How to Inspect Residential Electrical Systems, Panels, Grounding, Wiring

ELECTRIC PANEL INSPECTION - CONTENTS
- Electrical Panel inspection procedures

Electrical Panel Inspection Safety - separate article
Removing Electric Panel Covers - separate article
Electrical Panel Cover Screws - separate article
ELECTRICAL PANEL INTERIOR HAZARDS - separate article

Questions & Answers about visual inspection of electrical panels, panel installation, defects, repairs
References

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Electrical panel inspection guide: This electrical wiring article discusses 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. We include questions and and answers about common defects in electrical panels that may be discovered by visual inspection, that is, without performing electrical tests.

COURSE SUMMARY - Electric Panel Inspection Course Summary

SAFETY WARNING: Inspection of electrical systems risks death by fatal electrical shock. The procedures discussed in this class require that the cover of the panel be removed in order to expose the panel interior. Homeowners should not attempt this step, and no one lacking proper electrical safety training should remove the electrical panel cover nor attempt to perform the tasks discussed in this class.

ELECTRICAL CODE COMPLIANCE WARNING: these inspection procedures are designed to assist in the detection and reporting of electrical service defects which can be recognized by visual inspection. This inspection is not for the purpose of determining compliance with local or national electrical codes. Guidelines given here, such as overhead wire clearances, are based on widely-accepted codes and standards, but local building codes may specify other or different restrictions.

This material was first 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, April 2009, August 2011.

Readers of this article should also be sure to review Safety Hazards and Safe Electrical Inspection Procedures for Inspectors examining Residential Electrical Systems and should pay special attention to the following chapters from that article: Electrical Panel Interior Inspection - Removing Electric Panel Covers - Electrical Panel Cover Screws - Electrical Panel Interior Hazards - Testing Main Breakers or Fuses and Inspect Breakers, Fuses. Carson Dunlop's sketch at page top shows where the electrical inspection starts at a residential property.

Part I - Electrical Panel Defect Identification - Principles

Safety Procedures for Electrical Inspectors
Electrical Power Delivery System
Common Electrical Panel and Wiring Defects

Part II - Electrical Panel Defect Recognition - Photos of Electrical Defects & Examples

This section of the class contains annotated field photographs of certain electrical panel defects which can be recognized by visual inspection.

That is, no instruments, no measurements, and no insertion of any device into the electrical panel are required to perform these tasks. I have these photos on file and will add them to this presentation if readers request

ELECTRICAL INSPECTION SAFETY - Overview of the Residential Electrical System and Electrical Inspection Hazards

The Electrical System Function is to power home systems/appliances, providing safe distribution of electrical power throughout the building.
Costs: operation, repair, updating/expansion

Safety Procedures for Residential Building Electrical Inspectors

Electrical Panel Inspection Safety - Critical Warnings

Watch out: Do not:

touch electrical equipment if you can see evidence of existing dangerous conditions (such as the missing electrical grounding electrode shown at left)
touch SEC or other wires
insert probes/tools into panel
remove suspect panel covers. Later we explain that visual clues of water, leaks, short circuits, spring-loaded panel faces, all present possible electrocution hazards that can occur merely from touching or attempting to remove the panel cover).
touch electrical equipment from unsafe location (wet, off balance, grounded - current flows from a hot wire through you, etc.)
continue to touch or inspect the panel if you feel a charge, tingle, shock
stand in water or in wet conditions while touching electrical equipment

Watch out: Protect nearby observers, clients, etc. from hazards [added by DF 2/13/2006]

Do not permit observers to touch the inspector while that person is working on or at the electrical panel.
Do not permit observers to touch the electrical panel nor to insert any tool, pencil, or other object into the panel.
The inspector should stand with his/her body between observers and the panel, and should be prepared to physically block an attempt by the observer to reach towards or touch the electrical panel while its cover has been removed.
Explain, calmly and without exaggeration, but accurately, the shock and fire hazards to observers and instruct the observers on what to do if the inspector him/herself is being shocked by the panel.
[Don't touch a person being shocked. If a wooden board or stake is nearby, one might attempt to push the inspector away from the panel using that device or to turn off the main breaker or fuse. Call for help immediately.

Open electrical panels are dangerous (C) Daniel Friedman

Safety Warning: Do not attempt to work on your electrical wiring, switches, or outlets unless you are properly trained and equipped to do so. Electrical components in a building can easily cause an electrical shock, burn, or even death.

Even when a hot line switch is off, one terminal on the switch is still connected to the power source. Before doing any work on the switch, the power source must be turned off by setting a circuit breaker to OFF or removing a fuse. See SAFETY for ELECTRICAL INSPECTORS and Electrical Wiring Books & Guides

Frequently Asked Questions (FAQs) about visual inspection of electrical panels, panel installation, defects, repairs

Question: can an electrical panel be mounted upside down?

Can a circuit breaker panel be installed upside down and still pass national and local electrical code inspections? - Mike

Reply: Circuit breakers that operate vertically should be mounted so that "up" is "on" and "down" is "off"

How to Mount an Electrical Panel: Panel Position and "upside down" electrical panel code provisions:

Mike:

According to a number of electricians forums we reviewed, contemporary electrical panel circuit breakers will function correctly in any position, and there are quite a few electricians who mount panels "upside down" with the mains at panel bottom, in particular if the SEC cables are entering from the bottom of the unit. Just be sure that all panel labels including MAINS are properly oriented and legible so that the homeowners are not confused about which breaker controls which circuit.

There may however be both code (NEC) and user issues about breaker positions: in particular about clear "off" and on positions of circuit breakers in some electrical panel designs.

If the electrical panel MAINS switch operates "side to side" then you can mount the panel with either end "up" but if the MAINS switch operates "up and down" then putting the panel "upside down" would mean that "off" would be "up" - which is unsafe because that's not how most users think about switch on and off positions.

Perhaps part of the "off is down" convention derives from older knife-switch mains that were installed with "off = down" because of a concern that in the opposite position a worn or loose knife switch might fall from "off" (up) into on (down) in a panel - an unsafe condition.

See NEC 404.7. Also see NEC 240.81. That provision requires vertically-operating circuit breaker switches to be mounted so that "Up" is "On and "Down" is in the "Off" position.

Question: How do we know if an electric panel fuse has blown?

How do you know if say a solid type 40 amp four inch fuse on the condenser outside fan is blown? - Bruce

Reply: swap in a new fuse; remove the fuse and test it for continuity.

Bruce you're right that it may be impossible to tell that a cartridge type fuse is "blown" by simple visual inspection, unless by chance the fuse is discolored or deformed.

By contrast, round Edison-based fuses include a glass window through which you can observe the melted fusible link if that type of fuse has "blown".

In some countries cartridge type fuses actually use a re-usable cylinder into which a fusible link is inserted, can be removed, and can be inspected.

But a blown cartridge fuse will not conduct electricity from one end to the other - one could test such a fuse OUT OF THE PANEL (not in place in the panel, for safety reasons) using a multimeter or VOM in the Ohms setting.

Most homeowners simply swamp in a new fuse and see if that restores power.

Question: Is it safer to turn off all of the circuit breakers when inspecting an electrical panel?

If i want to visually inspect the wires behind the panel cover, could i just turn off all breakers to reduce the chances of shock if the panel hits a hot wire? Thanks!- JMW

Reply: Yes, ... and not exactly - electrical panel inspection tips

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem or spot an unsafe condition at the electrical panel, even before it is touched (see Touching Electrical Equipment).

Beginning at Electrical Panel Interior Inspection I've already called out evidence of water entry or rust (ELECTRIC PANEL MOISTURE), loose panel components, amateur workmanship, hazards just in removing the electrical panel cover (Removing Electric Panel Covers) and even arc burns or the heads of sheet metal screws affixing the panel cover (Electrical Panel Cover Screws) as red flags that mean that even touching the panel (Touching Electrical Equipment), much less opening it or removing its cover, must be approached with extra care.

That said, here are some things to consider: Once an external inspection of the electrical panel, surrounding wiring and devices, and the panel cover and even other site clues of amateur workmanship or poor maintenance have been considered, if you turn off the main circuit breaker to the panel it should de-energize all of the circuits below, making it unnecessary (and probably a mistake) to turn off individual circuit breakers.

Watch out: because there are serious safety hazards and risk of injury or death to the inspector or bystanders during an electrical inspection, be sure to review SAFETY for ELECTRICAL INSPECTORS

Watch out: turning off the main circuit breaker in an electrical panel will not de-energize the main service entry lugs nor possibly other electrical panel components so potentially fatal electrical shock hazards remain.

Watch out: do not turn off circuit breakers at an electrical panel that is in use supporting an active, occupied building. There are risks of disabling or even damaging computer equipment and also certain medical equipment that might be kept running to support the health, safety, even life of building occupants in some situations.

Watch out: in certain electrical panels such as FPE Stab-Lok equipment, operating the circuit breakers by switching them on and off can actually increase the risk that later the breaker may fail to trip in response to an overcurrent, risking a buildng fire. See FEDERAL PACIFIC FPE HAZARDS

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Electric Service Installation Manual, A guide for successful installation of residential, commercial and industrial electrical services, 5th Ed., Hawaiian Electric Company Hawaii Electric Light Company Maui Electric Company,A guide for successful installation of residential, commercial and industrial electrical services, original web search 08/15/2011, source: http://www.heco.com/vcmcontent/Energy%20Services/
Business%20Services/Customer%20Installations/ESIM_manual.pdf
* 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 System & Wiring Hazard Inspection, Detection, Cause, Remedy, Prevention - Main Electrical Page at InspectAPedia
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.
Multi-wire branch circuit inspection and defects
Rust and Corrosion in Electrical Panels, A Study and Report on Frequency and Cause for Electrical and Home Inspectors at Residential Electric Panels
"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.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

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)
"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.
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