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Author Topic: Power distros for entertainment like bands & concerts or stage & theatre shows  (Read 8098 times)

Lonnie Eldridge

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You can't just buy 5 conductor wiring and all of a sudden have a three phase system.
 
Well, I know it isn't "that" simple but to have a 3 phase setup, am I wrong in understanding that you do indeed need 5 wires instead of only 4 for it?  I understand that there would be some different wiring at the supply end (the venue or bar or gym's power center/junction box) and I wouldn't be the one to hook that up but, if the same 5 wire cable is used for 3 phase that would be used for a single phase setup for 240 like I'm talking (minus the 1 wire and only need 4 for 240 single phase), then why not have the additional cable for future needs?  Even if I don't "need" it, it's there if I do correct?  The 5 wire setup with 4 gauge is the correct wire for 3 phase is it not?  At least considering that I would be going 200 to 250 feet it would be 4 gauge.  Less distance would be smaller gauge obviously. 
 
The 14-50 plug you're talking about only has 4 pins. 
 
I understand this and I wasn't implying that 3 phase is run out of this same connector.  To my knowledge, wiring for a 3 phase setup is different.  However, I do believe I read somewhere that some people have been able to wire 3 phase out of those type of connectors and that some places have wired them up to be 208/3 phase.  At least I am pretty sure I read that somewhere.  Maybe I'm wrong.  But either way, I wouldn't be wanting to have it wired for 3 phase UNLESS it was needed.  In which case, I would be getting in touch with someone who understands this.  In any case, I just want to be prepared.
 
The only way to do high ampacity three phase is with single conductor wire and camlocks. 
 
Okay, I wasn't aware that ONLY camlocks can be used for 3 phase.  Is this code and standard or just what is "typically" done?  So nobody has ever done 3 phase without camlocks?
 
In this scenario you would have five individual cables (three hots, ground, neutral) with five individual camlock connectors on each end. This solution is VERY EXPENSIVE AND VERY HEAVY. Honestly it doesn't sound like you'll need this even in the future. 
 
Again, I agree that "more than likely" you're correct and I won't.  But I just don't want to kick myself in the future when I could have had this available early on and run into an issue somewhere.  Maybe I never will.  I don't know.  I suppose if I just plan on either 240 single phase with the 50 amp 14-50R plug as I'm discussing OR using standard wall outlets for my events, then I won't have to concern myself with 208/3 phase.  Again, I'm just trying to think ahead and be prepared. 

DO NOT MAKE A 250' LENGTH OF CABLE. YOUR EMPLOYEES/BACK WILL HATE YOU. 

 
Well, I guess I'll just have to hate myself then since I would "most likely" be the one setting up the shows along with some assistants in some cases.  And when I do have assistants, well....I guess since I've already discussed with them the necessity to be able to lift heavy objects such as cases, equipment, and yes, cables, maybe that is alreay covered.  But again, if this is something that I have to do myself, then so be it.  But let's be honest here, it's not like "nobody" has a long cable that has to be run.  Others have been doing it for years so it's not like I'm asking people to do something that's never been done.  And even if I was, does that make it wrong?  Hey, don't get me wrong, I want to save my back and my employees' too but come on, we're in an industry where we NEED to be able to lift heavy things.  So, somebody has to do it. 
 
Also, what was already said, leaving it coiled up will create an induction loop which could melt your cables and cause a fire 
 
Now THAT is an excellent point and one I forgot about and makes unbelievably great sense.  In which case, maybe it would be better to have two separate 100' cables and leave a 50' cable attached to the distro.  Or a 100' cable to the distro and two 75' cables.  Either way, the issue about heat and fire is an excellent point. so
even if you only need 20' for a certain gig, you'll still have to unroll the other 230'. 

 
Like I just said, damn good point to be safe. 

As for the calculator website not being accurate... The people on this site are professionals. They know more about this than you or some calculator. Listen CAREFULLY to what they're saying. 

 
I am listening and taking notes.  Don't confuse my questions with a simple concern about accuracy and/or clerification.  Here's the thing, I wouldn't have asked the questions if I already knew the answers.  So, I think it's obvious that I want to get the correct information.  But as I said, who am I supposed to believe for accurate information?  I know that is something that each individual has to decide for themselves and I want to take the knowledge of many trained pros here as very good information.  But, am I to consider that information off of that "wiring calculator" as NOT accurate?  In which case, then how do I know what is and what isn't accurate?  I don't know people on here from Adam so I have no idea what credentials people have in telling me what they are.  But I am hopeful that I am getting accurate info.  But if one person suggests to use that site's calculator for a reference and another person does not, then who am I to trust?  Do you understand the confusion there?

Hey everyone, I beg you not to take my comments the wrong way.  As mentioned on another site that I've asked this same question on, while I was doing research for distros on there, somebody made a VERY GOOD point about when people ask questions like these and then the comments made regarding them.  We NEED to consider that ANYONE reading these posts may be a brand new "newbie" that has no idea what we're talking about.  As such, it's important not to be throwing around "suggestions" unless you know yourself that they work.  And if they are different than code or what's "standard" or "acceptable" please state why what you did was ok for you.  Or at the very least, if you are to make a suggestion that is not "typical" in the setup, at the very least make a warning about what it is you did so the newbies don't get the wrong idea. 
 
As people have said, you never know who could be reading and then go and do things that we discuss on a regular basis without knowing any better simply because they read it on a forum.  Sure, we should "know better" than to take this stuff as gospel but some may do just that.  And actually, that's "sort of" the reason I posted my question.  I've seen and heard a lot of stuff but just because I've seen it done does NOT make it right or acceptable by codes, safety, and so on.  I would rather do things right and that's why I'm questioning the way I've seen it done in the past. 
 
Maybe those shows were doing it wrong and shouldn't have been doing things the way they were.  I don't know. 
 
An example would be the post that Greg had regarding using a 6/4 SOOW cable for a 300 foot run "in a pinch."  Now although it wasn't stated specifically, I think Greg's mention of "in a pinch" should tell someone that was reading this that this his "in a pinch" solution was probably not the best option.  To me, "in a pinch" has a warning in front of it.  But if others can't understand that, then that's their fault.  Perhaps it should have been stated to everyone "not to try this at home" as it will not pass code, isn't something you "should" do due to added load (power) requests on the cable which could potentially cause issues with heat and yes, potentially fire.  I suppose that should have been said.  I thought it "sort of" was implied though.  Probably among a few other things regarding that particular situation.  But even though Greg "got by", it may have still been up to code for all we know.  (I don't know).  In which case, if it is up to code, then that's a good place to start.   
 
So, I guess what I'm saying is that as I read the comments, suggestions, and experiences from other people, I am hopeful that UNLESS OTHERWISE STATED, they are making these comments with the understanding that what they say could be taken as good information.  Afterall, if you're going to make a comment, I hope you're not doing it with the intention to mislead anyone of put out false information.  If you are, then what good does that do other than cause people to do the wrong things?  Of course, that's where others need to come in and make sure that somebody isn't making a bad suggestion.  Which has been done on this post a few times regarding wiring and connectors and so on.  (No Greg, I'm not trying to call you out one bit because you probably have the knowledge to know what you were doing in your particular situation and could request only 60% or 70% of the load that the wire could handle and make it acceptable). 
 
One thing I know that has been said constantly over and over on every single forum is the mention of getting a "qualified electrician" to do the work.  I don't think anyone disagrees with this and I don't think that this is something that doesn't cross a person's mind when considering these things.  Maybe it doesn't.  I don't know.  But I just can't see someone that has no more knowledge than being able to plug in an outlet to a standard wall outlet trying to tie into a junction box with bare cable ends or trying to hook up cam locks or hooking up transformers for huge events.  In which case, I think pretty much everyone knows that getting an electrician to do the work is paramount.  So isn't the whole "get an electrician to do it" pretty overstated?  It's a given. 
 
But regarding the word "qualified", I'll bet there are tons of you on here that have WAY...WAY more knowledge than even some veteran electricians of 30 or 40 years when it comes to this stuff.  After all, a lot of veteran electricians are used to wiring up houses at best and maybe a lot of them are just doing typical outlet wiring in a home and not even messing with incoming power and wiring up junction boxes.  Maybe their just reserved to wiring outlets and putting in some breakers.  (Which a lot of people can do).  I'll bet a lot of electricians don't even have a clue what we're discussing here.  And I know this to be true by discussing this with a few of them because you know what some of them say when I ask them about some of these things?....."You need to talk to a production electrician." 
 
It's like asking a "general practice" doctor to diagnose cancer or a fungus that they have no clue how to because they are skilled in "general" diagnosis for "most" patients.
 
Well, as you know, we (this industry) are not "most" patients right?
 
So, I'm coming here to get industry specific questions answered (hopefully) by people I feel probably know a thing or three.  At the same time, I'm trying to learn and just want to back up statement or comments with facts and accurate info.  I hope that's not wrong.   ;)   
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Ray Aberle

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Okay, I wasn't aware that ONLY camlocks can be used for 3 phase.  Is this code and standard or just what is "typically" done?  So nobody has ever done 3 phase without camlocks?

That's not what Brian said. He said, specifically, "HIGH ampacity three-phase." In my rig, I use Motion Labs rack packs to service my amplifier racks. I have both 1 and 3 units; the 1 units take an L14-30 220V/30A twist lock connector and the 3 units take an L21-30 208V/30A twist lock connector. The service cables are 8/5 (or 10/5, depending on who is providing the cabling) multi conductor single jacket cables.

What was being referred to was running 100A/200A/400A input from a mains service to your distro; that's where you see the multiple single conductors with camlok connectors. The other advantage of going with single conductors is that they'll lay flat as opposed to a huge cable trying to hold everything together. When you're running service across large areas with cable ramps, you really want the individual conductors to be able to flow through each channel of the ramp!

Ray
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Lonnie Eldridge

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It IS 240volt service, that has 120volt available as well. The 240volt refers to the two hots, a neutral and a ground. You can then connect any 120volt device to a panel fed by the 240 service 
 
Well...as long as that 240 is broken down to two separate legs of 120 right?  Obviously you can't just go hooking 120 volts to a 14-50R 240 volt female connector since there aren't plug ins that allow this.  (which is a good thing).  , and it will feed from one of the hots, the neutral and the ground.
 
Gotchya.  Makes sense now.

In other words, if you were to look inside a standard electrical panel (in your house, for example), you have 240volt service coming from the street (unless you are pimping and have 3 service at home... I'd be jealous.). That comes in as two hots and one common (neutral) line. The grounding bar on your home panel is fed from the earth ground. So, 200A/240V gives you two hots, and when you look down the panel, "every other" breaker is set to access one leg or the other. When you install a 240volt breaker, you know how it's two poles, connected together? Since it's side-by-side, the two hots it gets are automatically split between the two legs.

Ok, got that now.
So, your house has 240volt coming in, but provides 120volt service to all of the branch circuits by the nature of landing the hot on one leg or the other. (Except for your 220volt appliances, range, maybe dryer, hot water heater, hot tub, heaters.)

Yep, understood.

The 50A circuit (NEMA 14-50) is rated as a 50A circuit because that's what the breaker is. Even though it's providing "100 amps" as in 50A on each leg, it's still a 50A breaker, because either leg will trip if you try to pull more than 50A.

Okay, I am pretty sure I understand the 50 amps on each leg that would equal a total of 100 amps in the distro (50 on each leg as stated) but, are you saying that if we pull more than 50 amps from the distro's legs combined or just if we pull more than 50 amps from "each" individual leg?  ---Follow me here----I've got this 240 coming in as 120 volts with 50 amps on each leg (as has been described very well now) and on "EACH" leg I've got say 3 separate 20 amp breakers and from there, I've got a pair of 20 amp outlets on each breaker.  Now, say I've got 3 of my amps hooked up to each outlet therefore one plug in on each outlet is not used.  So, we're using a total of 3 plug ins for the 3 amps.  Now, let's say that I'm running these amps hard and they are pulling close to 18 amps each (let's just say for arguement's sake they are ok)....in this case, if ALL 3 amps are pulling 18 amps at once (together), then this would be 54 amps total JUST ON THAT ONE LEG.  So, in this case, the 50 amp breaker either in the distro or the one back at the power supply should trip correct? 
 
If yes, that makes sense. 
 
But hear me out on this one.  Let's say I have the same exact set up on the other leg with 3 separate dual 20 amp outlets and I have the same 3 amps plugged into them.  --HOWEVER....this time all 6 amps are only pulling 15 amps at one time (all together).  Which would equal a total amp pull of 90 amps on the distro (45 on one leg and 45 on the other).  Since it's only 45 amps per side, will the breaker still be ok and not trip OR will the breaker pop since it's pulling a total of more than 50 amps? 
 
If it is no, the breaker will not pop, then I understand.  However, if it is yes, the breaker will trip, then I am confused. 
 
If you're explaining to me that the distro can NOT have a "TOTAL LOAD" *(between both legs) at any given time of 50 amps or more then I don't understand why they make 2 separate 50 amp services available to total up to 100 amps if 100 amps isn't actually available at a given time. 
 
I understand the load fluctuation and the need to distribute the load and that "most" times the distro may not see a total load of more than 45 amps so it wouldn't be an issue.  But I can't imagine that with running some of this high powered sound equipment along with older lights that consume high amounts of power that limiting them to only 50 amps (total) is what's happening. 

To address one of your statements-- if someone wired the plug with just one of the hots (let's say X is connected and Y is not), when you connect YOUR range plug to the outlet, half of your system will not work, because the half of your panel/distro (in this scenario, the Y leg) that relies on the Y connection will see-- nothing. Your panel/distro NEEDS to see current on BOTH legs to not only avoid overloading the upstream breaker but also to fully utilize the connections that it provides.  Although it would put a load on the upstream breaker, wouldn't one side of the distro still work?  Or since the neutral can't switch back and forth (I'm not sure about this in single/split phase) will it not work at all?  The side that I plugged into with the 20 amp breakers would still work since power is coming into that leg wouldn't it?  I'm not talking about "ideal" situations here but what would "actually" happen.  *(Again, this wouldn't be recommended kiddies)* 

As for the code adherence by others-- and your wondering why others are doing it-- well, the responsibility for proper electrical procedures and safety lies with one person: YOU. You cannot always change or dictate what others do, but you have the ultimate responsibility to make sure that every part of the production that you are involved with is carried out with the utmost professionalism and attention to safety.

Understood and that's why I'm here asking the questions.  I would like to do things the right way and not necessarily "the way I've seen it done."
What Brian mentioned about cam feeder is what was mentioned with "single conductor cables." You're looking at things like
http://www.lexproducts.com/cs/entertainment_product?id=350&market=Entertainment&productLineId=17&subCategoryId=93 whereupon you have five lines running from the source 
 
Gotchya.
 
(panel tie-in, camlok access points at the panel, or hardwired to a generator). That's a three-phase feed, and until you reach that point, don't worry about it. I've 200' of 1 #2 wire, and it's super friggin' heavy, so that's why people are warning you away from hauling around a 250' length of cable. For my 50A applications, I don't have anything longer then 100' -- partially for the voltage drop, but also partially that it's a pain in the butt to coil/uncoil even 100' at a time. I'd rather add a 50' length to a 100' length then deal with one 250' length.

 
After reading Brian's post and how he made a great point about a "potential" fire hazzard, I understand why limiting it to a smaller run may be better.  Otherwise, in the short runs that are only 75' or 100', as he said, to make sure that the wire doesn't heat up too much and have an issue by being coiled for the remaining 150' to 175', it would have to be unwound and laid out.  Which yes, would get tedious in the smaller situations.  But again, I will have to consider that when deciding on how we set up shows.  Yes, some shows will have power 75' or 100' away.  But I've read on the other distro posts (not just here but on other sites) that others agree that the power source isn't always as close as 50' or 75'.  As they mentioned, it can be through the halls of the kitchen or some other room and by the time you run it up over the rafters of the building or along the walls and around corners to minimize having a straight run, you may easily have 150' or more to unwind.  In which case, taking out another 100' takes what, 5 minutes? 
 
Again, I appreciate the concerns about weight and having to unwrap it each time and I'll have to decide that one.  As I mentioned, if it's me who's doing it, I guess I'll only have myself to bitch at. 


By the way, "split phase" is used to mean the same as "single phase," it's referring to two legs as opposed to the one phase. "Phase" refers to the degrees of separation between the two legs-- X to Y is the same as Y to X; X to Y is different then Y to Z, which is still different then Z to X.

 
Got it.  Good info.
You asked about getting, say, 4/5 as opposed to 4/4 now-- several things here:
- Once you go to 3 for main feeder cable, I NEVER see it that small (#4 wire) of a cable... everything is 100A to 200A service, which requires at LEAST the #2 cable.
 
Well, at this point I am considering 2 gauge.  But again, not to be a broken record and think that it is gospel but according to the "wire calculator", running 3 phase as long as I did actually reduces the voltage drop by anywhere from .5% to 1%.  So actually, worst case scenerio would be 240 single phase and 3 phase would actually be better.  Of course this was with 50 amp service so OBVIOUSLY, 100 amp or 200 amp would be different.  But I haven't considered that yet.  Is 3 phase NEVER less than 100 amp service?  Or now let's get this question figured out, is it 100 amps total or is it 2 separate 100 amp "legs" like with the 14-50R receptacle/service where it's 50 amp service but it's actually 2 separate 50 amp "legs?"  (I'm only going off of the calculator so don't get upset at me for just using that as an example).  If it's wrong, can someone point me to the correct site to determine the accurate cable size? 
- You can connect a single phase distro to a 3 service
 
Which would be good for versatility correct?  (Again, thinking ahead here)
 
, but you can't connect 3 distros to a single phase service.  So then why limit yourself to a distro that only has 3 phase service if it ONLY can be used for 3 phase and NOT single/split phase?  Seems like a waste to me.  Of course when you're a huge production company that tours, I'm sure it's different when money isn't an issue.  I'm just thinking it's best to utilize the distro for multiple uses if it "can" be set up to. 
 
Same concept as before when discussing why a NEMA 14-50 plug with only one hot connect will cause trouble with your 240V distro-- you connect the 3 distro in and one of the legs will be absent!
 
Yep, since the 3 phase distro would NEED 5 wires and the 14-50R connector ONLY has 4, I can understand how this would be an issue.  Makes sense. 

Electrical sure is fun, isn't it?!? :D
 
I don't know if I would use the word "fun" to describe it.  Confusing, challenging, or overwhelming would be words I would use.  At the very least, for my conversation regarding my current situation, it IS INTERESTING. 

I hope I answered your major questions; let me know if there's something that is still confusing!
 
Well, if you read above, you'll see I got "most" of what you were saying and it makes sense.  The parts I still don't understand I have pointed out. 
 
-Ray Aberle

Man, almost 700 views in only a couple days.  This must be one hot topic.  I hope that the people reading aren't staying away because they don't want to loan their knowledge or hate my long posts.  I'm sorry about that but the information should be good for othes like me who "don't quite" understand the situation.  Better to have good power set up than not. 
« Last Edit: January 30, 2013, 04:55:17 am by Lonnie Eldridge »
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Lonnie Eldridge

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That's not what Brian said. He said, specifically, "HIGH ampacity three-phase."

Okay, sorry about my confusion.  I didn't mean to imply that he stated that specifically but I thought by the mention of using camlocks that it meant that they "had" to be used for 3 phase.  Now that you've clerified that they (the cam locks) are used in High Amp/Load situations, then I understand now.  Thanks for clearing that up. 

In my rig, I use Motion Labs rack packs to service my amplifier racks. I have both 1 and 3 units; the 1 units take an L14-30 220V/30A twist lock connector and the 3 units take an L21-30 208V/30A twist lock connector. The service cables are 8/5 (or 10/5, depending on who is providing the cabling) multi conductor single jacket cables.

What was being referred to was running 100A/200A/400A input from a mains service to your distro; that's where you see the multiple single conductors with camlok connectors. The other advantage of going with single conductors is that they'll lay flat as opposed to a huge cable trying to hold everything together. When you're running service across large areas with cable ramps, you really want the individual conductors to be able to flow through each channel of the ramp!

That's true if you're using a ramp that has the individual cable slots allowed only.  Of course they have different walkway ramps available that would allow for use of larger diameter cable don't they?   

Ray
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TJ (Tom) Cornish

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Lonnie, I'm a little dizzy from all your external processing, so forgive me for not reading everything you wrote.

RE: 250' - I'm not saying you'll never need 250', just that you won't ALWAYS need 250'.  When you don't need it, you don't want it.  Smaller chunks give you more flexibility.  This also allows your first chunk of wire (at the distro end) to be 4/4, and only your extension cables need to be bigger than that.

RE: 500' wire length - when you are calculating the resistance of the circuit, you need to consider the whole circuit - the hot wire out and the neutral wire back.  For a 250' piece of SO cord, the path length is 500', hence my calculation.  Some calculators you may find may already take this into consideration.  I didn't look in detail at your calculation or your questions about it, but keep in mind that the feeder wire you need is dependent on 3 things: The allowable voltage drop, which depends on length as well as diameter, the amount of current that can flow through the wire before the wire heats up beyond it's 75C or 90C rating or whatever, and the number of conductors making heat.  Different calculators may make different assumptions for different situations.

For pro audio you have two choices for feeder wire:  SO cable, which is multiple conductors in one jacket, and SC (or similar) single conductor cable.  SO cable is used up to about 4/4, and you can terminate a NEMA 14-50 plug on it, so a non-electrician can use the system.  SO cable must be terminated in an appropriate device - one end in a junction box, one end in a plug, etc.  It's not allowed to cut the outer jacket off and use the wires individually. 
The closeness of the wires to each other and the fact that the outer jacket is an insulator means that you have to derate the cable's current capacity for more than 2 current-carrying conductors, as there's more heat in a confined space and you run into the temperature limit with less current than if there were only 2 wires.

SC cable is used for high current distribution because it's more manageable to have a loose bundle of 4 or 5 3/4" wires than a single piece of cable the thickness of your leg - it bends more easily, and there's more airflow, allowing more current to flow through an SC bundle before the heat is a problem.

RE 3-phase - you basically cannot do a 50A 3-phase system on SO cord distro.  You won't be money ahead trying to find 4/5 wire - it won't fit in your plugs for one thing, and there's no commonly available system with which to use it.  The jump from NEMA 14-50 is to a camlok distro, and attachment of that requires a whole 'nother set of issues, not to mention understanding how 3-phase power works.

I appreciate your trying to understand this, but at some point you need to just follow the rules rather than continue to question.  Your next stop should be a pre-packaged MotionLabs, Peavey, etc. distro with a piece of 4/4 SOOW maybe 75' long and a NEMA 14-50P at the end.  For more length, you can get another piece of 2/4 SOOW (if you can fit it in your plugs), and make an extension cord.
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Shane Ervin

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Power distros for entertainment like bands & concerts or stage & theatre shows
« Reply #35 on: January 30, 2013, 09:53:42 am »

Quote
  What is different at the power distro when needing to do 3 phase?  Are the components still built the same but when running into a 3 phase situation you have to change some wires around or is it a completely different junction box altogether?  I've read that the components are the same but you need to change the wiring (hence the additional wire for 3 phase vs. single phase).... <snip>

Can someone explain to me the advantages or disadvantages of 3 phase vs. 240 in simple terms?

Polyphase systems exhibit "ripple-free torque" in their transmission of power.  This is a very important attribute considering the large rotating machines (generators, motors, even hydraulic winches) involved.  In power distribution systems serving industrial and commercial areas, 3-phase is deployed for this most basic reason, historically.

From the perspective of a pro-sound provider, the question isn't so much what's the advantage for you.  Rather, it is: what's the best investment to make, knowing your gigs will take place in a mix of venues - some with 3-phase (208/120V), and some with split single phase (240V)?

For example, I chose a 3-phase RAC PAC since I know I can place all my loads on 4 breakers (leaving the remaining 2 de-energized).  Yet, I can cross rent the unit - or my entire monitor rig - to larger clients who are using 5-pin.

To interoperate with 4-pin twist, (or a 240V tie-in with tails), I use a short adapter cable (4-cond) with a 4-pin male on one end, and a 5-pin female that connects to the flanged inlet on the RAC PAC.  The "Z" light stays dark, only X & Y are lit.

A totally different approach is employed by a company nearby: they have multiple 4-pin twistlock RAC-PACs, but a 3-phase CamLok distro that powers some racks on L1/L2, some on L2/L3, some on L3/L1.  This obviates any need to re-assign loads within a rack, going from 240V venues to 208/120V shows.
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Art Welter

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Anyway, I am familiar with the voltage calculator and if I go in and put the specs in as follows:


Estimated voltage drop:  4.1%

---*(now, I put in 60 amps as a "worst" case scenerio for the type of load I "could" be pulling at a time.  Perhaps it wouldn't even be possible and the breaker at the power source would trip before it got to this point but I wanted to put that in to see what the results would be.  According to the calculations, it's still within the limits of 5% or under. 
Changing the gauge of wire to 2 gauge instead of 4 drops the voltage drop to around 2% at 50 amps and 2.4% at 60 amps so obviously that would be a benefit but it would be negligable considering the amount of money that would be spent on cable to go from 4 gauge down to 2 gauge. 
Lonnie,

You, and people with far more experience often don't realize that circuit breakers open when the average load is exceeded, short peaks as much as 10 times there rating may be sustained without blowing the breaker, but voltage drop will be severe.

Your amplifiers may have a 15 or 20 amp plug on them, but that in no way means they won't draw far more than that peak.

For example, a QSC PLX 3602 (18800 watts per channel) will draw 18 amps (average) at 1/8th power pink noise loaded at 2 ohms stereo, but 63 amps full power sine wave. It would current limit in a fraction of a second at full power and the internal breaker would pop (hopefully) before a downstream 20 amp breaker, but the point is a full power peak will draw around 60 amps from that single amplifier.

That single amplifier can easily brown out (cause excessive voltage drop) 250' of 4/4, especially considering the static lighting loads on the line already dropping voltage.
Nothing will blow except the sound on every kick drum beat.
The difference between brown out and stiff power can easily be a  6 dB loss in peak SPL.

Get 100' and 50' sections of serious wire if you need to go 250'.
That said, gigs that you need 250' of wire to reach the power source usually tend to suck so much that a 6 dB loss in PA output will usually be the least of the problems...

Art
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RYAN LOUDMUSIC JENKINS

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I really can't believe we have spend four pages on this thread.  We are talking about a person who is wanting to use possibly 250' of #4 or #2 cable to run a beer garden sound system.  I know of a very respectable company that is now using #4 for thier Very expensive name brand large format line array with Very expensive subs since the four channel companion amps are so efficient.  There is absolutely no reason for pieces of cable that long.  Where I work, our building codes specifically say that the generator must not be closer than 20 feet to the tents or stages.  Therefore, we have them dropped just over 20 feet away, sometimes as much as 50 feet away at the most.  I rarely use more than 50' cable lengths.

The OP doesn't need to get into this too much farther.  Buy a couple 50' pieces of 6/4 SOOW, get a Rac Pac and always have a generator setup by the provider for correct 120/240 Volt single phase operation.  Have the provider meter the voltage and then double check their work with your own meter.  Beyond that , you are not qualified based on your thread here.  Keep in mind that some people will look to the the NEC and tell you that the 6/4 SOOW is rated for 45 amps, which it is.  So don't pull more than 45 amps.  Electrical inspectors all around approve 6/4 SOOW on 50 OCPDs.  I have never met one who didn't.  You need to learn what YOUR local inspectors want. 

For what it's worth,  I don't think that you could pull 50 amps with a Beer Garden P.A.  I do lots of EDM shows and with a pretty sizable rig, way bigger than you are talking about I am only getting to around 55 amps.

If you must go into a venue that doesn't have a properly wired 50 Amp receptacle, be prepared to use extension cords.  It is really that easy and it is what we all do.
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Robert Piascik

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Man, almost 700 views in only a couple days.  This must be one hot topic.  I hope that the people reading aren't staying away because they don't want to loan their knowledge or hate my long posts.  I'm sorry about that but the information should be good for othes like me who "don't quite" understand the situation.  Better to have good power set up than not.

I'm sure I'm not the only one reading this thread but not contributing. What I like about this forum is the collective knowledge of members who know waaaaay more than I do. Sometimes reading the posts reinforces things I already knew, sometimes I learn new things. And sometimes I read the posts for the 'train wreck' aspect of guys who refuse to do things the correct way because it costs too much or who try to approach a problem from every different angle except the correct one in the name of saving money.
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Lonnie Eldridge

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Lonnie, I'm a little dizzy from all your external processing, so forgive me for not reading everything you wrote.

Tom, I'm sorry about my legthy responses.  I'm just trying to be as accurate as I can.  I know I'm not concise and never have been.  I apologize and still hope that won't stop people from contributing as I do sincerely appreciate all the help, suggestions, and knowledge I've gained so far.  I am still taking notes.

RE: 250' - I'm not saying you'll never need 250', just that you won't ALWAYS need 250'.  When you don't need it, you don't want it.  Smaller chunks give you more flexibility.  This also allows your first chunk of wire (at the distro end) to be 4/4, and only your extension cables need to be bigger than that.

I understand and I am considering a shorter length at the distro end.  But for a few reasons, I don't want it to be too short.  I do understand the hassle of dealing with unrolling a full 250' when we wouldn't need to and it would be a PITA.  I get that.  Also, the issue of "potential" heat transfer through the wires if it was coiled up in a rack and we're requesting a good chunk of power from it would be a concern.  That is noted.  Although it "may" never be an issue, I would rather err on the side of caution and not have to worry about that.  So, as someone said, it's either unroll it and spread it out for every show or use smaller chunks.  The smaller runs aren't as much of an issue but if I do split it up into say a 100' run from the distro and another 150' run for a main feeder line, I still have to deal with 2 more additional receptacles and/or plugs on that extension cable that's 150'.  Not to mention, I may or may not be able to use 4/4 SOOW cable.  I may have to jump to2/4.  I don't know and I will have to check on that. 

Again, this is where I am hopeful that some of the people's guidance on here can steer me in the right direction with the right answers.  If a 4/4 cable is safe and meets code for a 150' feeder cable from a 14-50R receptacle AND a 100' cable at either 4/4 or 6/4 from the distro is still both safe and within codes, then I would obviously be able to save a chunk of money AND WEIGHT (and size) by not having to have 2/4 feeder cable for my 150' extension.  But if 2/4 is mandatory, then that's that. 

And yes, in the end, it may come down to figuring in a few rentals of some 100' or 150' 2/4 feeder cable for a few shows since those cables aren't cheap.  $1200 to $1800 is a lot of money just to spend on cable alone so yeah, if places are willing to rent for $50 or $100, then maybe that's what I do for a few shows.  At this point, I don't know and I'll have to do some checking on rental prices.

My thing is:  if the rentals are outrageous by many places such as say $300 or $400 for a rental of a cable that big, then that's pretty hefty.  But I'll have to check.


RE: 500' wire length - when you are calculating the resistance of the circuit, you need to consider the whole circuit - the hot wire out and the neutral wire back. (I did not know this.  Thanks for the info.  But I believe the calculator I used asked for the amount of conductors for either single phase or 3 phase wiring.  They did ask for 2, 3, or 4 parallel runs for 3 phase and then a separate run or run(s) for single/split phase.  So, maybe they are allowing for that same 250' return when I put it in the calculator.  But I don't know and thank you for pointing that out.  I wasn't aware of that.)  For a 250' piece of SO cord, the path length is 500', hence my calculation.  Some calculators you may find may already take this into consideration. (yeah, I don't know and will check)  I didn't look in detail at your calculation or your questions about it, I know you probably didn't but if you did have a chance, I would appreciate checking it out.  I did try to use higher than normal figures to have a "worst case" scenerio.  But going off of what I am reading from others, 6/4 may take care of my needs for the most part.  At the very worst 4/4 would be more than sufficient and 2/4 is probably not even worth it.  But again, I don't know at this point and am still getting info.) but keep in mind that the feeder wire you need is dependent on 3 things: The allowable voltage drop (I understand and as I have said, according to the calculator site I used, the voltage drop was well within maximum limits of 5% or under), which depends on length as well as diameter, the amount of current that can flow through the wire before the wire heats up beyond it's 75C or 90C rating or whatever, and the number of conductors making heat.  Different calculators may make different assumptions for different situations.

Tom, as I have said, please refer back to the calculations I put in on the calculator.  I understand that it is not your job to do my work for me and I respect that your time is valuable so I don't "expect" you to put the calculations in for me.  However, the same things you are refering to are the same things I had to account for with that same calculator.  And I was using a longer run of 300' and even 350' and 400' just to "see" what would come up, the gauge of the cable used (2, 4, or 6 gauge), a higher amp load rating of 60 INSTEAD OF only 50 (which would be what we would be using but I used 60 just to err on the side of caution), and used a higher temperature of 90C (197F) instead of just the 75C temp "just in case" the wire was to heat up too high.   And with all of these figures being higher than the maximums, I still had voltage drops within the limits of 5% or lower.  Well, except in the case of the 6 gauge run of 350' and 400' but I'm not really considering 6 gauge at this point UNLESS it will work for sure.  Again, I would rather go bigger and be safe than not.

For pro audio you have two choices for feeder wire:  SO cable, which is multiple conductors in one jacket, and SC (or similar) single conductor cable.  SO cable is used up to about 4/4, and you can terminate a NEMA 14-50 plug on it, so a non-electrician can use the system.  SO cable must be terminated in an appropriate device - one end in a junction box, one end in a plug, etc.  It's not allowed to cut the outer jacket off and use the wires individually.  Huh, I'm finding SOOW cable up to 2/4 and 2/5.  I haven't looked for anything larger because at that point, it will be so far out of my price range that it won't even be considered an option at this point.  Maybe I'm getting wrong information about 2/4 or 2/5 cable or 4/4 or 4/5 cable.  I don't know.
 
In the situation where people use "tie ins", are you saying they CANNOT use standard SOOW cable (like a 6/4, 4/4, or 2/4 size) and "tie in" to the junction box?  Or they are not "supposed" to?  This isn't a smart butt question and is a serious one.  When I hear discussions about "tie in", I understand that cam locks are used in many cases but I also "assumed" that SOOW cable could be used as well.  Since some people discuss having multiple ends available with twist lock connectors so they can interchange for different venues with only 30 amp plugs or otherwise, I thought that they would have an interchangeable plug that would allow one for a "single strand" tie in.  In some cases, I have seen people promoting distros with no plugs or ends on them so I was "assuming" that this was so you could "tie in" to a junction box if needed.  Or is this not ok with SOOW cable? 
 
Please explain.
 
The closeness of the wires to each other and the fact that the outer jacket is an insulator means that you have to derate the cable's current capacity for more than 2 current-carrying conductors, as there's more heat in a confined space and you run into the temperature limit with less current than if there were only 2 wires.

Gotchya.  Well, I would "assume" that the calculator would take into consideration that if someone is putting in 4 gauge into the equation and putting in the amount of wires that it (the calculator) would KNOW that this would be with a SOOW cable.  But, looking at that calculator now, I am not sure since it only gives specs for 4/0 cable and NOT 4/4 cable.  Which would "possibly" mean that the calculator is indeed only figuring for each wire to be separate and NOT shielded.  It asks for conduit but does NOT ask for shielding so I would have to have that checked out.  Thanks for bringing that up. 

SC cable is used for high current distribution because it's more manageable to have a loose bundle of 4 or 5 3/4" wires than a single piece of cable the thickness of your leg - it bends more easily, and there's more airflow, allowing more current to flow through an SC bundle before the heat is a problem.

Sure, that makes sense but we're not talking about a thickness of 4" or 5".  We're talking about 2/4 SOOW cable and that is only 1 1/4" thick.  Sure, it's still heavy and a PITA and yes, "more manageable" but definately far from the thickness of our legs which is about 8".  (unless you're really skinny....not this fat boy).  Yes, airflow makes sense.

RE 3-phase - you basically cannot do a 50A 3-phase system on SO cord distro.  You won't be money ahead trying to find 4/5 wire - it won't fit in your plugs for one thing, and there's no commonly available system with which to use it.  The jump from NEMA 14-50 is to a camlok distro, and attachment of that requires a whole 'nother set of issues, not to mention understanding how 3-phase power works.

I definately agree that 3 phase is a "whole nother set of issues" and won't argue with that.  I just want to consider being prepared.  Yes, having the addional wire in that SOOW cable won't fit in any 14-50R receptacle and as such, I would have to figure out a way to leave it unavailable.  Of course I can "assume" that it can simply be left off from the connectors at each end and simply sit in the SOOW jacket couldn't it?  There wouldn't be anything wrong with that would there?  Other than it sitting there wasting space and taking up room and weight what would be the disadvantage of having it?
I appreciate your trying to understand this, but at some point you need to just follow the rules rather than continue to question.  Hold on, where am I not trying to "follow the rules?"  I'm not trying to "get away" with anything here and skip anything or not do things the right way.  I want to do things the right way.  That IS the whole point of my questions.  At the same time, I'm not going to spend $1200 to $1800 on a 2/4 cable for this project if it will not be necessary and a 4/4 cable will do just fine and save me almost half the cost.  (maybe even more depending on the overall lengths I end up using for the entire distro AND extensions)
 
Please don't tell me to stop questioning things.  That's like saying it's wrong to question things and I see nothing wrong in asking questions to get a better understanding of the situation.  I hope that wasn't your intention and if you're getting the wrong impressions from my questions, I'm sorry.  But I am sincerely trying to learn here.  I have better things to do than type novels about a subject that many may find "common knowledge."  I don't have that knowledge so I'm asking questions to learn.  And I appreciate all that's been given so far.
 
 
Your next stop should be a pre-packaged MotionLabs, Peavey, etc. distro with a piece of 4/4 SOOW maybe 75' long and a NEMA 14-50P at the end.  For more length, you can get another piece of 2/4 SOOW (if you can fit it in your plugs), and make an extension cord.

At this point, I am looking at a few options such as the Amp shop distros HOWEVER, I am concerned that those are not actually approved for UL certification or even code accepted.  Although I'm sure many have purchased them without issue, I would hate to invest even a few hundred into one of them only to find out that they are not approved for my use.  I am also considering a Furman distro as well.  Or yes, as others have mentioned, maybe even renting a few times first.  But even renting something I have to make sure that it's up to spec.  Just because I go into a place that rents distros does NOT mean that theirs are ok so, I have to kind of get the information anyway to be prepared right?
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