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A-H Hart-Lock 600V 50A twist lock Lunchbox?


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#1 Jim Menkol

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Posted 27 April 2011 - 03:43 PM

So my school needs to get a lunchbox to drop from the 50 amp circuits in the studio. The problem is that the circuits use an A-H Hart-Lock 600V 50A twist lock connection, which I cannot find anywhere for the life of me. I have found this lunchbox from Kaye Lites, but I can't tell if it has the right connection:

http://kayelites.com...1950557df66b112

Here is a link to a picture of the female connection:

http://www.maraindus...50a-250vdc.html

If anyone can enlighten this for me at all, it will be greatly appreciated. I've been searching for days with no luck.

Thanks
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#2 Jim Menkol

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Posted 27 April 2011 - 04:03 PM

I just got off the phone with the guys at Kaye Lites, ends up it can't be done since my circuit doesn't have a neutral.
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#3 Eileen Ryan

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Posted 27 April 2011 - 08:04 PM

I just got off the phone with the guys at Kaye Lites, ends up it can't be done since my circuit doesn't have a neutral.



If the circuit doesn't have a neutral, your one option is a step-down transformer. Call Guy Holt at ScreenLight & Grip. They make a step-down transformer that converts the enhanced 7500W output of their modified Honda EU6500is to a single 60A/120V circuit. You could use the same transformer/distro to step down the output of your 50A/240V Twistlock circuits to a 60A/120V circuit . Because the transformer will pull a perfectly balanced load, the opposing legs of the single phase 240V circuit will cancel and so there is no need for a neutral. Use this link for more details http://www.screenlig...former Distros.

- Eileen Ryan, Gaffer
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#4 Guy Holt

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Posted 28 April 2011 - 02:26 PM

If the circuit doesn't have a neutral, your one option is a step-down transformer…use the same transformer/distro to step down the output of your 50A/240V Twistlock circuits to a 60A/120V circuit. Because the transformer will pull a perfectly balanced load, the opposing legs of the single phase 240V circuit will cancel and so there is no need for a neutral. Use this link for more details http://www.screenlig...former Distros.


If the A-H Hart-Lock 600V 50A twist lock receptacle is on a single phase service (you read 240V between the two hot pins) you can safely and legally use a transformer as a distro as Eileen suggests. I have used the same transformer/distro that we make to step down the enhanced 7500W output of our modified Honda EU6500, to power Quartz lights up to 5k and even HMIs as large as a 4k on 50A/240V range receptacles as well as 30A/240V dryer receptacles. Other common 240 volt wall outlets are air conditioner outlets, outlets for large copy machines in offices, and the outlets for motorized equipment and compressors in industrial plants.

Like the A-H Hart-Lock 600V 50A twist lock receptacle in your schools studio, 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 an office or industrial plant. In residential settings, this is how higher voltages are supplied to household appliances like Dryers, Electric Ranges, Air Conditioners, and Heaters 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.

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The voltage of opposing legs of a single phase circuit add while the current carried on the legs subtract.


You run into trouble when you try to use a "Splitter Box" (like the one at Kayelites) without a neutral when you start to pull an unbalanced load. Since 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, like this A-H Hart-Lock 600V 50A twist lock receptacle, 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.

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


The only safe way to pull power from 3-wire 240V circuits (hot, hot, ground, no neutral) that meets the requirements of the National Electrical Code 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. What makes it safe to use a step down transformer is that the transformer automatically splits the load of whatever you plug into it evenly over the two legs of the 240V circuit. Where there is no high leg, the loads on each leg of the 240V circuit cancel out and there is no return that would require a separate neutral.

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. 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 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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A Distro System consisting of a 60A Full Power Transformer/Distro, 2-60A GPC (Bates) Splitters, 2-60A Woodhead Box distributes power from a modified Honda EU6500is. Even though the generator is 100' away to reduce noise, plug-in points remain conveniently close to set.


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 our our modified Honda EU6500is generator 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.

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


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 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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#5 Jim Menkol

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Posted 29 April 2011 - 04:12 PM

Eileen and Guy -

Thank you SO much for your quick and very informative replies. I've a lot to sift through, I'll post later what we end up doing. Thanks again, I really appreciate your help.
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