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Guy Holt

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Guy Holt last won the day on July 27 2019

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About Guy Holt

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  • Occupation
    Gaffer
  • Location
    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. To power a small HMI off of batteries for an unlimited time in a car rig you can use a "Battverter" - which is a Battery/Inverter system. A "Battverter" system consists of a 12V DC power source (usually large Marine Cells), a DC-to–AC True Sine Wave Power Inverter, and a Battery Charger. Here is a link to some production stills that show you two Battverter systems I built to run lights in vehicles at various times. The first is a 750W "Battverter" rig wired into a Calzone case. The second is a more elaborate 1800W Battverter system that I built to run 16 - 4’ kinos tubes inside an airport shuttle bus. Use this link - https://cinematography.com/index.php?/topic/70937-indie-tricks-of-the-trade-or-how-to-get-good-production-values-on-a-modest-budget/- for details. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boson
  2. There are two reasons why you should not replace the duplex receptacles on your gang box with GFCI receptacles. First, it is a code violation and, second, they are the wrong kind of GFCIs for the loads we use. First, while the Code permits you to build your own “cord set”, it requires that cord sets utilize GFCI protection listed for portable use. The reason for this is that such GFCIs include "Open Neutral" protection, which enhances personnel safety where such devices are subject to the possibility of losing a Neutral connection. For this reason, it is not permissible to utilize GFCI receptacles designed and listed for permanent installation without Open Neutral protection in portable cord sets. The second reason not to replace the duplex receptacles on your gang box with GFCI receptacles, is that they are the wrong kind of GFCIs for the loads we use. In addition to not filtering residual currents, hardware store type GFCIs use a much more aggressive trip curve than do film style GFCIs like those manufactured by Shock Stop, Littelfuse, and Bender. To understand the difference requires a little background information. To improve the generally poor reliability of early GFCIs, in 2003 UL published a new standard (UL 943) for GFCIs designed to prevent nuisance tripping by transient conditions that are not of a sufficient duration to pose a hazard. The new standard allowed GFCIs to trip on an "Inverse Time Curve." An inverse time curve can be mathematically expressed as I2T where "I" is current and "T" is the time it takes to trip. Since this is a logarithmic equation, the plot of I versus T (as can be seen in graph below) does not follow a straight line but introduces a delay that decreases as the magnitude of the current increases. 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. And, as mentioned in my previous post, UL 943 also permits GFCIs to incorporate high frequency filters to avoid nuisance tripping from GFCIs becoming sensitized by residual currents. Attenuated by a filter, high frequency harmonic currents drawn by non-linear loads won't trip or sensitize GFCIs. Even though the UL 943 standard was meant to enable GFCIs to operate more reliably in real world conditions, manufacturers of inexpensive GFCIs, like those found in hardware stores, do not implement the exact UL943 curve because it requires sophisticated micro-processors, which makes the design more complicated and the GFCI more expensive. Nor, do they filter high frequency residual currents for the same reason. Instead they use a more aggressive response (also illustrated in the graph below) that is lower and faster than that required by UL 943 (typically 25ms at 6 mA where UL 943 permits 5.59 seconds.) This more aggressive trip curve and lack of filtration does not generally pose a problem in the one-tool per circuit applications for which hardware store GFCIs are designed. After all, power tools are by their nature linear loads that do not draw high frequency harmonic currents. However, the more aggressive trip curve of this style of GFCI has proven to be a problem in applications involving non-linear lighting loads, namely the type of lights increasingly used in motion picture production. And, with the number of LED fixtures that have non-pfc power supplies increasing on set, nuisance tripping of inexpensive GFCIs will only become more frequent. So what’s a set electrician to do? Fortunately, NEC Section 215.9, Ground-Fault Circuit-Interrupter Protection for Personnel provides general permission for a feeder to be GFCI protected where it supplies 15- and 20A receptacle branch circuits requiring GFCI protection under Section 210.8. The section reads as follows: “Feeders supplying 15- and 20-ampere receptacle branch circuits shall be permitted to be protected by a ground-fault circuit interrupter 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 210.8, it permits the use of film style GFCIs (like the Shock Block SB100, LifeGuard LG100, and Shock Stop 60-100), with 100A Lunch Boxes to satisfy the recently expanded Section 210.8 requirement for GFCI protection on all single-phase branch circuits outdoors rated 150 volts to ground or less, 50 amps or less. This is good news for us since film style GFCIs, like the LifeGuard, Shock Block, or Shock Stop are a lot less prone to nuisance tripping because, unlike hardware store GFCIs, they employ high frequency filters and a trip curve that more closely approximates the inverse-time curve of UL943. Guy Holt, Gaffer, ScreenLight & Grip, Lighting sales and rentals in Boston
  3. Do a Google search for Shock Stop GFCI in parenthesis, that is enter "Shock Stop GFCI" in the Google Search Bar.
  4. I think you should hire a Gaffer that will keep you Code compliant. I salute your desire to learn but there comes a point where you can't expect to know everything and should hire a "Qualified Person." In Code parlance a Qualified Person is someone who has received formal training in the hazards posed by electricity and how to mitigate it. When it comes to using electricity a little knowledge can be dangerous. It may not seem like it, but this is a very complicated question. The Code requires that ground rods be 10ft, driven all the way into the ground, and the impedance to earth of the driven rod be no more than 25Ωs . If you are not able to satisfy this requirement with one rod, the code allows you to satisfy its requirement by driving a second rod not less than 6ft from the first. However, Honda EU6500s and EU7000s meet the Code requirements to be exempted from its grounding electrode requirement. They do not however meet OSHA's requirements to be exempted. To complicate the issue further, the NEC is a uniform code that is adopted into law in whole, or in part, by the local "Authority Having Jurisdiction" or AHJ. It is not uncommon for the AHJ to modify or augment the NEC in adopting it into law. For instance, in the City of Los Angeles you are not required to ground generators, but here in Boston we are required to ground generators. In the city of Boston, we are not permitted to use gas generators, but must use diesel generators. In short you need to check with the AHJ where you are shooting to see what the requirement is. To complicate the issue even further, the Code is the minimum required for electrical safety. Even though it does not require a Honda EU6500 or EU7000 to be earth grounded there are, IMO, good reasons to ground Hondas. For one, GFCIs will operate more reliably if they are, but that is more than I have time to get into now (perhaps later if you are interested). If you have not already, I suggest you read my white paper on the use of portable generators in motion picture production. It is available at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html. Guy Holt, Gaffer, ScreenLight & Grip, Lighting rental and sales in Boston.
  5. The Code article that mandated that any portable generator under 10kW with 240V output be GFCI protected grandfathered generators manufactured before 2014 which permits rental houses to continue to rent their EU6500s with Bates modifications. It does not, however, exempt the users of those generators from the Article 210 general requirement for GFCIs on outdoor circuits of 150V to ground or less, and 50A or less. To meet this requirement electrical manufacturers like Woodhead and Hubble introduced inline 120V and 240V 30A GFCIs, but since the 50A Bates mod was an after market modification done on a very limited scale, large manufacturers like Woodhead and Hubble did not see a market for an inline 50A/120V GFCI. Which means that until Shock Stop introduced their inline 60A /120V GFCI (pictured above) the only option was to use one of the 100A/120V Shock Block GFCIs manufactured by Littelfuse or Bender. The ability to use high amperage "film style" GFCIs like those manufactured by Shock Stop, Littelfuse, and Bender to provide the Code mandated GFCI protection required on the 20A receptacles of lunch boxes and gang boxes is a huge benefit to us because the alternative, hardware store style GFCI dongles, are prone to nuisance tripping with many motion picture lighting instruments. Thats because many of the manufacturers of lighting fixtures that use electronic power supplies (HMIs, Kinos, & LEDs) shunt the harmonic currents they generate to their equipment grounding conductor as a means of reducing RF. Since these harmonic currents, called residual currents, return to their source via the equipment grounding conductor rather than the neutral, inexpensive hardware store GFCIs sense a current imbalance and trip. Such trips are a nuisance because the residual currents these power supplies generate do not pose a shock hazard. What makes high amperage "film style" GFCIs like those manufactured by Shock Stop, Littelfuse, and Bender worth the extra expense is that they filter high frequency currents and thereby are not tripped by these residual currents. For this reason it is far better to use a high amperage film style GFCI just upstream of a lunch or gang box than to use 15A hardware store GFCI dongles on the 20A outlets of a lunch or gang box as pictured below. Guy Holt, Gaffer, ScreenLight & Grip, Lighting rental and sales in Boston
  6. The inspector that shut down the grad student thesis film I gaffed didn't care a bit that it was a non-Sag micro-budget student film. Guy Holt, Gaffer, Screenlight & Grip. Lighting rental and sales in Boston
  7. Impugning my motives won't change the facts. Take a look around your EU7000. It is designed to be compact and quiet. To be compact there is no wasted space. To be quiet there is a steel wall between the electrical compartment behind the power panel and the rest of the generator, which means there is no place else to put the Bates connector. We used to offer this mod and if it were still possible I would happily do it for you, but it is practically impossible after the power panel was redesigned to accommodate GFCIs. Not true. The NEC is written in blood. Everyone of its requirements is the result of someone being injured or property damaged. The NEC requires GFCIs on Hondas because they present, and have always presented, a particular hazard. What happened was Hurricane Katrina when there was a surge of electrical injuries from the operation of portable generators. Because they are designed primarily for home standby power, the Honda EU6500s and 7000s do not bond the equipment grounding conductor to the neutral of the generator as required by OSHA. Without a Neutral/Ground bond, as illustrated below, a multiple fault condition exposes an individual touching faulty equipment to 240 volt potential which is lethal. The NEC is law in all 50 states, the AHJ (or OSHA most likely) will enforce this requirement and shut down your production. Years ago I gaffed a grad student thesis film project that was shutdown by the electrical inspector because he happened upon our set on his way home from work. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston
  8. Slow down. As someone who used to offer this mod (the picture above is from our website) and can no longer do so, I can tell you that even if you could find someone to do it these days (I doubt you will) I wouldn't do it. While the modification was very straight forward with the Honda EU6500, there are mechanical issues that make it very difficult on the Honda EU7000. And, since January of 2020 there are now Code issues that make it illegal in many states. For these reasons, any responsible shop that used to do the mod no longer does so. Let's look at the mechanical reasons first. Starting with the 2017 Code, the NEC mandates that any portable generator under 10kW with 240V output be GFCI protected. To make it code compliant Honda has put GFCIs on the latest edition of the EU 7000 leaving no room for the 60A Bates on the redesigned power panel. Those companies that continued to offer the mod (Multiquip) could only do so by completely removing the 30A Twist-Lock from the panel, moving the control circuit board, building in overcurrent protection, and machining a cover plate to cover the hole in the panel left by the 30A Twist-lock. They also had to silk screen onto the cover plate the warnings required to reduce their liability. Of course all this was not UL tested and so voided the UL listing of the generator. Fast forward to January 2020. The 2020 edition of the Code greatly expanded GFCI requirements to include all outdoor circuits of 150V or less to ground and 50A or less whether fixed or portable. Since the Bates mode provided 50A at 120V it now requires GFCI protection which is why I suspect even Multiquip will discontinue offering the modification. The only way to get a 60A circuit capable of powering a 4kW HMI or 5kW Tungsten light out of a Honda EU6500 or EU7000 is to use a small step-down transformer to convert the 240V output of the generator to 120V. Since this circuit is 60A at 120V it is not required by Code to be protected by a GFCI. The NEC is the minimum required for electrical safety on set. Our industry standards writing group, ESTA, recommends the use of GFCIs on all branch circuits of 100A or less. For this reason we now offer a listed 60A GFCI that can be used on a step-down transformer, or on any 60 or 100A Bates circuit to provide unparalleled ground fault protection. And since NEC Section 215.9 permits the use of a GFCI on the feeder of branch circuits requiring GFCIs, it can also be used to provide the GFCI protection required on the 20A circuits of gang and lunch boxes as pictured below. Guy Holt, Gaffer, ScreenLight & Grip, Lighting rental & sales in Boston.
  9. Given the evolution of HMI technology over the years you can easily get stuck with a lemon if you are not careful. The history of HMI ballast design can be characterized as the proverbial two steps forward while making one step back. When electronic square wave HMI ballasts came on the market, they were at first thought to be the solution to all the problems inherent in running HMIs with magnetic ballasts on portable generators. Since they are not frequency dependent, it was thought at first that electronic square wave ballasts would operate HMIs more reliably on generators – even those without frequency governors. By eliminating the flicker problem associated with magnetic ballasts, they also eliminated the need for the expensive AC governors required for flicker free filming with magnetic HMI ballasts and portable generators. For these reasons, as soon as electronic square wave ballasts appeared on the market, many lighting rental houses replaced the expensive crystal governed Honda EX5500 with the less expensive non-synchronous Honda ES6500. The theory was that an electronic square wave ballast would operate reliably on a non-governed generator and allow filming at any frame rate, where as a magnetic HMI ballast operating on an AC governed generator allowed filming only at permitted frame rates. In practice, electronic square wave ballasts turned out to be a mixed blessing. The leading power factor caused by the capacitive reactance of the then new electronic ballasts proved to have a more severe effect on conventional AVR generators than did the old magnetic ballasts. In response lighting manufacturers introduced a second generation of electronic ballasts that incorporated power factor correction. But, Power Factor Correction (PFC) is not mandated in this country, as it is in Europe for any electrical device that draws more than 75W., and so in this country most HMI ballasts smaller than 6kW continued not to be power factor corrected. The early line of Lightmaker electronic ballasts were nick named by film electricians “Troublemaker” ballasts because they were not Power Factor Corrected and proved that PFC circuitry was absolutely necessary in large ballasts to reduce heat and returns on the neutral, and to increase ballast reliability (beware, some are still kicking around ebay). But, because of the added cost, weight, and complexity of PFC circuitry, ballast manufacturers in the US only offered PFC circuitry as an option in medium-sized 2.5-4kw ballasts. And, until fairly recently manufacturers did not offer PFC circuitry in HMI ballasts smaller than 2.5kw in the US (in the EU PFC circuitry in mandatory in all HMI ballasts sold.) Part of the reason was that PFC circuitry did not offer a huge advantage when plugging into house power. A typical 1200W Power Factor Corrected electronic HMI ballast will draw 11 Amps at 120 Volts verses the 19 Amp draw of a non-PFC electronic ballast. While not a huge advantage when plugging into house power, the added efficiency of a PFC 1200 ballast can make a huge difference when powering a lighting package off of a small portable generator or when using GFCIs. For example, when you consider what LEDs draw, the 8 Amp difference between using a PFC 1200W electronic ballast and standard non-PFC 1200W electronic ballast, can mean the difference between running a lot more lights on a portable generator or not – I think you would have to agree that is a major boost in production capability. A second drawback to non-pfc ballasts is that the harmonic distortion they create reacts poorly with the distorted power waveform of conventional AVR generators, which severely limits the number of them you can power on a portable generator. The adverse effects of this harmonic noise, can take the form of overheating and failing equipment, efficiency losses, circuit breaker trips, excessive current on the neutral wire, and instability of the generator’s voltage and frequency. For these reasons it has never been possible to operate more than a couple of non-pfc 1200W HMIs on a conventional 6500W portable gas generator. Harmonic noise of this magnitude can also damage HD digital cinema production equipment, create ground loops, and possibly create radio frequency (RF) interference. The increasing use of personal computers, hard drives, and microprocessor-controlled recording equipment in production has created an unprecedented demand for clean, reliable power on set. Unfortunately, it is the case that almost every 575 - 1200 W electronic ballast that you will find for sale used in North America will be a non-PFC electronic ballast. While older HMIs with non-pic ballasts are less expensive, Power Factor Correction (PFC) makes the newest electronic ballasts worth the extra money when it comes to lighting with portable generators. The substantial reduction in line noise that results from using power factor corrected ballasts on the nearly pure power waveform of an inverter generator creates a new math when it comes to calculating the load you can put on a generator. In the past we had to de-rate portable gas generators because of the inherent short comings of conventional generators with AVR and Frequency governing systems when dealing with non-PFC electronic ballasts. The harmonic distortion created by non-PFC ballasts reacting poorly with the distorted power waveform of conventional AVR generators limited the number of HMIs you could power on a portable generator to 75% of their rated capacity (4200Watts on a 6500W Generator). But now, where inverter generators have virtually no inherent harmonic distortion or sub-transient impedance and power factor correction (PFC) is available in small HMI ballasts, this conventional wisdom regarding portable gas generators no longer holds true. Where before you could not operate more than a couple 1200W HMIs with non-PFC electronic ballasts on a conventional generator because of the consequent harmonic distortion, now according to the new math of low line noise, you can load an inverter generator to capacity. And if the generator is one of our modified Honda EU6500is inverter generators, you will be able to run a continuous load of up to 7500W as long as your HMI and LED ballasts are Power Factor Corrected (a lot of LED ballasts are not.) For more detailed information on HMIs I would suggest you read an article I wrote for our company newsletter on operating HMIs on portable generators. This article is cited in the 4th Edition of Harry Box's "Set Lighting Technician's Handbook" and featured on the companion website. Of the article Harry Box exclaims: "Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working." "Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before." The article is available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html. Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston Guy Holt, Gaffer, ScreenLight & Grip Lighting Rental & Sales in Boston
  10. Time to revive this thread with some indie tricks-of-the-trade for lighting night exteriors in the woods in the winter. Michael Patti's biggest challenge will be keeping his light off the snow. If he doesn't, it will bloom. I see two problems with his approach. It will be impossible to cut the bounce light from the overhead 8x off the snow and it will be hard to get the reverse key modeling that a night scene requires from a single large bounce source. I would suggest that he instead use the M18 to light the deep background from ground level and use the S60s on boom arms to model your talent. Better yet, I would swap the S60s for a very lightweight fixture like the Litemat 2 that you can arm out on a 20' menace arm to get them into reverse key positions. Having the fixtures on a menace arm will give you the flexibility to quickly adjust their position to get just the right reverse angle to get the modeling required by a night scene. You can also put egg crates on the Litmats to keep them from spilling onto the snow in shot. I would use the M18 on a stand deep in the background to one side to back light the deep background. As a hard source it offers a number of advantages over an S60 in this capacity. It will project more deeply into the woods. You will be able to cut it off the snow easily, and you will be able to use blades or fat nets to cut it off trees so that it lights the background evenly. As an added touch I would use a dry ice fogger to add ground level fog. Since working in snow is tantamount to working in water, you should have ground fault protection on your distro. With a small package like this you can get by with a Honda EU6500 or EU7000 generator which will be much easier to get into the woods. A small step-down transformer will provide a 60A 120V circuit from the Honda's 240v receptacle (plenty of power for both lighting and camera) using the industry standard Bates receptacle. Since the ground and neutral are bonded in the transformer, you can use film style GFCIs like the LifeGuard, Shock Block, or Shock Stop GFCIs (pictured below) to bring the Hondas into OSHA compliance for use on set (they don't meet OSHA requirements otherwise.) From the GFCI you. can run 60A Bates extensions, splitters and breakout boxes to distribute power around set (the M18 in the deep background will operate much more reliably if you run 60A Bates extensions to it and then break out to 20A Edison at its ballast rather than running 300' of stingers to it from the generator.) This way you can avoid using the hardware store style 15A GFCI dongles that are prone to nuisance tripping with HMIs and non-pfc LEDs like the Litemats. A single LifeGuard, Shock Block, or Shock Stop GFCI will offer much more reliable ground fault protection (without a propensity to nuisance trip) anywhere downstream of the transformer. An added benefit to using a transformer is that it automatically splits the load of whatever you plug into its secondary over its primary so you no longer have to worry about balancing the load on the generator. Guy Holt, Gaffer, ScreenLight & Grip, Lighting rental & sales in Boston.
  11. Your biggest challenge will be keeping your light off the snow. If you don't, it will bloom. I see two problems with your approach. It will be impossible to cut the bounce light from the overhead 8x off the snow and it will be hard to get the reverse key modeling that a night scene requires from a single large bounce source. I would suggest that you instead use the M18 to light the deep background from ground level and use the S60s on boom arms to model your talent. Better yet, I would swap the S60s for a very lightweight fixture like the Litemat 2 that you can arm out on a 20' menace arm to get them into reverse key positions. Having the fixtures on a menace arm will give you the flexibility to quickly adjust their position to get just the right reverse angle to get the modeling required by a night scene. You can also put egg crates on the Litmats to keep them from spilling onto the snow in shot. I would use the M18 on a stand deep in the background to one side to back light the deep background. As a hard source it offers a number of advantages over an S60 in this capacity. It will project more deeply into the woods. You will be able to cut it off the snow easily, and you will be able to use blades or fat nets to cut it off trees so that it lights the background evenly. As an added touch I would use a dry ice fogger to add ground level fog. Since working in snow is tantamount to working in water, you should have ground fault protection on your distro. With a small package like this you can get by with a Honda EU6500 or EU7000 generator which will be much easier to get into the woods. A small step-down transformer will provide a 60A 120V circuit from the Honda's 240v receptacle (plenty of power for both lighting and camera) using the industry standard Bates receptacle. Since the ground and neutral are bonded in the transformer, you can use film style GFCIs like the LifeGuard, Shock Block, or Shock Stop GFCIs (pictured below) to bring the Hondas into OSHA compliance for use on set (they don't meet OSHA requirements otherwise.) From the GFCI you. can run 60A Bates extensions, splitters and breakout boxes to distribute power around set (the M18 in the deep background will operate much more reliably if you run 60A Bates extensions to it and then break out to 20A Edison at its ballast rather than running 300' of stingers to it from the generator.) This way you can avoid using the hardware store style 15A GFCI dongles that are prone to nuisance tripping with HMIs and non-pfc LEDs like the Litemats. A single LifeGuard, Shock Block, or Shock Stop GFCI will offer much more reliable ground fault protection (without a propensity to nuisance trip) anywhere downstream of the transformer. An added benefit to using a transformer is that it automatically splits the load of whatever you plug into its secondary over its primary so you no longer have to worry about balancing the load on the generator.An added benefit to using a transformer is that it automatically splits the load of whatever you plug into its secondary over its primary so you no longer have to worry about balancing the load on the generator. Good Luck. It sounds like a fun project. Guy Holt, Gaffer, ScreenLight & Grip, Lighting rental & sales in Boston.
  12. I’m a total Newbie when it comers to wireless DMX and want to put together a portable dimming system in a pelican case. I was thinking of getting Nomad for my 2013 Macbook Pro with Retina display. So that I can easily jump from there to a desk size EOS console I was thinking of also getting a Dell 16x9 Touchscreen to mount under the lid of the case and the cmd keyboard for ETC Eos. To output dmx to fixtures I was also planning on getting the ETC Gadget that provides two universes. What would be a good transmitter? Is there anything else I am missing? What more do I need in my Pelican case for a complete mobile package. Attached are some pictures I found online of such a system and I am trying to figure out what all the ports on the side of the pelican case are for? Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rentals & Sales in Boston
  13. I’m a total Newbie and want to put together a portable wireless dmx system in a pelican case as well. I was thinking of getting Nomad for my 2013 Macbook Pro with Retina display. So that I can easily jump onto on a desk size EOS console I was thinking of also getting a Dell 16x9 Touchscreen to mount under the lid of the case and the CMd Eos keyboard. To output dmx to fixtures I was also planning on getting the ETC Gadget that provides two universes. Is the Ratpac AKS Plus a good transmitter for this set-up or would you suggest something else? Do you think this covers all the bases for a system or am I missing something ? What more do I need in my Pelican case for a complete mobile package. Attached are some pictures I found online of such a system and I am trying to figure out what all the ports on the side of the pelican case are for? Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rentals & Sales in Boston
  14. While 60 and 100A Bates females are listed for 240V use, they are customarily used for 120V and so will cause confusion on set leading to the possibility that someone might plug a 120V light into 240V and fry it. If you want to run a large light at 240V off a dryer or range plug be sure to use the yellow coded 220 100A Bates female. On a four-wire system cap off the neutral. Again, bonding ground and neutral downstream of the main service head, as you suggest here, is against the code. Yes, the disadvantage is that you don’t have access to 120V and it is an inefficient use of the power available from 240V receptacles for the reason given above. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston
  15. The number of higher wattage lights that can run 240V are limited. While 240V 5k & 10K bulbs do exist, most rental houses lamp their fixtures with 120V bulbs. 4k HMIs with electronic ballasts will operate either 240 or 120, but operating them at 240 is a not very efficient use of power. A 4kw HIM with Power Factor corrected ballast will draw about 19A per leg operating at 240V. Which means you are tying up the remaining 11A/leg on a 30A dryer plug or 31A/leg on a 50A range plug just to power that one 4k. A more efficient way to operate the 4k is at 120V through a step-down transformer. That way you still have access to the 22A on a 30A dryer plug or 62A on a 50A range plug to power other 120V lights (you can power quite a few more lights with that 22A or 62A.) Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston
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