It is possible to test an ungrounded 2-slot receptacle for grounding of the box to see if an adapter would actually function properly, by using a “wiggly” tester, like the one shown below. They are available at most hardware and home-improvement stores. After confirming that the receptacle is live by placing a lead in both the hot and neutral slots so that the wiggly lights up, leave one lead in the hot slot (the smaller slot) and put the other lead on the center screw. If there is a ground connection, the pen will light up. Some wiggly testers have only a red light, but the one shown has two lights that so that it can differentiate between voltages.

  But, again, you will very rarely get the wiggly to light up at a two-slot receptacle. So hardware store adapter plugs essentially make a safe two-slot receptacle into an unsafe three-slot receptacle. They are a safety hazard that we regularly write up in inspection reports on older homes.

    A modern receptacle has a third bare-copper wire for grounding embedded in the electric cable serving it. Running a new ground wire back to the panel when upgrading an old receptacle to three-slot is difficult-to-impossible. But there is a code-approved alternative: install a three-slot GFCI-receptacle. The shock protection provided by a Ground Fault Circuit Interrupter receptacle (the kind with a TEST and RESET button in the center) is considered an acceptable alternative to grounding. The only additional step required is to apply a small sticker that says “No Equipment Ground” to the cover plate, which comes in the package with all GFCI-receptacles.

   This solution is only acceptable when replacing a receptacle and leaving the existing, older wiring in place. Any new wiring must be three-wire (grounded).

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.


More blogs about electrical service and distribution:

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

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

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

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

  3. What are the most common homeowner wiring mistakes?

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

How do the new tamper-resistant electric receptacles work?

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

  2. What is a three-way switch?

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

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

  1. What is knob-and-tube wiring?

  2. What is a split bus electric panel?

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

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

  5. Why does the bedroom have a light switch but there is no light in the ceiling?

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

  7. How can I figure out what a mystery wall switch does?

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

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

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

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

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

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

  14. Can wiremold be used at an exterior location?

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

  16. What is a false ground, bootleg ground, or cheated ground receptacle?

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

  18. What is an open electrical splice?

  19. Why is an old fuse panel dangerous?

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

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

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

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

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

  25. Can an electric panel be located over stairs?

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

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

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

  29. What could cause an extremely high electric bill?

  30. Why are extension cords dangerous?

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

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

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

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

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

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

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

  38. What is a “backstab” receptacle outlet?

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

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

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

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