The ambient temperature of the area where the wiring will be installed, the length of the wire run, along with the category of wiring used, may require an upward adjustment to these sizes. But they are a rule-of-thumb guide that we use in our inspections when checking the size of wiring connected to circuit breakers in an electric panel.  Many, but not all, larger wires have the size number embedded in a repeating strip of specification lettering along the side. However, we don’t recommend that a homeowner remove the dead front (cover plate) of an electric panel to check the wiring or any other reason—for their personal safety. Examining a “live” electric panel is best left to a professional.
   The size number is followed by the letters “AWG,” which stands for American Wire Gauge. We recognize the smaller #14, #12 and #10 wires by sight, and an experienced inspector can scan a panel rather quickly. Undersize wires—a #10 wire (too small) connected to a 60-amp breaker, for example—means the wire will overheat if these is too much current flow and possibly ignite a fire without the circuit breaker tripping. Conversely, a #8 wire (larger than required) connected to a 30-amp breaker is not a problem. In fact, a one-size larger wire is often necessary to avoid a voltage drop problem when the length of the wire run is long, such as from a main panel in a home to a subpanel in a detached barn.

   Multi-strand aluminum wiring is sometimes used for service cables or major appliance circuits, like a range or heat strip in an air handler, and is an acceptable alternative to copper for some circuits. Because it is a little more resistant to the flow of electricity, the wire size required is typically one size larger than the same circuit in copper. Also, an anti-oxidant paste must be applied at wire connections when using aluminum wiring.

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 Blog Posts About Electric Panels and Distribution:

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

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

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

  4. Can an electric panel be mounted sideways-horizontally?

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

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

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

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

  11. How dangerous is old electrical wiring?

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

  13. What are the most common homeowner wiring mistakes?

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

  15. What is a three-way switch?

  16. I heard that aluminum wiring is bad. Do you check for it?

  17. How far apart should the electrical receptacles be placed?

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

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

  20. What is an “open junction box”?

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

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

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

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

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

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

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

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

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

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

  31. Can wiremold be used at an exterior location?

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

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

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

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

  36. What is an open electrical splice?

  37. Why is an old fuse panel dangerous?

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

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

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

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

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

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

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

  45. Can an electric panel be located over stairs?

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

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

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

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

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

  51. Why are extension cords dangerous?

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

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

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

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

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

  57. When were GFCI receptacle outlets first required?

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

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

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

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

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

  63. What is a “backstab” receptacle outlet?

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

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

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

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

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

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

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

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

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

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

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

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

  76. Why is it unsafe to bond neutral and ground wiring at subpanels?

  77. Are wall light switches required to be “up” for “on” and “down” for “off”?

  78. What is the maximum number of circuit breakers allowed in an electric panel?

  79. Why do home inspectors get so picky about calling out minor electrical safety defects?

  80. Which house appliances need a dedicated electrical circuit?

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

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