When Electrical Power is Lost to Half the Circuits

By Dave Rongey - Summary:

Electrical Panel and Circuit Problems: Part of my house power is out. I checked outlets and no power was found.

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Home Electrical Power Failures

Electrical Question: Part of my house power is out. I checked outlets and no power was found.

  • I went to the breaker box and tested power coming out of each breaker and found that every other one had power and and every other one didn’t have power. This included testing the 4 breaker main switches, which 2 of the 4 had power and 2 didn’t.
  • I removed the breakers from the panel and ohm tested them. Two breakers seemed to work properly (open then switch to closed). Two showed very little chance or difference which ever position the switch was in.
  • I switched the wires from one to the other and different power worked. So it seems the breakers are bad. However this seems very strange to me that the would go bad.
  • The whole panel and breakers are only 8 yrs old.

Any thoughts or further ideas would be great.

This electrical question came from: Travis, from Orange, California.
See more about Home Wiring for California

Additional Comments: Great site and it did help.

Dave’s Reply:
Thanks for your electrical question Travis.

Electrical Panel and Circuit Problems

Application: Intermittent Electric Power Problem.
Skill Level: Advanced – Should be performed only by a Licensed Electrical Contractor and may require the local utility company or electric service provider.
Tools Required: Basic Electricians Pouch Hand Tools, Voltage Tester or Multimeter.
Estimated Time: Depends on personal level experience, ability to work with tools and troubleshoot and inspect electrical circuits and electrical system components.
Precaution: Depending on the symptoms, identify the main panel or panel circuit in question, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Burnt or damaged electrical wiring and circuit components should be replaced with new electrical materials of the same voltage and amperage rating.

Typical Causes of Electric Circuit Problems

  • Electrical Problems in the Panel
    • There are a few conditions that may cause half of the power to not work in a home.
    • Some brands of electrical panels are prone to having failures especially in the summer time when electrical loads are high which causes problem due to expansion and contraction with electrical parts which could lead to a deteriorated connection, which then causes arcing, which can then lead to damaged electrical components and the loss of electrical power to part or all of the electrical service.
  • Tripped Main Breaker
    • Main circuit breakers may trip into the OFF position, and sometimes only half of the 240 volt power will trip OFF while the other phase of power remains in the ON position.
    • A tripped main breaker may be caused by circuit over load or other circuit problems.
  • Faulty Main Breaker
    • Main circuit breakers may fail as well causing the same condition where half of the power is lost while half remains ON.
  • Electrical Circuit Testing
    • Before considering replacing circuit breakers it is best to have the condition thoroughly tested by a qualified licenses electrical contractor as it is not recommended that a homeowner perform work in an electrical panel.

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FAQs Frequently Asked Questions and Comments

2 Responses to “When Electrical Power is Lost to Half the Circuits”
  1. Bernadette Quinn says:

    Problem with Incorrect Voltage Readings

    I have little to no power from side A of the circuit box. I changed out the main switch. With no other circuits connected I am reading 240v grounded. Once I connect anything on side A I lose ground and not pulling full power. Side B is working perfectly. The electric company came out and checked their end and said everything is good.

    • Dave Rongey says:

      How to Locate a Faulty Circuit

      Hi Bernadette,
      If the panel has been tested and their is no indication of a faulty part or connection, then there may be a problem with a circuit, or equipment that is plugged in or connected to a circuit, most likely a 240v circuit that is connected on the B side of the panel. It may help to connect a circuit on the A side as before, and start removing circuits on the B side, one at a time, while monitoring the circuit on the A side.

      Another way to locate a faulty circuit or equipment is to disconnect or turn off all the circuits on the B side, and connect one circuit on the A side. Test the A circuit to make sure the reading is normal, then begin connecting one circuit at a time on the B side while monitoring the A circuit. Once the reading of the A circuit is not normal you will have identified the faulty circuit on the A side.

      I hope this helps you,


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