Sound & Stage Power

[TJ Cornish]

Re: Sound & Stage Power

So is this a benifit of a Soca cable run, since each of the 6 circuits has a breaker on the main distro, you don't need another breaker box system at the line array? This makes the CS50 route much more expensive.

IMO, Soca is a poor choice for non-dimmed power distribution. The cable needs to be derated substantially due to a large number of bundled conductors, and there are traps depending on how they're wired - number of grounds, wire gauge, etc. It's also REALLY heavy.

As to having all your breakers on a main distro vs branch distribution, I don't know if that's an advantage or not. Many folks like the flexibility of L21-30 or L14-30 at the distro so that can be broken out differently elsewhere in the system depending on need - 208v, 120v, feedthroughs, etc.

I don't think you've told us what system you are running - presumably something active? What is the manufacturer's power recommendation? I can't tell if you're hoping for 6 circuits because Soca can do that, or if you really need them.

I have a number of 50A 240 volt distros. I'm possibly looking into getting a larger distro at some point, but I have been able to keep my power consumption down due to LED fixtures and efficient audio so it isn't critical. If you always have 3-phase power available, L21-30 is probably the best choice. If you only have split-phase power, L14-30 may be more flexible. Of the two companies I work most closely with, one is a L21-30 shop, the other is an L14-30 shop.

 

[Chris LaRocque]

Re: Sound & Stage Power

Sean, you can contact www.ampshop.com or www.entertainmentmetals.com. They both have several options for break out boxes. We have some with tails (CS50) and edisons and L14-30 as well as boxes with surface mount CS50 (some with in and some with in and out). Of course we have a 50 AMP at the main distro, then the break out boxes are basically mino-distro with their own breakers for each outlet.

 

[TJ Cornish]

Re: Sound & Stage Power

The Motion Labs racpac you illustrated does have breakers for the six circuits. As to how many circuits you can run on a 50a service, as long as there is a 50a main breaker or fuse protecting the feeder that will limit the amount you can draw. So you don't actually have "120a potential".

Expanding on this, a two-pole 50A breaker is... wait for it... a 50A breaker. This means that if you draw 55 amps on one leg and 0 amps on the other leg, both poles of the the breaker will simultaneously trip. If everything is perfectly balanced - breaker tolerances notwithstanding, you can draw up to 50A on each pole; and if all loads are 120v Line -> Neutral, that is potentially 100A of capacity.

The reason 50A breakers are commonly broken into 6 20A circuits (3 20A breakers per 50A leg) is that it's very difficult to use all 20A possible capacity of every circuit simultaneously, so there is usually some headroom available.

 

[Shawn Keck]

Re: Sound & Stage Power

Indu Electric is great. I use them for all of my cable and distros. They are small enough a shop that they will build you whatever you want in whatever configuration you want and we have had their gear on the road for years with zero problems. Well built, cheap and great customer service.

They can build me edison 12/3 cable cheaper than I can buy the parts for myself and build!

 

[Rob Timmerman]

Re: Sound & Stage Power

So is this a benifit of a Soca cable run, since each of the 6 circuits has a breaker on the main distro, you don't need another breaker box system at the line array? This makes the CS50 route much more expensive.

You should price out a full system. I think you'll find that the cost of adding remote breakers is more than offset by the difference in cabling.

 

[Shane Presley]

Re: Sound & Stage Power

So is this a benifit of a Soca cable run, since each of the 6 circuits has a breaker on the main distro, you don't need another breaker box system at the line array? This makes the CS50 route much more expensive.

The only thing i can mention about using soca for regular a/c (and this might be obvious), but not to energize it until everything is connected. I use regular soca to run a/c and motor control up to my truss with custom splays. One of my guys disconnected before we were done landing the motors. Anyway, when they went to reconnect (lining up the key), some pins touched common areas and whap... Some sparks and minor charring. We powered down and reconnected, so if you dont mind that aspect, its probably the cheapest route for what you are trying to achieve.

 

[Mike Pyle]

Re: Sound & Stage Power

So is this a benifit of a Soca cable run, since each of the 6 circuits has a breaker on the main distro, you don't need another breaker box system at the line array? This makes the CS50 route much more expensive.

If you have a distro with edisons, you can always use soca by adding an edison breakin and breakout at each end.

 

[Shawn Keck]

Re: Sound & Stage Power

Ok guys, I am about 95% sure I'm switching consideration from Soca to CS50 cables and break out boxes for my 2 array towers and center sub power locations. Generators use the CS50 and many audio companies in Nashville have the CS50 cables and break out boxes. I like that I can make and fix those cables, don't want to mess with 19 pin Soca.

I've seen 6 Edison break out boxes that take a 50A CS50 feed, but DO NOT have individual 20A breakers for those 6 cirsuits. IS that an issue or problem? Can you run a 6X20A = 120A potential on a CS50 cable and 50A 2 pole main breaker?

Thanks again!

Here is what we use from Indu...

Cam feeder from source to Indu Cube Distro:

3 Phase cam in with cam pass through which breaks out to six CS50 outputs

http://www.indu-electric.com/catalog/26/?PAGEN_1=4
018 Cube

Then 6/4 to where we need it

Breaks out into their lunch box series CS50 in with CS50 pass trough which breaks out to six breakered 20A Edison

http://www.indu-electric.com/catalog/29/
FB-F5-PT-03

Cheaper option that is still breakered is the Floor Box Series:

http://www.indu-electric.com/catalog/30/
FB-F5-PT-03 Tail

Cheapest option is construction spider boxes off Craigslist...but that can be kinda ghetto!

Many hotels have either the CS50 or L14-50 connectors so Indu built us a few L14-50 male to CS50 Female adapters. Between those, one CS50 to bare wire tail and cam, we have yet to have a problem getting power anywhere.

Cam is readily available, 6/4 can be had from any United Rentals in any city, and the distros are the same in the construction industry if you need more. We don't have a set rig that needs the same power set up every time so for us it was a no brainier.

 

[Sean Thomas]

Re: Sound & Stage Power

Thanks for all the tips - they are very helpful.

Rob - I agree that a CS system with breakered sub-boxes could be more expensive than Soca. However, I also agree with what others have said about Soca - used in lighting can be confusing, no standard on cable and wiring (12/14 must be sharing grounds?).

Are these the only 2 options for getting 100-120 amps of power out to my line array towers? Anything else to consider? If not, I'm really leaning towards the CS50 route.

Thanks Again!

 

[Tim Weaver]

Re: Sound & Stage Power

Thanks for all the tips - they are very helpful.

Rob - I agree that a CS system with breakered sub-boxes could be more expensive than Soca. However, I also agree with what others have said about Soca - used in lighting can be confusing, no standard on cable and wiring (12/14 must be sharing grounds?).

Are these the only 2 options for getting 100-120 amps of power out to my line array towers? Anything else to consider? If not, I'm really leaning towards the CS50 route.

Thanks Again!

2 runs of L14-30 will do it too. That's what I have been using on our biggers rigs. It was easiest for us, because we had L14-30 based power everywhere else. When the systems grew, we just added another run to each side of the stage....

 

[Sean Thomas]

Re: Sound & Stage Power

One more thing - the guage to my 50A sub box? 4/4 or 6/4 or 8/4? I know the ratings are for a full load for machinery and constant draw. Since music is only bursts, I was told 6/4 = 45A or 8/4 = 35A would/should work. I assume length factors in as well. I was thinking 50' standard run, maybe 75' as the longest run.

Any adivce appreciated!

 

[Tim Weaver]

Re: Sound & Stage Power

One more thing - the guage to my 50A sub box? 4/4 or 6/4 or 8/4? I know the ratings are for a full load for machinery and constant draw. Since music is only bursts, I was told 6/4 = 45A or 8/4 = 35A would/should work. I assume length factors in as well. I was thinking 50' standard run, maybe 75' as the longest run.

Any adivce appreciated!

Obviously the loner the run, the more wire gauge you need to prevent voltage drop. Honestly I would go 4/4 everywhere if possible. Your amps will be happier. Less heat and less voltage drop means more usable go-juice at the amp.

 

[TJ Cornish]

Re: Sound & Stage Power

One more thing - the guage to my 50A sub box? 4/4 or 6/4 or 8/4? I know the ratings are for a full load for machinery and constant draw. Since music is only bursts, I was told 6/4 = 45A or 8/4 = 35A would/should work. I assume length factors in as well. I was thinking 50' standard run, maybe 75' as the longest run.

Any adivce appreciated!

Wire size depends on the size of the upstream over-current protection device. If you have a 50A breaker, you need to use wiring rated for at least 50A in the circumstance you're using it. For SOOW cord, that's #4. Some electrical inspectors will let #6 slide, but it does not pass the letter of the law, and is foolish anyway - the extra voltage drop at lengths we use is like buying a Lamborghini but refusing to put anything other than 87 octane fuel in it.

There are various voltage drop calculators around the net where you can play with numbers. The general rule of thumb is you only want a 3-5% voltage drop from the branch circuit wiring. Many calculators must have the round-trip length entered - i.e. a 50' cord is actually 100' of copper for the circuit. Also, as you mentioned, audio load is non-linear. The good news is that the average power is low; the bad news is that the instantaneous draw can be VERY high - several times the rating of the breaker, which means that the true voltage drop is much higher at the point of peak draw than what the calculator shows for a fully-loaded breaker.

I have started writing a series of articles on power consumption and distribution. Take a look: Understanding Power Consumption

What's your rig? How do you know you need 100A (presumably 120V) per side?

 

[Sean Thomas]

Re: Sound & Stage Power

TJ - our rig is dB Technologies, (8) T12's and (4) T8's per side and upto (12) S30 subs = 36 boxes total. So by the book, 2x (6) 20A circuits to the LA and (12) circuits to subs would do it.

However, I have ran (3) T12's over (1) S30 on a 20A in a club. I also had a Nashville production company tell me that their rig needed 300A by the book, but they metered the feeders at 45A, at what he called full load for the rock concert.

Why are we able to get away with so much less amperage than what is called for? I don't want to spend thousands more than I need to meet specs that may not be "real world".

Thanks again!

 

[Chris LaRocque]

Re: Sound & Stage Power

Based on your calculations thats a 240 AMPs on a 220-single phase circuit (480 @120v)you would need. We draw on average 12-20 AMPs per leg when we run 12 HDL20 over 6 S30 with backline, a bunch of led lighting, all monitors (side fills with subs, drum fill w/ sub and 8-10 floor wedges and front fills). This system ran for 2 weeks 16 hours a day and we never had an issue all on a 100 amp single phase feed. I have been amazed at how much less current draw there really is. Now we are not doing EDM (mostly country/rock stuff). You may need 12 outlets for your S30's but I can't see you needing 20 AMP per sub. Not even close in my experience with our subs. It is possible that our distro meters are off, they are set to average, but read in line with fluke reading.

 

[TJ Cornish]

Re: Sound & Stage Power

TJ - our rig is dB Technologies, (8) T12's and (4) T8's per side and upto (12) S30 subs = 36 boxes total. So by the book, 2x (6) 20A circuits to the LA and (12) circuits to subs would do it.

However, I have ran (3) T12's over (1) S30 on a 20A in a club. I also had a Nashville production company tell me that their rig needed 300A by the book, but they metered the feeders at 45A, at what he called full load for the rock concert.

Why are we able to get away with so much less amperage than what is called for? I don't want to spend thousands more than I need to meet specs that may not be "real world".

Thanks again!

Adding up the audio "wattage" will lead to a wrong answer for power consumption. Many products specify operating current, which is more real world. If you haven't already, read the article I linked to - this is explained there.

Briefly, many amplifiers are rated at two numbers - 1/8 power and 1/3 power. These numbers are designed to correspond with real music, and not trying to use your amp as a heater. 1/8 power is the right number for most musical genres, and indicates reasonable full-tilt-boogie - occasional clipping. The 1/3 power number sometimes specified indicates insane people who think the clip light is decoration and who enjoy visits to the speaker repair shop.

The reason you get more output power than required input power is that audio is not continuous. You get large spikes occasionally, and then, relatively speaking, long periods of low consumption. Energy storage in the amps (capacitors) buffer this, and the result based on many years of live data is the 1/8 power number.

A rule of thumb for products that don't specify actual power consumption at 1/8 power is to divide the output wattage by 3 or 4 to get an estimate of power consumption. I feel very confident that you can easily run 3 T12s per 20A 120V circuit, and very easily 4 T8s per 20A 120V circuit. On the sub side, you can get at least 2 boxes per 20A circuit.

That would be at most 3 20A circuits per side for mains and 3 20A circuits per side for subs; 12 120v 20A circuits total. This should all easily run on 100A split phase.

If it were me, I would try to take advantage of the universal power supplies in your rig and run at 208/240 volts when possible. This is a lot easier on your amplifiers, suffers much less voltage drop, and is potentially less wire, too. One option would be something like this:

Main distro is 200A 3-phase camlok input. Outputs are multiple circuits of 50A California and 30A L14-30. L14-30 fed via 10/4 cable to breakout boxes for 120v power. 50A California via 4/4 cable to breakout boxes providing 3 breakered L14-20 receptacles.

In many setups, you could run one California per side and probably run the whole non-sub part of the array on a single L14-20, and the subs on a second or possibly the remaining 2 L14-20s. For larger systems, a total of two Californias per side will provide more power than you will ever use.

A couple important principles: Every time you step down your ampacity, you need over-current protection. This means that your main distro needs to have 30A breakers and 50A breakers for the respective receptacles. Branch distros also must have breakers - an L14-30 breakout box usually has 4 20A breakers for the receptacles. Same on the California side - the 50A -> 3x 14-20 breakout distro needs to have 3 two-pole 20A breakers. It's not OK to chain your boxes from a 30A circuit, which is why you need to step down to 20A eventually.

There are other ways to do this, but 208v/240v power directly to your boxes is a really good thing.

Here's my real world experience:

I run ITech HD12000s, which are 8000w amps (12,000w by their most generous spec). I run these either from 120V power if that's all that's available, or 208v via L14-20 circuits if possible. One time I blew a 20A breaker with an amp, but I was being an idiot - sub duty in the 1/3 power range. Other than that "learning experience", they are more than fine on a 20A breaker. Interestingly, at the time of blowing the sub breaker, I was running two IT12Ks on a different 20A circuit powering the rest of the rig, and didn't blow the breaker.

Based on this data and other experiences, I have absolutely no concerns about running 2 8,000 watt amps on a 20A 208v circuit.

 

[Sean Thomas]

Re: Sound & Stage Power

Thanks TJ and Chris for your real world input.

So, going by the book, I am "over" planning my system because of the "divide by 3 or 4" real world power consumption. So why does dB suggest (2) T12's per 20A circuit. Sound like I can run 6 or 8 boxes per circuit.

Could I run each side of my LA on the 60A provided by the L14-30 or is that pushing it? Should I consider (4) L14-30 outs on my distro to feed (4) 60A sub boxes -vs- (4) CS50A outs? Or as TJ suggests 2 and 2?

Cable weight and cost is a big factor that I'm wanting to minimize.

Thanks again!

 

[Sean Thomas]

Re: Sound & Stage Power

TJ - If we are using 1/3 to 1/4 of the power as you stated, can't we also de-rate our cable guage too. By the book says use 4/4 for my CS50 feeds but if I'm only really using 1/4 of that, what can't 6/4 or 8/4 work? Seems like a logical correlation.

Thanks.

 

[Tim Weaver]

Re: Sound & Stage Power

Could I run each side of my LA on the 60A provided by the L14-30 or is that pushing it?

Yes, you would probably be fine, but in those situations where you need every ounce of output the rig would be happier with more copper.

Should I consider (4) L14-30 outs on my distro to feed (4) 60A sub boxes -vs- (4) CS50A outs? Or as TJ suggests 2 and 2?
!

I would always put an extra 2-3 14-30 outlets on a distro, no matter what. There may be a day when you need to crossrent some more PA for a show and having 2 more 14-30's on hand means you don't need an extra distro. Plus, you have flexibility to run 1 or 2 14-30's per array depending on the demands of the show.

 

[TJ Cornish]

Re: Sound & Stage Power

TJ - If we are using 1/3 to 1/4 of the power as you stated, can't we also de-rate our cable guage too. By the book says use 4/4 for my CS50 feeds but if I'm only really using 1/4 of that, what can't 6/4 or 8/4 work? Seems like a logical correlation.

Thanks.

You are already reducing the amount of cabling by going from one 20A circuit per box to one 20A circuit per 3-4 boxes. The code is absolute, and reasonable: If you have a 50A breaker, it does not matter if you're only using 10A of that, you must have infrastructure that can handle the current rating of the OCPD, as otherwise you have a fire hazard. If you truly only need 20A (hypothetically speaking) and want to run lighter cable, you need to downsize the breaker to match.

I suspect that you could get away with a two-phase 30A feed per side, though you only get 1 1/2 20A 208/240 volt circuits out of that, compared to getting 2 1/2 20A 208/240 circuits on a 50A feed. If you do standardize on 30A power you can always run another line, however I think if I went down that road, it may make sense to just skip right to L14-20 receptacles on your distro so you don't need any power breakouts downstream.

The beauty of L14-20 is that you can go directly to a Powercon plug to your rig (using the red and black wires for 208v), and you can also use a small unbreakered breakout box that provides 2 20A 120V circuits from a single L14-20 feed.

Lots of choices; just make sure you match your wiring to the breakers.