Here’s eight examples of original electrical equipment that is not acceptable today:

  1. 1)Knob-and-tube wiring - This system, shown below, uses the air space around the wires as an insulator, and porcelain knobs and tubes to turn corners and pass through wall framing. It was abandoned after the mid-1940s. New knob-and-tube wiring is no longer allowed by National Electric Code (NEC). Although the NEC does not require old knob-and-tube to be removed, 4-point inspection forms ask if there is any active knob-and-tube wiring in the home, and insurance companies will not insure the property if there is. You can find out more about this old wiring type at our blog post “What is ‘knob and tube’ wiring?”

  2. 2)Screw-in fuse panels - An example is shown at the top of the page and these panels are also not acceptable to insurance companies. They are now over 60-years old and their interchangeable fuses allow a fuse to be inserted that exceeds the capacity of the wiring.

  3. 3)Aluminum wiring - Aluminum wiring in small conductor sizes (#12 and #10 AWG) was installed in millions of home from the mid-1960s to mid-1970s. Unfortunately, the high rate of expansion and contraction of the metal with temperature changes caused wiring connections to work loose, and numerous electrical house fires resulted. Although special breakers and other fittings were created to solve the problem, many insurance companies will not insure homes with this wiring. We only see it as original wiring in homes from that era, since it is no longer available.
        Multi-strand aluminum wire, however, is approved and still in use for service cables and larger amperage circuits. Built-in twisting of the strand bundles along the cable absorbs the expansion and contraction, and a different aluminum alloy is now standard.

  4. 4)Deteriorated cloth-and-rubber wire insulation - A gum-rubber composition with cloth embedded around it was used for wire insulation up until the mid-1950s, when it was replaced by a thermoplastic material. Over time, and especially in the heat of an attic, the rubber cracks and the cloth deteriorates. Small pieces begin to break away, and exposed electrical wires are both a safety and fire hazard.

  5. 5)Federal Pacific Stab-Lok electric panel - Another product that proved to be faulty over time and is not accepted by many insurance companies, Federal Pacific breakers had an excessive rate of failure to trip when current exceeded the breaker rating, and the company was also found to have submitted fraudulent data to obtain UL-approval of the equipment. To learn more about Stab-Lok panels, visit our blog “Who is the manufacturer of those ‘bad’ electric panels I’ve heard about?”

  6. 6)Three-slot receptacles in two-wire system - Prior to the early 1960s, most house receptacles and lighting was “two wire” and the receptacles had two slots. The 1962 edition of the NEC required all house receptacles to be three slot. The third, rounded slot provided grounding, which greatly reduced the risk of electrical shock from appliances. Because the new appliances that followed had cords with three prongs that would not fit into a two-slot receptacle, some homeowners and handymen changed out the receptacles on two-wire circuits to three-slot even though the third slot was not connected to anything. The required safety benefit of grounding was voided.
        Existing two-slot receptacles in older homes are still acceptable but, when a home has no grounding receptacles, a new problem is created. How do you plug in all those three-prong cords? “Cheater plugs,” like the one shown below, are an easy solution available at any hardware store, but the little clip on them that is supposed to fit under the set-screw of a receptacle cover plate only creates the illusion of grounding, and most people don’t even bother to connect it anyway. We see them often in older homes with not enough three-slot receptacles.

  7. 7)Undersize electric service - An ampere is a unit of measurement of electrical capacity, and it is usually shortened to simply “amp” in common usage. Early electric panels were 30-amps and we haven’t seen one of them in a long time. 60-amp panels followed as electric usage grew. We rarely encounter them anymore, and a 60-amp panel is woefully inadequate for the level of electric usage today. Many 100-amp panels from the 1950s onward are still in use and may be satisfactory, especially for a small home or apartment, or one with a gas water heater and range. But sometimes an older home grows with additions over the years to 2,000 square feet or more, with air conditioning, electric clothes dryer, range, and dishwasher. The original panel is undersize in both electrical capacity and space inside the box to fit all the wiring.

  8. 8)Deteriorated receptacles and switches - Old electric receptacles that are used frequently lose the ability to grab and hold the prongs of a cord. They sit loosely in the slot, making a poor connection that allows arcing that causes burn marks around the slots, like in the photo below. Aging wall switches often have arcing that can be heard when you throw the switch and may function erratically. Both are electrical fire hazards and need to be replaced.

    Another problem we find specifically in homes from the 1930s and earlier, when they have not had an electrical upgrade, is too few wall receptacles for the level of usage today. Only one receptacle per room was required at the time. While we do not call it out for repair, because the receptacles themselves are not defective, it is brought to the attention of the homebuyer. Homes from this era usually have extension cords snaking around the base of the walls behind the furniture because of the lack of sufficient outlets.

    The principle behind all of this is simple: a grandfathered hazard is still a hazard.

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.
© McGarry and Madsen Inspection -


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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.

More blogs about electrical service and distribution:

  1. How come my generator hookup got tagged as defective by the home inspector?

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

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

  4. What are the most common homeowner wiring mistakes?

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

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

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

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

  9. How dangerous is old electrical wiring?

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

  11. Why does the electric company want my house electric system inspected before turning the power back on?

  12. What is a double tap at a circuit breaker?

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

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

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

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

  17. How far apart should kitchen counter receptacles be placed?

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

  19. What are those strange looking wall switches in houses from the 1950s and 1960s?

  20. What is a lock device on a circuit breaker for?

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

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

  23. Can wiremold be used at an exterior location?

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

  25. How can adding wood paneling or a wainscot create an electrical safety hazard?

  26. What are the most common electrical defects found in a home inspection?

  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. Can an electric panel be located over stairs?

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

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

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

  39. Why are extension cords dangerous?

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

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

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

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

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

  45. When were GFCI receptacle outlets first required?

  46. Where are GFCI receptacle outlets required?

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

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

  49. Why is bundled wiring in an electric panel a defect?

  50. Why are some electric receptacles/outlets upside down (ground slot up) in a house?

  51. Why is undersize electric wiring in a house dangerous?

  52. Why is a fuse box an insurance problem for homebuyers?

  53. What is a “backstab” receptacle outlet?

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

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

  56. What are the right words for talking about a house electrical system?

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

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

  59. Can a washer or dryer be located in front of an electric panel?

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

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

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

  63. What is the minimum clearance of overhead electric service drop wires above a house roof?

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

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

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

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

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

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