Earlier this year, iGround presented a series of blogs to address the methods of approaching the various levels of Power Quality site surveys, depending on the location to be investigated.

This latest installment focuses on the AC Distribution Panelboards, specifically sub-panels.

In Part 3 of this series, we addressed the issues related to investigating the AC Grounding Electrode (Earthing) System. In that installment, one of the things we DIDN’T address was the environmental aspect of being outside while digging up/testing the electrode system; namely the weather (extreme hot/cold), fire ants, spiders, snakes, alligators, tarantulas, more snakes, rats, and other nightmarishly dangerous things (did I happen to mention snakes?).

The danger INSIDE of a building is even less forgiving…electric shock. So, I want to make sure the reader understands that any metering investigation of a panelboard, regardless of its location, requires the participatory efforts of a trained professional (namely, an electrician) with the appropriate Personal Protective Equipment (PPE). Make sure you have updated and approved PPE if you are going to assist in any manner, including supervisory.

(Review OSHA 3151-12R or National Fire Protection Association’s NFPA 70E, Standard for Electrical Safety in the Workplace. Furthermore, your locale may have other requirements in place.)

Level 1 Survey

A Level 1 survey for an AC sub-panel will be broken into three subcategories; Visual, Mechanical, and Electrical (metering).
Recommended Tools and Equipment to have:

  • Aforementioned PPE
  • Checklist
  • Appropriate screwdrivers and wrenches
  • Torque wrench to check tightness
  • True RMS AC Volt-Ohm-Milliammeter (VOM)
  • True RMS AC Clamp-on Ammeter


Level 1 – (Visual)

Panelboards are available in many shapes and sizes so how we review the internal wiring may change our perspective, as well. Here are some of the things that I look for:

  1. Improper neutral-ground bonding. Those familiar with electrical codes are well aware that, for safety reasons, neutral and ground can only be bonded at two locations: the main service entrance or the source of a separately derived system (e.g., isolation transformer). Finding improper N/G bonds will require the use of a good set of eyes and a flashlight. Sometimes an improper N/G can take the form of a metal strap between the neutral bus and panelboard frame OR a discernably different GREEN screw that is connect to the panelboard frame behind the neutral bus.


(See Figure 1 for example of improper N/G bond in panelboard.)


I would also make sure to point out any white wires on the ground bus or green wires on the neutral bus. Having either of these conditions creates a N/G ‘reversal’ for the affected branch circuits and, thus, can be just as dangerous.

  1. If an IG busbar is mounted in the panelboard, be sure you verify that the equipment grounding conductor that references that busbar originates in the same conduit as the feeder conductors that enter the panelboard. If it doesn’t, you have a SERIOUS safety issues. Please refer to our previous blog, Facts and Myths of Isolated Grounding – Part 1, for more information.


Visual cues that may seem like minor housekeeping things: discolored terminations or conduit bushings (evidence of overheating), proper conductor identification (particularly of the feeder conductors), or more than one hot conductor on a breaker are worth noting.


Level 1 (Mechanical)

I cannot overstate the importance of tightening up connections at the main, the circuit breakers, and/or the busbars. It’s tedious, but your equipment will thank you for it.


Level 1 – (Electrical Metering)

The attached checklist should be self-explanatory in regards to ‘what’ we want to test for…but it’s going to hinge on experience and intuition, and some further knowledge of the power system, as to how we determine IF there are problems. Some rules to consider:

  1. An imbalance of current measurements between the feeder phase conductors is not a cause for concern if the upstream power source (transformer) is not loaded more than 40% of nameplate rating. Sure, there is a heat differential, but it’s likely NOT to be significant at ‘minimal loading’.
  2. Be sure to also measure current on the individual circuit breaker positions.
  3. Make current measurements on the feeder neutral, at a minimum. If the feeder neutral current is higher than the average feeder phase current, you can expect harmonic current to be present, requiring further investigation. To find the EXTENT of harmonic current, you can measure ac current with an average-responding meter and a True RMS meter. If the True RMS measurement is higher than the average responding meter, you can divide the two numbers to find out the harmonic current distortion.
  4. As a rule, I measure for current flow on any (and every) equipment grounding conductor within the panel…not just the feeder. This practice has led to finding other problems that could have been otherwise overlooked.
  5. Finally, if there’s an ‘isolated grounding’ (IG) busbar in the panelboard, verify that the equipment grounding conductor feeder is run with the rest of the electrical feeders (hot/neutral) (Figure 2) and NOT outside the panel to another ground rod.


<<Figure 2 with caption ‘Isolated Grounding (IG) busbar is referenced by a conductor run outside the panelboard frame. This is a safety and lightning damage concern…and often overlooked.’


Level 2 Approach

If I’m working alongside the customer’s electrician, I am always going to have a power line monitor that I can connect to an electrical panelboard that supplies power to sensitive equipment areas. Each power line monitor is different so the best advice I can give you is:

  1. Become familiar with the instruction manual and sampling rates for any device you use. Not all devices are created equal.
  2. Know the tolerances of the equipment before you begin setting monitoring ‘thresholds’.
  3. Fully utilize a power line monitor’s inputs. If the meter has five voltage inputs and four current inputs, utilize ALL of them. (See figure xxx for an example).
  4. The best-case scenario is to monitor the power at that panel for 7 full days, including weekends. Only then can you get a good idea of usage and repetitive disturbances.
  5. Have the customer keep an error log to correlate equipment/operational issues with your captured disturbances. Make sure you coordinate the customer’s clock with your PQ monitor’s.
  6. You may have to use more than one PQ monitor. For example, one each at the equipment location AND the subpanel will help determine if the PQ problem is at system-wide or localized.



Level 3 Surveys

The only marginally acceptable Level 3 testing that I can see doing at a panelboard is EMI measurements to make sure there is less than 1mG (milligauss) per meter…….and that is ONLY IF the panelboard in question is within six (6) feet of any sensitive electronic equipment device. Otherwise, Level 3 could be a waste of time here.

Infrared thermography, though popular, is a superficial (albeit safe) method of trying to find looses connections. However, since an IR meter will not detect loose ground connections (due to lack of current across the terminations), you have to open the panelboard, anyway. My suggestion is…dump the IR meter and get an electrician with a good set of wrenches, screwdrivers and appropriate PPE. Work with them to make useful measurements and you’ll get to the problem quicker.



As with other areas of this blog, retrieve a sample checklist, above, in the section for Recommended Tools and Equipment. It will cover all the things you may expect to encounter at a panelboard (some we’ve discussed here), but feel free to personalize it for your own needs.


Next Installment

PQ Surveys – Part 5
AC Outlets and Equipment Locations

Over the next few months, iGround will be presenting a series of blogs to address the methods of approaching the various levels of Power Quality site surveys, depending on the location to be investigated.

This installment focuses on Grounding Electrode System.

The range of testing with the Level 1-3 surveys are applicable at nearly every location within the electrical premises wiring system, with the exception of one…the Grounding Electrode System (GES). This area of the electrical distribution is no more complicated than a Level 1 survey. There are a number of reasons for this; some of them (the most important ones) will be discussed here.

Level 1 (Visual Investigation)

Recommended Tools and Equipment to have:

  • Checklist
  • Appropriate screwdrivers and wrenches
  • Torque wrench to check tightness
  • True RMS AC/DC clamp-on ammeter
  • Micro-ohmmeter
  • Earth Ground Tester (maybe…read below!)

 The first step in evaluating the GES is knowing exactly WHERE it is. Sometimes, you can practically trip over it while walking around the area just outside the building’s electrical service entrance. In other cases, you have to do a lot of digging for that information…literally.

In some cases, you’ll have buildings with more than one grounding electrode connection. The biggest mistake I find people making here is prioritizing (in their mind) as to what connection is more important compared to another. For example, some may make sure that the connection to building steel is of high integrity and ignore a supplemental connection to a ground rod. Granted, the metal frame of the building will be crucial in nearly all aspects of grounding and bonding. But overlooking the possibility of loose connections in any path of the grounding electrode system is inviting disaster. When a lightning strike occurs, the voltage drop across the connection’s resistance can create transferred earth potential differences high enough to be destructive.

(See Figure 1 for example of electrode not bonded.)


Example of an electrode not bonded


In the same light, you might want to make sure that there are no separately driven rods for any equipment or electrical system that are not bonded to the main grounding electrode system. This may take some walking around inside the building, particularly peaking under raised floors in data centers. Separately driven electrodes are one of the most common causes of lightning damage.

Another visual cue to work on is investigating the presence of corrosion on the GES components. Corrosion can be caused by a number of factors; dissimilar metals that create a DC battery effect being one of them (more on that in a sec). A study done by the International Association of Electrical Inspectors (IAEI) twenty years ago found that the ‘life expectancy’ of a 10-foot ground rod may only be 12 years. Corrosive elements in the soil (naturally-occurring or man-made) and other contributors influence this but, in any respect, it’s worth taking corrosion into consideration.

(See Figure 2 for example of corrosion on an electrode.)


Example of Corrosion on an electrode


Level 1 – (Metering)

Let me start with the biggest mistake that most people make…if you are attempting to making an earth ground resistance measurement on an already-operational building…YOU ARE WASTING YOUR TIME AND EFFORT! The results are meaningless and you’ll have better success of ‘finding’ bonding & grounding problems if you hire a psychic. (Psychics cost less per hour, too…)

There is a lot of money to be made by equipment manufacturers of the earth ground test equipment, particularly those that sell the clamp-on earth ground testers. But earth ground resistance meters (of any variety) are only useful in extremely limited applications; many of those outside the realm of your premises wiring systems. Save your money and buy a…

…MICRO-OHMMETER! There are many manufacturers of these devices, some of whom make earth ground testers, too. It always perplexed me as to why they don’t market these more. Micro-ohmmeters can be useful when performing Two-Point Bonding testing between electrodes to make sure they are bonded together. Some testing groups recommend bonding resistances of 5 milliohms (0.005Ω). The more testing I perform in my career, the less I get hung up on a particular value. Though a low value is good (my personal recommended maximum would be 100 milliohms (0.1Ω)), I would just make sure that all readings are within a certain percentage of each other.

(See Figure 3 for Two-Point Measurement)

Two-Point Measurement


One very good application of the Two-Point Bonding testing is to measure the resistance between the Main Service Entrance Panelboard and the nearest metal frame of the building (or other electrode). This will provide a good indication of the integrity of the connection between the panelboard and the electrode…WITHOUT having to open up the panelboard and endanger yourself or others.

Also, I would make AC and DC current measurements at each of the grounding electrode conductors for the building. AC current measurements will be useful for determining the precautions someone will need to take when making mechanical connections (or disconnections). It is neither unusual nor unexpected to see AC current on the grounding electrode system, but just be sure to record it. (FYI…Personal Protective Equipment (PPE) can be cited for any electrical work in panels, etc., but it is ambiguous for grounding electrode systems because it is not expected to have amperage.)

YET, if the amperage is over 3 amperes on any grounding or bonding conductor, I would make sure someone is taking precautions to wear safety glasses and rubber gloves when tightening anything on the grounding electrode system.

Finally, DC current measurements are useful, yet often overlooked. No one really expects DC amperage on an ‘AC system’, right? Guess again. Dissimilar metals (i.e., copper, steel, etc.) can create a battery effect, which will accelerate corrosion. It can also be an indicator that an Uninterruptible Power Supply’s (UPS’s) rectifier, equipment power supply, or other form of AC/DC power conversion is nearing the end of its life-cycle. And, though your average investigator may not be aware, DC current on any AC conductor (known as DC offset) can trigger a tampering tariff by your electrical utility if it causes watt-meter errors. This tariff, or penalty, can be substantial for large companies so it’s in any end-user’s best interest to monitor it.

(See Figure 4 for example of DC Current measurement being made.)

 Example of DC Current measurement being made



The GES investigation is where your on-site investigation begins and has many important aspects to it. Your can retrieve a sample checklist, above, in the section for Recommended Tools and Equipment. It will cover all the things you may expect to encounter on a site (some we’ve discussed here), but feel free to personalize it for your own needs. And, though I’d never do an earth ground resistance measurement, you may…so that data is in there, as well. But, if you don’t use this checklist…USE SOMETHING!

In our next installment, we’ll take a closer look at verifying the Levels 1-3 issues of an AC electrical sub-panelboards, particularly regarding the issues where power quality is concerned.


PQ Surveys – Part 4
AC Electrical Panelboard Investigations


Over the next few months, iGround will be presenting a series of blogs to address the methods of approaching the various levels of Power Quality site surveys, depending on the location to be investigated.

 This installment focuses on pre-survey checklists.

So…you field a call from someone that is experiencing an electrical problem (possibly grounding/bonding) and they need you to help them find out what it is. After a couple minutes of gathering background information, it’s not a stretch to see how some people that start out doing electrical investigations soon feel that they’re in over their head. There are a number of reasons for this.

  1. Most customers tell us their version of what the problem by describing it with their unique vocabulary (e.g., one customer described how he had ‘transients with harmonicas’. My response of ‘Do you mean hobos with mouth organs or something else?’ was met with ‘I’m not sure’).
  2. You’ve never been to the site.
  3. You don’t know the ‘players ‘involved.
  4. You’re not familiar with the equipment affected.
  5. The customer is usually only willing to pay for ‘one day’.
  6. They want you to locate the problem,
  7. …don’t shut anything off…
  8. …and need recommendations ASAP!

Yeah….so, like…it’s a challenge.

Best Place to Start

You can have all the confidence in the world as an electrical system investigator, but you still need to go in with a plan. Some of our customers think that we hang up the phone, don our superhero cape, and go solve the problem. (That only works in a very small percentage of scenarios.)

I recommend that you get the customer involved right off the bat by giving them a pre-survey checklist and making sure that someone knowledgeable about the problem has a hand in filling them out.

The ‘High-Level’ Checklist

This checklist is useful to finding out exactly what may be going on. Often, our customers don’t know how to describe the problem they’re experiencing so we give them a checklist that may have some key phrases on there.

>> High-Level Checklist (PDF)

See Checklist #1 for example. We want customers to focus on the left side of the page so, I recommend taking out any references to ‘WG’ (Wiring/Grounding), ‘VQ’ (Voltage Quality), or ‘HM’ (Harmonics) if you think they’ll misinterpret what/why you’re asking these things. Time of day/day of week correlation will be important for repetitive issues. Once this is filled out, then you can focus on the supplemental checklists.

The ‘Wiring/Grounding’ Checklist

This checklist is one that the customer can give their electrician or electrical maintenance person to fill out, especially if they’ve answered ‘YES’ to any of the questions on the ‘High-Level’ Survey checklist where ‘WG’ is likely. But, these items are the ones that would need to be checked anyway. So let those that are more qualified (electricians) do the work and have a chance to fill it out.

>> Wiring & Grounding Checklist (PDF)

But, let’s state the obvious…

Without question, this author has mentioned AD NAUSEUM that the majority of ‘power problems’ and equipment operational issues are Wiring and Grounding.  And, if that’s the case, don’t I run a financial risk for my company by having someone ELSE do my job and possibly find the problem before we had a chance to be the hero? Perhaps…

But, the customer is never going to forget who helped point them in the right direction in the first place. And, if they run into a future problem where that checklist doesn’t help, guess whom they’re going to call next…? Several of our clients have a long relationship with us now as a result of that strategy…everyone wins.

Voltage Quality/Harmonics Checklist

I struggle to write anything here that would accurately encapsulate the issues related to these two subjects. Having a checklist that could be ‘thorough’ would likely be 12-14 pages of questions.  But this is a good start.

>> Voltage Quality/Harmonic Symptoms Checklist (PDF)

If you recall from Part 1 of our blog, a Level 2 survey is where the voltage quality survey would take place. This checklist might be helpful for the customer to fill out so you definitely want them to have it. But, you might want to have it handy for yourself after your Level 1 survey since your impression of the site’s voltage quality may change based on some other data you might gather.

In Conclusion…

Pre-survey checklists help gets the customer involved in properly identifying where to start your survey. In some cases, they can use it to solve their own problems. In that case, it’s invaluable as a customer-service tool. But, BEWARE…….if, for any reason, they can’t/won’t/don’t fill it out, you better have an idea of ‘what’ to look for and ‘how’ get that information…before you get there.

In our next blog, we are going to look at a Grounding Electrode System investigation. A lot of people start at this area of electrical distribution, but that doesn’t always correlate into success. Nonetheless, we’ll talk about where to place priorities as to what to look for and how to perform certain tests.


Over the next few months, iGround will be presenting a series of blogs to address the methods of approaching the various levels of Power Quality site surveys, depending on the location to be investigated.

This installment focuses on a high-level view regarding the three levels of a survey as you begin to troubleshoot.

Let me begin by stating that every power quality site survey is different. There are a variety of reasons as to why and when we begin the task of an electrical system investigation. Sometimes, it’s to find a known problem. In other cases, it may be a suspicion that a problem exists. Some of us utilize a site survey to confirm NO problem exists!

As an instructor, I’ve struggled with the best methods to teach people how to do a site survey. I find it’s better to impart the knowledge of how I approach one. To those just beginning this path of their career, PQ/Grounding/Bonding site surveys can be very intimidating, especially with large sites; campus or high-rise building, for example. But the best way to look at surveys, from an overview, is to see how they’re broken down…and why.

Level 1 Survey (Visual, Mechanical, Wiring, & Grounding/Bonding)

A Level 1 survey covers the visual inspection, mechanical inspection, testing, and analysis of the ac premises wiring and grounding system that is supplying the equipment.

Figure 1 illustrates where the Level 1 surveys would take place, given the highlighted areas. This may change depending on the type of investigation you are doing. For example, if you are doing a Quality Assurance (QA) inspection, you will likely look at ALL areas within the electrical distribution. However, if you are troubleshooting at an equipment location, you should rarely have to go further than the secondary side of a transformer.

The concept of verifying proper wiring and grounding systems has been labored upon many times. I can sound like a broken record to some people on the importance of this. But just last week, I encountered yet another example of where an investigative team ignored the contribution of wiring and grounding to PQ disturbances, costing their customers value time and money. Power quality problems caused by improper wiring and grounding can be misdiagnosed, especially if the wiring condition problem is masking itself as a voltage quality condition.

In all likelihood, unless the quality of the wiring and grounding systems is tested and verified, the data produced by voltage quality monitors (or any other meter for that matter) will be useless. If possible, all premises wiring and grounding deficiencies should be identified and corrected BEFORE engaging in Level 2 or 3 surveys.

Key Point: In 95% of cases, a Level 1 survey locates and corrects the problem.

If a Level 1 survey does not readily identify the cause, the investigation progresses to a Level 2 survey or Level 3 survey, if needed.


Figure 1 Survey


Level 2 Surveys (Voltage Quality)

This survey level focuses on the monitoring of the ac applied voltage, power system transients, and load current for the electrical distribution. Figure 2 shows where typical VQ investigations will be concentrated (blue dashed boxes).

Voltage quality problems can be difficult to pinpoint and may require different levels of power line monitoring. Thus, it requires a lot of patience! Not my best attribute…but it does pay off eventually.

The investigations take the shape of either short-term or long-term power line monitoring. Short-term monitoring may last from one to seven days (complete business cycle). This type of monitoring is usually done at the facility’s electrical service entrance to determine the electric utility’s contribution (if any) to the voltage quality problem.

If you have only one power line monitor, it is recommended that voltage quality monitoring be done at the equipment location, FIRST. This will give an investigator a better knowledge of the quality of voltage delivered to the equipment. Unless the disturbance is readily apparent through the short-term monitoring, it may be necessary for a more extensive analysis of the power system, where the long-term monitoring can last for several weeks or months.

Key Point: <5% of all problems are found/corrected with a Level 2 survey.


Figure 2 Survey


Level 3 Surveys (Environmental)

This survey consists of monitoring the environmental site parameters. Figure 3 is straightforward…all environment monitoring will be done at the equipment location of the equipment that is being directly affected, especially if it is the ONLY device being impacted. Power quality investigations rarely get to the Level 3 but, if it does, a new world of complexity and intrigue awaits. I liken Level 3 surveys to carnival funhouses…a series of illusions where nothing is ever what it seems and, in the end, hardly makes sense.

The detailed evaluation of the following may be necessary to determine an affected device’s sensitivity to its environment:

  1. Electromagnetic interference (EMI), including Radio Frequency Interference (RFI).
  2. Electrostatic discharge (ESD).
  3. Thermograph signatures.
  4. Psychrometric evaluation (temperature/humidity).

Key Point:  <0.4% of all problems will be found/corrected via a Level 3 survey.

And, because of the ‘key point’ above, there are only three things I can write here as words of advice:

  • Know the tolerances of your equipment via operating specifications. This will help with voltage quality, for sure, but the only way you’ll know ‘operating temperature/humidity’, electromagnetic compatibility requirements, and such will be to review them in the spec’s.
  • If you’ve reached a Level 3 survey in order to troubleshoot (with the exception of temperature/humidity)…you’ve overlooked something on the Level 1 or 2 survey.
  • Even if you FIND a problem on a Level 3 survey, it is likely that you’ll have to just live with it. Very often, the environment is the last thing we’d have the ability (or money) to change.


Figure 3 Survey


In Conclusion…

Viewing surveys with the three different levels is a good starting point. And, knowing WHERE those surveys will take place is just as important.

In our next blog, I’ll provide insight on the kind of checklists I give customers when they suspect a power quality issue. Even if they don’t fill them out, they’re good discussion points on how/where a company like iGround approaches it. Our upcoming blogs will be addressing each of the areas (panelboards, grounding electrode systems, transformers, telecommunications systems, data centers, and receptacles) with their own checklists and measurements for Levels 1-3 surveys.

3 lamp

A friend of mine was fond of saying ‘the bitter taste of poor quality lingers long after the sweet aroma of low price is forgotten.’ I think a strong case could be made for that saying to apply to the widespread use of three-lamp circuit testers that are commercially available at any hardware store. But after 30 years of being in the business of Power Quality troubleshooting, I find it perplexing that the widely-known problems with these testers is still a well-kept secret when it comes to electricians, engineers, electrical inspectors, home inspectors, and just about anyone else who troubleshoots electrical systems.

Sure, we’ll spend thousands of dollars on high-end troubleshooting devices such as harmonic analyzers, power line monitors, oscilloscopes, spectrum analyzers, and many more in an effort to locate electrical problems. Armed with the knowledge that these only find a small percentage of power quality-related problems (less than 10%), it begs the question as to what is being used to test the quality of the electrical wiring. Most students in our classes tell us that they use the old standby…the three-lamp circuit tester.

‘Why?’, we ask. The response is almost universal…’they’re cheap’.

Yes, the three-lamp circuit tester is inexpensive. And, so I’m on the record here, I don’t want to misrepresent the validity of their product listing for safe use. They are indeed compliant with regulations on manufactured test equipment. But a product listing does not guarantee its indicated results.

And the simple truth is: these devices can be very inaccurate and give a CORRECT indication when, in fact the outlet has one or more problems…or give INCORRECT wiring indication when everything’s fine. On more than one occasion, some of those we speak to who have attempted to correct the wiring errors indicated by the circuit tester have admit to spending money on ‘problems’ that weren’t there or not correcting the problems at all.

When one considers that the vast majority of problems are caused, or worsened, by the polarity AND integrity of the wiring and grounding connections, it’s not a stretch to think of the money it can cost you in the long run, not to mention the underlying threat that shock or fire hazards go unnoticed!

So, why are these three-lamp circuit testers ineffective?

 Let’s start with the basic construction of them. If you take one apart, you’ll find that they are nothing more than three lights connected to the three blades of the device via resistors. These are commonly called ballast resistors, and they prevent each light from burning out when connected across 120VAC. That’s basically it! This is why it’s inexpensive…very few parts. But the simplicity is its downfall.

Two factors contribute to the tester’s inaccuracy:

  • Circuit capacitance.
  • Leakage current from loads on the circuit to be tested.

Circuit Capacitance

A capacitor is, by definition, two conductors separated by a dielectric (or insulator). We use them for filtering wanted/unwanted frequencies as well as for storing charges (or a voltage) between two points in an electrical circuit.

In electrical wiring, we can take this a step further and presume a capacitor can exist where two wires are separated by the insulation around one or more wires (or even the air!). This can be observed in the figure below.


3 Lamp


We have two circuit conductors for a 120VAC circuit – a hot and a neutral – and are using an equipment grounding conductor. As the length of the 120VAC circuit increases, the circuit conductor (hot) has distributed capacitance between it and the metallic conduit. The effects of the capacitance are diminished if all conductors are properly terminated and tightened. But, let’s assume the equipment grounding conductor pigtail from the metallic box to the receptacle becomes ‘open’. We can assume a capacitive voltage will now exist between either the hot or neutral conductors (or both) and equipment ground terminal at the receptacle.

This capacitive voltage causes the tester’s lamp (which is connected across these conductors) to light when they shouldn’t, thus giving an erroneous CORRECT WIRING indication. This open ground condition represents a serious safety hazard during fault conditions, while also being detrimental to the operation of electronic equipment. Yet, the three-lamp circuit tester indicates this circuit is GOOD.

The bad news doesn’t stop there…

Leakage Current

This sounds like a bad thing (and it can be) but it’s just another way of saying ‘capacitively-coupled current’. I tell people to imagine their equipment frame as a conductor, their internal electrical components as conductors (which they are), and the air between them as an insulator. If, over time, the barrier of the air ‘breaks down’ due to the build-up of dust, dirt, moisture, or insulation breakdown on wires between the frame and components, then some current will ‘leak’ on over to the equipment frame. At low levels, this current is harmless…but it’s there. Leakage current flows through our bodies all the time on some devices and we hardly feel it. Above certain levels, it can be harmful (that’s why we have Ground Fault Circuit Interrupters (GFCI’s)).  But we won’t address that now…

Suppose you connect a device that causes leakage current to an outlet (or a set of outlets) that are affected by a loose or open ground condition. You might think that there’s no path for leakage current to flow. But, once the three-lamp tester is plugged in at any outlet on the same string of outlets, guess what? The resistor between the ground blade and the light will provide a load to the circuit and falsely indicate a GOOD condition. Or, worse yet, it may cause one of the other lights to darken or illuminate when they shouldn’t, thus indicating a DIFFERENT condition.

This could lead you to ‘correcting’ a wiring condition that doesn’t exist or give you a false sense of security. In either case, it sows a seed of uncertainty that we don’t need in complex electrical systems, especially if we’re trying to troubleshoot wiring and grounding problems.

What to Do?

Your ability to successfully troubleshoot ac wiring and grounding problems (or even power quality problems) will hinge on two things: your methods (a later blog) and your tools. One of the most important tools in the bag will be a wiring polarity/impedance tester that can successfully indicate the wiring conditions at each outlet in a working electrical environment. This includes polarity AND integrity of the wiring.

I know what you’re thinking…‘iGround makes an impedance tester…it makes sense to bash the competition.’ Well, iGround isn’t the only company to make an impedance tester. Furthermore, NO tester is ‘perfect’ and finding some wiring conditions in an energized electrical environment requires a certain level of troubleshooting skills not taught these days, regardless of your tools. But, when the Institute of Electrical and Electronics Engineers (IEEE) Standard 1100 (Emerald Book) singles the three-lamp testers out specifically as what NOT to use for troubleshooting purposes, you know there’s something to it.

So, if you have a three-lamp circuit tester, don’t throw it out…keep it as a night-light…otherwise, you’ll be stumbling around ‘in the dark’, in more ways than one.

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.