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At what point electricians?


Phil Rhodes
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3 hours ago, Phil Rhodes said:

As a camera guy I do (well, did, really) get asked a lot about who we needed.

If possible, I would hire (or at least ask) an experienced local gaffer and defer to them on personnel if I felt that I was getting in over my head.

Personally, my comfort zone extends to what I can safely plug into household sockets or put-put gennies, lighting from the floor, and simple rigging like a speedrail goalpost for a backlight - beyond that, I want someone on set who knows more than me about rigging and set electricity safety. It’s just not worth the risk otherwise (to me). 

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12 minutes ago, Satsuki Murashige said:

If possible, I would hire (or at least ask) an experienced local gaffer and defer to them on personnel if I felt that I was getting in over my head.

Personally, my comfort zone extends to what I can safely plug into household sockets or put-put gennies, lighting from the floor, and simple rigging like a speedrail goalpost for a backlight - beyond that, I want someone on set who knows more than me about rigging and set electricity safety. It’s just not worth the risk otherwise (to me). 

I'm in very much the same position and it's very rare that I'd hit a need for anything I didn't feel able to safely rig personally. I guess what I'm asking about here is the grey area between "what I feel able to safely rig personally" and "what the insurance covers and the law requires."

P

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28 minutes ago, Phil Rhodes said:

I guess what I'm asking about here is the grey area between (1) "what I feel able to safely rig personally" and (2) "what the insurance covers and the law requires."

I don’t think there’s really much of a grey area there. (2) is a producer > production co > insurance co > legal question. Go up the chain as far as needed to get your answers.

I know you’re asking about very small shoots, perhaps as your own producer, also perhaps with somewhat dubious production insurance and hopefully at least an LLC. That’s a bit of a protection, but basically next to none if something catastrophic should happen. 

Even if you stay within (1) and feel a high level of personal safety, something could still go wrong and you could be potentially liable - old wiring could overheat in a stinger or small tungsten lamp and start a fire, or someone could trip over a cable, or a stand could tip over and break a window. That is to say, you might be covered by (2), but you also might not be. Small incidents are much more likely to be covered than large ones. Thus, I would plan accordingly. If the plan feels unsafe, then it most likely is unsafe. 

All of those things and more can also go wrong on big shoots with trained and qualified personnel. But their personal threshold for (1) is much higher than ours. And they are usually protected by (2). Otherwise, they wouldn’t be doing the things they do. 

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22 hours ago, Ed Conley said:

This certainly got confusing.

This is a complicated topic because there are three standards that can apply to the ground fault protection equipment we use: UL943, UL943C, and UL1053.  As well as a standard for portable power distribution equipment: UL1640.  There exists a lot of confusion and misinformation about “GFCIs” because too often manufacturer’s and their representatives conflate these standards, gloss over the differences, and use a single brush to paint everything as a “GFCI” when it is not.

The NEC is very precise in its definition of what constitutes a GFCI.  The NEC Article 100 definition for a GFCI is:

“A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a ground-fault current exceeds the values established for a Class A device”

An attached informational note states:

“Class A ground-fault circuit interrupters trip when the ground-fault current is 6mA or higher and do not trip when the ground-fault current is less than 4mA.  For further information, see UL943, Standard for Ground-Fault Circuit Interrupters.” (The bold and underscore are mine)

Which is very different than the NEC Article 100 definition for Ground Fault Protection Equipment (GFPE) that must conform to UL1053. Ground Fault Protection Equipment is:

“A system intended to provide protection of equipment from damaging line-to-ground fault currents by operating to cause a disconnection mean to open all ungrounded conductors of the faulted circuit. This protection is provided at current levels less than those required to protect conductors from damage through the operation of a supply circuit overcurrent device.”

As an example of how manufacturer’s and their representatives play fast and loose with these classifications, take Guardian’s description of their Model LG400 3-phase device rated for up to 400A and up to 480V:

“The LG400 is the workhouse of the larger GFCI's! With a total capacity of 1200 amps (400amps a leg) it is the perfect tool to protect those 4/0 cable runs. Larger GFCI's like this are classified as equipment protection. However, Bender was able to utilize the same technology incorporated in the smaller "Class A" devices into a large GFCI. When desired the user can have the trip level changed from 20mA to 5mA to be at the same level of protection available in our smaller devices. The LG400 is also capable of a voltage selection of 480, this is very handle when you need to protect those 480 volt power systems that are more and more common these days.” (the poor grammar is their own.)

The LifeGuard LG400 is not a GFCI according to the NEC definition. The NEC Section 100 definition of a GFCI is a “Class A device” as specified by UL943. UL943 defines GFCIs as devices having a fixed trip setting of 5mA (+/- 1mA). Even though it can be set-up to trip “at the same level of protection available in our smaller (Class A) devices”, the Guardian LG 400 is not technically a GFCI because they offer user adjustable trip thresholds. Since they do not meet the complete UL943 standard, they technically do not meet the Code requirement for GFCI protection where prescribed.

The LifeGuard LG400 is sometimes erroneously described as a Class C GFCI. It is not a Class C GFCI because the UL943C standard requires a fixed trip threshold of 20mA and ground-connection monitoring not provided by the Guardian LG400. To meet the UL943C standard, a Class C GFCI must automatically disconnect the supply if the load is not properly bonded to ground (the total ground resistance must be less than 38 ohms.)  To assure that happens an insulated pilot wire from the device to the load, and a termination device located at the load are required to monitor the load-ground connection – neither of which exist in motion picture applications. Since this monitoring function is required for Class C GFCIs installed in NEC applications, the LifeGuard LG400 is technically not a Class C GFCI either. So clearly the LifeGuard LG400 is not a GFCI regardless of what their website says.

If the LifeGuard LG400 is not a GFCI, what are they?  I put this question to Nehad El-Sharif, a former engineer in Littelfuse’s industrial GFCI division, and author of many articles on the UL943C standard (Littelfuse is the manufacturer of the Shock Block brand of film GFCIs.) He thought they must conform to a different UL standard than GFCIs, UL1053, making them instead Ground-Fault Protection Equipment (GFPE.) The distinction is important because GFPE uses very different trip parameters than GFCIs.

Ground fault protection devices generally fall into four different classifications. To improve the generally poor reliability of early GFCIs, in 2003 UL revised the standard for Class A GFCIs (UL943) to prevent nuisance tripping by transient conditions that are not of a sufficient duration to pose a hazard. The revised standard allowed Class A and subsequently Class C GFCIs to trip on an "Inverse Time Curve." The advantage to an inverse time trip curve is that it permits transient spikes in leakage that are sufficiently short in duration so as not to pose a shock hazard to pass while keeping current through the body to safe levels. UL943 also defines outer limits to the curve. A Class A GFCI must trip within 5.59 seconds if the differential between the current going out on the hot and returning on the neutral exceeds 5mA (+/- 1mA), and 20 ms if it exceeds 300 mA.  Class C GFCI’s must operate within the same inverse time curve as Class A devices, except that their operating threshold is 20 mA (non-adjustable). There is a third category of device, Equipment Ground-Fault Protective Devices (EGFPDs) that also operate within the Class-A formula but have a 6- to 100-mA threshold setting range. And finally, Ground-Fault Protection Equipment (GFPE) that must conform to the UL1053 standard.

I asked Nehad El-Sharif if high amperage multiphase devices like the LifeGuard LG400 could be EGFPDs and he couldn’t say with certainty but thought not. The distinction is important because GFPE uses very different trip parameters than the inverse time curve of EGFPDs.

In UL1053 there is no fixed inverse time trip curve as in UL943. Instead, to conform to the UL1053 standard, the operating time (the time from which the trip threshold is exceeded to the time the circuit is interrupted) depends on the percentage of the current differential relative to the trip threshold. If the ground current is 85% of the trip threshold, the device shall not trip. At 115% of the trip threshold, the device will ultimately trip – there is no set time.  At 150% of the trip threshold, the trip time can’t be more than 2 seconds. At 250% of the trip threshold, the trip time can’t be more than 1 second. It could be a lot less than one second, but it can’t be more than 1 second.  In other words, under the UL1053 standard the operating time is the same regardless of the trip threshold.

Besides using different trip parameters, the operating principle of GFPE is very similar to GFCIs. A sensor comprising a toroid that surrounds the conductors detects the algebraic sum of the current in the live conductors (phases and neutral). In the absence of a ground fault, the algebraic sum of the currents in the conductors is equal to zero and the toroid does not detect any flux. If a fault occurs, the sum is no longer equal to zero and the current difference in the toroid generates a current in the winding. This current is rectified, filtered for high frequency harmonics and amplified. If the resulting signal is greater than the user adjustable threshold (usually between 10 and 30mA), a time delay is initiated (it may be equal to zero for an almost instantaneous response or prolonged for a delayed response). If the fault is still present at the end of the time delay, an opening order is issued to a control device (usually a breaker rather than a contactor as in the case of most GFCIs.) Since this is consistent with Guardian’s description of their LG400, it is likely a GFPE rather than a GFCI. But because Guardian conflates these different standards and refers to all their devices as GFCIs, regardless whether they meet the NEC definition or not, it is not clear whether the LG400 is an EGFPD or GFPE.

The Shock Stop 400D, with Bender RCM420 residual current monitor, is clearly a GFPE.  Like the Guardian LG400, the Shock Stop 400D is a 3-phase device rated for up to 400A with adjustable trip thresholds. Rather than use the maximum operating time allowed by UL1053, the RCM420 uses a more aggressive trip curve, similar to that used in European RCDs (1 x ID ≤ 180ms, 5 x ID ≤ 30ms, where ID is the trip threshold.)  As such, the operating time of the SS400D is very short in comparison to the UL943 curve.  For instance, a SS400D set for a trip threshold of 10mA must trip within 180ms at 10mA, compared to approximately 4 seconds required by the UL943 curve. This more aggressive trip curve makes it possible for the user to program a time delay yet still fall within safe limits (superimposing the time-current characteristic curves for the SS400D with thresholds  10, 30 and 100 mA over the safety curves published in IEC 60479-1:” Effects of current on human beings and livestock” clearly illustrates this.) And, since user handled loads statistically account for most shocks, a time delayed GFPE, like the SS400D, can provide adequate ground fault protection for personnel if set up properly, given the low touch voltages involved in a solidly grounded 120/208V service (ungrounded (two prong) systems require Class A protection).

How does this relate to Kyle Perritt’s lunchbox? It establishes that manufacturers and their representatives play fast and loose with UL classifications in their marketing material.  Sometimes what they don’t say is as revealing as what they do say.  For example, the Shock Block marketing literature for their 100A GFCI with Bates Connectors (model SB100) clearly states that it is “UL Listed per UL 943 Class A”. In contrast their marketing literature for their GFCI Lunchbox (model LB100), which is also made by AC Power Distribution, simply states that it is “UL listed” without specifying to which standard. Is this because it is not listed to UL943 as is the SB100? What UL standard could it be listed to if not UL943? AC Power Distribution boxes are UL listed, but to Standard 1640 – the standard for portable power distribution equipment. The requirements of UL1640 pertain to protection against contact with live conductors and placement of breakers and not ground fault protection with GFCIs.  Under UL1640, GFCIs can be incorporated into portable power distribution equipment as “supplemental devices” without changing its classification. Given that I can’t find a wall box style GFCI receptacle like those  found on the AC Power Distribution, Guardian, and Shock Block GFCI Lunchboxes  that has open neutral protection, leads me to believe the only UL standard these boxes conform to is UL1640.

I could be wrong and there is a wall box style GFCI receptacle with open neutral protection.  There is only one way to settle this debate definitively.  That is for Kyle to take the cover off his Guardian boxes to get the manufacturer and part number of the wall box style GFCI receptacle. A Google search of the part number will tell us if it provides open neutral protection as required by UL943 and by extension the National Electrical Code.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.  

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2 hours ago, Ed Conley said:

But the LG520 that Kyle linked is UL943- at least they state it is.
https://www.guardiangfci.com/products/lg520

They also state their LG400 is a GFCI when it clearly is not.  Shock Block prevaricates whether their LB100 (also made by AC Power Distribution) conforms to UL943 or UL1640. As I said before,  I could be wrong and there is a wall box style GFCI receptacle with open neutral protection.  There is only one way to settle this debate definitively.  That is for Kyle to take the cover off his Guardian boxes to get the manufacturer and model number of the wall box style GFCI receptacles  on the box. A Google search of the part number will tell us if it provides open neutral protection as required by UL943 and by extension the National Electrical Code.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.

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I feel like I now bear the responsibility to bring some kind of resolution to this wild digression I kicked off, so once I'm reunited with this lighting package in about two and a half weeks I'll take the cover off and snap a pic and see what we're working with.

Though it would seem highly irresponsible, possibly unethical for a company to market a portable GFCI box to crews who are solely rigging portable electrical distribution systems as being up to code for that kind of use when it's really not. I don't know the story with the LG400. Honestly, most portable GFCIs I encounter on set are the 100 amp Shock-Blocks    

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10 hours ago, Kyle Perritt said:

... it would seem highly irresponsible, possibly unethical for a company to market a portable GFCI box to crews who are solely rigging portable electrical distribution systems as being up to code for that kind of use when it's really not. ...

Yes, but this is the same company that calls a product  (the LG400) that does not meet the NEC definition of a GFCI by that name and promotes the use of it in a manner that does not satisfy the NEC requirement for GFCI protection where prescribed by the Code.

It would be great if you could send me that picture.  My email address is rentals@screenlightandgrip.com

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.

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On 2/8/2021 at 6:53 PM, JB Earl said:

thanks for the detailed info Guy.  I looked at the manufacturers you cited, the only product I could find that is appropriate to what I'm doing would be the one by Lifeguard, https://www.guardiangfci.com/products/lg20-line.  I use the Voltec https://www.voltec-industries.com/copy-of-04-00103  for extremely small projects involving a couple lights. I haven't had a problem with them tripping (yet).  Typically I'll plug in a parcan or a couple litemats/panels.

I appreciate your thorough explanations, but can you give a non-electrician comparison of these 2 devices, and a dealer for the LG20 if you know of one?

Don’t try to power an ARRI 1200 HMI Par with non-pfc electronic ballast with the Voltec. To reduce the amount of RFI emitted into the atmosphere, the ARRI 575/1200 non-pfc electronic ballast shunts the high frequency harmonic currents drawn by the ballast to the EGC. The end result is 16.4mA of leakage current on the EGC that trips unfiltered GFCIs like the Voltec every time.  I’m not sure the Guardian LG20 has harmonic filtration (I haven’t found an inline GFCI dongle that does.)

I don’t know for certain, but I suspect the Guardian LG20 is a rebranded Southwire Model 25230.  They look identical and Southwire sells them unbranded in quantity only.  If that is the case, they don’t provide the harmonic filtration required to eliminate nuisance tripping with non-linear loads.

Fortunately, where 15- and 20A circuits must be GFCI protected, Section 215.9 of the Code permits the feeder to be GFCI protected instead. Section 215.9 reads as follows:

“Feeders shall be permitted to be protected by a ground fault circuit interrupter installed in a readily accessible location in lieu of the provisions for such interrupters as specified in 210.8 and 590.6(A).”

Since this section prescriptively identifies feeder GFCI protection “in lieu of” that required in NEC Section 210.8, it permits the use of film GFCIs (like the Shock Block SB100, LifeGuard LG100, and Shock Stop 60-100), with 100A Lunch Boxes to satisfy the Code's requirement for GFCI protection on all single-phase branch circuits of 150V to ground or less, rated 50 amps or less. With a more accommodating trip curve and high frequency filtration, it is better to use a film GFCI just upstream of a 100A Lunch Box, then to use individual GFCI dongles on each 20A circuit of the Lunch Box.

Unfortunately you can’t buy the Shock Block SB100, or LifeGuard LG100 (they can only be rented.) Shock Stop, however sells the SS60-100.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.

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34 minutes ago, Ed Conley said:

What kind of GFI are installed on portable generators? They look the same as the ones on the LG520

The GFCI outlets on portable generators are not portable.  They are hardwired into the generator. UL943 requires open neutral protection of portable GFCIs because they are likely to be used on wiring of questionable integrity that could have an open neutral, such as the temporary power systems of construction sites or the portable power systems of motion picture sets. Where open neutrals with GFCIs can create hazardous conditions UL943 requires portable GFCIs to interrupt power to the load if there is a break in the line side neutral conductor. It is nearly impossible for the neutral conductor of a GFCI hardwired into a generator to break.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.

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27 minutes ago, Brian Doran said:

I seems like the only online traces of Shock Stop are on your blog, Guy. Do you know who might carry them for sale or rental? 

Not really supposed to market products on these boards.  Contact me off list through message or at rentals@screenlightandgrip.com for details.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting  Rental & Sales in Boston

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2 hours ago, Guy Holt said:

Not really supposed to market products on these boards.  Contact me off list through message or at rentals@screenlightandgrip.com for details.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting  Rental & Sales in Boston

Sure thing, I'll send you an email tomorrow morning.

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On 2/10/2021 at 10:28 AM, Guy Holt said:

 

Since this section prescriptively identifies feeder GFCI protection “in lieu of” that required in NEC Section 210.8, it permits the use of film GFCIs (like the Shock Block SB100, LifeGuard LG100, and Shock Stop 60-100), with 100A Lunch Boxes to satisfy the Code's requirement for GFCI protection on all single-phase branch circuits of 150V to ground or less, rated 50 amps or less. With a more accommodating trip curve and high frequency filtration, it is better to use a film GFCI just upstream of a 100A Lunch Box, then to use individual GFCI dongles on each 20A circuit of the Lunch Box.

Unfortunately you can’t buy the Shock Block SB100, or LifeGuard LG100 (they can only be rented.) Shock Stop, however sells the SS60-100.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.

so it sounds like there is literally no solution for GFCI use when we just want to use a small HMI  in the backyard, plugged into a 20a residential outlet?

 

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4 hours ago, JB Earl said:

so it sounds like there is literally no solution for GFCI use when we just want to use a small HMI  in the backyard, plugged into a 20a residential outlet?

No. It depends on the ballast.  I have only been able to do limited testing of HMIs but for example an Arri 4k power factor corrected ballast dumps 16.22mA of current into the EGC while a Power Gems  4k non-power factor corrected ballast dumps only 2.47mA.

In order to reduce the amount of RF emitted, UL permits but does not require manufacturers of electronic devices to capacitively couple high frequency harmonic currents to ground (UL1244, UL1950, UL3101.) To accomplish this, some but not all ballast  manufacturers include a mains input filter to stop electrical noise from being passed in or out of the ballast via its mains lead. Such filters typically include a pair of small capacitors, one connected between the hot and earth and the other between the neutral and earth wires of the incoming mains. The value of the capacitors is chosen to snub the high frequency noise by shunting it to ground. As such, these RF filters can be a source of appreciable leakage current on the EGC. Arri shunts the noise their  ballasts generate while apparently Power Gems does not (use this link for more details.)

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.

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