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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.

8 CIRCUITS13_How_do_I_trace_and_identify_each_circuit_breaker_in_my_electric_panel_to_make_a_circuit_directory_files/CircuitDirectory8.pdf
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More blog posts about electric service and distribution:

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

  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 the right electric wire size for a home?

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

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

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

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

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

  16. Where are smoke alarms required to be located?

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

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

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

  20. What is the 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. Can wiremold be used at an exterior location?

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

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

  25. What is an open electrical splice?

  26. Why is an old fuse panel dangerous?

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

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

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

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

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

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

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

  34. Can an electric panel be located over stairs?

  35. Does a GFCI-receptacle that is not grounded still function properly?

  36. Is a house required to have outdoor electric outlets?

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

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

  39. Can old electric wiring go bad inside a wall?

  40. What could cause an extremely high electric bill?

  41. Why are extension cords dangerous?

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

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

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

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

  46. Why are electrical outlets and plugs polarized?

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

  48. When were GFCI receptacle outlets first required?

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

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

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

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

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

  54. What is a “backstab” receptacle outlet?

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

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

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

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

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

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

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

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

   The reason you want to differentiate between the two types of breakers is that the 240-volt ones are for major appliances, such as a water heater, range, or air conditioner, while the 120-volts are for outlets, lights, and smaller appliances like the refrigerator and dishwasher. This difference will help you know where to look at the beginning of your process of tracing each circuit, and we suggest you start with the 240-volt breakers. 

    The number of the slot for the each breaker will usually be stamped in the metal to the side of opening that the breakers stick through, with odd numbers (1.3,5,7...) on the left and even numbers on the right (2,4,6,8...)

    To start, turn everything on in the house. Then, leave the main breaker on, but turn all the other breakers off. Turn the breakers on one-by-one turn one, starting with the 240 volt breakers. They are marked with the amperage rating on the switch and a 50-amp breaker will likely be for the range, and 30-amp for the water heater. The air conditioning condenser (outside unit) breaker will can be anywhere between 15 and 60-amps, depending on the size of the unit.

    While it will be easy to detect when the range circuit is activated, air conditioning systems require a 240-volt breaker for the condenser and a 120-volt breaker for the air handler (indoor unit) in order to function. So, if you don’t know which breaker is for the air handler, you will have to turn on all the 120-volt breakers temporarily to find the breaker for the condenser. There may also be a 240-volt breaker for the electric resistance heat strip in an all-electric HVAC system.

    The water heater circuit can be hard to verify without a non-contact voltage detector (about $15), also called a tic-tracer. One is shown below checking for current at a receptacle and, when held next to the electric cable serving an appliance, it will indicate with a flashing light and beeping sound when the circuit is live.

    But, if you don’t have one, leave the undetermined 240-volt circuit off for about a half-hour and then test it. Most water heaters will make a small amount of noise, varying from a soft buzz to a rumbling, bubbling sound when turned back on after the water has cooled off a little.

    After you have identified the 240-volt breakers, the 120-volt ones may require a little more patience to find. A tic-tracer is useful, or a plug-in receptacle tester like the one shown below, or even a small lamp or nightlight that you can plug into each receptacle as you walk around. The receptacle tester (about $7) has the bonus feature that it will also check to make sure each receptacle is wired correctly.

   One circuit may serve receptacles in two rooms, and it is not unusual to have one receptacle in a room that is on a different circuit than the other ones. Multiple bathrooms are often on the same circuit, as are garage and exterior receptacles. Although a dishwasher is required to have it’s own circuit breaker, a remodeled older home may have the dishwasher wired to the kitchen counter receptacles circuit.
     If your panel has multiple breakers with stickers next to them that say “MAIN BREAKER,” like in photo below, then you have a split-bus panel. To learn about these unique panels, which were only manufactured in the mid-20th century, see our blog post ”What is a split bus electric panel?” to understand what you are dealing with before you start tracing the circuits. 

   You can make your own circuit directory form, or use one of ours that you can download below. Keep a backup copy, of course, filed away in case the one on the inside of the panel door disappears again. Click on the green box that corresponds to the number of circuits in your panel to download the right form.

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.
©2016 - McGarry and Madsen Inspection  -


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