While backfeeding a panel in itself is not unsafe, it becomes unsafe when there is no foolproof safety device to lock-out the electric utility service when the panel is being backfed by a generator. Sometimes we see printed
instructions posted on the panel to first turn off the main breaker before turning on the generator breaker. But printed warnings are not sufficient. Connecting a generator directly to the electrical system of a building in this manner has the potential to feed through the building’s electrical system to the outside utility service lines, and can kill or injure a person repairing service lines if the instructions are overlooked--which is easy to do in the clamor and confusion after a major storm event.

    Also, if your electric utility’s line crew restores electrical service while the generator is connected to the incoming utility service, you could start a fire or seriously damage the building.

   One safe solution to this problem is shown in the photo above. The metal plate slides up-and-down between the lower breaker (main electric service breaker) and the upper breaker (backfed generator breaker) in a way that makes it mechanically impossible to have both breakers in the “ON” position at the same time.

   Another solution is a separate subpanel that feeds only selected circuits in the home, with a double-pole double-throw transfer switch to connect the generator panel to the building’s electrical system. Connections must also meet the local ordinances and building codes. A minimum of #10 AWG wire is typically required. An example of one is shown below.


   And a third solution is an automatic transfer switch, like the type that often come installed with larger, permanently-mounted generators providing 12,000 watts or more of power.

   The most important thing is to have a qualified, licensed electrician do your generator connection system installation. They will know the right way to do it to keep you and your family safe in the aftermath of a storm or other power outage event.


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 on Similar Subjects:

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

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

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

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

  5. Is there an adapter that can be placed on a two-slot receptacle to make it safe?

  6. What are the most common homeowner wiring mistakes?

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

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

  9. When should I replace my smoke alarms?

  10. How dangerous is old electrical wiring?

  11. My GFCI reset button is hard to push and won’t reset. What’s wrong?

  12. What’s my chance of getting a high radon reading at a house in Gainesville?

  13. What do you look for when inspecting stairs?

  14. What is a split bus electric panel?

  15. What is a ground wire?

  16. What do you check when you inspect an electric garage door?

  17. Do you check the wall plugs?

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

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

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

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

  22. Why is the circuit breaker stuck in the middle?

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

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

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

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

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

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

  29. What is an open electrical splice?

  30. What does it mean when a wire is “overstripped” at a 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. Is a house required to have outdoor electric receptacles?

  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. What could cause an extremely high electric bill?

  40. Why are extension cords dangerous?

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

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

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

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

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

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

  47. What is a “backstab” receptacle outlet?

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

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

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

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

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

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

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

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

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

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

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

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

  60. Which house appliances need a dedicated electrical circuit?

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

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