ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
AFCIs ARC FAULT CIRCUIT INTERRUPTERS
ALUMINUM SECs & WIRING
ALUMINUM WIRING HAZARDS
AMPS & VOLTS DETERMINATION
CIRCUIT BREAKER FAILURE
Classified CIRCUIT BREAKER WARNING
DEFINITIONS of ELECTRICAL TERMS
DIRECTORY OF ELECTRICIANS
ELECTRIC METERS & METER BASES
AMPACITY - the LIMITING FACTOR
ELECTRIC PANEL AMPACITY
ELECTRIC PANEL INSPECTION
ELECTRICAL BASICS
Electricity Basics - how it works
Electrical Circuit ID, Map & Label
Electrical Circuits, shorts
Electrical Code Basics
Electrical Conduit Tips
Electrical Definitions
Electrical Grounding Basics
Electrical Outlet-how to add
Electrical Splices, how to make
Electrical Tools & Tests
Electrical Wire Stripping Tips
Electrical Wiring Books & Guides
Electrical Wiring in Old Houses
FEDERAL PACIFIC FPE HAZARDS
GROUND SYSTEM INSPECTION
Why Grounding is Needed
Gas Piping Ground Bond
Table of Ground Wire Sizes
Case History: Double Fault Leads to Loss of Power
Case History:Loss of Neutral Shocks Homeowner
Electrical Service Grounding Checklist
FEDERAL PACIFIC FPE HAZARDS
GROUND SYSTEM INSPECTION
KNOB & TUBE WIRING
LIGHTNING PROTECTION
LOW VOLTAGE BUILDING WIRING
MAIN DISCONNECT AMPACITY
MULTI-WIRE CIRCUITS
RUST in ELECTRICAL PANELS
SAFETY FOR ELECTRICAL INSPECTORS
SE CABLE SIZES vs AMPS
SQUARE-D RECALLS
UNDERGROUND SERVICE LATERALS
VOLTAGE MEASUREMENT EQUIPMENT
ZINSCO / SYLVANIA HAZARDS
More Information
InspectAPedia ® Home & Site Map
Air Conditioning
InspectAPedia Bookstore
Electrical
Environment
Exteriors
Heating
Home Inspection
Insulate Ventilate
Interiors
Mold Inspect/Test
Plumbing Water Septic
Roofing
Structure
Accuracy & Bias Pledge
Contact Us
|
How to Inspect Residential Electrical System Grounds, Ground Wiring, Grounding Conductors, Grounding Electrodes
ElectricAPedia ©
- How to inspect the electrical ground system: wires, grounding conductors, connectors, ground rods
- Case histories of ground system failures, loss of electrical power, electrical shocks
- Class on how to inspect electrical panels
- Home inspection procedures and safety
|
Our site offers impartial, unbiased advice without conflicts of interest.
We will block advertisements which we discover or readers inform us are associated with bad business practices,
false-advertising, or junk science. Our contact info is at
inspect-ny.com/appointment.htm.
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. 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.
Readers of this article should also be sure to review 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.
See Definitions of Electrical Ground, Grounding Electrode, Grounding Conductor, Grounded Conductor, Ground Wire, Neutral Wire, Ground Rod, for definitions of these confusing electrical terms.
© Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Guide to Inspecting Electrical Service Grounding Equipment for Defects
|
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.
|
|
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
- Aluminum - insulated multi-strand
- Aluminum - bare vs. insulated (risk of corrosion, break in wire, loss of safe grounding)
|
Gas Piping May Need to Be Bonded to the Electrical Ground System
|
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.
|
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.
|
Where do Ground Wires Go?
|
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
|
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.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
ELECTRICAL GROUND SYSTEM INSPECTION
Why Grounding is Needed
Gas Piping Ground Bond
Table of Ground Wire Sizes
Case History: Double Fault Leads to Loss of Power
Case History:Loss of Neutral Shocks Homeowner
Electrical Service Grounding Checklist
Also, see details about electrical grounding at Electrical Circuits, shorts, and at Electrical Wiring in Old Houses and at Electricity Basics - how it works.
Electrical Service Grounding Defects & Conditions to Check For During an Electrical Inspection
What 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.
|
|
- 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.
|
|
- 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. |
List of Additional Electrical Grounding System Checkpoints:
|
- 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.
|
- 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
- Spliced ground conductor between the electrical panel and the ground rod or water pipe is improper (the connection may be unreliable)
|
- 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.
|
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 Case History: Double Fault Leads to Loss of Power, it's not safe to rely on just the utility company's ground connection.
- Inaccessible connections to the grounding system (can't be inspected or maintained)
- Grounding wire not found in main electrical panel
- Grounding wire not found in sub panel feeder
- 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
- Main electrical panel enclosure not bonded to grounding system
- Undersized ground wire - see Table of Ground Wire Sizes
|
 
|
- 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 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.
|
- 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.
|
|
- 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.
|
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!
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. |
ELECRICAL PANEL INSPECTION
COURSE SUMMARY
ELECTRICAL INSPECTION SAFETY
ELECTRICAL VOCABULARY
SERVICE DROP
SERVICE ENTRY WIRING
DETERMINE SERVICE AMPACITY
ELECTRICAL GROUND SYSTEM INSPECTION
MAIN DISCONNECT
SYSTEM GROUNDING
DISTRIBUTION PANELS
More Information
InspectAPedia ® Home & Site Map
Electrical
Contact Us
|
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).
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
ELECTRICAL GROUND SYSTEM INSPECTION
Why Grounding is Needed
Gas Piping Ground Bond
Table of Ground Wire Sizes
Case History: Double Fault Leads to Loss of Power
Case History:Loss of Neutral Shocks Homeowner
Electrical Service Grounding Checklist
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.
Technical Reviewers & References
Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to
the material. Content suggestions, technical corrections and content critique are invited for any of the content at our website.
- Daniel Friedman - principal author/editor of the InspectAPedia TM Website
- Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
- Timothy Hemm, Yucala, CA, contributed the photographs of electrical equipment installed in California buildings. Mr. Hemm can be contacted at TimHemm@yahoo.com
- Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
More expert information on this topic
|
ELECRICAL PANEL INSPECTION
COURSE SUMMARY
ELECTRICAL INSPECTION SAFETY
ELECTRICAL VOCABULARY
SERVICE DROP
SERVICE ENTRY WIRING
DETERMINE SERVICE AMPACITY
ELECTRICAL GROUND SYSTEM INSPECTION
MAIN DISCONNECT
SYSTEM GROUNDING
DISTRIBUTION PANELS
More Information
InspectAPedia ® Home & Site Map
Air Conditioning
InspectAPedia Bookstore
Electrical
Environment
Exteriors
Heating
Home Inspection
Insulate Ventilate
Interiors
Mold Inspect/Test
Plumbing Water Septic
Roofing
Structure
Accuracy & Bias Pledge
Contact Us
|
More Information on Electrical Inspections, Building Diagnostic Inspections and Repairs
- * Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
- Aluminum Wiring Information Website Aluminum Electrical Wiring Hazards and Repairs: in-depth authoritative info, photos, documents including selection of proper vs. ineffective repair methods. E.g.: Ideal 65 "Twister" purple connector fails in field and lab testing with aluminum wire.
- Ampacity of an Electrical Service: How to determine the electrical service size or ampacity entering a building
- Circuit Breaker, a bad one fails to trip failure at aluminum bus-to-circuit breaker connection - field report and photographs
- Electrical Panels, How to Inspect in Buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects, defective products. Inspection Class Presentation
- Federal Pacific Electric (FPE) Stab-Lok Circuit Breaker Panel Hazards Website -
Latent fire hazards, in-depth authoritative research, documents, advice on Stab-Lok electric panel and circuit breaker failures and what to do when this equipment is found in buildings.
- Lightning Strike Risk Assessment, Protection Systems & Services
- Multi-wire branch circuit inspection and defects
- Zinsco Electrical Circuit Breaker Failures: overheating, failure to trip, burn-ups involving Zinsco and certain Sylvania electrical panel components - page under development March 2006.
- "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.
- "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.
- "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.
- Rust and Corrosion in Electrical Panels, A Study and Report on Frequency and Cause for Electrical and Home Inspectors at Residential Electric Panels
- Directory of Home Inspectors accessible via internet
- Electrical System & Wiring Hazard Inspection, Detection, Cause, Remedy, Prevention - Main Electrical Page
 InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest. |
The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
|
Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab
| |
Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.
|
Building Inspection, Problem Diagnosis, Forensic Investigation & Testing, Repair Consulting |
|
Contact Daniel Friedman for website content suggestions or for fee-paid consulting
|
|
Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice 
Directory of Professionals to Inspect or Test a Building 
