military/government entities, it is rare to encounter a company who has a regimented program. Simply put, most people will not establish a PM program because it depletes money & manpower. I would be the first to admit that inspecting everything is time-consuming based on my personal site survey experience.

Loose connections are unforgiving and hidden from view. They have such a negative impact on nearly everything related to the safe and efficient operation of your equipment, including:

  1. Exposing your site to electrical shock and fire hazards.
  2. Lack of high frequency (HF) noise mitigation.
  3. Improper application of power conditioning equipment.
  4. Uninterruptible power supply (UPS) efficiency (or lack thereof).
  5. Little to no equalization during lightning and electrostatic discharge issues.
  6. Poor end-use equipment operation.


And while there is no time to visually inspect the connections, some effort should be made to use test equipment to ‘see’ behind the walls. Some of the testers that could be useful are:

  1. Ground impedance testers (for polarity AND integrity of the wires).
  2. Micro-ohmmeters (for telecommunications bonding).
  3. Voltmeters.


grounding electrode system


Whatever you decide to use to test your ac circuits, (a) follow the IEEE recommended practices and (b) stay away from the three-lamp circuit testers you get at your favorite hardware store! They are notoriously inaccurate. Why, you ask?  Maybe that’s another episode for this blog…

To get started on a good PM plan; consult NFPA-70B (Electrical Equipment Maintenance) to get some background on what would need to be done. Then, engage a properly trained and licensed electrician to assist and implement a PM plan that works best for you.

Once you find a deficiency (you and your equipment will be glad you did, trust me), then you can focus the electrician’s efforts exactly where it should be…that is, becoming proactive to correct problems without waiting for something to go wrong.  It is important to remember that one loose connection in a hot, neutral, equipment ground, or bonding conductor will impact EVERYTHING in the room so they must be inspected periodically; at least once per year.

Telecommunications bonding should be inspected, as well. There are many types of wiring lugs, connectors, bolts, nuts, and other hardware that is used in a telecommunications bonding infrastructure. Every connection is a potential point of failure…so every one of them must be inspected.

The best advice I can give you for inspecting telecommunications connections is to:

  • Be thorough.
  • I strongly recommend measuring all connections with a micro-ohmmeter, NOT an earth ground resistance tester. I have used an EGT in the not-too-distant past and encountered a few instances where they are unreliable or lack the resolution needed to check compliance.
  • Recognize that each bolt and termination has a torque requirement. To simply state that everything should be ‘as tight as possible’ is ignoring the fact that bonding connections can be too tight, thus distorting the desired ‘metal-to-metal’ contact. Consult the manufacturers of your terminals, lugs, and nuts/bolts to find out exactly what is required.

Finally, if you are measuring your bonding resistance, make sure to retain that data for comparison a year or so down the road. Even if the connection is good today, it could be next year’s problem area.

Good luck and stay grounded!


In our previous blog, we outlined the perceived need for an IG system and the issues surrounding electrical ‘noise’, or common-mode voltage. In part 2 of this discussion, the realistic issues that come about AFTER it’s installed are addressed.

Proceed with Caution

Recently, a customer informed me they used IG outlets in their Tier 4 data center was because ‘our electrical designer said it was a Code requirement for electronic equipment’. He was surprised when I told him this is 100% FALSE! The NEC has wiring requirements (Section 250.146(d)) should you choose to install it but it falls far short of an ‘endorsement’.

Additionally, if you have an electrical system already installed, do not specify IG ‘after the fact.’ Doing so may, literally, cause more harm than good (see our previous blog on Isolated Grounding on more of the safety factor). From an electrician’s standpoint, an IG system cannot be installed safely per the Code due to the unsafe environment for ‘fishing’ wires back through energized feeder conduits. Most electricians understand this and may result in your site getting orange IG outlets…but without IG wiring. But, on occasion, it can be found where ground rods driven in to an electrical room floor reference IG busbars in subpanels. This is easy for me to say ‘it’s a Code violation’ (which it is) but for those on site who lack the education on what to look for, it can be a safety and lightning damage issue waiting to happen.

To further the point, I’ve done upwards of 2,500 power and grounding site surveys in my 30-year career…with about a quarter of those related to IG wiring in one fashion or another. And in that 30-year career, I’ve only seen it installed correctly about a dozen times…that’s it. And, for those dozen customers, I was there because of problems IN that IG system.

It’s Just a Wire’…Or Is It?

So, the Code requirements aside, IG can have the following effects on your site:

  1. It may help.
  2. It can have no effect.
  3. It can make existing problems worse.
  4. It can introduce problems that weren’t there.

Once one learns a little about basic electrical wiring, it is no wonder to them that the majority of sites that use IG systems fall into numbers (3) and (4).

You see, most people open up their outlets at their home or business and all they see are wires. To give further credit, we will assume that all who see the wires understand they have resistance (See Figure 1). But that model only works in a ‘DC world’.


AC wiring is more complicated. A single conductor model can be seen in Figure 2, which shows the resistance AND inductance along it’s single path.


Now, let’s add in the neutral and equipment grounding conductor…and what do we have? Resistance, inductance, and capacitance between the wires (See Figure 3).

Long story short…you’ve got yourself a low-pass and high-pass filtering network. And though it’s quite capable of carrying any 60Hz currents, it’s equally adept at working against you by rejecting disturbances in the higher frequency spectrum, particularly those associated with radio frequency interference, lightning, some harmonics, and electrostatic discharge.

Here’s Where It Can Get Ugly

The saving grace for a solidly grounded system (SG, or non-IG) is the fact that all conduits, panels, junction boxes, etc., are mechanical, permanent, and continuous. But an IG system? It’s a single-conductor wiring system grounded at one end (that’s the definition of an antenna, folks) so now it becomes a receiver for unwanted signals.

So, even if installed per Code, it makes the site more susceptible to common-mode events because it can’t really equalize high-frequency currents and voltages unless it can get back to the main panel. And, if that main panel or transformer is many feet away (more than 10 meters), your chances are practically nil on being able to mitigate high frequency (HF) noise. This is due to an electrical phenomenon called parallel resonance (which is a subject for another blog article, I suppose) where any signal on the metallic conduit or an ‘intended path’ (like an IG conductor) now must find another way to travel.

In a nutshell, two negative outcomes are likely. One, it can couple on over to other hot and neutral conductors within your electrical wiring and affect (or ‘infect’, if you will) many other devices in your room. Or, in a worse case scenario, the common-mode currents will reflect back to the equipment. Yikes.

What Can We Do?

  1. Well, the short version is, if you’re not using it…don’t start! The old adage of ‘if it ain’t broke, don’t fix it’ works here.
  2. If you’re considering specifying IG systems without knowing what ‘type’ or frequency of noise to be mitigating, you’re already behind the curve and setting yourself up for some heartache.
  3. If you are already using an IG system, there’s one fool-proof way to tell if your system is compromising your current operation.
    1. Step 1 – Make a True RMS voltage measurement between neutral and the IG (third prong) of the receptacle and record it.
    2. Step 2 – Make a True RMS voltage measurement between neutral and the SG (case) of the outlet box and record it.
    3. Step 3 – Compare both values. If they’re the same, no need to panic (at this time). If they are not the same value, say separated by more than 100mVRMS, trouble is knocking at your door (if not already stealing money from your top dresser drawer). The ONLY way to mitigate the differences between the two voltages is to have an electrician bond the IG terminal in the receptacle to the outlet box. And, if you do that, what’s the point of having IG systems???
    4. This needs to be done at EVERY outlet! And check them at least once a year…



The blanket recommendation of an IG system may do more harm than good. We’re finding that more voice/data sites are not provided an IG system and, yet, the equipment performs remarkably well. Whether an IG system is utilized or not, always make the aforementioned voltage measurements, check the outlet wiring, and measure the existing system’s hot, neutral, and ground impedance (max 1 ohm per IEEE) appropriately prior to making any changes. This will help pinpoint existing wiring deficiencies that may be corrected with a couple of turns of a screwdriver or a means other than an unpredictable wiring system. But, if everything’s within acceptable limits and the equipment is working fine, the existing equipment grounding system configuration may be best left alone.


It is not uncommon to step into a data center or communications room and spot an orange outlet mounted on the wall. Ask anyone what that is and you’ll generally get a response like ‘that’s our emergency power’ or ‘that’s our noise-free ground’. It is just as common, though, to get a shrug of the shoulders from that person when asked ‘why’ they have one. To this day, I find that many data center and communications personnel are unaware that the telecommunications standards frown upon their use…in fact, Building Industry Consulting Services International (BICSI) specifically instruct a communications distribution designer to stay away from such wiring schemes in their reference manuals.

Why is Isolated Grounding (IG) a concern? Where did it originate? And is there any truth to an IG system helping noise issues?

This two-part blog article addresses these questions, and others, so the reader may be educated about their use and, to some degree, be forewarned if they’re already employed on site. The first part of this article will focus on electrical noise and the theoretical need for IG, as well as the installation requirements and safety violations that could arise with the poor wiring methods of the IG system. The second part of the article will focus on the technical issues with IG and the quick and easy measurement to determine if IG is a problem for you on your site.

Where to Start?

An isolated grounding (IG) system is often specified where there is a concern regarding electrical noise on the equipment grounding system causing operational problems for electronic equipment. By incorporating an IG system as opposed to a solidly grounded (SG) system, one would be inclined to think that something had been done to fix potential problems. Unfortunately, even properly installed IG systems create significant operational problems, even if it is installed according to National Electrical Code requirements and Institute of Electrical and Electronics Engineers (IEEE) recommended practices.  To understand how to install IG systems, and whether or not they really work, we need to understand the reasoning for specifying such a system. This requires a close look at the cause and effect of ‘electrical noise’…

What Is ‘Electrical Noise’?

Electrical noise is a general term used by the professional and layperson alike to describe an event that disruptions the operation of electronic equipment. The correct term for it, though, is common-mode voltage. Common-mode voltage is an unwanted signal that occurs between circuit conductors and ground that can mimic intended signals between devices, often at the wrong intervals. Specifically, the common-mode voltage between neutral and ground is of the utmost concern for power supply designers. This is because there is a lack of filtering between these two points within the equipment’s power supply. As a result, a disturbance that is generated on the ac side of the power supply (i.e., the ac grounding system) is common to the dc side (known as chassis ground), hence the term common-mode.

Sources of Common-Mode Voltage

Nearly all equipment, with the exception of incandescent lighting, is a source of common-mode voltage. Any device that contain motors will direct-couple common-mode currents to the equipment grounding conductor. These include vending machines, copiers, laser printers, refrigeration units, UPS’s, etc.

Studies have also shown that loose connections on the equipment grounding or neutral conductors that are subject to mechanical vibration may also cause mid-level electrical noise or could compound the problem where there is an existing common-mode voltage. Other sources can induce a voltage on the grounding circuit via electromagnetic interference (EMI) or radio frequency interference (RFI). Radio/TV antennas, motion detectors, two-way radios, cellular phones, pagers, and fluorescent lighting bring about these types of disturbances.

Regardless of the source of the disturbance, it is accepted by the (IEEE) Standard 1100 (Emerald Book) that any voltage greater than 1 volt between neutral and ground at the input to electronic equipment will likely cause equipment malfunction.

How Does it Affect Equipment?

Electronic equipment communicates both internally, and with other devices, through a digital pulse that is known as a bit or a string of bits known as bytes. A typical bit, shown in Drawing 1, resembles that of a square wave pulse though, realistically, the waveform is less linear than often depicted. The amplitude of this pulse varies with equipment design and application. Typically, transistor-transistor logic (TTL) and complementary metal oxide semiconductor (CMOS) logic operates at 5 volts. When the pulse is active, it is said to be at Logic 1, or high, state. When the pulse is not active, it is referred to as Logic 0, or a low state.



At the leading and trailing edge of the pulse are transition points. Here, for a short time, the pulse is neither at logic 1 or logic 0. If a random common-mode voltage occurs between the neutral and ac equipment ground at the same time that the transition points occur, it is possible that the intended signal could be reversed. As a result, there is one less bit in the stream of information travelling to circuitry within the device or to an external device. When this occurs, the internal circuitry will not function as a result of parity error to the bit structure, resulting in equipment malfunction.

Pandora’s Box

In 1980, with the unveiling of their high-speed data processing products, a reputable equipment manufacturer began specifying a unique grounding design called an isolated ground. The intent was to require an insulated equipment grounding conductor to be run to the grounding terminal of orange IG receptacles, which are designed to separate the grounding terminal for cord-connected equipment from the mounting strap of the outlet itself. Thus, TWO equipment grounds are installed (and, therefore, to be maintained). The objective of the IG system was to extend the zero volt reference (created by the neutral-equipment ground bond at the electrical service entrance) to the neutral-ground input at the equipment location. The desired intent (and NEC-compliant) of the IG should look something like Drawing 2, below.



Over the next few years, other equipment manufacturers specified the same type of grounding system. Unfortunately, most equipment manufacturers were lax in the exact requirements of an IG installation. Some electricians had to rely on their own interpretation of how it should be installed. To make matters worse, the National Electrical Code and the IEEE did not have requirements for the installation of such a grounding system. As a result, many sites experienced serious safety and equipment performance issues due to the improper installation of the IG circuit. In fact, many of the systems still in use today are potential safety (electric shock and fire), lightning, and operational hazards.

The NFPA Gets Involved

In 1981, a company in Chicago, IL experienced considerable fire damage that was be directly attributed to a ground fault on an improperly installed IG system where the physical installation prevented it from allowing sufficient current to trip the breaker. A basic diagram of this type of improper wiring can be seen below, where a separately driven ground rod is used to reference the insulated equipment grounding bus in a sub-panel.



In 1984, responding to this and other incidents, the authors of the National Electrical Code provided installation requirements for an isolated equipment grounding conductor.

In the 2002 version of the NEC®, Section 250.146 (d) provides the installation requirements of the IG system, however it does not guide the installer as to whether or not its use is beneficial. In summary, the Code requires that an insulated equipment grounding conductor (minimum size per Table 250-122) be run with the circuit conductors from the equipment ground terminal at the receptacle to the equipment grounding terminal at the derived system or service. For safety purposes, it is important to note that the IG equipment grounding conductor cannot be run in its own conduit or run outside the branch circuit or feeder conduit. Furthermore, the IG equipment grounding conductor cannot be terminated to a lone ground rod.

For equipment performance purposes, the IEEE recommends that the IG conductor and the circuit conductors be contained in metallic conduit to protect against radiated EMI/RFI. They also recommend a separate hot, neutral, and equipment grounding conductor be provided for each individual branch circuit. However, this IEEE recommended wiring practice is viewed as cost-prohibitive by most electrical contractors and is rarely encountered in the field. But even if the required and recommended design practices are followed, one must ask….

Does an IG System Actually Work?

The short answer to this question is “NO”. And, not only does it not work, studies have shown it can introduce problems where you wouldn’t expect them. In some cases, IG systems have been known to make common-mode voltage problems worse…or, in extreme cases, create common-mode voltage where no should be!

There are many reasons why the IG system is ineffective. But, overall, consider the fact that each site is unique. As such, the electromagnetic compatibility (EMC) between devices, let alone each branch circuit, can change dramatically. For this reason, the variables that cause, prevent, and amplify electrical noise disturbances are equally dynamic. In our next installation, we’ll address the technical issues that prevent IG from helping us. And, if you’re already using it, we’ll discuss how can you test it to see if it’s causing a problem for you…all with a run-of-the-mill VOM?

Did you know that there are three distinct components for the Telecommunications Systems Bonding Infrastructure? They are the Grounding Electrode System, the Equipment Grounding System, and the Telecommunications Bonding System. Some people have a hard enough time understanding just ONE of these systems; let alone three! But no need to worry…there’s a simple but accurate way to understand them. We call it, the ‘3 E’s’ and here’s how to break them down.

Grounding Electrode System – Often called ‘earthing’, the purpose of this system is to Establish the voltage reference for the electrical service entrance and other power sources within the building.

The Equipment Grounding System – Commonly called the ‘safety ground’, the purpose of these connections is to Extend the zero-volt reference to equipment frames.

Telecommunications Bonding System – The sole purpose of this system is to equalize potentials during lightning, electrical fault, static discharge, or electromagnetic interference (EMI) conditions.

Below are the three systems visualized.

Telecommunications Bonding System

Why are there three systems, you ask? Well, consider this:

  • There are three separate reasons why we have each.
  • There are three different methods of testing each.
  • There are three different methods of improvement.

As a final note, please remember that telecommunications installers, designers, and technicians have no jurisdiction outside of the telecommunications bonding infrastructure. As such, it is very important to understand these other two systems as much as possible and inspect ALL of them periodically.

If you’re looking for more information on this subject, iGround, LLC has several grounding and bonding courses, including unique ‘hands-on’ classes to meet your training needs. If you do not see a course that covers your installation requirements, please contact us for more information on putting together a custom solution to enhance your team’s educational experience.

I have a challenge for you, the reader of this blog.

Walk into your data center or telecommunication spaces and point out a bonding conductor to a technician/installer/designer…then ask them what it actually does.

Some will say that the bonding conductor is for safety.

Others will say ‘lightning protection’.

Some say both.

They’re all wrong.

The differences between them were provided in a previous blog entry here on this site so we won’t cover the same ‘ground’, so to speak (sorry, couldn’t help it). But did you know the actual SAFETY factor for any site is provided by the Equipment Grounding System (known by many as the safety ground), which is the third prong in receptacles, the conduits, the power panels, and so on. That system is so crucial for safety and equipment performance but few out there even realize it…or understand the implications of it being loose or improperly installed.

I can’t stress enough the need to know this system, its components, purposes, and test methods. It’s also important to know what happens when it done right…and when it’s done wrong. If you’re in the telecommunications industry and you’re reading this, it is unlikely you are an electrician. But, even if you were, could you answer any of the below questions with any confidence?

  1. What is the primary and secondary purpose of the equipment grounding system?
  2. How much current does it take to fatally electrocute a typical human being?
  3. How much ac current does it take to fatally injure YOU, personally?
  4. Does it happen instantaneously? And, if not…
  5. …How much time would it take?
  6. What factors influence the integrity of the equipment grounding system?
  7. How does the equipment grounding system affect equipment performance?
  8. How much current do we need to trip a 20-amp rated breaker? (If you’re thinking 20 amps or slightly above that then you are WAAAAAAAAAAAAYYYY off).
  9. What would happen during a ground fault if someone removed the ground rods for the electrical system (theoretical, of course).

If you honestly answered ‘I don’t know’ to ANY of these…you might be in for a shock…in more ways than one.

If you’re looking for more information on this subject, iGround has several grounding and bonding courses, including unique ‘hands-on’ classes to meet your training needs. Contact us today for information on putting together a custom solution to build upon your team’s educational experience.

It is possible that no two terms create so much controversy in the telecommunications industry as ‘grounding’ and ‘bonding’. Ask ten people and it is a good bet that you’ll get ten different definitions that, more than likely, are more opinions (if not guesses!) rather than a good technical definition. And relying on the National Electrical Code to define them for us? GOOD LUCK! The most recent versions of the Code are even less of a help (it simply says grounding is ‘the earth’). The key to understanding them is their intent.

Let’s keep it simple, shall we? Here’s the two terms in a nutshell…

‘Grounding’ – Grounding is the actual mechanical connection to earth for the electrical system/equipment, known as the ‘grounding electrode system’. With the exception of outside plant (OSP), this connection is made for us by the electricians. The purpose of this system is to act as a voltage reference for the electrical system. It also provides a path for lightning stroke currents and static discharge currents that may be present on, or in, the building. But, more than anything, think of it as an anchor…everything is referenced to it!

‘Bonding’ – Bonding is the joining of metallic surfaces, via conductor or mechanical connection, for the sole purpose of equalizing potentials during lightning, ground faults, static discharge, electromagnetic interference, and other issues. In other words, it will equalize potentials while other components in the grounding system are doing their job (i.e., while the Earthing System is diverting lightning energy or the Equipment Grounding System is carrying fault current, etc.).

Let’s put it this way…if you’re in structured cabling telecommunications, you’re bonding ONLY! A question often asked is, ‘What if I’m connecting my busbar to building steel? Is that ‘grounding’?’ The answer is ‘no’ because you are bonding to a grounding electrode that’s already been established for the building.

If you’re looking for more information on this subject, iGround has several grounding and bonding courses, including unique ‘hands-on’ classes to meet your training needs. Contact us today for information on putting together a custom solution to build upon your team’s educational experience.