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Author Topic: GFI questions  (Read 8597 times)

Craig Hauber

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GFI questions
« 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?

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.
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Mike Sokol

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Re: GFI questions
« Reply #1 on: November 03, 2013, 03:05:03 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?
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.

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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?)
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.

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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)
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. 

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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?
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.

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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.
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
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Jeff Bankston

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Re: GFI questions
« Reply #2 on: November 04, 2013, 06:36:13 am »


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?

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).
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Greg_Cameron

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Re: GFI questions
« Reply #3 on: November 04, 2013, 08:12:31 pm »

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).

Kissing the ground certainly can present some hazards.
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Stephen Swaffer

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Re: GFI questions
« Reply #4 on: November 04, 2013, 11:29:35 pm »

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).

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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TJ (Tom) Cornish

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Re: GFI questions
« Reply #5 on: November 05, 2013, 08:47:18 am »

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
I care less about cost than efficacy.  GFCI devices have proven themselves to be viable and life-saving devices for many years now.  AFCI - the jury is more than still out.  I would be curious to see if anyone has tried to compile statistics of folks who have removed the AFCI equipment after the inspector leaves due to nuisance tripping.
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Stephen Swaffer

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Re: GFI questions
« Reply #6 on: November 05, 2013, 03:47:10 pm »

I care less about cost than efficacy.  GFCI devices have proven themselves to be viable and life-saving devices for many years now.  AFCI - the jury is more than still out.  I would be curious to see if anyone has tried to compile statistics of folks who have removed the AFCI equipment after the inspector leaves due to nuisance tripping.

Tom, I don't do as many homes as some contractors-but I have had zero complaints the last couple of years on nuisance trips-and in spite of being around other electricians at supply houses and ce classes never hear complaints.  The early afcis  were troublesome but they have improved them considerably-and its a good thing because in just a few weeks they are going to be mandated in a lot more places (I am not an advocate of that-just caught in the middle between the inspector and the homeowner :) !)  His point was-and what I was saying-is that we often grumble about the cost of safety-but will gladly spend much more on something that catches our fancy.  Of course, no sound or lighting engineer ever spends more money on gear-just for bragging rights, do we? :D

Steve Swaffer


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TJ (Tom) Cornish

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Re: GFI questions
« Reply #7 on: November 05, 2013, 04:18:05 pm »

Tom, I don't do as many homes as some contractors-but I have had zero complaints the last couple of years on nuisance trips-and in spite of being around other electricians at supply houses and ce classes never hear complaints.  The early afcis  were troublesome but they have improved them considerably-and its a good thing because in just a few weeks they are going to be mandated in a lot more places (I am not an advocate of that-just caught in the middle between the inspector and the homeowner :) !)  His point was-and what I was saying-is that we often grumble about the cost of safety-but will gladly spend much more on something that catches our fancy.  Of course, no sound or lighting engineer ever spends more money on gear-just for bragging rights, do we? :D

Steve Swaffer
What's your definition of "older"?  Mine date from 2007 and they are a pain, though admittedly I do some strange things in my house.
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Rob Spence

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Re: GFI questions
« Reply #8 on: November 05, 2013, 10:43:30 pm »

What's your definition of "older"?  Mine date from 2007 and they are a pain, though admittedly I do some strange things in my house.

I have 40+ AFCIs from 2008 and I don't recall a nuisance trip in 5 years.  They are all Siemens.


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Stephen Swaffer

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Re: GFI questions
« Reply #9 on: November 05, 2013, 11:08:20 pm »

What's your definition of "older"?  Mine date from 2007 and they are a pain, though admittedly I do some strange things in my house.

Tom,

The 2008 NEC started requiring CAFCI (Combination AFCI) kind of off topic to explain that-but depending on a lot of variables you could certainly have an older design-I have even heard of non-combination winding up on big box store shelves in the last 2-3 years even though they no longer meet code.  I think 2005 was the first code cycle to require AFCI-so 2007 would be the early days.

As for doing strange things-keep in mind that AFCI's will trip on a ground to neutral short as well as a ground to hot or hot to neutral-so if you have any home brew electronics that have neutral the to the chassis as was often done, and if a 3 wire power cord has been added the AFCI will be unhappy.

I don't always agree with the code requirements-just have to understand and live with them.  I will say though, that as much as I hate to admit it, more often than not I eventually learn that someone was smarter than me when they made the rule!

Steve Swaffer
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Steve Swaffer

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Re: GFI questions
« Reply #9 on: November 05, 2013, 11:08:20 pm »


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