In my country. Our homes mostly don't have third ground wires connecting to the neutral wires of the utility pole because contractors are all into cost cutting. Although some important facilities have them. My old house didn't have neutral/ground lines and it's so far to the utility pole. Someone suggested at the home improvement forum how to provide neutral to the GFCI breaker input I bought for a project so as to power its circuit which needs 120V, but he fell short of providing any more details. He said: "on the need for 120V to power the GFCI's guts, here's an idea: a North American panel in the Phillippines has a neutral bus that is completely unused. Use it. Install a 5 VA (that should be enough) 240V center-tap autotransformer in there, tie the center tap to the neutral bar. Then land all the GFCI pig's tails on the neutral bar".

I have a Siemens QF260A GFCI Breaker:


The poster instructs me to connect the GFCI Pigtail to the 240v autotransformer center-tap. Can it really work? Any possible problem that can occur?

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    I leave this in a comment because while technically correct, actually implementing this answer is, at the very best, highly questionable. I'd be looking into installing grounding wires on the critical circuits if I could. The red leads look like secondary leads. What you're proposing would "work" to the extent that the GFCI circuits wouldn't trigger when you don't want them to -- but it's because you're fooling the thing into not triggering ever. There could be flashes of blue light and smoke and screaming in the bathroom, and the GFCI wouldn't trigger. – TimWescott Oct 31 '18 at 22:27
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    What kind of service do you have - two wire 230V grounded? If so, you have to be very careful with the grounding when using a transformer. An isolation transformer that creates a "separately derived system" might be the best / simplest / safest. – batsplatsterson Nov 1 '18 at 13:12
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    Are you sure your two wire service is ungrounded? I am betting one of your service wires is 0v to ground. This is important. – batsplatsterson Nov 1 '18 at 13:48
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    OK that is helpful. (Are you in the Phillipines?) – batsplatsterson Nov 1 '18 at 14:04
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    Grounding the secondary of the transformer will help with surge protection as mentioned in your other comment and makes it possible for an equipment ground conductor to clear ground faults. (No idea what your code says about EGC.) – batsplatsterson Nov 1 '18 at 14:26

In that case you would hook the red "outside" wires to a 240V supply, i.e. A different 240V breaker. That would cause the center black wire to synthesize a midpoint at ~120V.

Since the GFCI breaker is getting its outside wires from the exact same bus bars, the center black would appear as a neutral to it, and should suffice to power it.

GFCI devices don't care about safety earthing, so you're all set.

It wouldn't work to attach the two red wires to the outputs of the GFCI breaker; those are inside the GFCI protected zone, and you intend to use the black (pseudo neutral) wire outside that zone, so it would be a fault, exactly what the GFCI is designed to detect and trip on!

There is one problem, though. There is no listed method for attaching supply power to that breaker; it's designed to snap into a Siemens service panel and engage its bus bars. Therefore your best bet is to get a small Siemens panel that is compatible. That panel could support several such breakers: you could set it up as a subpanel.

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    @Samzun you can't have a device partially hooked up inside the GFCI protected zone, and partially outside it. That violates a basic rule of GFCI. Also, how is the GFCI breaker going to power up if it doesn't have a neutral supply? If it doesn't power up, how will it supply power to the red wires to synthesize a neutral? – Harper - Reinstate Monica Nov 1 '18 at 0:01
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    If you ignore the brown wires and leave them disconnected, the one in your pic is fine. That's what I figured you planned to do. The point is the neutral is on the same primary as the endpoint wires. That's an autotransformer, which is what you have been talking about. General observation, the stuff you're trying to do here is way too complex to walk you through by rote as a step by step -- you need to understand the underlying concepts. Keep at it. Aim to learn broadly for life, rather than learn barely enough to rush this project done. – Harper - Reinstate Monica Nov 1 '18 at 0:20
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    Those aren't autotransformers. Didn't we discuss this at length over on DIY? The defining characteristic of an autotransformer is it doesn't have a secondary, but does have more than 2 taps on the primary. (Well it can have a secondary, but all the autotransforming is done on the primary. For instance if the above transformer had a 24V secondary, you could use that for thermostat and doorbell. ) – Harper - Reinstate Monica Nov 1 '18 at 0:39
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    The diagram is correct. I do not agree with the use of the word "secondary" to describe the middle taps on what I call the "primary" though. – Harper - Reinstate Monica Nov 1 '18 at 0:42
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    With North American style panels, you can't mix and match breakers. The shape of the busbars is too different, Siemens breakers go only in Siemens panels. Get one of those, easy peasy. North American panels tend to be 14.5" wide which fits in standard wall cavities, this leaves plenty of room for the long breakers. One transformer can power any number of breakers, >5VA is fine. – Harper - Reinstate Monica Nov 5 '18 at 6:52

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