How To Look At A House
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Why do home inspectors get so picky about calling out minor electrical safety defects?
Thursday, July 5, 2018
The big disaster that can result from improper installation of electrical wiring is fire, or explosion followed by fire. Then there’s also electrocution, a terrible way to die. America’s first electrical safety code was published back in 1897 by the National Board of Fire Underwriters, because the insurance industry was alarmed at the number of claims due to house fires started by unsafe wiring. That early code evolved into the National Electrical Code (NEC) in 1911, which has been updated every three years since by the National Fire Protection Association (NFPA).
The authors of the NEC evaluate potential electrical hazards based on the risk of damage, likelihood of occurrence, and the possible severity. What their investigators have found over the years, however, is that most major incidents that result in fire or death are the result of a chain-reaction of multiple minor defects that align to create a “perfect storm” of destruction. Which brings us to why home inspectors like us are so darn picky about small defects that seem more annoying than dangerous. The one shown at the top of the page seems harmless enough: an electric panel box (shown with the dead front cover plate removed) that is set back a little behind the surrounding wall.
It is a recessed type panel, meaning that the panel box sits inside the wall with a dead front plate that screws to the font of the box to seal it. The dead front is wider and taller that the box dimensions, to cover up any small gap in the wall opening around it. It also has tightly-fitted openings in the center (called knockouts) for the breaker switches to peek through. The dead front is supposed to mount flush with both the front of the panel box and the adjacent wall when closed. This is because the electric panel assembly needs to be inside a fireproof box that will contain any arcing or sparking that might occur, thereby preventing a fire from spreading to the flammable wood around the box.
No gap is allowed by the National Electrical Code between the front of a panel box and the wall surface that the dead front of a recessed panel will sit against in a regular wood stud (combustible) wall structure. Also, the NEC says the gap around the sides of the box cannot exceed 1/8” (NEC 312.3 and 312.4). This panel enclosure above fails on both counts: it is almost an inch inset from the wall surface and the drywall was also cut back too far around the box. When the dead front snugs to the wall, there is an opening between it and the box all the way around the panel perimeter. Any fire in the box has a quick route to escape.
Okay, maybe this is not a horror by itself. But combine it with a couple of the following other defects and you have the makings of a house fire:
Paper tags labeling the circuits, or other flammable material in box.
Aluminum wire connection at service lug with heavy oxidation and getting super-hot, as shown in upper photo with an infrared overlay.
Loose wires near breaker connections.
Wires overstripped at breakers
There’s plenty more, but these are just the first ones that come to mind. Douglas Hansen lists another example in his excellent book Electrical Inspection of Existing Dwellings (Code Check, 2013): reversed polarity plus a false ground at an receptacle outlet. Individually not such a big deal, but deadly in combination for an electrical shock.
All of the citations in the NEC are there to prevent electrical mishaps, and we try to catch as many of the seemingly small defects as we can during an inspection.
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To learn more strategies for getting the best possible home inspection, here’s a few of our other blog posts:
To read about issues related to homes of particular type or one built in a specific decade, visit one of these blog posts:
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