Electrical Panel Interior Hazards for Electrical & Home Inspectors InspectAPedia® -
Hazards to electrical inspectors that lurk inside the electrical panel
How to spot signs of water leaks into electrical equipment
How to inspect electrical panels for overheating, melting, shorts, arcing - visually
Signs of burned or overheated wires in electrical panels
Identify unsafe or unreliable electrical panel brands, models, or components, FPE, Zinsco, aluminum wiring
How to spot extra-risky equipment or conditions during electrical panel inspections
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This article discusses safety hazards inside residential electrical panels that are of special concern to inspectors and electricians, and suggests safety procedures for the electrical inspector, home inspector, or other professionals who examine residential electrical systems.
These electrical inspection suggestions are not a complete inventory of all electrical safety procedures nor of all electrical components that should be inspected; these notes focus on identification of conditions that may present special electrical hazards for the electrical inspector. Contact Us by email to suggest changes, corrections, and additions to this material.
Fatal Shock Hazard Warning: Inspecting electrical components and systems risks death by electrocution as well as serious burns or other injuries to the inspector or to others. Do not attempt these tasks unless you are properly trained and equipped.
What to Look for Inside the Electrical Panel as Immediate Safety Concerns to the Inspector
Evidence of water entry inside the electrical panel (photo at below right) means that circuit breakers may be corroded and won't trip, connections may be unreliable, neutral or ground connections may be lost, and touching the equipment could be dangerous.
Evidence of overheating, melting, burnups inside the electrical panel (photo at below left) - this was the ground that overheated when there was no neutral connection in the sub panel and neutral and ground buses were improperly bonded.
Evidence of missing bonding or improper bonding (such as ground to neutral in a sub panel) may combine with evidence of overheating (photo above left) to indicate improper wiring, damaged equipment, and unsafe conditions.
The loss of net ural in a garage sub panel (the steel screw bound in the aluminum neutral lug in photo at below right) combined with improper bonding (ground to neutral - red wire in photo at below left) and other conditions to shock an owner when he touched his metal workbench. See Case History:Loss of Neutral Shocks Homeowner for details of this case.
Evidence of burned or overheated wires or damaged circuit breakers, aluminum wiring, faulty equipment, mis-wiring, linking, bus and bonding defects, and many other defects form part of the electrical panel inspection and are described outside of this safety procedures article - see ELECTRIC PANEL INSPECTION
In addition to examining the electrical panel before touching it, looking for dangerous conditions like water, rust, sheet metal screws, rats, and blocking client access, the inspector should also recognize that certain brands or models of electrical equipment are known to be unsafe and may be dangerous to inspect or operate.
Federal Pacific Electric Stab-Lok equipment includes breakers which remain internally "on" when switched "off", as well as too often failing to trip off in response to an overcurrent, and which have been reported to result in electrical arc explosions when manually or otherwise exercised.
Zinsco: Similar bus burnups and electrical arc explosions have been reported regarding Sylvania/Zinsco electrical panels.
Contact Us by email to add field reports of problems regarding these or other electrical products.
Opening the electrical panel to examine overcurrent devices - fuses or circuit breakers, is discussed at ELEC PANEL & GROUND
Inspecting overcurrent devices - visual: see ELECTRIC PANEL AMPACITY and ELECTRIC PANEL INSPECTION for detailed procedures. There is a huge amount of information about the electrical system inside of the electrical panels.
Do not try to "exercise" the breakers in these panels. Turning the circuit breaker on and off in an FPE Stab-Lok panel can actually increase the risk of a future failure to trip. We also have field reports of electrical arc explosions when these breakers have been switched on or off. Some examples are included in this series of electrical safety articles.
The inspector is not required to insert anything, finger, screwdriver, probe, into the electrical panel. The required inspection is visual. Observe. However an inspector is of course permitted to perform other tests or services which s/he chooses to provide (presuming s/he is qualified, trained, and that three are no conflicts of interest).
General Electrical Safety Suggestions describes important basic safety procedures, clothing, and equipment for home inspectors and electrical inspectors.
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Electrical shock injury statistics: www.healthatoz.com - September 2008;
Carson Dunlop, Associates, 120 Carlton Street Suite 407, Toronto ON M5A 4K2Toronto. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
"Frequency of Occurrence and Sources of Rust and Corrosion in Electrical Panels," Daniel Friedman, IEEE HOLM Conference, Philadelphia PA, 1992 - see ELECTRIC PANEL RUST for an online version of this article.
Jim Simmons: Personal communication, J. Simmons to Daniel Friedman, 9/19/2008. Photographs contributed to this website by Jim P. Simmons, Licensed Electrician, 360-705-4225 Mr. Electric, Licensed Master Electrician, Olympia, Washington Contact Jim P. Simmons, Licensed Master Electrician, Mr. Electric, 1320 Dayton Street SE
Olympia, WA 98501, Ph 360-705-4225, Fx 360-705-0130 mrelectricoly@msn.com
Kenneth Kruger: Original author of the sidebar on testing VOM DMM condition: Kenneth Kruger, R.A., P.E. AIA ASCE, is an ASHI
Member and ASHI Director in Cambridge, MA. He provided basis for this article penned by DJ Friedman.
"How to Use DMM's Safely," Leonard Ogden, CEE News, 888 Seventh Ave., New York, NY 10106, Dec 1990 p.10.
Dr. Jess Aronstein, consulting engineer, Poughkeepsie NY, 1991 protune@aol.com
Rex Cauldwell, master electrician and contributor to the Journal of Light Construction on electrical topics
New York State Central Hudson Gas and Electric Company, G&E/1-2/85 consumer safety pamphlet
American Society of Home Inspectors, ASHI Training Manual, Al Alk -[obsolete, and includes unsafe practices-DF]
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
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)
Aluminum Wiring Information WebsiteAluminum 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.
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.
"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.
More Information on Building Diagnostic Inspections and Repairs
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