Fuse panel with improper fusing 
(C) Daniel Friedman Should you Pull a Main Fuse or Test a Main Circuit Breaker? - Procedures for Electrical Inspectors & Home Inspectors
     


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Electrical Main Fuse/Breaker Inspection: should you ever pull the main fuse or switch off the main circuit breaker in the electrical panel? 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.

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Testing Main Circuit Breakers or Main Fuses in Electrical Panels

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.

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

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.

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

Fuse panel with improper fusing (C) Daniel Friedman

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,

ELECTRICAL INSPECTOR SAFETY PROCEDURES describes important basic safety procedures, clothing, and equipment for home inspectors and electrical inspectors.

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