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Guy Holt

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    Gaffer
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    Boston
  • Specialties
    Custom Honda generator systems for motion picture production including paralleling systems with 100A output.

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    http://www.screenlightandgrip.com

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  1. Time to revive this thread with some indie tricks-of-the-trade for lighting large rooms with drop ceilings. You don’t necessarily have to go to the expense of bouncing big HMIs into the ceiling. One of the biggest challenges in situations like this is getting light into the eyes of your talent. If you don't, your talent's eye will look dark and bruised because a very toppy bounce won't dig into their eyes. As an alternative, the OP may want to consider the approach we took on a short film called "Act Your Age" that takes place in a senior center (use this link to see production stills.) We hung 4'-4 Bank kinos with Opal coved below the fixture to make a "Bay Light." Coving the Opal under the light, redirects it so that it will dig into the talent’s eyes. And you can skirt the fixtures to keep the light off the white walls (something you won’t be able to easily do with a bounce source.) You may also want to consider using a combination of hard and soft light as we did here to create contrast in a situation where the practical lighting is usually very flat. For a hard light source, we powered a 4k Fresnel off the wall. Most schools have a 240V receptacle of some kind. Common 240V circuits in schools include, Copier receptacles, range receptacles, and special receptacles installed for air conditioners. The latest generation of 2.5/4k HMI ballasts will operate on either 120V or 208-240V and fit comfortably in these circuits. If you are using an older ballast that runs only on 120V, you can step-down a 240V circuit to 120V with a transformer. A step-down transformer will convert the 240 volts supplied by 240V receptacles to 120 volts in a single circuit that is the sum of the two single-phase legs of 30/50 amps each (60A usually). Now that you have a larger 120V circuit, you can operate larger lights like 2.5 or even 4k HMIs, or more smaller lights, than you could otherwise. A step-down transformer can do the same with the enhanced 7500W/240V output of a Honda EU7000is Generator. By giving you access to more "house power" through common 240V household outlets, a Transformer/Distro can eliminate the need for dangerous tie-ins or expensive tow generators (use this link for details.) As you can see from the production stills, we used a special drop ceiling hanger that enables you to use a drop ceiling like a studio grid. Use this link for more pictures of productions that used drop ceilings on location as if they were a studio grid. Another alternative is to cut ¼” Luan plywood to the size of the ceiling tiles and screw a baby wall-plate into it. Then replace the ceiling tiles with the plywood wherever you want to hang a light. Guy Holt, Gaffer, ScreenLight & Grip, Lightng Rental & Sales in Boston
  2. Not necessarily. One of the biggest challenges in situations like this is getting light into the eyes of your talent. If you don't, your talent's eye will look dark and bruised because a very toppy bounce won't dig into their eyes. As an alternative, you may want to consider the approach we took on a short film called "Act Your Age" that takes place in a senior center (use this link to see production stills.) We hung 4'-4 Bank kinos with Opal coved below the fixture to make a "Bay Light." Coving the Opal under the light, redirects it so that it will dig into the talent’s eyes. And you can skirt the fixtures to keep the light off the white walls (something you won’t be able to easily do with a bounce source.) You may also want to consider using a combination of hard and soft light as we did here to create contrast in a situation where the practical lighting is usually very flat. For a hard light source we powered a 4k Fresnel off the wall. Most schools have a 240V receptacle of some kind. Common 240V circuits in schools include, Copier receptacles, range receptacles, and special receptacles installed for air conditioners. The latest generation of 2.5/4k HMI ballasts will operate on either 120V or 208-240V and fit comfortably in these circuits. If you are using an older ballast that runs only on 120V, you can step-down a 240V circuit to 120V with a transformer. A step-down transformer will convert the 240 volts supplied by 240V receptacles to 120 volts in a single circuit that is the sum of the two single-phase legs of 30/50 amps each (60A usually). Now that you have a larger 120V circuit, you can operate larger lights like 2.5 or even 4k HMIs, or more smaller lights, than you could otherwise. A step-down transformer can do the same with the enhanced 7500W/240V output of a Honda EU7000is Generator. By giving you access to more "house power" through common 240V household outlets, a Transformer/Distro can eliminate the need for dangerous tie-ins or expensive tow generators (use this link for details.) As you can see from the production stills, with the right rigging equipment, you can use drop ceilings like a studio grid. Use this link for more pictures of productions that used drop ceilings on location as if they were a studio grid. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston
  3. If you are looking for a Power Quality Analyzer there are a number of options. At a list price of $1495, the Fluke 41B Power Quality Analyzer was Flukes’ entry level single-phase scope meter. It combined the ease of use of a digital multimeter, the visual feedback of an oscilloscope and the power of a harmonics analyzer in a single instrument. It provided numeric values for rms, peak and total harmonic distortion (THD) for the complex voltage and current waveforms generated by motion picture lights. A bar graph showed the distribution of harmonics in complex waveforms, while its scope provided a graphic representation of both voltage and current waveforms. I use the past tense because, unfortunately, the 41B has been discontinued. Flukes’ entry level scope meter is now the 43B Power Quality Analyzer which sells for about $3800. Besides offering all the same capabilities of the 41B, the 43B trends voltage, current, frequency, power harmonics and captures voltage sags, transients, and inrush current. As far as I know (Fluke’s product line is constantly changing) the 43B is the only instrument that combines the capabilities of a Power Quality Analyzer, a 20 MHz oscilloscope, a multi-meter and data recorder in a single tool. The next step up in Power Quality Analyzers in Fluke’s product line is the 434-II, which sells for about $6900. It offers all the same capability as the 43B, but for all three phases simultaneously. It also offers a cool bar graph screen that combines power quality parameters (RMS Voltages, Harmonics, Flicker, Dips, Interruptions, Rapid Voltage Changes, Swells, Unbalance, Frequency, Mains Signaling) all on one screen. The length of a bar increases if the related parameter is further away from its nominal value. The bar turns from green to red if an allowed tolerance requirement is violated. These two options have several drawbacks. They are expensive but are available for rental in major markets. Their screens are poorly designed and exhibit dead scan lines after a while. The dead scan lines don’t affect their measuring capability, so they are just a nuisance. The screens can be swapped out for a couple hundred bucks at independent service shops (Fluke charges a lot more). The final drawback is that they are cluttered with features that have no benefit to set lighting technicians. The latest in metering technology designed specifically for set lighting technicians is GenNet IoT. Employing the latest Internet of Things (IoT) technology, GenNet IoT provides an unprecedented level of accessibility to the critical information required to manage generators and power distribution by delivering it to an operator’s phone, tablet, or laptop via 4G LTE wireless technology. It has an embedded web server that can display not only comprehensive power quality measurements but also engine data using standard internet browsers and allows for device configuration from the browser. To help you interpret the vast amount of information it generates (such as phase loading, voltage and power levels, power factor, and power quality measurements), its embedded web server presents real time, historical, and event information in easily understandable browser-style graphic displays. If a generator is equipped with InteliVision 5, GenNet IoT will also display critical engine data such as oil pressure, fuel level, and water temperature. To alert operators to problems before they can get out of hand, GenNet IoT also offers configurable event triggers. Max/Min limits can be set for any measured parameter. If any of the limits are exceeded, GenNet IoT will dispatch an e-mail alarm alerting you of the event. For example, to alert operators of a voltage unbalance that can degrade the performance of a generator and connected loads, its web server displays numerical and graphic phasor representations of the voltage of each phase, its phase angle, the average voltage, and will push an email alarm to your mobile device if the % (-) sequence harmonics (VNeg) exceeds two percent. Gen Net IoT’s email alarms can be a show saver for set lighting technicians since it is easy to miss load induced power quality issues in the thrash to get the first shot of the day. Gen Net IoT can also be used to prevent engine failure in Tier 4 generators caused by “wet stacking.” Wet stacking is the build-up of carbon in a generator’s engine caused by light loading. Generators need to operate at high temperatures to completely burn diesel fuel. When run under light loads, less heat is generated in its combustion chamber, leaving some fuel unburned. The unburned carbon coats the fuel injector nozzles, compromising their ability to adequately vaporize fuel. This, in turn, further lowers the combustion temperature and allows more unburned fuel to clog the fuel injectors. If left unchecked, wet stacking can result in premature engine failure. Operators of Tier 4 generators must be particularly vigilant. Tier 4 generators are more efficient, but they are also more vulnerable to the effects of light loading. They need to operate under higher loads (at least 75% of the nameplate rating) to reach the temperatures necessary to prevent carbon buildup and engine failure. With the reduced loads characteristic of sets lit predominantly by LED fixtures, wet stacking is an increasing concern for operators of Tier 4 generators. GenNet IoT prevents wet stacking by controlling a digital load bank to “auto-load” a generator. It does so by a Modbus control signal over ethernet that will initiate a digital load bank to automatically apply load to a generator in a step fashion if the lighting load drops below 75%, and to decrease the load it applies if the combined load begins to exceed 75%. In this fashion, GenNet IoT assures that the generator is sufficiently loaded to prevent wet stacking and premature engine failure. A tremendous benefit with Tier 4 generators when operating under the reduced load of sets lit predominantly with LED fixtures. To take one more thing off the plate of a generator operator, GenNet IoT can also automate the process of ghost loading. To maintain voltage unbalance within a narrow range when the impedance of the system neutral is high, GenNet IoT can control a companion load bank manufactured by Simplex specifically for it. If GenNet IoT senses unbalanced phases, it will trigger the load bank to apply load to the low phase in 5kVAR load steps. In this fashion GenNet IoT can maintain balanced phases thereby reducing deleterious unbalanced voltages. To further customize the load bank for film production Simplex has engineered it to apply an inductive load rather than the resistive load of standard industrial load banks. An inductive load offers several benefits in motion picture production. Without the tremendous heat generated by resistive coils, an inductive load bank eliminates the requirement for loud cooling fans and is thereby nearly silent in operation which permits the generator to be closer to set. An inductive load also corrects the leading power factor of motion picture lights these days. HMIs, Kinos, and LEDs are capacitive loads that cause voltage to lead current. Typically ghost loading is required when powering sets lit predominantly by LEDs. By applying an inductive load, Gen Net IoT corrects the power factor of the system (by pulling voltage back in phase with current) while maintaining a 75% load on the generator to prevent wet stacking. One Gen Net IoT on its own provides unparalleled access to the critical info required to manage a generator. Multiple Gen Net IoTs in a wireless 4G network, provides the ability to manage multiple generators from a central location. When there is more than one operator, Gen Net IoT enables them to share data and work in shifts – allowing them to get needed rest during overnights. One drawback to GenNet IoT is that it is only available for rental (most lighting technicians couldn’t afford one anyway.) As part of their rental model, a GenNet IoT customer support technician also receives the email alarms and is on hand to offer advice on how to correct the problem. It’s a whole new world from when I started in this business thirty years ago. Guy Holt, Gaffer, ScreenLight & Grip, Lighting equipment sales and rentals in Boston. P.S. In the interest of full disclosure I am involved in the development of GenNet IoT and so get overly excited about its features.
  4. You are correct that without a neutral in their mains cable these ballasts will not contribute to the elevation of return current on the system neutral of a distribution system – only smaller non-pfc ballasts operating line-to-neutral will do that. But, elevated neutral current is not the only adverse effect the harmonic currents drawn by these ballasts have on a distribution system whether it is single phase or three phase. Ed has already pointed to one: they draw an excessive amount of power (72A) compared to a power factor corrected ballast (55A). Since this watt-less power does not contribute to illuminating a set, it effectively reduces the capacity of your service. But that is not all. The current they draw is severely distorted by their large smoothing capacitors, which only draw current during a very brief period as the voltage waveform peaks. Since the ballast draws power for only a brief period, it draws a spiked current waveform with a high crest factor and harmonic content. This distorted current will have an adverse effect on the distribution system whether it is single phase or three phase. First, since the load of the light is only on the peak of the voltage waveform, in high impedance systems like generators, voltage drop occurs only at the peak, resulting in the flat-topping of the voltage waveform in the entire distribution system. Which means all connected loads encounter a chopped voltage waveform. Since the switch-mode power supplies of smaller HMIs, Kinos, and LEDs also only draw current at the peak of the voltage waveform, they can be starved of power. Second, since the harmonic currents drawn by these ballasts oscillate at high frequencies they travel on the perimeter of conductors (skin effect). Since more current is traveling through less copper the effective resistance of the conductor increases leading to further voltage drop, but more importantly an exponential increase in I2R heat loss, resulting in the possible nuisance tripping of breakers, and the overheating of conductors and the generator stator. Power factor correction circuitry is expensive - adding up to 25% to the cost of a ballast. For this reason, the manufacturers of HMI ballasts only incorporate it where it is absolutely necessary. Now a days all HMI ballast greater than 4kw include power factor correction because it is essential to the reliable operation of the ballast and connected loads. Which means you will need to take several precautions in using them. First, oversize generators and transformers by a factor of two. Second, oversize your feeder cables. Finally watch out for voltage flat-topping using a digital mulit-meter or power quality analyzer like GenNet IoT that can read peak voltage as opposed to rms voltage (the rms value of flat-topped voltage is the same as a sinusoidal voltage waveform.) This is a complicated subject, I strongly recommend you read a series of articles I wrote for Protocol Magazine (the qtrly journal of ESTA) on Production Power on a Budget and Power Quality in the Age of LEDS available at our website at http://www.screenlightandgrip.com/html/hd_plug-n-play_pkg.html. Harry box cites these articles in the latest edition of his handbook. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston
  5. You can use the 1kW Iris lights without flicker. The reason that you get flicker from small filament bulbs (<5kW) is that at high speeds the camera will capture the changing intensity of the light output of the bulb as it rises and falls as the voltage waveform rises and falls. If you use three 1kW Iris where you would normally use one, and put each fixture on a separate phase of the power service, the light output between the three fixtures will be constant as each compensates for the drop in intensity of the other. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rentals & Sales in Boston
  6. 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.
  7. 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
  8. Let's try this again. Use this link to Shock Stop's marketing material and training guide. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.
  9. Use this link to Shock Stop’s marketing literature and training guide. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
  14. 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.
  15. This is a good case in point why electrical distribution should be left to qualified persons. As you may recall from my post above, NEC Article 530 requires that an individual using portable lighting and power distribution equipment know how to comply with NEC safety rules when performing installations. The NEC Section 100 definition of a GFCI is a “Class A device” as specified by UL943. Among UL943’s many requirements is that portable GFCIs trip if there is a break in the line side neutral conductor of a circuit. It does not require the same of GFCIs meant to be permanently installed in a wall outlet box. Since the GFCI Lunch Boxes you bought from Kayelites incorporate wall box style GFCIs without open neutral protection they do not meet the code requirement for the use of portable GFCIs outdoors. (For the same reason Phil’s shop made RCD boxes would not pass US code.) A qualified person, trained in ground fault protection, would know the difference between GFCIs suitable for portable use and permanent installation. The same is true of OSHA. OSHA29 CFR 1926.404(b)(1)(i) states: “The employer shall use either ground fault circuit interrupters as specified in paragraph (b)(1)(ii) of this section or an assured equipment grounding conductor program as specified in paragraph (b)(1)(iii) of this section to protect employees on work sites . . .” Under §1926.404(b)(1)(ii), when using GFCIs to comply with paragraph (b)(1)(i), the employer must use an "approved" GFCI. Under §1926.449, approved equipment is equipment that is "acceptable." Section 1926.449(a) defines acceptable equipment as follows: “(a) If it is accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a qualified testing laboratory (like UL) capable of determining the suitability of materials and equipment for installation and use in accordance with this standard…” As I mentioned previously, UL requires portable GFCIs to offer protection against an open-neutral condition. Why the different requirements for portable vs. permanently installed GFCIs? Since portable GFCIs are likely to be used on wiring of questionable integrity, such as the temporary power systems of construction sites or the portable power systems of motion picture sets, UL943 requires portable GFCIs to interrupt power to the load if there is a break in the line side neutral conductor. Given the wear and tear equipment receives in these environments, it is more likely that one of the circuit conductors could be broken on the supply side of the GFCI. If it is the energized, or Hot, conductor that is broken, no hazard exists at the GFCI, and it is readily obvious because there is no power. If, however, it is the grounded circuit conductor, or neutral, that is broken on the line side of the GFCI, it is less obvious. The line voltage terminals would still be energized. The only indication of an open neutral would be that a load plugged into the circuit doesn’t turn on. Since the brain of the GFCI relies on a complete circuit in order to operate, under this circumstance the GFCI would not trip if there were a ground fault on its load side. Of course, the problem would be detected if the unit were tested with the test button before each use as required by Code, but we know that precaution is seldom taken. It is because of this possible hazard that UL943 requires that the load terminals of portable GFCIs must be de-energized when the neutral is interrupted on the line side of the device. Portable GFCIs accomplish this by using “NO”, or normally open, relays rather than the more common “NC”, or normally closed, relays. With NO relays power must be complete to the relay in order for the contacts to be closed. If there is no power, such as from an open neutral, the relay contacts are opened by spring pressure. Power is necessary to overcome the spring pressure, closing the contacts. Sorry to say that your GFCI Lunchbox is not a UL approved Class A GFCI and therefore does not meet Code where a Class A GFCI is required. Guy Holt, Gaffer, ScreenLight & Grip, Lighting equipment rental and sales in Boston
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