GFCI protected circuits

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GarthS
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Re: GFCI protected circuits

Post by GarthS »

I have both a 500 that I have owned for 35 years and power pro 520 and never had an issue until I built a new house two years ago. With the new arc preventing breakers I have had to change out to conventional breakers. No problem since.
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dusty
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Re: GFCI protected circuits

Post by dusty »

I am confused.

Does this mean that modern day electrical features are protecting us in a way that didn't exist before?

Is the new equipment (PowerPro) defective (non-compliant) in some way?

Is it comforting to know that you are not the only one with this issue?
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DLB
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Re: GFCI protected circuits

Post by DLB »

dusty wrote: Sun May 02, 2021 12:23 pm I am confused.

Does this mean that modern day electrical features are protecting us in a way that didn't exist before?

Is the new equipment (PowerPro) defective (non-compliant) in some way?

Is it comfortng to know that you are not the only one with this issue?
I'm confused too. But for sure, depending on one's definition of modern, more of these features are protecting us. Ground Fault(GF) protection has been around, I believe since the 70's. Arc Fault (AF) detection is much newer first effective in 2002 I've read, and only in bedrooms. The National Electric Code (NEC) changes every three years and expands the circuits requiring GF protection, AF protection, or both, in every update. Complicating that, adoption of the version of the code varies by state and locality. IIUC we currently vary from NEC 2008 to NEC 2020. So, debatable whether we actually have a National Code in my view because the minimum requirements in AZ (NEC 2008) for example and TX (NEC 2020) are different. Neither of those is an isolated case, and all five versions from 2008 to 2020 apply somewhere. AF, GF, and combined solutions can be in a breaker, receptacle, or a disconnect. That might not be a complete list.

Ground Fault is well defined IMO, with a clear definition of a threshold and tolerances around the threshold. A PowerPro sensitivity is documented, but several of us report not experiencing it. My educated guess is that it has some ground current, not enough to be above the max trip threshold. But it may trip at the minimum trip current or it may break the threshold if other devices on the circuit have a ground current. For example if the PP has a 3mA ground current, that is not enough to trip. But two devices on the circuit with the same ground current, total 6mA, would be a mandatory trip where any protection device should trip.

Arc fault is not as well defined in anything I've seen so far. Some devices arc if they are working correctly. Brushed motors for example. Lots of variation there. My understanding is the devices work on a form of arc signature analysis with a goal of distinguishing between arcs and arc faults. Depending on what you did in USAF or elsewhere you may have some experience with signature analysis, not arcs but same principle. So, another educated guess here is that this is proprietary and one brand won't work the same as another on nuisance trips. If either a conventional or PP tripped an arc fault, I would want to know why, I don't thing either should arc as a normal function. (I have two houses, with zero arc fault detectors. I'm trying to buy a new house as an investment, it will have roughly 15 arc fault detection CBs, a few of those combined with GF.)

More recently, UL entered the fray and mandated a self test function for the interrupt devices. Adding more complexity, internal circuitry, and 'software.' Probably not software as someone with a military background would use the term, probably not even firmware. Programmed hardware. This is the case I wrote about in an earlier post in which the breaker can indicate seven different reasons for tripping.

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Re: GFCI protected circuits

Post by RFGuy »

As I mentioned before I have no hands on experience with AFCI's like I do with GFCI's. However in reading online what I see mentioned many times is that AFCI's are known for nuisance tripping. So it really is no surprise, to me, that the PowerPro is temperamental on an AFCI breaker. AFCI's are intended to sense an arc which is essentially a leakage from the hot wire to the neutral wire. Any brushed motor is expected to have issues with AFCI nuisance tripping based on online anecdotes. In addition to this, the PowerPro has active power factor correction according to this (https://www.shopsmith.com/shopsmithpowe ... nology.htm). In my opinion this is also another solid candidate for why a PowerPro might trip an AFCI. Not to mention that the power supply is a switching power supply on the PowerPro which could result in switching transients on the line side that could trip the AFCI. Beefier input filtering would help this, but I don't think the PowerPro has sufficient line filtering inside it based on the multiple radio interference complaints for it over the years. Bottomline is the AFCI is a new technology and there are devices that are known to be incompatible with them...the PowerPro is probably one of those devices. There really shouldn't be any expectation that a PowerPro MUST work with an AFCI or even a GFCI (IMHO). However, if someone feels that way then I recommend they start lobbying Shopsmith to get them to fix the PowerPro to make it compatible because that is what would be required. Likely will require a huge bank of filter caps which won't fit inside the headstock but maybe you can hang them from the benchtubes underneath...
Last edited by RFGuy on Sun May 02, 2021 7:27 pm, edited 1 time in total.
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Re: GFCI protected circuits

Post by Hobbyman2 »

one thing that has been proven over and over is the false promise that you can not be shocked with GF protection with out tripping the GF circuit , this has been proven untrue over and over ,depending on the situation you body can act as resistance just as a lightbulb that has one side to the positive and one side to ground . unless it is a direct short the GF protection will not know the difference .If I recall this use to be called a indirect short . AF was usually found in special situations where there were combustible /toxic locations and were very expensive , hair spray was considered to be explosive , . not sure how the consuming device would ever know or detect the difference between a GF and AF circuit as the current is still just current , I have never read any where that it changed the wave form , in the situation described above wouldn't this be a amp issue with the old breaker or the load on the circuit ? after years of service some breakers wear out , springs may have over heated or maybe have broke after so many times of being reset or circuit load being maxed , the old Pushmatic breakers had a lot of issues with wearing out if the circuit was loaded on the high side of the breakers limits , and some were IMHO just had junk springs , but there are still a lot of them in use .JMO
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Re: GFCI protected circuits

Post by JPG »

Filtering? I believe line filters are the reason many devices trip GF devices. Filtering on an unbalanced line can be tricky(not totally effective). 120 in the US is unbalanced. 240 in the US is balanced. A filter that connects to the grounding conductor is asking for GF trips.

BTW one can get shocked with a GF, but that shock WILL BE short lived. After all it is the shock current that trips the GF. It keeps you from latching on and getting killed(or cooked).
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Re: GFCI protected circuits

Post by DLB »

I think the phrase "nuisance trip" may be used excessively, too. Any device that plugs in could have a latent arc fault until it gets plugged into a AFCI circuit which would detect it. Similar, probably way less likely, for a ground fault. Most users would not be qualified or equipped to distinguish between a nuisance trip and an actual fault. At the same time, I'm sure the nice people that came up with this did not do regression testing for the millions of designs and variations that plug in downstream of the protection device. But the whole point of ACFI is to detect faults that have been historically latent. Or to transfer money from one group of people that don't have a lobby to a group that does. ;)

Arc Fault is not required by NEC in the garage (yet) so I'd guess the number of users that have plugged one into a AFCI outlet are few. Seems that we'd need more data on that. Of course, that doesn't mean AFCI is not sometimes put in garages.

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Re: GFCI protected circuits

Post by edma194 »

The entire upper floor of my addition has combination AFCI/GFCI breakers with the fancy LEDs. The addition has it's own panel, the original house has those ancient regular breakers that don't cost $50 bucks a pop. I have to check what the basement breakers are in the addition, they aren't GFCI but AFCI may have been required. So far I've had trips on the basement breakers from likely simple overloading. I'm not overly concerned, if the breakers are AFCI and they get tripped occasionally by the PowerPro, it's not surprising from a DVR motor setup like that. I do wonder if some kind of line filtering could eliminate that problem, it would be helpful for all sorts of electronic devices.

I did note this bit from an article on AFCI Nuisance Tripping:
"Wiring Problems – when an AFCI circuit breaker is installed, the wiring for that circuit needs to be done a little bit differently. When AFCI devices first started being installed, it was common for electricians to have problems with nuisance tripping because the neutral conductors for different circuits were connected together at some point outside of the main panelboard. This has never been correct, but it would often happen with no ill effects, so nobody knew it was wrong. With AFCI circuit breakers, this improper wiring will cause the breaker to trip."

Should not be a problem in the addition but the old house is a log cabin with a mix of wiring installed over many decades and I'd have to check carefully what was done there if I ever upgrade, although I would likely rewire most of it even without a major upgrade just for piece of mind. Seriously, when I moved in there was knob and tube wiring in the attic with bare wires running inches away from cardboard boxes full of old clothes and magazines, not to mention plenty of other questionable wiring that needed replacement right away.
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Re: GFCI protected circuits

Post by RFGuy »

JPG wrote: Mon May 03, 2021 2:49 am Filtering? I believe line filters are the reason many devices trip GF devices. Filtering on an unbalanced line can be tricky(not totally effective). 120 in the US is unbalanced. 240 in the US is balanced. A filter that connects to the grounding conductor is asking for GF trips.

BTW one can get shocked with a GF, but that shock WILL BE short lived. After all it is the shock current that trips the GF. It keeps you from latching on and getting killed(or cooked).
I don't disagree with you on the unbalanced vs. balanced line differences in filter design and a leaking cap (in a filter) could theoretically trip a GFCI, i.e. a bad filter design could make things worse. Honestly I don't know the internals of an AFCI breaker so I am just speculating here. Any switched power supply is notoriously noisy and backfeeds noise and spurious harmonics into the supply main. Below is a graph from a published paper I previously pointed out here on the forum. In the graph, the top is the input line current & voltage going into the power supply for a switched reluctance motor design (should be similar to the PowerPro because it is also a switched reluctance motor), while the bottom graph shows the difference with a 1µF low pass filter added. As you can see in these graphs, the input supply is significantly cleaner on the filtered one. I suspect the spurious harmonics and noise getting back to an AFCI breaker from the PowerPro are causing the "nuisance tripping" and coincidentally this is also what is causing the radio interference experienced by some PowerPro owners. In a switched mode power supply, very large currents are being switched in/out of storage elements (L's and C's). Unfortunately the switches (FET) aren't ideal so there is a ramp as well as transit time to consider but also leakage currents due to parasitics in the storage elements. Because of this, it is possible that the hot and neutral current waveforms may not mirror each other over brief transients thus tripping the AFCI/GFCI. Filtering on the supply side of the PowerPro serves to not only significantly reduce noise & spurious harmonics, but also serves to provide a source of local charge to supply any short term transients due to the PowerPro - preventing the AFCI from even seeing them. At least, this is my theory and what I am going with at this time...

With regard to AFCI and GFCI, I do believe they save lives but there is always context to consider. I do believe that the great expansion of AFCI/GFCI requirements in the latest NEC is most likely the result of lobbying by breaker manufacturers. Personally I can see how an AFCI might save lives in a bedroom application, I am far from being convinced that AFCI adds benefit in a shop environment.

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Last edited by RFGuy on Mon May 03, 2021 10:47 am, edited 1 time in total.
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JPG
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Re: GFCI protected circuits

Post by JPG »

I am curious how a capacitor by itself performs a LOW pass function?
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