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I have found three receptacles in my home for which a three-light receptacle tester indicates open ground. Can I safely resolve this issue by replacing these receptacles with GFCI receptacles? Would that be up to code?

Given the placement of these three, I suspect that they are in a row on the circuit. If this turns out to be true, can I just use one GFCI receptacle at the box closest to the breaker, and then pass power to the other two on the load side of the GFCI?

In case it matters, this is in Chicagoland, so ground is provided by conduit throughout the home.

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    Since you have conduit, you should verify if the boxes are actually grounded. If so, the solution may be as simple as adding ground pigtails or replacing with self-grounding outlets. – DoxyLover Mar 23 at 2:33
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    Yeah, can you check to see if the boxes are grounded properly? This could be a stupid simple thing to fix (either dodgy receptacle-to-box grounding, or a conduit pullapart somewhere) – ThreePhaseEel Mar 23 at 3:00
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    You should try to resolve this by fixing the ground connection. You can check the connection between outlets to see where the actual break is. If the pipe is inaccessible, it may be possible to pull a ground wire into the pipe, although my preference would be to repair the pipe and pull a ground wire. In a case where a ground wire can not be added, your electrical code may permit you to protect the circuit with a GFCI breaker or dead front GFCI located next to the panel, although I'm in the wrong country to tell you that. – K H Mar 23 at 4:12
  • I think that I can check whether the boxes are grounded by using a multimeter to look for a potential between receptacle hot and the box. Is that right? – Matthew Bourque Mar 23 at 12:21
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Receptacles should pick up enough ground via the mounting screw heads to have a 3-light tester report grounded. However, if you are pushing somewhat on the receptacle when you test it, you can actually push it off the mounting screw heads enough to break that ground contact. That's why it's not allowed for receptacles as a grounding method.

The proper method is to either run a ground pigtail to the metal box, or use a receptacle UL-listed as "Self-grounding". That means it has an extra brush to reliably pick up ground from the mounting screw shaft.

If even that does not ground it, then "metal conduit" is a lie, and the branch was installed substandard for Chicago.

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