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gfci gfci2 In the US, there are two phases that is 120V each to neutral. If you connect it phase to phase, then you get 240V. In my country. It's illegal to use phase to neutral of 120V because we are promoting our local products which run at 240V only (to avoid buying stuff from US). Hence are only allowed to use phase to phase of 240V.

Now I just bought a 240V Ground Fault Circuit Interrupter. A normal line to neutral GFCI would have current flowing from line to neutral. But in my case, it's 2 phases without neutral. So can the GFCI still work?

How does the current flow in phase to phase connection versus phase to neutral? Are they the same?

  • Can you add some details about this GFCI? – Machavity Oct 18 '18 at 3:39
  • see updated post above with front and back pictures – Samzun Oct 18 '18 at 3:51
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    Where on this planet are you?! The Philippines? – ThreePhaseEel Oct 18 '18 at 4:17
  • yup.. when the US colonized us.. they left us with their power system.. but after Indepedence Day we were not allowed to tap phase to neutral (120 volts) or jail time.. we are only allowed to tap phase to phase or 240 volts.. so how does the current of phase to neutral and phase to phase differ? – Samzun Oct 18 '18 at 4:33
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    The easiest way is to read the answer(s) to your question. – Harper - Reinstate Monica Oct 19 '18 at 17:38
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GFCI's don't care.

GFCI has no relationship with ground. They don't care if the two wires are line-line or line-neutral. In fact your GFCI's labeling reflects that.

Also that is not 2-phase, it is single-phase with center ground.

You didn't mention you are in the Philippines. You don't have neutral, unless you are in the US-built territories that are still officially split-phase with a 3-wire feed from the transformer. If you are only getting 2 wires off the pole, the thing in the middle is only your ground rod, and it is definitely not made for returning current. If you try to hook a 120V load line-ground, in the Philippines, you will only electrify all your house's grounds.

Also, using a step-down autotransformer in the Philippines is a bad, bad idea. Both 120V outputs will be hot, and it will be very important that you get grounding right. In the Philippines you need an isolating transformer.

  • I have 3 wire coming to the service entrance.. the 3rd wire is the neutral which gets feed back to the pole transformer center tap. When I measure one of the phases to neutral, it's 120V, when phase to phase, it's 240V. That's how the 240V came from. We never use 120V. Only 240V. About using step-down autotransformer with this setup and both 120V outputs being hot. How does this differ to the US where the autotransformer takes a phase and neutral? This is why I asking what was the difference between phase to phase and phase to neutral in terms of current, etc. – Samzun Oct 18 '18 at 6:11
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    Comments are not for extended discussion; this conversation has been moved to chat. – Michael Karas Oct 19 '18 at 11:42

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