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Running 2k off 15A stinger


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#1 Salil Sundresh

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Posted 10 March 2009 - 01:30 PM

How long is it ok to run a 2k off a 15A stinger before the cord may start to get damaged? How long do I need to let the 15A cord rest/cooldown after turning it off befor firing it up again? Will be using 2x50' stingers for the run to the head. Working in the USA with 20A circuit @125V AC

Edited by Salil Sundresh, 10 March 2009 - 01:33 PM.

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#2 Adrian Sierkowski

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Posted 10 March 2009 - 02:25 PM

Short answer, you need to get a properly rated cord. . . else it'll start to melt pretty quickly/catch on fire/be un-usable/unsafe. Get the right cord, or find a new light.
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#3 jeff woods

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Posted 10 March 2009 - 03:55 PM

I'll second Mr. Sierkowski's reply.

Shorter answer: 0:00

You are overloading the cable by almost 2 amps (assuming 120v (I rarely see 125v unless it's off a genie)), and if something did go wrong (property or personal damage to say the least), one of the first questions would be "was everything cabled appropriately?". And though the production may have production insurance, you could also be held personally responsible for any damage or injury.

In essence, you are asking "How long can I break the rules?", and I don't think anyone here would be willing to put their name on quantifying electrical failure.

One man's opinion,
-j
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#4 JD Hartman

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Posted 10 March 2009 - 05:06 PM

How long is it ok to run a 2k off a 15A stinger before the cord may start to get damaged? How long do I need to let the 15A cord rest/cooldown after turning it off befor firing it up again? Will be using 2x50' stingers for the run to the head. Working in the USA with 20A circuit @125V AC


The reality is that on a set or location somewhere, it is being done every day, without damage or personal injury. Is this a 12ga. cord (stinger), or is it a orange extension cord? The stinger will be carrying at least 16.66 amps, exceeding the working rating. The cord may become warm, but even carrying only fifteen amperes the cord will become warm over time. Will it be permanently damaged, catch fire, melt down, explode in a shower of molten copper, maiming cast and crew? No.
A larger issue is the length, excessive voltage drop will cause a drop in color temperature. In your case voltage drop will exceed the accepted 3%. If color temp. is an issue, use a 10ga cord.

Study your Harry Box Set Technicians book. It's all in there, if you don't have one buy it. This is all very basic stuff if you're going to be a Spark.

Edited by JD Hartman, 10 March 2009 - 05:09 PM.

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#5 Adrian Sierkowski

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Posted 10 March 2009 - 06:58 PM

Just because it's done on locations does not make it the right thing to do, or OK to tell someone else to do it especially when it comes to electrical things. That is my honest opinion, and in this specific case, it comes speaking as someone whose own 2Ks have melted 12ga cord after less than an hour.. I would not recommend it.
A 2K will pull 16.7 amps, and one a longer run such as yours you'll want to have the proper gauge cord anyway.
I again do not recommend it. What's better; buying the right cord or risking major damage... If anything you'll have 10ga cord or two for your own usage.
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#6 JD Hartman

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Posted 10 March 2009 - 07:18 PM

Just because it's done on locations does not make it the right thing to do, or OK to tell someone else to do it especially when it comes to electrical things. That is my honest opinion, and in this specific case, it comes speaking as someone whose own 2Ks have melted 12ga cord after less than an hour.. I would not recommend it.
A 2K will pull 16.7 amps, and one a longer run such as yours you'll want to have the proper gauge cord anyway.
I again do not recommend it. What's better; buying the right cord or risking major damage... If anything you'll have 10ga cord or two for your own usage.


I don't think I told him to do it, or advocated the practice in any way. I just stated the facts. If you re-read my post, I provided the facts which indicate that for the current draw of the fixture, the length of the cable and acceptable voltage drop (3%), 10 gauge is necessary. I don't know what type of cable your stinger was constructed from, but I've never melted a stinger. If 15a is the rated capacity of the wire and it self-destructed after being used at a slightly higher load, something else had to have contributed to the overheating of the wire. Loose wire connections in the stinger cap and body, oxidation on the blades or even plugging into a receptacle that doesn't grip tightly anymore.

Edited by JD Hartman, 10 March 2009 - 07:19 PM.

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#7 Adrian Sierkowski

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Posted 10 March 2009 - 07:22 PM

JD, the line I took issue with was your first one where you said "its done every day. . ." which could be construed as an endorsement of the practice. That was my tripping point and I'm sorry if I read that wrong. As for my own stinger, can't say much more than it worked fine with every other fixture, till I threw a 2K on it and wham, melted at the terminals on both end. Really was a pain in the _____. So, its anecdotal proof, I know, but when it comes to power things I always advocate better safe than sorry.
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#8 Michael Collier

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Posted 10 March 2009 - 07:23 PM

When cabling becomes warm, its current rating goes down. So its not just a 1.6 amp overdraw. As you draw more current than the cable can handle, the actual ability to pass that current degrades. The point at which that degenerative cycle reaches terminal velocity is the point where it will fail, and that could be rather quick fail point after a long warm up period. So you can be just fine most of the day, and then the sun comes out and your cords start frying, or worse just the jacket melts off, and makes a cart or c-stand hot. Then when someone touches it--zapp, lawsuit, negligent homicide. Most DAs could make a case for NH, especially if your a professional electric (and if your on set, paid or unpaid, high or low budget, they will label you a professional who should have known better)

Don't do this. Get the heavier gauge cable. With short runs overdrawing is not advisable. with typical long runs we see on set it can be catastrophic. At what point is risk too much risk? Don't chance it, play by the numbers. Stingers are cheap.

Plan overhead, don't plan for failure. 2k=minimum 20amp to be safe. 60 amp bates would be better.
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#9 Phil Rhodes

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Posted 10 March 2009 - 07:41 PM

I'm so pleased I live in a place where we can run 3K loads off a normal household socket with normal household extension leads.

No, wait - I'm not.

P
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#10 JD Hartman

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Posted 10 March 2009 - 08:10 PM

"till I threw a 2K on it and wham, melted at the terminals on both end. ", that's the key point. It sounds as if it wasn't the wire conductors, or the insulation on them, it was a loose or oxidized connection on the cap or body (male or female connector). More resistance, drawing more current, producing more heat.

"So you can be just fine most of the day, and then the sun comes out and your cords start frying, or worse just the jacket melts off, and makes a cart or c-stand hot." What?? If air temperature was even a minute factor, every shoot in NYC in the summer time would be having massive failures.

Here is a typical cable manufacturers spec.

SEOW Cable and STW Cable are composed of bare, annealed flexible copper. Color coded TPE thermoplastic rubber assembled round with fillers as needed. A separator is applied over the assembly. Black oil resistant TPE thermoplastic rubber Jacket. SEOW Cable and STW Cable have a temperature range of 105 °C to -50°C. or 221 F to -98
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#11 Michael Collier

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Posted 10 March 2009 - 08:56 PM

What?? If air temperature was even a minute factor, every shoot in NYC in the summer time would be having massive failures.


I wasn't trying to imply the air temp was the factor, I was saying the cables ability to safely pass current depends on the conductors temperature. My intent was to say that if your running at the limit, and a hot sun (IR heat, not ambient air) comes out and heats up the BLACK STINGER jacket, thus heating the conductor (at a rate much greater than air temp would do) then your cables current rating will decrease. Think car with black interior in full sun. My aim was to point out that conductor temp and current ratings are symbiotic, and can become degenerative if ignored.

I once ran HMI's near the limit on long cable runs, but only because it was -30 outside, so the stinger was nearly a superconductor, actually improving the cables current rating (most ratings are pegged at a specified conductor temp, usually room temp). Even in that condition however I would not exceed the calculated safety factor, just feel better about getting close.

The key words though is 'if your near or exceeding the limit', if your trying to push more current than the cable can handle.

Edited by Michael Collier, 10 March 2009 - 08:58 PM.

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#12 Salil Sundresh

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Posted 10 March 2009 - 09:57 PM

Thanks everyone for your replies.

I realize this isn't exactly the most professional thing to do. This is for a time lapse shot where the DP (he's paying/renting gear...so this is incase he doesn't get a 20A stinger and buys his own cheap ones in hopes they don't melt) wants to use a 2k to simulate the light of a sunrise coming through the window. So we'd just capture a frame then dim up/raise the stand, then repeat a million times. Most of the time it would be under 80% intensity on the 2k dimmer. 2k will be outside on a fire escape stairway on a mombo combo stand which will go to a max height of 15ft shining through a window. The light and most of the cable will be outside in Chicago in March so it won't be hot weather and we're going to be shooting at night with more than a couple hours till sun rise after wrap.
Any other thoughts? I wanna get an idea of how long it might be good to run it and how long it should cool for before going again.
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#13 Ollie Bartlett

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Posted 20 March 2009 - 01:48 PM

I'm so pleased I live in a place where we can run 3K loads off a normal household socket with normal household extension leads.

No, wait - I'm not.

P


I was looking to order Harry Box's book this weekend, but am now wondering if it covers UK electrical practice. Does anyone have any ideas, or does the book deal with things in a universal way?

Incidentally, if anyone has an old copy they'd like to sell id be more than grateful and can promise it a good home. Technical books dont come cheap over here... just one more reason why i can understand the way Phil feels about this country.
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#14 JD Hartman

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Posted 23 March 2009 - 10:55 AM

I was looking to order Harry Box's book this weekend, but am now wondering if it covers UK electrical practice. Does anyone have any ideas, or does the book deal with things in a universal way?

Incidentally, if anyone has an old copy they'd like to sell id be more than grateful and can promise it a good home. Technical books dont come cheap over here... just one more reason why i can understand the way Phil feels about this country.


Yes, it does deal with things like current capacity of conductors and voltage drop in a universal way. The formula(s) for things like circular mills of a conductor and Ohm's law apply in the USA or "across the pond" equally. I believe it deals with electrical distribution in the UK as well.
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#15 Saul Rodgar

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Posted 23 March 2009 - 02:44 PM

Thanks everyone for your replies.

I realize this isn't exactly the most professional thing to do. This is for a time lapse shot where the DP (he's paying/renting gear...so this is incase he doesn't get a 20A stinger and buys his own cheap ones in hopes they don't melt) wants to use a 2k to simulate the light of a sunrise coming through the window.


I am with those who advocate the use of the properly rated gear for the job at hand. In this industry it is never a good idea to get in the habit of doing things knowing full well they are not safe to use. Safety first!! There is a reason why the 20 A stingers exist.

I would go to a rental house in Chi and rent the 20 A stinger from them, it shouldn't be more than a 10 bucks a day and you will get the satisfaction of getting the right piece of gear for the job and keeping people and equipment safe, and that _as the commercail goes_ it is priceless.
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#16 timHealy

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Posted 23 March 2009 - 10:02 PM

for what it is worth 12/3 gauge wire is the standard gauge on film sets in the U.S. for anything 2k and down. If any part burns up it is either a hubble plug that is not rated for 2k loads or a 20 amp rated plug that was not built correctly or set screws have loosened with time and abuse and resistance builds up and melts the plug.

just my 2 cents

Best

Tim
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#17 Dino Giammattei

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Posted 11 April 2009 - 05:44 AM

Just this week I lost two 2K Ianero's that had been in place for years. The Hubbell twistloks between the fixture and the stinger just started dripping. And this was with 12g wire. The connectors just got oxidized I’m guessing. I’m now checking every light and stinger I have for signs of trouble. I should have been doing that all along I guess. My point is, you might get away with it for a while, or ten years in my case, but you could just as easily burn the place down tomorrow.

I’ve also had problems when I was forced to daisy chain cords over a long distance. The number of connectors involved will have a profound effect. Four 25ft cables will be more problematic, especially at the connection points, than a single one hundred footer will be.

Please be careful, we want you see you safely back here..

Old dino
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#18 Chris Pritzlaff

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Posted 12 April 2009 - 07:11 PM

Im surprised though by this because it seems to be pretty standard practice to use 15amp hubble connectors on 2K fixtures. The wire may be correctly rated, but every rental house I go to provides stingers with 15amp connectors. Most of the 2ks have also had their connectors replaced with them as well.
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