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GFI questions

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Craig Hauber:
Just some curiosities I have,
1)  What part in a GFI is the part that wears-out and requires the "test" function that they all have?

2)  Why couldn't they make one that doesn't wear out?  (I have some in public park facilities that probably have never been used but they are all dead -could it be an unheated/freezing-related thing?)

3)  Is there any GFCI units out there that are self resetting?  in other words, without a fault present for a few seconds could turn themselves back on.  (Yes I know it would be a much more complex device but it would be something you could bury in a panel somewhere near the switchgear)

4) And finally, is there a GFI rig capable of camlock-level distro use (200A 3-phase)?  Was picturing a spider-box looking thing that you could put inline on your feeder near your disconnect point  -which opens up another question, how would a GFI work on 3-phase no-neutral loads like chain motors?

These are all just questions that pop into my head while on the jobsite.  Used to be a bit of a GFI skeptic, but this particular forum has opened my eyes quite a bit.

Mike Sokol:

--- Quote from: Craig Hauber on November 03, 2013, 12:34:14 PM ---Just some curiosities I have,
1)  What part in a GFI is the part that wears-out and requires the "test" function that they all have?

--- End quote ---
Nothing in a GFI really "wears out". But the electronics can be damaged by electrical spikes from nearby lightning strikes. Also, the GFCI outlets outside can really take a hit from the moisture which can corrode the latching relay contacts. Those are the two main failure modes I'm aware of, but there could be more.


--- Quote --- 2)  Why couldn't they make one that doesn't wear out?  (I have some in public park facilities that probably have never been used but they are all dead -could it be an unheated/freezing-related thing?)

--- End quote ---
As mentioned above, it's about the environment they're in. Outside outlets in public parks live a hard life. All kinds of lighting spikes and all kinds of rain. Of course, they're supposed to be in weatherproof boxes, but how many times have you seen the door broken off of an outside receptacle. I don't think they want to use circuit breaker units because you would need access to the circuit breaker panel to reset them, and that's not going to happen in a park.


--- Quote --- 3)  Is there any GFCI units out there that are self resetting?  in other words, without a fault present for a few seconds could turn themselves back on.  (Yes I know it would be a much more complex device but it would be something you could bury in a panel somewhere near the switchgear)
--- End quote ---
I've never seen one, but since current models are mechanically reset, that would require an entirely new design. I'm guessing there are fail-safe versions for use on-board ships and military installations, plus there's a 30 mA trip version used for deep mines and industrial gear with a lot of residual leakage current. Some of those may be self resetting, but I've never seen one. 


--- Quote ---4) And finally, is there a GFI rig capable of camlock-level distro use (200A 3-phase)?  Was picturing a spider-box looking thing that you could put inline on your feeder near your disconnect point  -which opens up another question, how would a GFI work on 3-phase no-neutral loads like chain motors?
--- End quote ---
I do know of some 3-phase GFCI units for industrial use, but I think it's better to have individual GFCI's at each receptacle. That's because leakage currents are additive, so by the time you get back to your camlock there could be 10's of mA of leakage current from the normal operation of all the circuits. So by dividing each distro branch into its own sensing path, you can still use 5 mA trip points. Plus, you wouldn't really want to take down power to an entire show just because somebody plugs a guitar amp with a leaky mains transformer into your backline power. Better to trip just that one GFCI for troubleshooting and show continuance.


--- Quote --- These are all just questions that pop into my head while on the jobsite.  Used to be a bit of a GFI skeptic, but this particular forum has opened my eyes quite a bit.

--- End quote ---
I'm doing some new GFCI experiments to get a better handle on how they interact with audio and lighting gear. I'll post any experiments and results on this forum.

Mike Sokol

Jeff Bankston:

--- Quote from: Craig Hauber on November 03, 2013, 12:34:14 PM ---
4) And finally, is there a GFI rig capable of camlock-level distro use (200A 3-phase)?  Was picturing a spider-box looking thing that you could put inline on your feeder near your disconnect point  -which opens up another question, how would a GFI work on 3-phase no-neutral loads like chain motors?


--- End quote ---
starting way back some years ago we started getting switch gear and panel boards with with a gfi main breaker. i live in los angeles and i dont know if this is a nationwide code but it is in los angels. i have seen 3 phase panels with 200 amp & up gfi main breakers and switch gear with 2000 amp gfi main breakers. we had to hire a company to come out with meters and adjust the gfi trip current once it was installed. the electrical inspector ask for the paperwork and the company puts a sticker on with the trip current and date it was set. i'm not sure if this would work in a portable enviroment because a the setting had to do with the ground buss resistance which comes from the cold water ground and the ground rod(s).

Greg_Cameron:

--- Quote from: Jeff Harrell on November 04, 2013, 06:36:13 AM ---i'm not sure if this would work in a portable enviroment because a the setting had to do with the ground buss resistance which comes from the cold water ground and the ground rod(s).

--- End quote ---

Kissing the ground certainly can present some hazards.

Stephen Swaffer:

--- Quote from: Jeff Harrell on November 04, 2013, 06:36:13 AM ---starting way back some years ago we started getting switch gear and panel boards with with a gfi main breaker. i live in los angeles and i dont know if this is a nationwide code but it is in los angels. i have seen 3 phase panels with 200 amp & up gfi main breakers and switch gear with 2000 amp gfi main breakers. we had to hire a company to come out with meters and adjust the gfi trip current once it was installed. the electrical inspector ask for the paperwork and the company puts a sticker on with the trip current and date it was set. i'm not sure if this would work in a portable enviroment because a the setting had to do with the ground buss resistance which comes from the cold water ground and the ground rod(s).

--- End quote ---

Jeff,

I worked for years in an industrial facility that had a similar setup.  A key here is that those GFIs are intended for equipment protection with a 30 mA trip level.  GFCI receptacles on the other hand are designed for personal protection (far more important to me personally!!) with a 3 mA trip level.  The 30 mA level can leave a person permanently horizontal.

GFCI receptacles are now designed to not reset and force replacement if they are not working properly-lets face it a $15 receptacle (I won't install the cheap ones myself) is cheaper than an ER visit or a funeral.

They do make weather resistant receptacles now that handle the weather better-pricier, but code required in most places.

Guess everyone has to decide if safety is worth the cost. Recently an electrical inspector commented to me that he was always amazed when people complained about the cost of AFCI and GFCI protection in their homes while leaning on their $1500-$2000 granite countertops.

Steve Swaffer

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