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How to Inspect Residential Electrical System Grounds, Ground Wiring, Grounding Conductors, Grounding Electrodes
- ELECTRICAL GROUND SYSTEM INSPECTION -Class on how to inspect electrical panels, home inspection procedures and safety, definition of ground, grounding, grounded, grounding conductor, grounded conductor, bonding, earth, earthing
- Questions & Answers about how to inspect residential electrical wiring ground system, & about defects in electrical ground system wiring
- References
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
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 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Guide to Inspecting Electrical Service Grounding Equipment for Defects
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.
Here we define electrical ground, grounding, bonding, and earthing terms and explain why there are important differences among these words.
“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.”
See Definitions of Electrical Ground, Grounding Electrode, Grounding Conductor, Grounded Conductor, Ground Wire, Neutral Wire, Ground Rod, for definitions of these confusing electrical terms. Readers of this article should also be sure to review False Ground at Receptacles where we describe false grounds and un-grounded or un-polarized electrical receptacles and circuits, and see Safety Hazards and Safe Electrical Inspection
Procedures for Inspectors examining Residential Electrical Systems and Local Electrical Grounding for safety procedures during inspection of the grounding system.
Sketch courtesy of Carson Dunlop Associates.
Why we need electrical grounding
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.
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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.
Some discussion points about electrical grounding are listed just below.
- Required for safety, lets fuses blow
- Example: toaster falls into metal sink
- Grounding Electrode Conductor wire from service equipment to
- House plumbing (grounds the plumbing)
- Entering metal water pipe (grounds the system)
- Grounding Electrode (two now recommended)
- Continuous, no splices, meter bypass
- Copper ground wires and grounding conductor (corrosion resistant)
- Aluminum - insulated solid conductor (See ALUMINUM WIRING HAZARDS & REPAIRS and also ALUMINUM GROUND WIRES)
- Aluminum - insulated multi-strand
- Aluminum - bare vs. insulated (risk of corrosion, break in wire, loss of safe grounding - illustrated below)
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What is Meant by the "Grounding Equipment " in a Building?
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.
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Where do Ground Wires Go?
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As Carson Dunlop's sketch shows here, from the main electrical panel a grounding conductor connects to:
- a pair of grounding electrodes,
- a metal water pipe entering the building from outside,
- a strip footing which contains metal in contact with the earth
- to the metal casing of a private well
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Why is Building Water Supply Piping Connected to the Ground System?
 The NEC (section 250-81 through 250-83) requires that the electrical system connected
to all of the following, if available for grounding purposes:
- metal frame of building [if the building has metal framing]
- concrete encased electrode (rod, pipe, plate, braided wire)
- ground ring
- metallic water pipe with 10 lineal feet in contact with earth
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
NEC Citations on grounding water piping
- NEC 250.50 "All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present at each building or structure shall be bonded together to form the grounding electrode system."
- 250.52(A)(1) Metal Underground Water Pipe - any connection to the water pipe must be within 5 feet of it entering the structure
- 250.52(A)(1) Water pipe electrode to be supplemented by another type of electrode (2) through (6) [listed just below]
- 250.52(A)(2) Metal Frame of Building or Structure grounding requirements
- 250.52(A)(3) Concrete-Encased Grounding Electrode
- 250.52(A)(4) Ground Ring requirements
- 250.52(A)(5) Rod and Pipe Grounding Electrodes
- 250.52(A)(6) Plate Electrodes (7)(B): Gas lines and aluminum electrodes are not permitted
- 250.53(D)(2) Supplemental Grounding Electrode Required,
Gas Piping May Need to Be Bonded to the Electrical Ground System
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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.
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Table of Electrical Ground Wire Sizes
| Ground Wire Gauge CU (Copper) - wire size |
Electrical Service Size |
#8 |
to 100A |
#6 |
to 125A |
#4 |
to 165A |
#3 |
to 200A |
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 Electrical Circuits, shorts, and at Electrical Wiring in Old Houses.
Also, see details about electrical grounding at Electrical Circuits, shorts, and at Electrical Wiring in Old Houses 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.
Guide to Inspecting Electrical Service Grounding Equipment
Table of Electrical Ground Wire Sizes Required by Electrical Service Size
| Ground Gauge CU (Copper) |
Service Size |
| #8 |
to 100A |
| #6 |
to 125A |
| #4 |
to 165A |
4* |
| #3 |
to 200A |
Electrical Service Grounding Defects & Conditions to Check For During an Electrical Inspection
Here are the Most-Common Electrical Service Grounding Defects & Conditions
- not found in sub panel feeder (a)
- attached to plastic pipe (b)
- attached to abandoned pipe
(b)
- spliced
(b)
- loose or missing connections
(a) or (b)
- inaccessible connections
- no water meter bypass or other dielectric plumbing fitting bypass (bonding jumper)
- local grounding electrode conductor not found in main panel
- ground bond between neutral and ground and panel enclosure not found in the main panel
- no water meter/water shutoff valve bypass (bonding jumper) (a)
- neutral (the grounded conductor) bonded to ground downstream of box (or upstream)
- neutral bus not bonded to the ground bus (equipment grounding conductors & ground bus) at main panel
- main panel not bonded to grounding electrode conductor and ground bus
- undersized grounding electrode conductor wire
- ground rod (grounding electrodes) cut off or short (or only one grounding electrode connection at new construction)(b)
- corroded grounding electrode conductor (b) - More about the galvanic scale and corrosion between dissimilar metals is at GALVANIC SCALE & METAL CORROSION.
- loose or missing grounding electrode conductor clamp at the grounding electrode (b)
- loose or missing bonding jumper clamp(s) such as at a water meter or water pipe (b)
- bare aluminum grounding electrode conductor
exposed to corrosion (b) - More about the galvanic scale and corrosion between dissimilar metals is at GALVANIC SCALE & METAL CORROSION.
- neutral bonded to the equipment grounding conductor (the ground wire) in sub panel or junction box (a)
- neutral not bonded to ground at the main service panel (b)
- main panel not bonded to ground wire
(b)
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More about the galvanic scale and corrosion between dissimilar metals is at GALVANIC SCALE & METAL CORROSION.
What Other Defects Should We Check for in an Electrical Grounding System?
- Jumper wires to ground plumbing: As Carson Dunlop's sketch shows at (A), if the building plumbing includes dialectic fittings or non-conductive sections of piping (such as plastic piping) then the building plumbing system may not be safely grounded.
A jumper wire is installed to assure that the building metal plumbing pipes are safely grounded to earth.
The purpose of the ground jumper is to ground the building plumbing, not to use the building plumbing as a grounding system.
That is to say, we're making the plumbing safe, we're not using it to provide a ground for the electrical system.
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- Grounding system jumper wire around the water meter: as the same sketch shows at (B), if the building water main piping is being used as a source to provide a ground for the electrical system, then the main ground wire between the electrical panel and the water piping should be clamped on both sides of the water meter.
In this case the building water supply piping is being used as part of the electrical grounding system, and we need to be sure that that connection to earth is not interrupted by non-conductive components of the water meter itself.
In our photo you can see that the meter bypass jumper has become disconnected (where our flashlight is shining) and that the system ground wire was also spliced.
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.
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- Corroded copper grounding wires can also be unreliable as our photo shows.
We would be reluctant to trust this connection for the building grounding system.
More about the galvanic scale and corrosion between dissimilar metals is at GALVANIC SCALE & METAL CORROSION. |
List of Still More Electrical Grounding System Checkpoints:
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- Confirm that a grounding connection to earth is present: New electrical installations should have two grounding electrodes at the building; older homes may have only one grounding electrode, or no ground rods but a connection to an incoming water pipe, or in the worst case, no local ground at all.
You may have to look closely even to find the grounding electrode, but following the ground wire should lead to it if an electrode is present. Photo courtesy of Tim Hemm.
- Confirm that grounding is present in all sub panels: Check for grounding not found in sub panel feeder cable
- Follow building piping to be sure that its ground path is electrically continuous. A main ground wire attached to plastic pipe is completely ineffective.
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- Corroded aluminum electrical ground wire - aluminum ground wires corrode through and ground can be lost. That's why new electrical work that uses aluminum ground wires should be performed only using wires that are insulated.
We've seen this happen, as shown in our picture at left, leading to loss of the local building ground connection when the bare aluminum ground wire was touching the edge of a masonry block foundation.
Moisture in the foundation wall and probably the chemistry of the masonry block, mineral salts left by water entry, and the aluminum wire itself led to through-corrosion of the ground wire.
At ALUMINUM GROUND WIRES we discuss proper repair of aluminum ground wires found in solid conductor branch circuit wiring. |
- Loose or missing ground connections securing the ground wire to a water pipe or to a grounding electrode.
As you can see in our photo, someone just skipped the clamp intended to secure the copper ground wire to the incoming water pipe, and left it wrapped around the pipe quite loosely.
Often we find this condition when someone needed to temporarily disconnect the ground wire, perhaps during a plumbing repair.
The plumber may not have taken seriously the need to re-connect the building ground system.
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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.
- False Grounds - are wiring "tricks" that can make an electrical circuit appear to be properly grounded when it is not. A conventional plug-in circuit tester will not find false grounds, as we explain at False Ground at Receptacles where we provide details.
- False Neutrals - are wiring "tricks" that make an electrical circuit appear to have a good neutral wire connection when it does not. Since the ground wire or ground path may have been (improperly) used for this, we illustrate an example of a false neutral using a ground path just below, and we discuss this foul-up in detail at False Neutral Connections
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.
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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!
- Grounding Electrode Cut Off, Short, or Inadequate - see below
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.
- Grounding wire not found in main electrical panel
- Grounding wire not found in sub panel feeder
- Inaccessible connections to the grounding system (can't be inspected or maintained)
- Main electrical panel enclosure not bonded to grounding system
- Main ground wire attached to abandoned pipe such as a metal water pipe that used to run underground to a remote well but which, now that it's abandoned in the building, may have been also cut off outside of the building, or may have rusted away
- Neutral wire bonded to ground wire downstream of the main electrical panel, in a sub panel - see Case History:Loss of Neutral Shocks Homeowner
- Neutral bus not bonded to ground bus in the main electrical panel
- Spliced ground conductor between the electrical panel and the ground rod or water pipe is improper (the connection may be unreliable)
- Undersized ground wire - see Table of Ground Wire Sizes
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.
More details about electrical grounding can be read at ELECTRIC SERVICE GROUNDING SYSTEM INSPECTION and Electrical Circuits, shorts, and at Electrical Wiring in Old Houses.
SYSTEM GROUNDING - A Summary of Inspecting Residential Electrical System Grounding for Defects
- Electrical grounding improves building electrical safety because it provides better path for current than a person, blows fuse/breaker, dissipates static, may dissipate lightning
- Example of a potential shock waiting for someone: loose black wire in a metal junction box touches the side of the box. If the electrical box is connected to ground lots of current will flow (this is a short circuit) and the fuse or circuit breaker protecting the electrical circuit will blow or trip.
But if the electrical box is not grounded, current flows through a person when the electrical box or anything connected to it (electrically) is touched, if the person has the bad luck to also be herself grounded (say by touching building piping or standing on a wet floor).
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Frequently Asked Questions (FAQs) About How to Inspect the Electrical Ground System at Buildings
Question: testing for or controlling voltage leakage
How I can control voltage leakage ? - Rikio 8/9/11
Reply: find and fix the wiring error
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.
Question: can I put plants near the grounding electrode
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
Reply:
[pending]
Question: pinhole in copper water pipe under the slab
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.
Thanks
Donald McKinley 10/19/11
Reply: Causes of pinholing in copper water supply or drain piping
Donald,
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.
- the pipe could have been defective from day one
- the pipe could be a lower quality thin-walled material more vulnerable to corrosion
- the pipe could have been damaged in transport or installation or even during the slab pour
- just as you posed, on occasion a bad or improperly-connected electrical ground or another electrical problem can contribute to plumbing or other pipe corrosion at a building. I recall a ground water sourced air conditioning system that kept blowing out a very expensive cooling coil for which the problem was finally traced to just this issue.
- the water chemistry itself can be a source of metal water pipe (and even drain pipe) corrosion.
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.[1]
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).
Question: comment that copper in concrete corrodes
Copper pipe failure in concrete is common. - anonymous 12/1/11
Reply:
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.
Question: is a lead water line from the street a good electrical ground?
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
Reply:
Brad,
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.
Question: follow-up on pinhole leaks in copper piping traced to bad (grounded) neutral connections at the utility transformer
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
Reply:
Rod,
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.
Daniel
Question: jumper across dielectric fittings is asking for galvanic corrosion
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
Reply:
Galvanic,
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.
Current NEC Citations on grounding water piping
- NEC 250.50 "All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present at each building or structure shall be bonded together to form the grounding electrode system."
- 250.52(A)(1) Metal Underground Water Pipe - any connection to the water pipe must be within 5 feet of it entering the structure
- 250.52(A)(1) Water pipe electrode to be supplemented by another type of electrode (2) through (6) [listed just below]
- 250.52(A)(2) Metal Frame of Building or Structure grounding requirements
- 250.52(A)(3) Concrete-Encased Grounding Electrode
- 250.52(A)(4) Ground Ring requirements
- 250.52(A)(5) Rod and Pipe Grounding Electrodes
- 250.52(A)(6) Plate Electrodes (7)(B): Gas lines and aluminum electrodes are not permitted
- 250.53(D)(2) Supplemental Grounding Electrode Required,
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?
We ground building water piping for electrical safety for the occupants, not to provide an additional electrical ground path
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.
Question:
in a house with no ground electrical ie two prong outlets not three, will a circuit tester read correctly? - Jim 10/31/12
Reply:
Jim
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.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- [1] "Publication No. 37: Electrical Grounds - A Controversial Necessity", The State of Connecticut Department of Public Health
Environmental Health Section, Private Well Program
450 Capitol Avenue, MS#51REC, PO Box 340308, Hartford, CT 06134
Phone: 860-509-7296, retrieved 2/7/13, original source: http://www.ct.gov/ [copy on file]
- 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 Electrical Circuits, shorts, and at Electrical Wiring in Old Houses.
- At ALUMINUM GROUND WIRES we discuss proper repair of aluminum ground wires found in solid conductor branch circuit wiring.
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
 Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- Timothy Hemm, Yucala, CA, contributed the photographs of electrical equipment installed in California buildings. Mr. Hemm can be contacted at TimHemm@yahoo.com
- Special thanks to Bud - a master electrician in Minnesota who contributed text and suggestions for explaining why we need electrical grounding, and for discussing the shortcomings of neon testers and plug-in receptacle testers - 1/22/2009
- "Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
- "Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
- "How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
- "Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
- "Home Wiring Inspection," Roswell W. Ard, Rodale's New Shelter, July/August, 1985 p. 35-40.
- "Evaluating Wiring in Older Minnesota Homes," Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108.
- "Electrical Systems," A Training Manual for Home Inspectors, Alfred L. Alk, American Society of Home Inspectors (ASHI), 1987, available from ASHI. [DF NOTE: I do NOT recommend this obsolete publication, though it was cited in the original Journal article as it contains unsafe inaccuracies]
- "Basic Housing Inspection," US DHEW, S352.75 U48, p.144, out of print, but is available in most state libraries.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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- Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
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