Non-standard sheet metal screws, loose screws, pierced electrical cables, & related safety warnings
Distractions are safety hazards especially at the electrical panel
Safety procedures for home inspectors & electrical inspectors
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This article discusses safety hazards involving the screws used at some electrical panels and suggests safety procedures for the electrical inspector, home inspector, or other professionals who examine residential electrical systems.
Safe electrical inspection procedures and safe use of
volt meters, DMMs, multimeters, and similar electrical test equipment
is discussed at the end of the article.
Looking: Look carefully for evidence of burning, arcing, or other damage before touching or
moving components. Eg.: sharp sheet metal screws in panel covers may short hot wires.
Unsafe Electrical Panel Screws: the electrical panel cover screws have been replaced with sharp pointed sheet metal screws
Electrical Panel Access, Rats & Other Distractions: (distractions from being careful) there are rats at your feet, or there is a rats nest of wires or other obstruction to safe cover removal - watch what you say.
At an inspection the author had encouraged a nervous buyer to accompany him into an ugly dark muddy basement to inspect the mechanical systems.
The client, a woman not properly dressed for an inspection, wore high heels and a tight skirt.
She was wobbling in the dirt floor in a dark crowded corner of the basement, terrified and already shaking in the dim light. The author, encountering a maze of wires in the way of the electrical panel, forgot to edit his thoughts, and muttered aloud: "geez what a rats nest."
The client screamed "RATS!!!" and ran terrified from the basement, falling towards the dark stairs.
Distractions during an electrical inspection are themselves dangerous. A NE ASHI inspector reported that
As I just touched an electrical panel cover screw with my Milwaukee screwdriver I saw a tremendous flash of light - as bright as the sun. I was certain I was dead. As moments passed I realized I was still standing there, alive. Am I alive? I asked myself. I learned that from behind me and my client, the real estate agent had chosen that moment to take a flash photograph of the proceedings. - to DF Randolph MA 09/2008
This distraction is more risky than it may appear. A sudden flash, a sudden shout or movement, could cause an inspector to lurch, touching an electrically live and dangerous component. It is important for the inspector to learn and practice calm, steady movements and to resist distractions.
How to Look for Unsafe Panel Cover Screws & for Evidence of Burning and Arcing When Approaching the Electrical Panel
Look at the electrical panel before touching the electrical panel cover; is there evidence of a problem such as
Arcing, Overheating or Burnups: you see evidence of electrical failures such as burned or overheated components. In the photo at left the ground wires are clearly overheated - something is wrong. In this case a homeowner was badly shocked when he touched his metal workbench. See Case History:Loss of Neutral Shocks Homeowner for details.
The pair of photos just below shows at left, electrical arc flashover soot, and at right, the repair - tape on the electrical wire, but the wire is still too close to the screw mounting hole for the panel cover.
Look for improper and unsafe electrical cover screws, sharp pointed sheet metal screws, and look for electrical cables that pass too close to the screw openings in the electrical panel.
Sharp sheet metal screws: If you find that a sharp-tipped sheet metal screw has been used (usually to replace a lost original fastener) you should
be alert for pierced, damaged, short-circuited wires in the panel - both during removal and during panel cover replacement.
We will
not reinstall a sharp-pointed screw in a panel cover if wires are crowded close to the screw opening. Having seen more than one shorted
and burned panel from precisely this cause, we warn clients about this unsafe detail. It is trivial to correct.
It's an easy fix: use a blunt tipped screw, or file off the sharp point of the SMS.
Before re-installing the cover of the electrical panel, check to assure that no electrical wires have moved close to the panel cover screw mounting holes where they might be pierced or damaged.
General Electrical Safety Suggestions describes important basic safety procedures, clothing, and equipment for home inspectors and electrical inspectors.
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Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Electrical shock injury statistics: www.healthatoz.com - September 2008;
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.
"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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