Electrical – Ungrounded Electrical Boxes

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I recently purchased a house that was built in the 1950's and just about half the outlets in the house test with an open ground. After quite a bit of reading and research I tried to ground 2 of the outlets to a screw in the box, but they still read open ground. I then used a multimeter to test if the box was grounded, both show that they are not grounded properly as they read 0 volts when I test hot to the box.

I am wondering if there is anything I can do to fix this problem short of calling an electrician? All of the ungrounded outlets in the house are ones that our important electronics plug into and I would feel better knowing they are grounded and I can use a surge

Tester showing open ground

Box with ground wire but not grounded

Multimeter showing ungrounded box

Best Answer

Retrofit grounds

In recent Code changes, they greatly liberalized the rules for retrofitting ground wires (alone). You can do it pretty much any reasonable way.

  • Each ground wire must run back to the same panel as the conductors are served out of (this is relevant if you have a subpanel).
  • Circuits out of the same panel can share grounds, so your ground wire only needs to reach a point which is grounded.
  • while sharing and branching are OK, the entire ground path to the panel must be big enough for the circuit. So a 14AWG circuit only needs to reach a 12AWG ground wire... But a 50A range circuit can only be grounded to a path the required ground size (10 AWG?) all the way back to the panel.

It makes sense to run the biggest grounds (range, dryer, water heater) as a backbone, then branch the other grounds off of that.

This forking and splitting is allowed only because grounds normally do not flow current, and only momentarily while the breaker trips, and it's rather unlikely for 2 circuits to need to use their ground at the same time. You can't do this with neutrals.

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