# GFCI for a DC Circuit



## McClary’s Electrical (Feb 21, 2009)

DPIG said:


> There has been a issue with a client on the safety of a DC circuit. they were wanting a GFCI on a DC outlet source. The only need of a Safety measure for a DC Circuit an any case, "that i know of" is if the pathway back to source is broken and an indiviual completes the pathway back to source. In which case seems high unlikely.
> 
> Was wondering if any one has a different Interpentations of this, and a NEC code reference to support that a DC circuit needs to have a GFCI.


 
Where is the circuit and what does it do? Are you speaking of a ground fault circuit interupter? or ground fault for equipment protection? 
DC photovoltaic circuits are required to have GF protection. 690.34 (c)


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## DPIG (Dec 2, 2010)

mcclary's electrical said:


> Where is the circuit and what does it do? Are you speaking of a ground fault circuit interupter? or ground fault for equipment protection?
> DC photovoltaic circuits are required to have GF protection. 690.34 (c)


It is a DC circuit outlet on a Rig Welder which is being used to power up AC/DC Power tools(Grinders, End Grinders, Drills, etc). The welding Machine in Question is a Lincoln SA200.


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## BBQ (Nov 16, 2010)

I will be very surprised if anyone makes a UL listed Class A GFCI for DC circuits.


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## DPIG (Dec 2, 2010)

BBQ said:


> I will be very surprised if anyone makes a UL listed Class A GFCI for DC circuits.


I've contacted Cooper, Pass and Seymour, and Leviton: and your right they do not have an GFCI product for DC circuits. 

Also Talked to a Bender inc. Rep and there are two way to go about this. if the Circuit is grounded then they have a GFCI product that would be useful. If the DC Circuit is floating system then he advise to go with a _Insulation monitoring Device._

Eather way my search is still the NEC code to Advise my client if this a legalize safety issuse or not.


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## BCSparkyGirl (Aug 20, 2009)

BBQ said:


> I will be very surprised if anyone makes a UL listed Class A GFCI for DC circuits.


I sure as hell never heard of one.......and I have installed many a dc outlet......:blink:


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## micromind (Aug 11, 2007)

BCSparkyGirl said:


> I sure as hell never heard of one.......and I have installed many a dc outlet......:blink:


Same here; I work with 125 and 240DC on a regular basis. Never heard of GFIs for DC. 

Of course, most of my work with DC involves relays and breaker trip circuits, so I could see where a GFI would introduce serious hazards if it tripped without a reason.

Or even with a reason, for that matter!


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## Rockyd (Apr 22, 2007)

DPIG said:


> There has been a issue with a client on the safety of a DC circuit. *they were wanting a GFCI on a DC outlet source*. (Ask them if they know why, or what they are talking about. I like safety, but this doesn't sound like safety talk, it sounds like PC gone bad) The only need of a Safety measure for a DC Circuit an any case, "that i know of" is if the pathway back to source is broken and an indiviual completes the pathway back to source. In which case seems high unlikely.
> 
> Was wondering if any one has a different Interpentations of this, and a NEC code reference to support that a DC circuit needs to have a GFCI.


My take -

Not code, but the explanatory notes in the 2005 NECH 210.8 *Ground Fault Circuit-Interupter Protection for Personnel*. GFCI's came into the code in 1971. Both Hot and Nuetral pass through a toroidal coil to sense any unbalance in either conductor causing the GFCI to trip. I see the GFCI as a protective device for AC. Can't see a common GFCI device working on anything but an AC circuit.

Be intrested in the follow up. I am of the opinion that this is somebody overthinking our line of work (somewhere off in a ivory glass tower), and should leave the electrical work to the professionals (like us) to do.

When you see them next time ask if they want a class A (4-6 mA to protect personnel)), or a class B (30mA to protect equipment), GFCI on that circuit. It may buy you just enough time to keep them busy while you complete the job without their help.


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## BBQ (Nov 16, 2010)

Rockyd said:


> When you see them next time ask if they want a class A (4-6 mA to protect personnel)), or a class B (30mA to protect equipment), GFCI on that circuit. It may buy you just enough time to keep them busy while you complete the job without their help.



FWIW Class B GFCIs are also for personal protection but could only be used for certain pool applications. I am not even sure anyone makes class B GFCIs any longer.


If the device is for personal protection it is a GFCI.

If the device is for equipment protection it is a GFP.


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## frenchelectrican (Mar 15, 2007)

I have heard it in France but it do not work very well what I heard few details due the DC not always be in smooth wavefourm or consant wavefourm due majtory of manufacterd DC source useally chopped DC waveforum and the GFCI will not read very well and not always able to trip.

And we genrally don't use the RCD on DC appations at all. 


Now on other hand if anyone work on Railroads with DC traction motours yes we do have ground fault relay kinda a crude GFCI for trains { I never like it at all especally if you go over the road crossing that where the issue arise }


Merci.
Marc


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## Jlarson (Jun 28, 2009)

BBQ said:


> FWIW Class B GFCIs are also for personal protection but could only be used for certain pool applications. I am not even sure anyone makes class B GFCIs any longer.
> 
> 
> If the device is for personal protection it is a GFCI.
> ...


Didn't we have this argument before?


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## underwaterguy (Apr 5, 2011)

*GFCI for a DC circuit*

First, I am just an electronic engineer, not really an electrician, however, I can see a need for the DC equivalent of a GFCI. We have a free flooding, underwater manned system with a power distribution system of 28 VDC. Because we are talking about men in seawater in contact with equipments on different power legs, all within a metal frame, we have to maintain zero probability of any stray currents anywhere. We need a DC GFCI. I do understand that this is not a common situation.


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## Rockyd (Apr 22, 2007)

underwaterguy said:


> First, I am just an electronic engineer, not really an electrician, however, I can see a need for the DC equivalent of a GFCI. We have a free flooding, underwater manned system with a power distribution system of 28 VDC. Because we are talking about men in seawater in contact with equipments on different power legs, all within a metal frame, we have to maintain zero probability of any stray currents anywhere. We need a DC GFCI. I do understand that this is not a common situation.


I understand the need for concern, howewver, I think it's outside the general knowledge of most in the industry in a R & D situation like you are describing.

I can tell you that I was in the Navy from 78 to 82 on A Sub-Tender and we never had anything like what you mention. That was thirty years ago... it might not be a bad idea to see if the Navy might be able to shed some light on your issue, or at least see if there is any R & D where you are looking. Best of luck with it.


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## Big John (May 23, 2010)

While I know we don't allow spam here, that guy did actually post a Class A GFCI that was apparently rated for DC.... Isn't that the whole point of the thread?

-John


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## McClary’s Electrical (Feb 21, 2009)

Big John said:


> While I know we don't allow spam here, that guy did actually post a Class A GFCI that was apparently rated for DC.... Isn't that the whole point of the thread?
> 
> -John


 

Yes, now if he'll only pay to advertise , we'll be ok:thumbsup:


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## Robert Redditt (Jan 29, 2011)

Rockyd said:


> I understand the need for concern, howewver, I think it's outside the general knowledge of most in the industry in a R & D situation like you are describing.
> 
> I can tell you that I was in the Navy from 78 to 82 on A Sub-Tender and we never had anything like what you mention. That was thirty years ago... it might not be a bad idea to see if the Navy might be able to shed some light on your issue, or at least see if there is any R & D where you are looking. Best of luck with it.


Ok, one more time without the pic or web addy on who makes them. But there is a company out there that does make the device talked about in this thread.

And it is UL-listed (UL 943 - Class A) for Single & Three-phase AC & DC systems.

Was just trying to get this info out there to those who might find it useful.
And no I do not sell or work for the company that makes them. I just your normal D.A.E.


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