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According to the diagram below the two (non-GFCI) downstream receptacles are said to be GFCI protected. Does this mean that if someone were to accidentally create a ground fault at either of the two rightmost receptacles the GFCI receptacle in the middle would trip and cut off power to all receptacles downstream from it?

GFCI diagram http://www.jimspect.com/livesite/wp-content/uploads/Receptacle-Type-GFCI-Protection.png

Is there anything wrong with replacing the two rightmost receptacles with GFCI receptacles?

Finally, if you did perform this replacement and if you pressed the TEST button on the rightmost GFCI receptacle, would the two GFCI receptacles upstream also trip?

  • There's no point in replacing the downstream receptacles with GFCI's, unless you just have an unquenchable desire to spend more money. ;-) – Craig Oct 15 '15 at 19:50
  • The outlets in our master bathroom are downstream from the GFCI outlet in the guest/kids bathroom, so I would like to change that. It's annoying to have to go into the other bathroom to fix if someone thinks they're being funny and hits the TEST button... – JPhi1618 Oct 15 '15 at 21:20
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    If you want to replace the downstream outlets and have them function individually you would wire them to the "Line" side of the existing GFCI rather than the "load" side. That way they are no longer "downstream". – JPhi1618 Oct 15 '15 at 21:26
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Yes, anything connected to the LOAD terminals of a GFCI device is GFCI protected. So a ground-fault anywhere on the circuit "after" the GFCI device, would cause the device to trip. This will cause the receptacles on the GFCI device, and all the devices attached to the LOAD terminal to lose power.

Connecting GFCI devices on the LOAD side of a GFCI device, should cause no problems other than wasting money.

If you wired three GFCI devices in line as you suggested, and then pressed the test button on the last GFCI in line. The previous GFCI devices should not trip.

Internally, a GFCI looks similar to this.

GFCI Internal

So when it's set and the test button is pressed, it looks like this.

GFCI set test button pressed

When the test button is pressed, current flows through the test button, through a resistor, around the current transformer (CT), and back to the grounded (neutral) terminal. I've highlighted the current path in yellow.

GFCI set test button pressed current highlighted

So as you can see, you'll have 6 mA on the ungrounded (hot) terminal, and also 6 mA on the grounded (neutral) terminal. This GFCI device tripped, because the return path of the test circuit bypassed the CT. The current will not bypass the CT in the other GFCI devices, so they should not detect the test ground-fault.

enter image description here

This blog post might help you understand how GFCI devices work.

  • Why should the previous GFCI devices not trip? Doesn't the TEST feature simulate a ground fault? – derNincompoop Oct 15 '15 at 17:52
  • @derNincompoop Please see my edit for an explanation. – Tester101 Oct 15 '15 at 18:21

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