Should you Pull a Main Fuse or Test a Main Circuit Breaker? - Procedures for Electrical Inspectors & Home Inspectors InspectAPedia® -
Special hazards are faced when pulling a main fuse block even though this is a device intended for emergency use by a homeowner
Special hazards are faced when switching on or off a main circuit breaker
Should I pull the main fuse or switch the main circuit breaker?
Standards for Electrical System Inspections
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This article discusses safety hazards at residential electrical panels when the main fuse is pulled or main breaker is switched. While we recommend that a professional inspector check these devices in some circumstances s/he should not do so, and extra care is always needed. These articles suggest safety procedures for the electrical inspector, home inspector, or other professionals who examine residential electrical systems.
Readers of this article should also see
Touching Electrical Equipment and also
Safety for Building Inspectors
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.
Homeowner advice for electrical panel safety: These safety suggestions are for professional inspectors and are not a guide for homeowners. Homeowners should not remove the cover from an electrical panel - it is unsafe to do so. Homeowners should look at their electrical equipment for signs of trouble and should contact a licensed electrician to address any concerns that arise. Without removing the electrical panel cover, but by opening the hinged electrical panel access door, homeowners can access the main circuit breaker or fuse, as well as individual circuit breakers and fuses. These devices may be turned on or off by the homeowner as safety or other needs require.
Testing Main Circuit Breakers or Main Fuses in Electrical Panels
8.1.D. [The inspector shall observe] branch circuit conductors, their overcurrent devices, and the compatibility of their ampacities and voltages
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. See FEDERAL PACIFIC FPE HAZARDS for details.
Zinsco: Similar bus burnups and electrical arc explosions have been reported regarding Sylvania/Zinsco electrical panels. See ZINSCO / SYLVANIA HAZARDS for details.
Contact Us by email to add field reports of problems regarding these or other electrical products.
8.3.B. [The inspector is NOT required to] test or operate any overcurrent device except Ground Fault Circuit Interrupters
I continued to put my arm behind my back and close the breaker with my left hand with my head turned to the left.
BAM, a light as bright as the sun and an explosion.
This knocked us down and blinded us.
We were rushed to the hospital. I spent the night in the ER with an ICU nurse and was off of work for 3 weeks and have had to have a stronger prescription.
These FPE panels are all over the building
Pulling fuse blocks: At one inspection the author pulled the main fuse block in a 60-Amp
panel, only to have the pullout block disintegrate in his hand.
The
failure left one fuse in place and one half out of the panel.
"What
did you just do to the panel?" asked the client (from a safe distance).
"I destroyed it." was the answer.
With permission of the owner, and following accepted home inspection practice of exercising normal user controls intended for use by the homeowner, the home inspector was performing
a normal, if uncommon operation which a homeowner would be expected to do, for example, during an emergency or other need to shut off
electrical power to the building.
At a minimum one would have had to
perform this operation during an emergency or if the panel were to
be worked on.
The client wanted to know if the fuse pullout disintegration was normal. [No.]
The inspector wanted to know if he was going to pay for a new panel. [No.]
A new panel was needed as the service and equipment were obsolete, not because
the fuse pullout needed replacement. But we pose that it may be difficult to find a replacement fuse pull-out for some older fuse panels.
If you had not pulled the fuse shown at lower right in this photo, something interesting would have been missed.
Is that smaller fuse unsafe? No, installing a smaller fuse means that the overcurrent device will open the circuit under less current flow.
What about the other wiring in the panel? There is an unsafe open splice at the right side of the panel.
Are some of the edison-base fuses oversized? Can't tell for sure from the photo. In older fuse panels people are too often tempted to get around a frequent problem with blown fuses by installing an over-sized fuse - this is an unsafe action and is a fire hazard. Be sure that fuses in the panel are matched properly to the wire size.
#14 copper wire wants a 15-Amp fuse.
#12 copper wire circuits can be fused with at 20-Amp fuse.
More Reading: Electrical Panels, How to Inspect in Buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects,
General Electrical Safety Suggestions describes important basic safety procedures, clothing, and equipment for home inspectors and electrical inspectors.
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Additional technical contributors & reference sources for this article are listed below.
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 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
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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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