Electrical ground system inspection procedures & checklists.
This document discusses procedures the inspection of the grounding system components of a building electrical system when performed by trained building inspection professionals, home inspectors, electrical inspectors, and electricians.
Green links show where you are. © Copyright 2017 InspectApedia.com, All Rights Reserved.
\Here we define electrical ground, grounding, bonding, and earthing terms and explain why there are important differences among these words.
[Click to enlarge any image]
“Grounding”, article 250 in the NEC, is probably one of the most difficult of the often used articles. In 2005 article 250 became “Grounding and bonding”. In the 2008 NEC there has been a major revision in language, and phrases like “shall be grounded” have changed to “shall be connected to an equipment grounding conductor.”
Sketches above and at page top courtesy of Carson Dunlop Associates.
The grounding system at a building provides an easy path for electricity to flow to earth should a problem, such as a short circuit, occur.
Allowing current to flow to earth through the ground system helps assure that a circuit breaker will trip or fuse will blow should a problem occur. Properly operating these overcurrent devices help prevent fire and shock.
Should an electrical fault occur where no ground path is present, the electrical potential is just sitting there waiting for a person to come along, touch some component of the system, and by accidentally providing a path to earth through their body, receive a burn or potentially fatal shock.
Sketch courtesy of Carson Dunlop Associates.
Details of why we need grounding, and definitions of electrical grounding and electrical bonding (what's the difference between these two terms) can be read at Why Grounding is Needed.
Bud, a master electrician from Minnesota has offered these important clarifications:
"Grounding" has 2 main functions.
One is to provide a path to trip a breaker in the event of a 'short' as in the text above. That function relies on a "ground"-to-neutral connection required at services in the US (the "main bonding jumper"). The path is (branch circuit ground wire) to (N-G bond at the service) to (service neutral) to (utility power transformer).
This path *must* be metallic back to the power transformer to provide low resistance to trip a circuit breaker. This function will work even if the service is not connected to earth. And the NEC *does not allow* earth to be used as part of this path.
One reason is the resistance of an earth path is too high. Assume the earthing is only through a ground rod and the rod has a quite good 10 ohms resistance to earth. Further assume there is a 'short' connecting hot to "ground". The current to earth will be 12A. There is a good chance this won't even trip a 15A circuit breaker. If the circuit is loaded the breaker will trip, but after a significant time delay. In the mean time, the "ground" potential with respect to the earth away from the ground rod will be 120V.
Note that if you are using the earth as in the quote above, the path is not just into the earth. It is back to the power source, and also depends on the earth connection at the power transformer.
This would be better termed a *bonding* function.
Carson Dunlop's sketch shows how the electrical current in a building can find its way to earth by way of the electrical grounding system. But as you may want to read in our case study of loss of all ground connections at a building, don't assume that the current will always find its way to earth.
Loss of electrical ground at a building is extremely dangerous and risks electrocution.
As Carson Dunlop's sketch shows, the grounding equipment includes wires which bond the ground and neutral bus in the main electrical panel with an outdoor component that conducts electricity to the earth (ground).
The outdoor component may be grounding electrodes (ground rods), or in some jurisdictions a metal water pipe or possibly other metal components.
As Carson Dunlop's sketch shows here, from the main electrical panel a grounding conductor connects to:
The NEC (section 250-81 through 250-83) requires that the electrical system connected to all of the following, if available for grounding purposes:
The reason we ground in-building plumbing is not to provide an additional grounding conductor in a building but to ground the plumbing.
Picture someone knocking a toaster into a stainless steel sink or into any sink with a metal drain and drain piping.
If the sink and piping are grounded the fuse or breaker will blow. If not, the system is waiting to electrocute the building occupant when s/he touches the live water/toaster in the sink and perhaps a nearby metal faucet, radiator, or other component that is ultimately connected to earth. Similar hazards exist at other building locations such as basement laundry equipment & sinks, at building tubs and showers, etc.
In a properly-wired building, the grounding conductor and bonding system do not normally carry current, and would not be blamed for copper pipe pinholing etc. The grounding system is intended to conduct electrical current only in the event of a fault or emergency [such as a lightning strike or a hair dryer dropped into the bath tub or sink].
Details about the causes of copper pipe pinhole leak complaints are at COPPER PIPE PINHOLE LEAKS, Pinhole Leaks: cause, cure, prevention
In some communities, as Carson Dunlop's sketch shows, the metal gas piping in a building must be bonded to the electrical ground system.
Bonding anything to the ground system, including metal gas piping, helps prevent an electrical spark that might otherwise result in an explosion in the case of a gas piping system.
The bonding of the gas piping to the building ground system is not the same thing as attempting to use the metal gas piping as the primary or only connection to earth in a building.
|Ground Wire Gauge CU (Copper) - wire size||Electrical Service Size|
See Definitions of Electrical Ground, Grounding Electrode, Grounding Conductor, Grounded Conductor, Ground Wire, Neutral Wire, Ground Rod, for definitions of these confusing electrical terms.
More details about electrical grounding can be read at ELECTRIC SERVICE GROUNDING SYSTEM INSPECTION and
and at OLD HOUSE ELECTRICAL WIRING.
Also, see details about electrical grounding at ELECTRICAL CIRCUITS, SHORTS,
and at ELECTRICITY BASICS, HOW IT WORKS.
At ALUMINUM GROUND WIRES we discuss proper repair of aluminum ground wires found in solid conductor branch circuit wiring.
Readers should see our complete electrical ground inspection information at ELECTRICAL GROUND SYSTEM INSPECTION
This article series describes procedures for safe and effective visual inspection of residential electrical systems including electrical panels and other components, when the inspection is conducted by trained building inspection professionals, home inspectors, electrical inspectors, and electricians.
This information was presented by Daniel Friedman - InspectApedia.com, at & discussed by the Hudson Valley chapter of the American Society of Home Inspectors - HVASHI Seminar 12 Sept 2002, Updated April 2006, April 2009.
Carson Dunlop's sketch at page top shows where the electrical inspection starts at a residential property.
|Ground Gauge CU (Copper)||Service Size|
(a) Equipment grounding conductor defect
(b) Grounding electrode conductor defect
More about the galvanic scale and corrosion between dissimilar metals is at GALVANIC SCALE & METAL CORROSION.
Thanks to reader Bill O'Reilly (not that one) for the following excellent comment.
7/21/2014 Bill O'Reilly (not that one) said:
There's a spoonerism in the "Electrical ground inspection" article in the phrase ..."if the building plumbing includes dialectic fittings"... Dialectic fittings could be decorative, but wouldn't serve the intended function.
The word dialectic should be dielectric.
A dialectic is a form of formal argument first popular in the golden age of greece. [Dialectic is defined as The art of investigating or discussing the truth of opinions, inquiry into metaphysical contradictions and their solutions - Ed.]
A dielectric separates two electrically conducting materials so that they can be at two different potentials, more formally an electric di-pole. In the formal sense, a dielectric can be a solid (e.g. glass, porcelain, nylon, polyvinylchloride), a liquid (e.g. oil), a gas (e.g. dry air, sulfur hexafluoride), or a vacuum, which is nothing at all. In the particular sense of the phrase's context, the dielectric blocks the flow of electrons between the dissimilar metals, thus preventing the flow of dissolved ions from the water to the cathode and (metallic) ions from the anode into the water.
XXX at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
We bond the building water pipe to the grounding wire on the street side of the water meter to be sure that the building electrical system is grounded to earth.
We bond the building water pipe to the grounding wire on the building-side of the water meter to be sure that the building water piping is safely grounded too.
This grounding wire should be continuous, through both pipe clamps securing it to the water piping before and after the water meter, and continuing into the main electrical panel where it joins the ground bus and neutral bus.
More about the galvanic scale and corrosion between dissimilar metals is at
At ALUMINUM GROUND WIRES we discuss proper repair of aluminum ground wires found in solid conductor branch circuit wiring.
No one may notice this problem because even if this ground connection is totally ineffective, the building may be still grounded through the service entry ground wire. As we demonstrated at DOUBLE FAULT, LOSS OF ELECTRICITY, it's not safe to rely on just the utility company's ground connection.
The ground system wiring is for emergency-use only - it should never be wired so as to carry current during normal operation. (E.g. This occurs if a
sub panel bonds the neutral to ground wires).
We've found cases in which someone used the ground path to complete an electrical circuit because the neutral wire was broken somewhere that could not be found.
As a result, the ground path was electrically live when it should not have been, leading to an electric shock.
In our photo at left, someone used telephone wire to connect the neutral side of this electrical receptacle to the receptacle's steel mounting strap, knowing that that would in turn connect the neutral side of the receptacle to the steel junction box and through it, to the armored BX electrical cable, forming an electrical path back to the main electric panel. We discuss this crazy wiring in more detail at False Neutral Connections.
Indeed this got the receptacle "working" by using the ground path in the system after the original neutral path had been lost.
We were working on renovating the home where we found this condition. How did we find it? We were replacing two-prong un-grounded receptacles with grounded devices. We turned off electrical power to this circuit and began working on it. When our assistant plugged in and began using a vacuum cleaner in the same room we got an electrical surprise - a shock while touching the BX cable!
Ground rod cut off or short - don't assume that because you see a grounding electrode that it has been properly installed. If the installer hit rock and couldn't drive the rod fully into the soil s/he may have cheated and simply cut off the top of the rod.
Grounding electrodes in some locales have an embossed code on their upper end - if the rod was cut off the embossed letters will be missing. If a grounding electrode cannot be fully driven into the soil the electrical code provides procedures for driving the electrode in cut-sections to achieve sufficient total earth contact.
As we and our inspection client discovered (photos above), the bent-over grounding electrode made us wonder what was happening. When the grounding electrode was just nudged with a toe, it fell over. Our client was kind enough to demonstrate just how ineffective this electrical ground system was, thanks to someone's shortcut.
Readers should also see Definitions of Electrical Ground, Grounding Electrode, Grounding Conductor, Grounded Conductor, Ground Wire, Neutral Wire, Ground Rod, for definitions of these confusing electrical terms.
While we have frequently updated and added to the material, in its original form this information was presented by Daniel Friedman - InspectAPedia.com, at the Hudson Valley chapter of the American Society of Home Inspectors - HVASHI Seminar 12 Sept 2002, Updated April 2006, February 2013, March 2014, July 2014, December 2014
Watch out: for safety, also review SAFETY HAZARDS & SAFE ELECTRICAL INSPECTION PROCEDURES for Inspectors examining Residential Electrical Systems
Reader Question: 4 June 2015 Bill Said:
I am replacing my service panel,in my condo, and the conduit running from the sub panel is being used as the earth ground. How can I test this ground?
When the conduit is being used as the earth ground it must meet certain UFER specifications and impedence requirements. Below is a general answer discussing local electrical ground electrode testing.
See ELECTRICAL GROUND REQUIREMENTS
If a local ground is isolated from the electrical company's ground (neutral wire in the panel) and does not conduct electricity or shows high resistance (or more generally, high impedence) it is not safe. How much is "high impedence" when testing an electrical ground system at a building?
The NEC specifies 25 ohms as an acceptable limit for electrode impedance. The IEEE Standard 142 Recommended Practice for Grounding of Industrial and Commercial Power Systems (“Green Book”) suggests a resistance between the main grounding electrode and earth of 1 to 5 ohms for large commercial or industrial systems. - Fluke Corporation, "Checking ground electrode impedence for commecial, industrial, and residential buildings", [PDF] Fluke COrporatio, PO BOx 9090, Evrett WA, USA 98206, Tel U.S.A. (800) 443-5853, Fluke Europe, B.V., PO Box 1186, 5602 BD Eindhoven, The Netherlands, In Europe/M-East/Africa +31 (0) 40 2675 200 , In Canada (800)-36-FLUKE From other countries +1 (425) 446-5500 Website: http://www.fluke.com
Watch out: this test needs to be performed by a trained electrician as there are shock and electrocution hazard risks. As Fluke and other experts point out, to perform testing of the local grounding electrode it must be disconnected from the building. The ground testing instructions that we cite below include additional important safety warnings and procedureal details from which we excerpt. From reading the literature our opinion is that this test is technically difficult, requires expertise, and should not be attempted by a homeowner nor by anyone else who lacks the necessary expertise.
Here is an excerpt from Fluke Corporation, a producer of a wide range of electrical test equipment:
There are two types of ground impedance testers. Three and four point ground testers and clamp-on ground testers. Both types apply a voltage on the electrode and measure the resulting current.
A three or four-pole ground tester combines a current source and voltage measurement in a “lunch box” or multimeter-style package. They use multiple stakes and/or clamps.
Ground testers have the follwing characteristics:
Clamp-on ground testers resemble a large clamp meter. But they are very different because clampon ground testers have both a source transformer and a measurement transformer. The source transformer imposes a voltage on the loop under test and the measurement transformer measures the resulting current. The clamp-on ground tester uses advanced filtering to recognize its own signal and screen out all others. - Op. Cit.
Fluke Corporation describes a simplified grounding electrode test in which the technician drives additional spikes into the ground to permit several measurements fof impedence that are compared at different distances from the grounding electrode under test. Measurements are made by connecting test leads to the grounding electrode, to a "current spike" driven at a specified distance "d" from the test electrode, and one to three "potential spikes" driven at a distance equal to 62% of distance "d". Details are in the document that we cite and link-to above.
You may be able to use a shortcut if your test meets the following criteria:
Under these conditions you can place the current stake 100 feet or more from the electrode under test. Place the potential stake at 62 % of the distance between the current stake and the electrode under test and take a measurement. As a check, take two more measurements: one with the potential probe 3 feet closer to the electrode under test, and one 3 feet farther away (see Figure 5 in Fluke's document). If you are on the flat portion of the fall-of-potential curve then the readings should be roughly the same and you can record the first reading as your resistance. - Op. Cit.
Continue reading at ALUMINUM GROUND WIRES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see ELECTRICAL GROUND ERROR-CAUSED LEAKS - leaks in metal water pipes traced to improper grounding
Or see ELECTRICAL SERVICE ENTRY DAMAGE - service entry wire melts & shorts to ground
Or see GAS PIPING, FLEXIBLE CSST for a discussion of lightning protection needed for flexible stainless steel tubing used as gas piping
Or see these
Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
How I can control voltage leakage ? - Rikio 8/9/11
Rikio I'm not sure I correctly understand the question but in general, if you are measuring voltage leaking say to ground, you want to find and fix the wiring error.
can i put a shrubs or plants near the grounding system, or can i put river rocks surrounding the ground system? - David 8/10/11
I have a home that is 7 yrs old in Burleson Tx. We are on a co-op water supply. I recently had a pin hole in my copper water pipe under the slap. I though it was the water but had the water dept lab test my water and all was normal. I then read about electrolysis could cause this. I do have a ground on my water pipe and a rod out side my main. I checked whit a meter and I do have continuity between the main panel and my plumbing and my gas pipe to the hot water. can this possible cause my plumbing to fail?
The water has been ruled out so it has to be something else the pin hole was from the inside out and my house water connections are green and blue. need some help bad. I did disconnect the one ground off the plumbing when I read about the electroylis. Please advise.
Donald McKinley 10/19/11
With just the info in your note I can only guess at some possible causes for the pinhole leak in copper water piping under your building slab.
If the pH is low <6.0, the hardness low generally<50ppm, the alkalinity low generally <40ppm, the water could be considered
extremely “soft” and aggressive to the home’s metallic plumbing system. If the
chlorides are elevated >100ppm this would only compound the problem. The
water should be treated to make the water less aggressive by raising the pH, alkalinity or hardness. - CT DOH.
If you do nothing but fix the pipe and the problem never recurs I'd suspect the pipe itself. But if it were me, I'd also have a licensed electrician check that the home's grounding and neutral systems are properly wired, that the grounding electrodes are properly sized and installed, and that there are no stray currents on the neutral system nor shorts or leaks in the wiring system (an AFCI or GFCI can help detect these too).
Copper pipe failure in concrete is common. - anonymous 12/1/11
Yes, Anon, depending on the chemistry of the concrete and also moisture exposure there can be problems with corrosion - which is why for grounding conductor wiring the electricians I know use insulated grounding conductors. I haven't seen that demanded for copper piping.
My main water line coming in from the street is lead. Can I ground the electrical panel to the lead pipe? I read that lead does not conduct electricity very well. Thanks. - Brad 6/2/12
Indeed it's common to see the electrical panel bonded to a lead water main entering the building.
Watch out: Lead conducts electricity but corrosion and unreliable connections within the piping make it an unreliable main electrical ground.
Good procedure would be to connect a ground to the lead water main but ALSO to install two (current NEC) driven ground rods at the property. I would not install less than one additional grounding electrode (ground rod). For a reliable and compliant installation, use two.
Dan, concerning the pin hole pipe leak and all the green and blue plumbing from Oct. 19 & 21, 2011. I have seen this before and traced it to bad grounded (neutral) connections at the utility transformers or tap boxes causing all the neutral loads to be carried on the grounding system such as the copper plumbing.
I even seen it in one house but show the signs of trouble in a neighbors house because of a common city water pipe. This situation eats the copper water piping from the inside out and can cause green/blue water color, usually the first sign.
Also, these pin hole can develop because of excessive flux being used before sweating. The excess flux lays in the bottom of the pipe and corrodes the copper, hence pin holes on the bottom only. - Rod, electrical contractor, 8/1/12
thanks for the important and helpful comment - we agree completely. Bad electrical grounding and incorrect connections among grounding connections can cause a wide range of odd problems, including corrosion and leaks in plumbing, HVAC equipment, even equipment internal parts such as the coil in a water to air heat exchanger coil in a groundwater sourced heat pump.
The excessive solder flux corrosion problem is not one I'd realized -thanks for that tip. I suppose we could confirm that problem cause after the fact by noticing just where the copper piping leaks are occurring - all at solder joints - and then disassembling or cutting one of those joints apart to inspect the interior of the pipe. Water chemistry may also play a part in that corrosion problem.
Thanks again. Astute and helpful. If you want us to cite and refer readers to you in your area email me contact information.
You show a jumper wire across a dielectric plumbing connection (between copper & galvanized pipe). This will promote galvanic corrosion & make the dielectric connection pointless. Instead of at the connection the corrosion will now take place inside the galvanized pipe near the jumper wire clamp.
Grounding the plumbing does not make a house safer. It places half an electrical circuit through out the house. This increases the likelihood of connecting that circuit with some current. - Galvanic 9/20/12
If we don't jump across a non-conductive dielectric fitting on water piping then the water piping is not grounded. By current NEC, metal piping may not be used as a grounding conductor, but metal water piping in contact with the earth for a length of ten feet or more, that piping is indeed connected to the electrical ground system.
For protection from lightning and possibly leakage from a high voltage transformer, the current National Electrical Code (NEC) requires two grounding electrodes at a building. If one of these is water piping it is tested and must show less than 25 ohms of resistance to earth.
Typically, pinholing in copper piping that is traced to an electrical grounding problem (electrolysis) is, if we exclude neutral/ground wiring errors, traced to inadequate local grounding electrodes.
Thanks for the interesting comment. I'm not sure where your surmise takes us, since there are both code and basic safety reasons for grounding house plumbing. Also I am nor sure which jumper you saw, but connecting a ground between similar metals ought not create the concern youncite. Can you give us a citation or article to review?
The reason people ground in-building plumbing is not to provide an additional grounding conductor in a building but to ground the plumbing. Picture someone knocking a toaster into a stainless steel sink or into any sink with a metal drain and drain piping. If the sink and piping are grounded the fuse or breaker will blow. If not, the system is waiting to electrocute the building occupant when s/he touches the live water/toaster in the sink and perhaps a nearby metal faucet, radiator, or other component that is ultimately connected to earth.
Incidentally, as we discuss pinholing and bad neutral connections, keep in mind that the return path for current in a building's electrical system is not intended to be primarily through the building's local grounding electrodes. Rather it is on the neutral wire that is connected back to the pole transformer.
See LOST NEUTRAL SHOCKS HOMEOWNER for details of what can happen when this connection is not made or goes bad.
in a house with no ground electrical ie two prong outlets not three, will a circuit tester read correctly? - Jim 10/31/12
A circuit tester should show that there is an open ground IF 3-prong grounded outlets are installed. But with just 2-prong outlets installed in a home, the circuit tester cannot reliably test for ground and you must assume that no ground is present.
In some such installations we find that the wiring is BX (armored cable) that along with metal junction boxes, actually provides an (improper, that is not to be relied-on) ground path from the metal electrical box, through the BX cable sheathing, back to the main electrical box, through a panel jumper or connection to the panel ground bus, to ground. But that's not a proper nor safe electrical ground path. I mention this connection because we can, for example using a neon tester, often confirm the existence of that path by connecting the neon tester between the hot wire or hot slot in the 2-slot receptacle over to the wall plate mounting screw.
In that (UNRELIABLE) "ground" path, current flows from the hot wire through the electrical receptacle hot tab or slot, through the neon tester, to the wall plate screw, to the metal strap on the face of the receptacle, through the receptacle mounting screws, to the metal electrical box, through the BX cable to ground. This is not a true, safe, proper ground path and cannot be used nor relied upon.
Back to your question... it depends .. on how what tester is used, how it is connected, and how the results are understood.
(Nov 5, 2012) HARDIK SANJAYKUMAR SHUKLA said:
Can u pls suggest a device to check if a motor is silently attached to a pipe.
A continuity tester
(Feb 17, 2013) CathyA said:
Since this fall, after a smart meter was installed on our home, we have had a ringing noise in our electrical wiring, dimmer switches, water pipes. An electrostatic filter, two clock radios and a wireless router are no longer working. There are also sparks jumping out of some outlets when we plug in our laptops (we now use surge protectors). The utility says the meter is fine. There is a transformer on a phone pole at the foot of our driveway which they also checked. The gas meter was checked (sort of). I am wondering if this is an easy (not too expensive) or difficult (expensive) problem to fix and am assuming I need an electrician. For instance, is it in the $100's or $1000's of dollars? Just an educated guess would help. Thanks.
(Mar 9, 2013) Charles said:
The grounding wire from my circuit box is attached via a clamp to a hot water copper pipe. Just a few inches further, and it could be attached to a cold water copper pipe. My question is, would it be better if the grounding was done to the cold water pipe, since then it would not have to go through the water heater, and be more directly connected to the city main water supply line?
It can be confusing figuring out if your water piping is actually serving as an electrical ground (it would have to be continuous metal, into soil outdoors, for a suitable distance and depth) or if instead the connection you see is intended as a safety feature to ground the building piping.
Certainly we wouldn't expect a workable ground connection for the electrical system to run through piping and the water heater.
As you will read in this article series, current codes want two grounds at the home - via grounding electrodes, for safety reasons.
Thanks for your response Dan.
I did not open the circuit box, but inspecting all the wires coming out of it, this one seemed to be the only one consisting of a few exposed copper wires twisted around each other. If this was meant to ground the house piping, should it be connected to the circuit box? If there is another wire going to electrodes, where else should I look to find it? Even if this was meant to ground the piping, would it be better if it was connected to a cold water pipe?
This all started when I went to insulate some of the hot water pipes in my basement. That's when I ran across the wire attached via a clamp to the hot water pipe. I was not rewiring or looking to update the grounding for my electrical system. It is a 1915 house which looks like it had its wiring updated, maybe in the 90's. Other than what may be in the hot water heater, there is no other non-metallic materials in between it and the water meter, and then its metallic piping going out of the house from there. In any event, is it OK, if not better, to attach this wire to the cold water pipe.
PS: While I was down there I found another wire going from the phone line also to another hot water pipe for grounding. Did they just not care back in the day what pipe they were grounding to, or was it actually better to use the hot water pipe than the cold one?
Sounds odd Charles. Send me some sharp photos so i can see the ground wires coming out of the panel and where they go. You may need an electrician to be sure your house groundis proper and safe.
(Feb 10, 2014) Folarin said:
In developing countries where power supply is erratic, what frequency would you advise inspection of electrical and earthing systems?
Interesting question Folarin, I don't know a solid answer.
It seems to me that in thinking about electrical ground safety I'd be less worried about erratic power delivery or varying voltage levels in delivery and more worried about conditions that immediately affect the safety of the electrical system, or if we confine that safety to a subtopic of grounding, and if I were thinking off the cuff about country differences I'd want to identify
- areas where grounding is not adequately provided
- areas where workers are under-trained or not educated about grounding, bonding, &c.
- areas where soil conditions such as moisture affect the adequacy of grounding
(Feb 16, 2014) Anonymous said:
My trailer is grounded but it still shocks you when you open the door can't find the problem
Watch out: Anon, you really should call a licensed electrician - a ground fault such as the one you describe could kill someone. Certainly I can't imagine diagnosing the problem by message exchange - you need an experienced eye on the scene.
(Mar 6, 2014) steve said:
i'm measuring +/- 15 volts on a ground wire at light fixture. Is this normal?
it is not normal to find voltage on the ground wire; that wire carries current in the event of a fault or short.
(Mar 12, 2014) Scott said:
I want to erect a 40 meter ham radio antenna onto our old outdoor tv antenna mast. The more I read about what it takes to ground all three legs of the mast correctly for lightning protection, and to then properly bond it to the house electrical ground, the more I am inclined to realize I need an electrician to supervise my work and an inspector to bless the whole project. My question is, when it comes to connecting the recommended #4 solid copper wire to each grounding rod, is it true that the grounding rod can only be fully buried in the ground if the wire was cad-welded, and if it were clamped on, the grounding rod top needs to remain slightly above ground so that it can be inspected annually? I'm inclined to think that the cad-welded idea is the better solution.
Scott, thanks for the interesting question. I don't have an answer but will do some research - as you might too, using Google Scholar or NEMA or the NEC.
Start at NEC Article 250 — Sections 250.20 through 250.34
www.mikeholt.com - Mike Holt's forum has the most clear and authoritative discussion of grounding I've been able to find. I've asked Mike for some help on your question.
In general, I have never, in thousands of inspections, come across a welded ground wire-to-electrode connection at a building. Most often we see a few inches of grounding electrode above ground and a clamp connecting the grounding conductor to the ground rod.
A shortcut might be to check with your local building department to see what they will accept.
I'll post further when I can find an authoritative citation on the connection we are discussing.
Mike Holt adds,
see article 250 part III
You can clamp or weld, keep above ground or bury it. I prefer to se the ground electrode tip above ground to confirm its presence and status of the connection.
(July 31, 2014) Anonymous said:
will bonding to a gas meter outside need to be in conduit
(Aug 18, 2014) S. Moore said:
If there is work done that bumps into the outside component of a water meter (my meter is in the basement and it's the new type that can be read as drive by) but I understand there is an outside component somewhere. If work, an inspection of the meter, or say there is a car accident...something affects this outdoor component, can it affect the indoor meter and reading. ie cause the meter to register too high or too low. I heard too high in this case. Can other appliances like a dishwasher or disposal be affected?
If I understand the question correctly, you ask if damage to an outdoor water meter would affect the proper operation of a subsequent water meter that is down-stream from the damaged one. I don't think so.
The only oddball case that occurs to me would be one of damage to an upstream water pressure reducer/meter combination that sent a surge of unanticipated high water pressure into a building. That might cause leaks at or damage to building plumbing system components including piping, valves, or even a meter.
(Sept 4, 2014) firstname.lastname@example.org said:
can I splice a ground wire together to make it longer thank you email@example.com
Generally grounding wires can be spliced, with some exceptions where use of a continuous conductor is recommended. An example of the latter is the wire connecting the building metal water supply piping around a water meter an onwards to the grounding electrode.
(Sept 12, 2014) Sam Herschler said:
Can a electric panel be grounded to a steel gas line? Had new furnace and a/c installed. They put in new breaker for unit and grounded to gas line
(Sept 13, 2014) (mod) said:
Sam, in the article links above check out GAS PIPING GROUND BOND
Can I test ground wire connections at an electrical switch or outlet?
A trained electrician (that is someone who knows how to avoid getting electrocuted while messing with wiring) might use a DMM or VOM to check for current flow from hot to ground; if the ground is disconnected no circuit would be completed and no current would flow.
I also check that the metal box is grounded and as we warn in these articles, we emphasize the importance of following NEC on grounding and grounded conductor wiring and connections - e.g. don't rely on a "ground" obtained through the receptacle or switch mounting strap.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website