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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.
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Here we define electrical ground, grounding, bonding, and earthing terms and explain why there are important differences among these words.
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“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.”
Sketche courtesy of Carson Dunlop Associates.
These questions & answers about electrical ground systems at buildings were posted originally at ELECTRICAL GROUNDING BASICS - be sure to see that article.
Watch out: improper electrical grounding at a building can cause or contribute to fire, electrical shock, even death. If you are not qualified / trained in working safely with electrical wiring, leave any suspect electrical circuits off and ask for help from a licensed electrician.
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) email@example.com said:
can I splice a ground wire together to make it longer thank you firstname.lastname@example.org
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.
Continue reading at GROUND SYSTEM INSPECTION - home, 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 GROUNDING FAQs-2 - more questions & answers posted originally the ground system inspection article recommended above.
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
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