Here’s our “Top 10” list of the most common electrical defects found at a home inspection, and each of them fits into one of those two categories:

  1. 1)Double Tapped Circuit Breakers - Most breakers in an electric panel are designed to accept a single wire, with the exception of certain ones manufactured by Square D and Cutler Hammer. If you read the tiny print on the side of the breaker, it will say “2 pole” or have a graphic showing two wires, for the breakers that are rated for more than one wire connection. When two or more wires are connected under the lug at a “1 pole” breaker,
    the connection may not be secure or have adequate contact surface. See our bog post
    “What is a double tap at a circuit breaker?” for more on this subject.

  2. 2)Receptacles Wired Incorrectly - There are three wires connected to a modern electrical outlet: hot, neutral, and ground. They are, in order, the black, white, and bare copper wires you see in the back of the box. When they get mixed up or poorly secured by an amateur electrician, you can get reversed polarity, open neutral, open ground, false ground, high resistance to ground, or excessive voltage drop under load. In the photo below, the receptacle is mounted forward of the box. See our blog post “What are the most common problems with electrical outlets?” for details on these defects and their inherent dangers.

  3. 3)Ungrounded 3-Slot Receptacles In An Older Home - This is a particular type of incorrect wiring that deserves its own place on the list because it is so common, and also it is not a mistake. It’s a deception. The NEC (National Electric Code) mandated that electrical outlets go from 2-slot (ungrounded) to 3-slot (with the third, round hole for grounding) in 1960. Some homeowners and less-than-ethical remodelers upgrade to new 3-slot receptacles when renovating an older home, but the ground slot is connected to nothing. An ungrounded receptacle will light make only the center light glow in a three-light plug tester, as shown below. To understand why this is a dangerous defect, see our blog post “Is an ungrounded electric receptacle/outlet dangerous?”

  4. 4)Non-Functional GFCI or AFCI-Protection - GFCI stands for Ground Fault Circuit Interrupter, and a GFCI-device can be integral with a circuit breaker in the electric panel or at the center of a wall receptacle. It provides shock protection for wet areas of the home, such as bathrooms, kitchen, garage, and exterior. Each GFCI-breaker and receptacle has a test button to verify that it is still working. You push the test button, it trips the circuit, then you push an adjacent reset button at a receptacle, or throw the breaker switch back to the “on” position at a panel, to re-energize the circuit. Like any mechanical device it eventually stops working, usually after 10 to 20 years, and requires replacement.
        AFCI is an acronym for
    Arc Fault Circuit Interrupter. This device is integral with some circuit breakers in homes built since 2002, and trips the circuit whenever it recognizes any arcing or sparking in the wiring, as protection against electrical fires. They also have a 10 to 20 year lifespan, and need to be replaced when the test button does not trip the breaker. To learn more about AFCI and GFCI-protection for electrical circuits, go to our blog post “Why do some breakers in my electric panel have a ‘TEST’ button on them?”

  5. 5)Open Splices and Open Electrical Boxes - An “open” wire splice is when a connection of two wires is not protected inside a fire-resistant box, such as a receptacle box or electric panel. An open box (shown at the top of the page) is one that is missing a cover plate to seal the box, often because there are so many wire connections in the box that it cannot be closed. See our blog post “What is an open junction box?” for more on this subject.

  6. 6)Extension Cords - When we see extension cords running along the baseboard around the rooms of home, it actually not so much a defect in itself as a symptom of different problem: too few receptacles. The required spacing for wall receptacles in a home has been set at a maximum of 12-feet since 1956 by the NEC, under the logic that the average power cord for a lamp or appliance is 6-feet long—so, anywhere along a wall with correctly spaced receptacles should have an outlet within reach of a standard cord. Because fewer receptacles were needed in older homes, sometimes have only one receptacle in a bedroom and none in the dining room. Also, when a homeowner encloses a back porch, installing receptacles along the new exterior walls sometimes get forgotten. The worst offender is an extension cord running under a carpet, which is a fire hazard when the cord becomes frayed from being walked over.  When extension cords appear to be a permanent installation in the home, it means more outlets are necessary. See our blog “How far apart should electric receptacles be placed?” for a more detailed listing of spacing requirements.

  7. 7)Unprotected Electrical Cables - Electrical cables below 8-feet above the floor (in other words, within reach) are required to be protected—either inside a wall or running in conduit. The cable running to the bottom of the disposal under a kitchen sink or to a water heater in an older house is often unprotected. If the appliance is connected by a cord to a receptacle, it is not a defect.

  8. 8)Unsecured Cables Entering Electric Panel - Because a loose wire connection can begin to spark at a circuit breaker if it is only slightly pulled away from the connection, it is required that all electric cables be secured where they enter an electric panel. The clamp that is used is called an NM-connector, and when wiring is connected to a panel without an NM-connector, there is the potential for someone climbing through the attic to trip over a cable and yank the connection loose in the panel. The wrong way to connect a cable in a panel is shown below: pop open one of the perforated “knockouts” and just pull it through, with no securing clamp.

  9. 9)Obsolete Equipment - Forgotten, but not gone in some older homes,  screw-in fuse panels and knob-and-tube wiring go unnoticed until an inspector points them out to a homebuyer. See our blog posts “What is knob and tube wiring?” and “How dangerous is old electrical wiring?” to find out more.

  10. 10) Improperly Wired Subpanel - Any electric panel downstream from the main service panel is defined as a subpanel, and must be wired a little differently from the first panel: neutral and ground wires should be on separate bus bars, with the neutral bar isolated. Also, many subpanels are “backfed,” meaning that the power comes into the panel through a breaker located in the same column with the other breakers feeding power out. While a backfed panel is acceptable, the backfeed breaker must be clearly marked as “MAIN” breaker and mechanically secured to the box. The red plastic clamp shown in the photo below is an example of correctly securing a backfed main breaker. And the photo below it shows a subpanel bus bar with neutral and ground wires on same bus, along with multiple neutrals under one lug, both of which are not allowed.

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
©2015 - McGarry and Madsen Inspection. -


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More blog posts about electric service and distribution:

  1. What is the best emergency back-up generator for the power outage after a storm?

  2. How can I tell if the electric outlets are grounded?

  3. Is the electric panel big enough for this house?

  4. The electric panel is marked “Trilliant” and it’s all grey plastic. Is it alright?

  5. Why do you pay so much attention to electrical safety?

  6. How do the new tamper-resistant electric receptacles work?

  7. Why does that wall plug have push-buttons in the middle?

  8. Does this place have one of those “bad” electric panels I’ve heard about?

  9. What is the life expectancy of a circuit breaker?

  10. What is a split bus electric panel?

  11. What is the right electric wire size for a home?

  12. My circuit breaker won’t reset. What’s wrong?

  13. Is a bare bulb light in a closet alright?

  14. What is reversed polarity at an outlet/receptacle? Why is it dangerous?

  15. My bathroom electric receptacle/outlet is dead, and there is no tripped breaker in the electric panel. What’s wrong?

  16. What is a “missing twistout” at an electric panel?

  17. Where are smoke alarms required to be located?

  18. What is the switch on the wall with only two pushbuttons for?

  19. How far apart should electric receptacle outlets be placed in a garage?

  20. Will the electric company remove branches rubbing against the overhead service lines to my home?

  21. What is the lock device on a circuit breaker for?

  22. Can multiple neutral or ground wires be secured under the same terminal in an electric panel?

  23. Can wiremold be used at an exterior location?

  24. Why are Zinsco and Sylvania-Zinsco electric panels a problem?

  25. What is the life expectancy of electrical wiring in a house?

  26. What is an open electrical splice?

  27. Why is an old fuse panel dangerous?

  28. What does it mean when a wire is “overstripped” at a circuit breaker?

  29. What is the difference between “grounded” and “grounding” electrical conductors?

  30. What is the difference between a Combination Arc Fault Circuit Interrupter (CAFCI) and an Arc Fault Circuit Interrupter (AFCI) circuit breaker?

  31. How can I tell if a receptacle/outlet is tamper resistant?

  32. What is a Dual Function Circuit Interrupter (DFCI)?

  33. Will a GFCI receptacle that is not grounded still function properly?

  34. Does a home inspector remove the electric panel cover plate and examine the inside of the panel?

  35. What are the most common defects with over-the-range microwaves?

  36. Can an electric panel be located over stairs?

  37. Is a house required to have outdoor electric receptacles?

  38. What are the code requirements for NM-cable (nonmetallic-sheathed cable or Romex®) in an attic?

  39. How can I change a 240V circuit to a 120V circuit?

  40. Can old electrical wiring go bad inside a wall?

  41. What could cause an extremely high electric bill?

  42. How do I trace and identify each circuit breaker in my electric panel to make a circuit directory?

  43. Why are extension cords dangerous?

  44. What problems does having too many electrical outlets on a single circuit cause?

  45. How can I find out the size of the electric service to a house?

  46. What happens when you press the “TEST” button on a circuit breaker in an electric panel?

  47. How many electric receptacles (outlets) are required in a hallway?

  48. Why are electrical outlets and plugs polarized?

  49. Why does painting an electric receptacle (outlet) make it unsafe?

  50. What is the difference between GFCI and AFCI circuit breakers?

  51. What causes flickering or blinking lights in a house?

  52. What electrical hazards does a Ground Fault Circuit Interrupter (GFCI) not protect against?

  53. What is the color code for NM cable (Romex®) sheathing?

  54. What does “listed” and “labeled” mean for an electrical component?

  55. What does it mean when I find buried yellow "CAUTION" tape when digging a hole in the yard?

  56. How far away should a sink be from an electric panel?

  57. What are the requirements for NM-cables entering an electric panel box?

  58. How can I tell if the electrical service is 3 phase or single phase?

  59. What is the building code requirement for receptacle outlets at stairs and stair landings?

  60. Can a home surge protector be installed loose in the bottom of an electric panel box?

  61. Can a bare bulb “lampholder” light fixture be installed outdoors?

  62. Can you add circuit breakers by different manufacturers to an electric panel if they fit?

  63. When did arc fault circuit interrupter (AFCI) breakers first become required?

  64. What is the difference between an electrical receptacle, an outlet, and a plug?

  65. Should I buy a house near a high-voltage power line?

  66. When should I replace electric receptacle outlets?

  67. What is a “while-in-use” weatherproof electrical receptacle outlet cover?

  68. What causes copper wires to turn green or black in an electric panel?

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We want you to be an informed homebuyer, and each blog post is a question that we have answered for our friends and customers over the years. Hope they help you make a good choice for your next home.

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