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Title: Distributed Power
Post by: Jared Koopman on December 20, 2013, 12:10:03 pm
Hello,

My company is small time and the majority of what we do is "use whatever they give you" electrical service. That being said, I (think)would very much like to have a distribution point for all of our equipment if for no other reason than it keeps things neat and tidy and looks professional.

Basically I would like a 5-6 point distribution (Main L, Main R, FOH, Backline, Lighting). so 150 AMP service for 6 legs?

Is there a way that input can be either 3-phase or single phase? Or does would I need to have 2 separate distribution racks for each type?

What do you recommend I do? I assume there is something already out there that does this so is there one you recommend?

Thanks
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 12:26:00 pm
Hello,

My company is small time and the majority of what we do is "use whatever they give you" electrical service. That being said, I (think)would very much like to have a distribution point for all of our equipment if for no other reason than it keeps things neat and tidy and looks professional.

Basically I would like a 5-6 point distribution (Main L, Main R, FOH, Backline, Lighting). so 150 AMP service for 6 legs?

Is there a way that input can be either 3-phase or single phase? Or does would I need to have 2 separate distribution racks for each type?

What do you recommend I do? I assume there is something already out there that does this so is there one you recommend?

Thanks
Hi Jared.  There isn't really a one-size-fits-all solution, unfortunately.  There are basically 4 levels of distribution:

1. Run extension cords all over the place
2. Run extension cords to a "poor man's distro"
3. Small dryer plug distro - NEMA 14-50P or Cali-plug to a spider box, or the like - provides usually 6 20A circuits from split phase power.  Requires the venue to have a NEMA 14-50P or Cali receptacle
4. Large single or 3-phase camlok distro.

All the audio you mention will fit comfortably on 3 20A circuits.  Options 1 and 2 are workable at that size.  Your next step up is option 3, and the cost is pretty manageable.  This would give you a little bit of room to add some lighting.  Option 4 is probably beyond where you should be looking at the moment - it's $6000 - $10000 to get a real distro, feeder, and a few breakout boxes.
Title: Re: Distributed Power
Post by: Tim McCulloch on December 20, 2013, 02:21:55 pm
Hello,

My company is small time and the majority of what we do is "use whatever they give you" electrical service. That being said, I (think)would very much like to have a distribution point for all of our equipment if for no other reason than it keeps things neat and tidy and looks professional.

Basically I would like a 5-6 point distribution (Main L, Main R, FOH, Backline, Lighting). so 150 AMP service for 6 legs?

Is there a way that input can be either 3-phase or single phase? Or does would I need to have 2 separate distribution racks for each type?

What do you recommend I do? I assume there is something already out there that does this so is there one you recommend?

Thanks

Yes and no.  Leprecon offers single (split) phase 120/240v or 3 phase 120/208v input.  It operates by mechanical interlock.  In essence, half of the the "Z" leg connections get switched to the "X" leg and the other half to the "Y" leg in single phase mode; in the 3 phase mode it operates like you'd expect.  You can see it near the bottom of the rack in the back view in this PDF  http://www.leprecon.com/productfiles/VXMX280047C1.pdf  That's a dimmer rack but the same concept applies.

You'd use 3 phase distribution to your amp racks, stage stringers and other stuff.

Have fun, good luck.

Tim Mc
Title: Re: Distributed Power
Post by: Nils Erickson on December 20, 2013, 02:38:56 pm
Hey Jared,

I use both options 2 and 3 that TJ listed above, depending on the gig and what is available.  They work great and it does very much tidy things, up as you said.  I have a motion labs distro http://www.motionlabs.com/c-83-50a-125250v-in-thru.aspx (http://www.motionlabs.com/c-83-50a-125250v-in-thru.aspx) in my amp rack with a 50 amp Cali connector on it; this breaks out to six 20 amp circuits, and makes it easy to distribute power all over the stage and to front of house.
My smaller rig has a "poor man's distro" http://www.triktags.com/power.htm (http://www.triktags.com/power.htm) that lets me combine the ground from several circuits.

Both systems use similar cabling (except the feeder of course), so a couple of trunks of cable can go with either system.

Hope that helps.

Cheers,
Nils
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 03:03:05 pm
Hi Jared.  There isn't really a one-size-fits-all solution, unfortunately.  There are basically 4 levels of distribution:

1. Run extension cords all over the place
2. Run extension cords to a "poor man's distro"
3. Small dryer plug distro - NEMA 14-50P or Cali-plug to a spider box, or the like - provides usually 6 20A circuits from split phase power.  Requires the venue to have a NEMA 14-50P or Cali receptacle
4. Large single or 3-phase camlok distro.

All the audio you mention will fit comfortably on 3 20A circuits.  Options 1 and 2 are workable at that size.  Your next step up is option 3, and the cost is pretty manageable.  This would give you a little bit of room to add some lighting.  Option 4 is probably beyond where you should be looking at the moment - it's $6000 - $10000 to get a real distro, feeder, and a few breakout boxes.

THanks TJ.

So...currently we are doing #1 which is fine for a majority of the venues we work in. How do I do #2? I am not a DIY'r when it comes to electrical so do I need to hire an electrician and ask him to "build me one of those?" If so what am I telling him to build and what are the restrictions and "no-no's"?

Jared
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 03:05:18 pm
THanks TJ.

So...currently we are doing #1 which is fine for a majority of the venues we work in. How do I do #2? I am not a DIY'r when it comes to electrical so do I need to hire an electrician and ask him to "build me one of those?" If so what am I telling him to build and what are the restrictions and "no-no's"?

Jared
You're in luck - a recent thread on this very topic, including a link to Tim Padrick's build with pictures:
http://forums.prosoundweb.com/index.php/topic,147370.0.html
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 03:07:43 pm
Yes and no.  Leprecon offers single (split) phase 120/240v or 3 phase 120/208v input.  It operates by mechanical interlock.  In essence, half of the the "Z" leg connections get switched to the "X" leg and the other half to the "Y" leg in single phase mode; in the 3 phase mode it operates like you'd expect.  You can see it near the bottom of the rack in the back view in this PDF  http://www.leprecon.com/productfiles/VXMX280047C1.pdf  That's a dimmer rack but the same concept applies.

You'd use 3 phase distribution to your amp racks, stage stringers and other stuff.

Have fun, good luck.

Tim Mc

So more along the lines of these items? http://www.leprecon.com/productfiles/PwrDis.280061B.pdf

I have stage stringers from Ampshop. I have looked at his website at their distribution productions and the descriptions leave a bit to be desired so I am not really sure what I am looking at.

Would I be looking at either of these products
http://www.ampshop.com/images/h50pnl.jpg
http://www.ampshop.com/images/kdistro.jpg

Or this one
http://www.ampshop.com/images/2srp.jpg

Thanks!
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 03:10:40 pm
Hey Jared,

I use both options 2 and 3 that TJ listed above, depending on the gig and what is available.  They work great and it does very much tidy things, up as you said.  I have a motion labs distro http://www.motionlabs.com/c-83-50a-125250v-in-thru.aspx (http://www.motionlabs.com/c-83-50a-125250v-in-thru.aspx) in my amp rack with a 50 amp Cali connector on it; this breaks out to six 20 amp circuits, and makes it easy to distribute power all over the stage and to front of house.
My smaller rig has a "poor man's distro" http://www.triktags.com/power.htm (http://www.triktags.com/power.htm) that lets me combine the ground from several circuits.

Both systems use similar cabling (except the feeder of course), so a couple of trunks of cable can go with either system.

Hope that helps.

Cheers,
Nils

So forgive my ignorance how does this work. If the service to the breakout is 50A how can you have 6 x 20amp circuits off that?
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 03:14:31 pm
So forgive my ignorance how does this work. If the service to the breakout is 50A how can you have 6 x 20amp circuits off that?
You get 50A times 2 legs, sort of 100A total (kind of sort of).  Since it's extremely unlikely that all circuits are operating at full capacity, 3 20A circuits are powered off each 50A leg, and that amount of oversubscription is fine. 
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 03:17:49 pm
So more along the lines of these items? http://www.leprecon.com/productfiles/PwrDis.280061B.pdf

I have stage stringers from Ampshop. I have looked at his website at their distribution productions and the descriptions leave a bit to be desired so I am not really sure what I am looking at.

Would I be looking at either of these products
http://www.ampshop.com/images/h50pnl.jpg
http://www.ampshop.com/images/kdistro.jpg

Or this one
http://www.ampshop.com/images/2srp.jpg

Thanks!
Your first link is the only switchable 3-phase/single-phase distro I'm aware of.  I'm not sure if it's a listed product or not.  AmpShop products are not, AFAIK, which may not matter most of the time, something that isn't a big deal if it's a branch breakout box, but may be more important for the main distro.

3-phase distros can be operated on single phase power by not powering up the C-leg, however this typically (other than the switchable Leprecon) means that as much as 2/3 of the distro receptacles are not fully powered, depending on configuration.  This may or may not be a big deal, but I still stick to my opinion that your next stop is a spider-box, and/or a MotionLabs RackPack, which is pretty much the same thing.
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 03:19:27 pm
You're in luck - a recent thread on this very topic, including a link to Tim Padrick's build with pictures:
http://forums.prosoundweb.com/index.php/topic,147370.0.html

Thanks!
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 03:19:42 pm

My smaller rig has a "poor man's distro" http://www.triktags.com/power.htm (http://www.triktags.com/power.htm) that lets me combine the ground from several circuits.
I hadn't seen a commercial product of this.  It's interesting - they list as a "feature" that you can un-bond the grounds between sections.  Not sure why that's a good idea.  Presumably this is not a listed product.  Hopefully they've done the math and some testing to be sure that their circuit board traces and fast-on connectors are suitable for the full 20A load.
Title: Re: Distributed Power
Post by: Lyle Williams on December 20, 2013, 03:20:46 pm
I'm in the "run extension cords all over the place" camp.

Most of my stuff is outdoors, and the wiring standards call for IPX4 protection.  I use construction industry power boards (IP44 with RCD) and heavy duty leads with IP66 connectors.  For 240v/10A here the rules require 11ga conductors to span 300'.  Regular domestic leads here are 17ga.

If I want to tie rack grounds together I do this with 8ga ground leads.
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 03:22:18 pm
You get 50A times 2 legs, sort of 100A total (kind of sort of).  Since it's extremely unlikely that all circuits are operating at full capacity, 3 20A circuits are powered off each 50A leg, and that amount of oversubscription is fine.

That makes more sense, thanks.
Title: Re: Distributed Power
Post by: Josh Millward on December 20, 2013, 04:15:55 pm
3. Small dryer plug distro - NEMA 14-50P or Cali-plug to a spider box, or the like - provides usually 6 20A circuits from split phase power.  Requires the venue to have a NEMA 14-50P or Cali receptacle
Along these lines, the Peavey Distro (http://www.peavey.com/products/index.cfm/item/964/117526/distro) is an ETL listed product. I have one for my personal use and it is fantastic!
Title: Re: Distributed Power
Post by: Mike Sokol on December 20, 2013, 04:36:14 pm
Just remember that when you're connecting into split-phase 120/240-volt or 3-phase power, your neutral integrity is VERY important.
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 05:20:20 pm
Just remember that when you're connecting into split-phase 120/240-volt or 3-phase power, your neutral integrity is VERY important.

What does this mean in laymen terms?
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 05:45:24 pm
You're in luck - a recent thread on this very topic, including a link to Tim Padrick's build with pictures:
http://forums.prosoundweb.com/index.php/topic,147370.0.html

So couple of questions, not sure if that should be in the other thread or this one.

But does this have to be an enclosed box or can it simply be a rack plate?  Like this http://www.audiopile.net/products/Cases/EWI_Case_Hardware/Rack_Panel_Blanks/D_SERIES_BLANKS/D_SERIES_PANEL.shtml

Can they be mounted in a standard rack case (EWI road case for example) or does that also have to be metal?
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 06:25:34 pm
What does this mean in laymen terms?
This means that if the neutral wire is loose, high resistance, or broken, it may not be able to carry the current imbalance between phases. In that situation, the 240 or 208 volts is divided between your gear in proportion to your equipment's apparent impedance. For example, if you have a 1000 par can on one leg and a 100 watt mixer on the other leg, the par can will take 21 volts, and the mixer will then receive 219 volts from a 240 volt service. This is really bad.
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 06:26:22 pm
So couple of questions, not sure if that should be in the other thread or this one.

But does this have to be an enclosed box or can it simply be a rack plate?  Like this http://www.audiopile.net/products/Cases/EWI_Case_Hardware/Rack_Panel_Blanks/D_SERIES_BLANKS/D_SERIES_PANEL.shtml

Can they be mounted in a standard rack case (EWI road case for example) or does that also have to be metal?
NEC is pretty clear on this - must be totally enclosed in metal. A wood rack is not sufficient.
Title: Re: Distributed Power
Post by: Mike Sokol on December 20, 2013, 07:00:06 pm
This means that if the neutral wire is loose, high resistance, or broken, it may not be able to carry the current imbalance between phases. In that situation, the 240 or 208 volts is divided between your gear in proportion to your equipment's apparent impedance. For example, if you have a 1000 par can on one leg and a 100 watt mixer on the other leg, the par can will take 21 volts, and the mixer will then receive 219 volts from a 240 volt service. This is really bad.

Yup, that's the point. When you're into extension cord mode, a lost neutral just shuts down the power to a piece of gear. However, when you're running a 240 or 208 volt distro that splits down to 120-volts, if a neutral then fails then you'll likely create an over-voltage condition on the less loaded side of the distro split. And few pieces of audio gear will sustain 200 volts AC for even a few seconds.

This just means that your 120/240-V AC distro wiring has to be perfect and properly maintained. No cuts or pulled out wires, no corroded connectors allowed. I always checked the lug screws in my power distro gear at least once a year. Funny how 10,000 miles in the back of a truck loosens everything up. That's because a loose neutral lug can cost you lots of money in a heartbeat. Don't get me wrong, 240-volt split-phase or 208-volt 3-phase distro is great. You just have to respect that's you're playing with a lot more power.

When you get into camlocks and 2/0 cable, then it's very serious power and you really need to up your game. At that point arc-flash explosions became a real possibility. I'm putting together a recommended list of PPE gear for sound and lighting crews connecting to these high amperage systems and should have an article published early in the new year.
Title: Re: Distributed Power
Post by: Rob Spence on December 20, 2013, 07:38:31 pm
I hadn't seen a commercial product of this.  It's interesting - they list as a "feature" that you can un-bond the grounds between sections.  Not sure why that's a good idea.  Presumably this is not a listed product.  Hopefully they've done the math and some testing to be sure that their circuit board traces and fast-on connectors are suitable for the full 20A load.

I have a single section version (1 in, 3 out) that they gave me since I had documented my build of one using many parts from them. The unit is built with up to 3 modules and the ground ties between are external (on the rear) jumpers. The "feature" is simply a byproduct of the manufacturing.
Internally (not easy to open up) the PC board is well made with very wide, heavy traces.


Sent from my iPad using Tapatalk HD
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 08:36:18 pm

NEC is pretty clear on this - must be totally enclosed in metal. A wood rack is not sufficient.

So a metal chassis mounted in a wood rack is ok since the electrical bits are enclosed within the chassis?
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 08:38:33 pm

This means that if the neutral wire is loose, high resistance, or broken, it may not be able to carry the current imbalance between phases. In that situation, the 240 or 208 volts is divided between your gear in proportion to your equipment's apparent impedance. For example, if you have a 1000 par can on one leg and a 100 watt mixer on the other leg, the par can will take 21 volts, and the mixer will then receive 219 volts from a 240 volt service. This is really bad.

Thanks.

Is this something measurable that can be detected before plugging in anything to the circuit?

Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 08:42:16 pm
So in the other threads I see everyone cramming everything in a single rack space. Any reason a 2u enclosure can't work?

This looks like something we could use and simple enough to craft.
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 10:12:24 pm
So a metal chassis mounted in a wood rack is ok since the electrical bits are enclosed within the chassis?
Correct.
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 10:12:58 pm
Thanks.

Is this something measurable that can be detected before plugging in anything to the circuit?
Absolutely.
http://soundforums.net/hub/1856-basic-receptacle-testing.html
Title: Re: Distributed Power
Post by: TJ (Tom) Cornish on December 20, 2013, 10:13:48 pm
So in the other threads I see everyone cramming everything in a single rack space. Any reason a 2u enclosure can't work?

This looks like something we could use and simple enough to craft.
No reason it can't work - just takes more rack space.
Title: Distributed Power
Post by: Jared Koopman on December 20, 2013, 10:39:24 pm
So the stage stringer I have shares a neutral between the two circuits "12/4" with pigtail of two Edison plugs.

http://www.ampshop.com/distro.html

When using this type of poor mans district, is there any danger to plugging in both circuits of the stringer to the same "circuit" on the distro when venue source is limited to one circuit? (Equivalent to plugging both pigtail ends into the same Edison duplex)
Title: Re: Distributed Power
Post by: Tim McCulloch on December 20, 2013, 11:02:18 pm
Thanks.

Is this something measurable that can be detected before plugging in anything to the circuit?

You need a load (a 1000w PAR can or shop floodlight will do nicely) and your voltmeter.

For single (split) phase, after verifying no-load voltages to be acceptable, plug the load into a circuit on, say, the Black leg.  Meter the voltage between neutral and the RED leg.  It should be 120v-ish, now meter the voltage on the Black leg... should also be 120v-ish.  Measure between the Black and RED leg and see if you have 240v.  Whatever you read, you should have HALF that voltage (a volt or 2 difference wouldn't worry me) between neutral and Black/neutral and RED.  If you don't, you have a neutral problem.  Switch the load to the RED leg.  Does the voltage difference follow?

Like Mike suggests, once a year we go through every AC connector we have and check for arcing, corrosion and terminal torque.  Distro (outlets, breakers, lugs) cables, quad boxes... everything.  Unless every AC cable in the shop has molded connectors, you (yes, all of you) should be doing this.  It's common to find a few screws that needed a quarter-turn or more to be snug again.
Title: Re: Distributed Power
Post by: Mike Sokol on December 20, 2013, 11:04:31 pm
So the stage stringer I have shares a neutral between the two circuits "12/4" with pigtail of two Edison plugs.

http://www.ampshop.com/distro.html

When using this type of poor mans district, is there any danger to plugging in both circuits of the stringer to the same "circuit" on the distro when venue source is limited to one circuit? (Equivalent to plugging both pigtail ends into the same Edison duplex)
At first look I believe the real danger comes when both Edison plugs are connected to two separate branch circuits of 20-amps each, but on the same phase (L1 or L2). Under those conditions the neutral currents are additive rather than subtractive. So you can easily exceed the 20-amp limit of the neutral by a significant amount. For instance, 20 amps on each pigtail connected to the same phase on two circuits would not subtract to zero amps as it does on two different phases of a 120/240-v circuit. That 40 amps in the neutral can be a problem if neutral paths aren't double-sized to handle the extra current and overheating can result.

Now maybe I'm misunderstanding this hookup, so please correct me if I'm thinking about this incorrectly.
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 11:11:28 pm

You need a load (a 1000w PAR can or shop floodlight will do nicely) and your voltmeter.

For single (split) phase, after verifying no-load voltages to be acceptable, plug the load into a circuit on, say, the Black leg.  Meter the voltage between neutral and the RED leg.  It should be 120v-ish, now meter the voltage on the Black leg... should also be 120v-ish.  Measure between the Black and RED leg and see if you have 240v.  Whatever you read, you should have HALF that voltage (a volt or 2 difference wouldn't worry me) between neutral and Black/neutral and RED.  If you don't, you have a neutral problem.  Switch the load to the RED leg.  Does the voltage difference follow?

Like Mike suggests, once a year we go through every AC connector we have and check for arcing, corrosion and terminal torque.  Distro (outlets, breakers, lugs) cables, quad boxes... everything.  Unless every AC cable in the shop has molded connectors, you (yes, all of you) should be doing this.  It's common to find a few screws that needed a quarter-turn or more to be snug again.

Thanks Tim

Maybe it's me but I check my power cable connections before they go out for every gig.
Title: Distributed Power
Post by: Jared Koopman on December 20, 2013, 11:17:18 pm
At first look I believe the real danger comes when both Edison plugs are connected to two separate branch circuits of 20-amps each, but on the same phase (L1 or L2). Under those conditions the neutral currents are additive rather than subtractive. So you can easily exceed the 20-amp limit of the neutral by a significant amount. For instance, 20 amps on each pigtail connected to the same phase on two circuits would not subtract to zero amps as it does on two different phases of a 120/240-v circuit. That 40 amps in the neutral can be a problem if neutral paths aren't double-sized to handle the extra current and overheating can result.

Now maybe I'm misunderstanding this hookup, so please correct me if I'm thinking about this incorrectly.

So the cable I have has an l14-20 on an adapter that converts that into two Edison  pigtail.

So are you saying that plugging them both into the same circuit it is additive due to the shared neutral? And therefore shouldn't be done? I should only plug in one half of the pigtail?
Title: Re: Distributed Power
Post by: Mike Sokol on December 20, 2013, 11:20:37 pm
You need a load (a 1000w PAR can or shop floodlight will do nicely) and your voltmeter.

For single (split) phase, after verifying no-load voltages to be acceptable, plug the load into a circuit on, say, the Black leg.  Meter the voltage between neutral and the RED leg.  It should be 120v-ish, now meter the voltage on the Black leg... should also be 120v-ish.  Measure between the Black and RED leg and see if you have 240v.  Whatever you read, you should have HALF that voltage (a volt or 2 difference wouldn't worry me) between neutral and Black/neutral and RED.  If you don't, you have a neutral problem.  Switch the load to the RED leg.  Does the voltage difference follow?


Good advice. In fact, I used to build an AC voltage panel meter into my early 120/240-v distros. I also added a rotary switch which allowed me to check voltage between neutral to leg-1 or neutral to leg-2 as well a leg-1 to leg-2. If you don't want to risk blowing up a PAR, a little 1,200 watt ceramic heater is a good load. Or you could mount 3 separate panels meters to monitor all 3 voltages if you wish.  I found some really cool imported fluorescent AC panel meters for $6 each including shipping from China. They work great and can easily be seen from across the room, even by my aging eyes.

With portable 120/240-volt split-phase or 3-phase power distro, the neutral is really the most important connection. Lose that, and you can lose a lot of gear.
Title: Re: Distributed Power
Post by: Mike Sokol on December 20, 2013, 11:23:03 pm
So the cable I have has an l14-20 on an adapter that converts that into two Edison  pigtail.

So are you saying that plugging them both into the same circuit it is additive due to the shared neutral? And therefore shouldn't be done? I should only plug in one half of the pigtail?
Draw me a simple picture and I'll tell you for sure. I want to make sure I understand the hookup.
Title: Re: Distributed Power
Post by: Jared Koopman on December 20, 2013, 11:31:17 pm
Draw me a simple picture and I'll tell you for sure. I want to make sure I understand the hookup.

https://photos-4.dropbox.com/t/0/AABEMTfRWJEaYQGJUsZDfnRQVIrsT-J21VahRWVVcHbQOA/12/124632247/jpeg/256x256/3/_/1/2/Photo%20Dec%2020%2C%209%2028%2024%20PM.jpg/UKDvhgJHWTNcvi2-zG5sU3p_hh9TRKXzQZ9RrSqvxN8?size=1024x768
Title: Re: Distributed Power
Post by: Corey Scogin on December 20, 2013, 11:46:02 pm
This means that if the neutral wire is loose, high resistance, or broken, it may not be able to carry the current imbalance between phases. In that situation, the 240 or 208 volts is divided between your gear in proportion to your equipment's apparent impedance. For example, if you have a 1000 par can on one leg and a 100 watt mixer on the other leg, the par can will take 21 volts, and the mixer will then receive 219 volts from a 240 volt service. This is really bad.

I'm considering purchasing or building option 3 that Tom mentioned above.  A 50A Cali plug was one of the line side connectors.  As far as I can tell, that plug is a 240V 3 wire setup X-Y-G -- so no neutral.

**Edit: I saw after posting this that some of those connectors have a ground around the outside for a 4 wire setup.  I was looking at a different pinout previously that didn't show that.  Sorry for the stupid question. **
**Edit2: Removed the "dangerous question" portion **
Title: Re: Distributed Power
Post by: Doug Johnson on December 21, 2013, 08:59:00 am
 >:(
I'm considering purchasing or building option 3 that Tom mentioned above.  A 50A Cali plug was one of the line side connectors.  As far as I can tell, that plug is a 240V 3 wire setup X-Y-G -- so no neutral.  I'm assuming the load-side neutral will be bonded to the line side ground at the distro.

If I'm plugging an unbalanced load to this, how does the ground on the line side keep from becoming a current carrying conductor?

**Edit: I saw after posting this that some of those connectors have a ground around the outside.  I was looking at a different pinout previously that didn't show that.  Sorry for the stupid question. **
The 50 amp CALI connectors come in several voltages, and both single and three phase.  The CS6375, CS6365c and the CS6364c are the 125/250v 3 pole, 4 wire configuration.
Title: Re: Distributed Power
Post by: Geoff Doane on December 21, 2013, 02:22:06 pm
At first look I believe the real danger comes when both Edison plugs are connected to two separate branch circuits of 20-amps each, but on the same phase (L1 or L2). Under those conditions the neutral currents are additive rather than subtractive. So you can easily exceed the 20-amp limit of the neutral by a significant amount. For instance, 20 amps on each pigtail connected to the same phase on two circuits would not subtract to zero amps as it does on two different phases of a 120/240-v circuit. That 40 amps in the neutral can be a problem if neutral paths aren't double-sized to handle the extra current and overheating can result.

Now maybe I'm misunderstanding this hookup, so please correct me if I'm thinking about this incorrectly.

The other reason that such an adapter (two Edisons into an L14-20) is a bad idea, if not illegal, is that if there is a 240V volt load across the two hots, once you plug one Edison in, the line blade of the second one will have 120V on it, and that is a shock hazard.  In most cases, you only have 120V loads on the stringer, so it's not a problem, but since that isn't guaranteed, such adapters are frowned upon (although they certainly exist  ::) ).

If you have to use such an adapter, just build it with a single Edison feeding both hots in the L14-20.  You can only supply  half the power, but you can't overload the neutral, and there can't be any exposed live terminals.

GTD
Title: Re: Distributed Power
Post by: Rob Spence on December 21, 2013, 04:17:02 pm
I'm considering purchasing or building option 3 that Tom mentioned above.  A 50A Cali plug was one of the line side connectors.  As far as I can tell, that plug is a 240V 3 wire setup X-Y-G -- so no neutral.  I'm assuming the load-side neutral will be bonded to the line side ground at the distro.

If I'm plugging an unbalanced load to this, how does the ground on the line side keep from becoming a current carrying conductor?

**Edit: I saw after posting this that some of those connectors have a ground around the outside.  I was looking at a different pinout previously that didn't show that.  Sorry for the stupid question. **

How did you conclude the CS connector was 3 wire?
If you had looked where the wires go you would see 4 connections.
 It has X, Y, N & G.

/Snark coming...

 Why did you not use this great internet to actually look up the connector rather than take the time to write down for all to see that you are clearly not qualified to be building any electrical gear. Buy a properly built distro before you kill some one.

End snark\

And, yes, I am not having a happy day

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Title: Re: Distributed Power
Post by: Corey Scogin on December 21, 2013, 04:35:21 pm
How did you conclude the CS connector was 3 wire?
If you had looked where the wires go you would see 4 connections.
 It has X, Y, N & G.

/Snark coming...

 Why did you not use this great internet to actually look up the connector rather than take the time to write down for all to see that you are clearly not qualified to be building any electrical gear. Buy a properly built distro before you kill some one.

End snark\

And, yes, I am not having a happy day

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Damn Rob.  That's harsh.  The attached image was the only pinout I saw for the 50A Cali connector the first time before I edited that post.  THERE ISN'T A NEUTRAL THERE.  I don't appreciate your snark even with start and end tags.  You assume I'm not qualified to build any electrical gear just because I missed the proper pinout diagram?  I don't think that's fair.
Title: Re: Distributed Power
Post by: Jared Koopman on December 21, 2013, 04:35:58 pm

The other reason that such an adapter (two Edisons into an L14-20) is a bad idea, if not illegal, is that if there is a 240V volt load across the two hots, once you plug one Edison in, the line blade of the second one will have 120V on it, and that is a shock hazard.  In most cases, you only have 120V loads on the stringer, so it's not a problem, but since that isn't guaranteed, such adapters are frowned upon (although they certainly exist  ::) ).

If you have to use such an adapter, just build it with a single Edison feeding both hots in the L14-20.  You can only supply  half the power, but you can't overload the neutral, and there can't be any exposed live terminals.

GTD

So what is the safest way to use this stringer? Does it need to be re-wired?
Title: Re: Distributed Power
Post by: Rob Spence on December 21, 2013, 06:48:41 pm
So what is the safest way to use this stringer? Does it need to be re-wired?
The safest way is the way it was built, to use on a 120/240v circuit.

The adapter is the problem. It is never legal and most times could be very unsafe.

There are insufficient wires in the stringer to use on 120v by only changing the cord cap. The problem was described above.

If you want to use it on 120v, then the only safe modification would be to open up each intermediate box and move the outlets connected to the red wire to the black one and then put a 120v cord cap on connecting only the black, white and green.



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Title: Re: Distributed Power
Post by: Rob Spence on December 21, 2013, 06:51:33 pm
Damn Rob.  That's harsh.  The attached image was the only pinout I saw for the 50A Cali connector the first time before I edited that post.  THERE ISN'T A NEUTRAL THERE.  I don't appreciate your snark even with start and end tags.  You assume I'm not qualified to build any electrical gear just because I missed the proper pinout diagram?  I don't think that's fair.

Yes, harsh. Fair isn't relevant. This is dangerous stuff. The internet is not an electricians training class.


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Title: Re: Distributed Power
Post by: Lyle Williams on December 21, 2013, 07:12:38 pm
For me a great part of the challenge is being clearly compliant with the applicable standards.

Any sort of y-combiner (as opposed to y-splitter) in power would be enough of a red flag to have me shut down.

I could drill holes in my construction-grade power strips to link grounds, but that may or may not pass an inspection.  I could make a male-male power cable with only earth pins present to tie grounds together, but that would fail any and every inspection (despite being electrically equivalent to the solution I use).  I just run regular power and bond the racks together.  Every inspector is 100% happy with that.
Title: Re: Distributed Power
Post by: Mike Sokol on December 21, 2013, 07:36:08 pm
Yes, harsh. Fair isn't relevant. This is dangerous stuff. The internet is not an electricians training class.

Now everybody play nice... and as I noted before, once you get into 240-volt power, you had BETTER know what you're doing. One of the projects I'm working on is an electrical safety course for sound and lighting technicians. This would be both online as well as a day-long training course at a number of trade shows next year.

One thing interesting is that there's almost no information about arc flash safety for sound and lighting technicians. And that includes hearing protection. For instance, an arc flash explosion not only has the potential to blind and burn you, but many electricians have also lost their hearing from the blast of an arc flash. And there are few things worse than a deaf sound engineer. While a large arc flash is generally not possible from the limited energy available in a 20-amp branch circuit, once you get into cam-locks and circuit breakers over 100-amps, an arc flash gets very possible and very dangerous.

Let's all be careful out there. And if someone comes to this forum with a dangerous question, then let's inform them as gently but firmly as possible. You really don't want to be on the "Earn While You Learn Program" while hooking up live power. It's way too dangerous.
Title: Re: Distributed Power
Post by: Jared Koopman on December 24, 2013, 01:55:22 am
The safest way is the way it was built, to use on a 120/240v circuit.

The adapter is the problem. It is never legal and most times could be very unsafe.

There are insufficient wires in the stringer to use on 120v by only changing the cord cap. The problem was described above.

If you want to use it on 120v, then the only safe modification would be to open up each intermediate box and move the outlets connected to the red wire to the black one and then put a 120v cord cap on connecting only the black, white and green.



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Thank you
Title: Re: Distributed Power
Post by: Mike Pyle on December 26, 2013, 11:35:39 am
I had some small single rack unit distros built that can be plugged into two 120v circuits. The neutrals are isolated from each other, so it is essentially two distros in a single chassis. The front end of each circuit up to the breaker is wired with 10 gauge, and the input connectors are 32a powercon, so it can be plugged into a 30a service. One could also make a breakout adapter to plug it into an L16-30R or similar (the reverse of what you are doing with your dual-edison plug adapter).

(http://audiopyle.com/1RUfront-nologo.jpg)

(http://audiopyle.com/1RUback-crop.jpg)