Delta wired gfci

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Old 01-06-19, 04:35 AM
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Delta wired gfci

Iím a marine electrician. I was recently working gfci circuits on a vessel that where wired in delta. Gfci is wired with 60v on each leg. When checking the gfci with a tester it showed an open ground and tester would not trip the gfci. There is 120v with meter and test button on gfci itself works properly. Gfci is grounded properly. Iím wondering if the tester is only made to work on y wired system with a hot and nuetral rather than delta with two hots? Thanks for any clarification.
 
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Old 01-06-19, 05:05 AM
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The plug in tester needs a ground to shunt current so the GFCI will sense a fault.

Those testers are designed for a system where neutral and ground are at the same potential. Who knows how they will react in a setup like you describe.
 
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Old 01-06-19, 11:21 AM
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Are there testers that are set up for delta wiring?
 
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Old 01-06-19, 11:58 AM
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Delta with 60v on each leg ? Are you sure ? That's pretty strange
A delta circuit doesn't usually have an available neutral.
 
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Old 01-06-19, 03:39 PM
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Are you wiring a GFCI receptacle for personal protection, or a GFCI for equipment protection on a service? If it is the former, it will not matter if it is a delta, wye, or just a single phase single transformer, if it is 120 volts with a grounded neutral, they are all the same.
 
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Old 01-06-19, 03:56 PM
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On a delta service..... if one leg is not grounded or there is not a neutral tap between two legs.... then there is no ground reference to trip a GFI.

Are you using a setup like this.....
Name:  high leg delta.jpg
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Old 01-06-19, 04:07 PM
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A gfci does not need a ground to work. Current flow is the same throughout a circuit. Thatís what it is monitoring. If it detects a difference between the two it assumes that some is taking a different path. A faulty hand held drill maybe. The ground is just there as a less resistant path than a person would be.
 
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Old 01-06-19, 04:11 PM
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There is no nuetral. This is three phase 450 primary to three phase 120 secondary. Two pole breaker gives the desired 120v to the receptacle.
 
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Old 01-06-19, 05:16 PM
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This is three phase 450 primary to three phase 120 secondary.
Is this in the US? Normally that type of system would be 480 volt 3 phase delta primary (no neutral) to 120/208 3 phase wye secondary.

I’m a marine electrician.
As in an electrician on a boat? Or an electrician at a marina?
 
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Old 01-06-19, 05:24 PM
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Marine as in building supply boats ATBs car carriers.......at a ship yard. Yes the transformer u described is the norm. But this is not that. Navy uses 450v from gens. This panel is fed with that and secondary is 3 phase 120v open delta no nuetral.
 
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Old 01-06-19, 05:46 PM
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A gfci does not need a ground to work. Current flow is the same throughout a circuit. That’s what it is monitoring. If it detects a difference between the two it assumes that some is taking a different path.
It doesn't need a ground to work but the difference in legs is referenced to ground. A GFI technically is measuring a leak TO ground. If you have a true delta system and one of the phase legs is not grounded.... A GFI won't work.
 
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Old 01-06-19, 06:12 PM
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They will work with no ground at all. They donít need it to do their job. Any difference in current on the two legs will cause it to trip. Iím just not sure how the tester itself works it may need a ground to perform test.
 
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Old 01-06-19, 06:15 PM
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GFCI measures leak to ground, so if it doesn't trip, guess it is safe to say it won't electrocute someone.

One thing that concerns me is aren't most GFCI receptacles only trip one pole? Neutral pole is not neutral anymore so it won't be safe. I'd say it needs 2 pole GFCI breaker to be safe.
 
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Old 01-06-19, 06:27 PM
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That is a very good point. Iíll have to see if these open both sides or just one. See thatís why I like kicking these things around some else may think of some u donít. Iíll let u know what I find out.
 
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Old 01-06-19, 06:50 PM
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Without doing any research, I don't believe a GFCI receptacle is UL Listed for use without a neutral conductor.
 
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Old 01-07-19, 09:54 AM
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Ok guys here we go back at work and checked some things. There is a ground fault light in the panel which I’m asumeing in some way is give a path back to each leg. I say this because I can read 65 volts on each leg at receptacle to hull of vessal. And the good thing is that when tripped both sides do open at gfci. So both legs gone.
 
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Old 01-07-19, 03:01 PM
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Do you have a "standard" Delta system or is it a open Delta or corner grounded Delta?
 
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Old 01-07-19, 03:17 PM
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In order for him to get two lower voltage legs to ground..... it would have to be what I posted back up in post 6. Corner ground won't give you two low voltages. I believe this would be a high leg delta system.
 
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Old 01-07-19, 05:50 PM
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But in a high leg delta the voltage would be 120 volts to ground and 208 volts between the B phase and ground. He says he gets 120 volts between phases using a 2 pole breaker. Ship wiring sounds very odd.

This is three phase 450 primary to three phase 120 secondary. Two pole breaker gives the desired 120v to the receptacle
I should have also asked the OP, what country is this?
 
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Old 01-07-19, 07:26 PM
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Itís an Open delta. Iím in the United States
 
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Old 01-07-19, 07:48 PM
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Marine electrical systems are specifically NOT "grounded" to the ship's hull to reduce the hazard of "ground" faults. A common GFCI will NOT work work in this application.

Ships have ground fault indicators on their switchboards to indicate when a true ground fault occurs and this tells the ship's electrician to go look for the fault. Some GF indicators may also be used to trip a circuit breaker via a shunt trip.

It's been more than forty years since I had anything to do with a shipboard system so things might be a bit different these days.
 
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Old 01-08-19, 05:43 AM
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. It’s an Open delta
Everything is becoming clearer now Thanks for the info Furd.

This is uncharted territory for me so take it for what that is worth. I would think a standard GFCI receptacle would work if the voltage is 120 volts regardless if it is phase to phase voltage or phase to neutral. Gfci's measure imballance in the circuit. Remember, that a gfci's tolerance is 4-6 miliamps.

Also a bit more info after reading your original post:

Gfci is wired with 60v on each leg.
That is not how voltage works. Your voltage is 120 volts phase to phase. Just like a 3 phase wye connected transformer is 120 phase to neutral (ground) and 208 phase to phase.

When checking the gfci with a tester it showed an open ground and tester would not trip the gfci.
This is common where there is no ground. A GFCI tester uses the ground connection to test the device.

There is 120v with meter and test button on gfci itself works properly. Gfci is grounded properly.
If it functions correctly and is truley grounded, the GFCI tester should also work. The device must be fully installed in order to work.
 

Last edited by Tolyn Ironhand; 01-08-19 at 05:19 PM.
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