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How to Plug 5k Quartz & 6k HMIs into wall sockets


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#1 Guy Holt

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Posted 04 December 2009 - 12:10 PM

Shooting a short soon and for some of the scenes we will not have a generator, but will have a 5K light. My question is how do you tie into a breaker box to get the necessary output to power the 5K?


Unless done by a licensed electrician, it is illegal to tie into a breaker box. You probably don't even need to tie-in a special circuit to power your 5k. There are a number of 240 volt wall outlets in a typical house, office, or industrial plant that you can safely and legally use to power a 5k and even HMIs as large as a 6k. The most common are air conditioner outlets, dryer outlets, range outlets, outlets for large copy machines in offices, and the outlets for motorized equipment and compressors in industrial plants.

If you look at the breaker of these circuits on the building service panel you will notice that they use two pole breakers - either 30A or 50A. Each pole of the breaker is in a sense an independent 30A or 50A 120 volt circuit. That is, if you measure the voltage from each pole of the breaker to ground it will be 120 volts, and if you measure the voltage between the two poles of the breaker you will notice that it is 240 volts. The 120 volts of the two poles adds up to 240V because the 120V circuits are on opposing legs (and are therefore additive) of either a single phase electrical service of a house, or a single phase secondary step down transformer of a office or industrial plant. In residential settings, this is how higher voltages are supplied to household appliances like Dryers, Electric Ranges, Air Conditioners, Motors, etc. that require more power than can be reasonably supplied by a single 120V circuit. Many of these household and industrial 240V receptacles use a three wire system (no neutral) because they are designed to power single phase motors or heating elements that draw a perfectly balanced load and return no current because the single phase service legs are 180 degrees out of phase and cancel each other out.

Where a state of the art Power Factor Corrected (PFC) Electronic HMI ballast, like the Power -2- Light 6kw ballast, draws only 25 Amps on each leg of a single phase 240V circuit, its' load is well within the capacity of these common 240V circuits. In our rental inventory we keep an assortment of adapters because all of these 240V wall receptacles use a different pin configuration. You can also power 5ks from these 240V circuits by using a 240v-to-120v step down transformer like the 60A Full Power Transformer/Distro we make for our modified Honda EU6500is generators. Like it does with the 240V output of the Honda EU6500is Generator, our 60A Transformer/Distro will convert the 240 volts supplied by these industrial and household receptacles back to 120 volts in a single circuit, that is the sum of the two single phase legs of 30/50 amps each, and is capable of powering bigger lights, like a 5k or a 6000W Six Light Mole Par. It can also be used to power multiple 120V luminaries off of 240 Volt circuits because our Transformer/Distro automatically splits the load of whatever you plug into it evenly over the two legs of the 240V circuit so there is no neutral return.

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4k & 1.2ks HMI Pars powered from 30A/240V dryer outlet through step-down transformer/distro for Bose still shoot.


I would be negligent if I did not caution you that some people will advocate the use of a "Splitter Box" on 240V outlets. A "Splitter Box" is a special distro panel that a rental house will make up that is wired to split out the two 120V circuits that make up the 240V outlet. If the 240V outlet is a 4-wire 50A/240V Range plug (the receptacle has four slots: one for ground, one for neutral, and two for hot), you could use a splitter box to power a 5k. But, you have to be really careful when splitting 240 volt circuits. If the 240 volt circuit is a four wire system, one can use a distro box as long as it is wired so that each circuit has a ground and neutral. Where you run into trouble is when the 240V circuit uses a three wire system (the receptacle has three slots: one for ground, and two for hot, and no neutral.) Many household and industrial 240V receptacles use a three wire system (no neutral) because they were wired for the sole purpose of powering single phase motors or heating elements that draw a perfectly balanced load and return no current. A perfectly balanced load doesn’t require a neutral because the single phase service legs are 180 degrees out of phase and cancel each other out – hence there is no return that would require a separate neutral.

You run into trouble with this kind of circuit when you start to pull an unbalanced load on your "Splitter Box." And, where under most production situations you can never perfectly balance your lighting load, the two 120V circuits that make up this 240V circuit will not have 100% phase cancellation and the extra current of the high leg will not have a safe return path because by necessity with a three wire system you have had to bond the ground and the neutral in the splitter box (after all what else can you do with the ground and neutral of your splitter box but to bond them when plugging into a three wire 240V circuit.) There are some people that will argue that it is not such a big deal to carry current on the ground wire. I would argue that it is both unsafe and unwise to carry current on the ground wire. It is unsafe because the ground wire is intended only as a default conduit in the event of equipment failure (which is why it is permissible according to the National Electrical Code (NEC) to use a smaller conductor for the ground wire.) It is unwise because bonding ground and neutral after the service side of a main service head (which is what you have to do with the ground and neutral of a splitter box when plugging into a three wire 240V circuit.) is a violation of the NEC. To quote Mike Holt, of Mike Holt Enterprises, Inc. again: “The National Electrical Code (NEC) requires a neutral-to-ground connection to be made at service equipment only and there shall not be any neutral-to-ground connection on the load side of service equipment [250-23(a), 250-24(a)(5)]” (full excerpt is available online at his website) If some one were to fall off a ladder because they took a non-lethal shock because the cable they were handling was carrying current on the ground wire your liability insurance would be null and void because you were using equipment that need not meet code.

It is also unwise to carry current on the ground wire because it can induce ground loops. It is a given that whenever you carry current on the ground wire there will be a slight difference in the voltage between receptacles in the power distribution system. A ground loop occurs when there is more than one ground connection path between two pieces of equipment and there exists a voltage differential. Under these circumstances, the duplicate ground paths form the equivalent of a loop antenna that very efficiently picks up interference currents. Lead resistance transforms these currents into voltage fluctuations. As a consequence of ground loop induced voltages, the ground reference in the system is no longer a stable potential (a floating ground), so signals ride on the noise. The noise becomes part of the program signal. The result is that the unwanted signal will be amplified until it is audible and clearly undesirable. Whenever you have current on the grounding system as well as the multiple connections between electronic components that is typical of HD production packages, there is the potential for a "ground loop."

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Interference bars caused by current induced on a ground loop by high THD.


Small voltage differences just cause noise to be added to the signals. This can cause an audio hum, interference bars to video signals (above), and transmission errors in computer networks. Higher currents can cause more serious problems that can damage equipment like sparking in connections and burned wiring. As more and more electronic components, like lap top computers, hard drives, and HD monitors, are integrated into the typical location HD production package, ground loops become more of a hazard.

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Left: Conventional generator power w/ THD over 100 percent caused by pkg. of non-PFC Elec. HMI & Kino Ballasts. Right: Same lighting Pkg. but with PFC HMI & Kino Ballasts powered by our modified Honda EU6500is inverter generator. Note the THD is now under 7 percent.


It is also worth noting that “ground loops” can result from the harmonic currents that non-power factor corrected electronic ballasts (HMI & Kino) throw back into the distribution system. Current on neutral conductors with a high Total Harmonic Distortion (THD) value will induce voltage in ground wires greater than the 2 volt maximum stipulated by IEEE Standard 1100-1992 "Recommended Practice for Powering and Grounding Sensitive Electronic Equipment." For instance, there was an episode, recently reported on CML, of a pilot shooting in HD that found they had 50 volts between the shield of the SDI line and ground. In that case the problem was fixed by running a "Drain" wire from the SDI Shield back to the Genny via the electrical lunchbox at the DIT station. For more details on why this is I suggest you read my newsletter article on the use of portable generators in motion picture production. The article is available on our website.

The only safe way to pull power from a three wire 240V wall outlet that meets the requirements of the National Electrical Code, and won't create ground loops, is to run your lighting load through a 240v-to-120v step down transformer. A transformer converts the 240 volts supplied by these industrial and household 240V receptacles back to 120 volts in a single circuit that is the sum of the two legs of the circuit. For instance, a transformer can make a 60A/120v circuit out of a 30A/240v dryer circuit that is capable of powering bigger lights, like a 5k or 4k HMI. What makes it safe to plug a step town transformer into three wire 240V outlets is that the transformer automatically splits the load of whatever you plug into it evenly over the two legs of the 240V circuit so that you have 100 percent phase cancellation. In other words, where there is no high leg, the loads on each leg of the 240V circuit completely cancel out and there is no return that would require a separate neutral and there is no return current on the ground wire to create ground loops.

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A PFC 2.5 & 1.2 HMI Pars, PFC 800w Joker HMI, Kino Flo Flat Head 80, 2 ParaBeam 400s, and a ParaBeam 200 powered by a modified Honda EU6500is through a 60A Full Power Transformer/Distro



You can maximize the power you can pull from 240 Volt wall receptacles if, rather then plugging a 4k HMI directly into the 240 receptacle, you plug it in through a combination Transformer/Distro (like the one we make for our modified Honda EU6500is generators pictured above) and operate it at 120 Volts. Where the Power-2-Light (P2L) 4/2.5 LVI ballast operating a 4k HMI luminary at 120V draws only 36 amps, you will still be able to power additional lights, like a 1200 Watt HMI luminary powered by a P2L 575/1200 ballast (11 Amps) and a 800 Watt HMI luminary powered by a P2L 800/1200 ballast (8 Amps), off of the same circuit.

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The PFC 2.5 & 1.2 HMI Pars, PFC 800w Joker HMI, Kino Flo Flat Head 80, 2 ParaBeam 400s, and a ParaBeam 200 of our HD P&P Pkg. powered by our modified Honda EU6500is through our 60A Full Power Transformer/Distro


Unlike a 240V "Splitter Box," where you have to meticulously balance your load, a transformer greatly simplifies your set electrics by automatically splitting the load evenly. As long as you plug lights in through the transformer, you no longer have to carefully balance the load over the two 120V circuit/legs because the transformer does it for you automatically. If you outfit the transformer, like our Full Power 60A Transformer/Distro, with a 60 Bates receptacle, you can use 60A GPC extension cables, 60-to-60 Splitters, and fused 60A GPC-to-Edison Breakouts (snack boxes) to run power around set - breaking out to 20A Edison outlets at convenient points (rather than one central point.) The best part about using a transformer with a 240V receptacle in this fashion is that no matter where in the distribution system you plug in, the transformer automatically balances the additional load, so that you don't have to.

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Wide Shot of Night exterior scene lit with our HD P&P Pkg.


I use transformers to power bigger HMIs (2.5-4Kw) in situations where a tie-in is not an option and the budget doesn’t permit for a tow generator. Where the production budget is particularly tight, I use a package consisting of two transformers and a portable generator. I use one transformer to access more power through a 240V circuit on location to run lights inside; while the other I use to bring larger HMIs in the windows from outside. This approach eliminates the need for a dangerous tie-in or expensive tow generators, it also greatly reduces the amount of cable that has to be run.

In my 20 plus years as a Gaffer I have found the three wire 240V circuits (hot, hot, ground, no neutral) to be much more prevalent and accessible than the four wire circuits (usually just range plugs with a hot, hot, ground, neutral.) Over the years, I have used a combination of 3 wire/240V wall outlets, step-down transformer/distros, and Honda EU6500is generators without problem on many historical documentaries I have gaffed. For example, I have used this approach repeatedly at a historical mansion in Easton MA called the Ames Estate.

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Scene from "Unsolved History" powered from 50A/240V range outlet through step-down transformer/distro at the Ames Estate.


A popular state fee free location, the Ames Estate, like many historical house/museums, does not permit tie-ins and the electrical wiring in the house is so antiquated that it is unusable. Fortunately, they have a 50A/240 volt circuit in the carriage house for a welder they use to repair the mowers they use at the park. Our standard mode of operation when shooting there is to run 250V extension cable from the welding receptacle to our 60A Full Power Transformer/Distro placed in the entry hall of the house. Using a 60A Siamese at the Transformer/Distro, we then run 60A 6/3 Bates extensions, down to the library, to the second floor, and back to the maid’s pantry. At the end of each run we put another 60A Siamese. A 60A snackbox on one side of the Siamese gives us 20A branch circuits. The other side we leave open for a large HMI or Quartz Light. Now we can safely plug 1200 & 2500W HMIs, or even a 5k Quartz, into our own distribution anywhere in the house.

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Typhoid Mary in quarantine on an island in New York's East River. Note the view out the window of the East River shoreline at the turn of the century.


To maintain continuity between shots on these dramatic historical recreations, we usually bring a 4kw HMI Par in a window on one side of the room as a sun source and a 1200 par through a window on the other side as a northern light source. We power both heads off of our modified Honda EU6500is through a Transformer/Distro. We are able to power both lights off our modified EU6500is because the Transformer/Distro provides access to the enhanced 7500W capacity of the generator in a single 60A/120V circuit (for more details on how this is accomplished I suggest you read my newsletter article on the use of portable generators in motion picture production available on our website.
And, since the Honda EU6500is can be placed right on the lawn, we are saved from running hundreds of feet of feeder back to a tow generator in the drive.

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(The exterior of the actual location used for the quarantine island. A 30' blowup of a picture of the East River at the turn of the century was rigged outside the windows of a house in Arlington MA.)


We have been able to use this same basic distribution package (two Transformer Distros, 1- modified EU6500is) at numerous museums and historical houses throughout New England including Sturbridge Village. Fortunately for us, to make ends meet, many historical houses rent themselves out for events and weddings. For that reason, they usually have at least one updated service with 30 or 50 Amp 240 volt circuit for the warming ovens of caterers. I have included in this post several production stills from these shows. For those who would like to see samples of what can be accomplished with this basic package, I have attached these links to production stills of the PBS and History Channel historical documentaries shot entirely, or in part, with just a couple of transformers and a Honda generator.

The History Channel’s “Unsolved History” episode “Presidential Assassins”

American Experienes Typhoid Mary Biography "The Most Dangerous Women in America"

WGBH’s Ben Franklin Biography “Franklin”

Or, use this link for more details about using step-down transformers on set: . By giving you safe and legal plug-in access to more house power through common 240V house outlets, a transformer can quite often eliminate the need for tie-ins or generators.

- Guy Holt, Gaffer, ScreenLight & Grip, www.screenlightandgrip.com
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#2 John Sprung

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Posted 04 December 2009 - 02:16 PM

Much as I hate to imply that that post isn't long enough.... ;-)

One other thing you need to know about when you look at big high power outlets with lots of holes is three phase power. What Guy describes is all single phase. If you find a neutral and two hots, each hot 120 Volts from neutral, and 240 Volts between the hots, that's single phase. If you find three hots at 120, but only 208 Volts between pairs of hots, that's Wye connected 120/208 three phase. There are others, such as 277/480, and Delta connected. Bottom line, when you scout a location, bring a Voltmeter. Check out those strange big wall sockets so you know what you have -- and that they're actually connected to the power. Unfortunately, the location's person who shows you around rarely knows much about their electrical system. There are transformers for three phase, too, but you have to know exactly what you have in order to get the right kind.

Guy -- Do you use your transformers as isolation transformers, or do you reference your secondary to the supply side or equipment ground?




-- J.S.
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#3 Phil Rhodes

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Posted 04 December 2009 - 05:08 PM

Or you can shoot in the UK, where more or less every household outlet provides 240V at 13 amps with a maximum of 32 amps per ring main and usually two or three ring mains per house, plus a 63-amp cooker circuit.

Marvellous!

US wiring is mad.

P
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