Correct feeder cable for distro

[Ian Appleby]

Motion Lab 3 Space Rac Pac

ETL Listed, L21-30 In/Thru, 8 x 20A Duplex (Breakered @ 20 Amps), Fully Enclosed 3RU, 19" Rack Mount, Chassis Depth 5.5" I deal with large venues now and I need a distro. I acquired this distro, but need the feeder cable. Most of the venues have Cam hook ups. Can I get an L21-30 hubble to Cam lock cable? My system is. Mains Rack 3xEV P3000 Mon Rack 2xEV CP4000 2xEV Cp3000 Other then that I run two lines across the stage for the band gear. Thanks for the help!

 

[Rob Timmerman]

Re: Correct feeder cable for distro

Motion Lab 3 Space Rac Pac

ETL Listed, L21-30 In/Thru, 8 x 20A Duplex (Breakered @ 20 Amps), Fully Enclosed 3RU, 19" Rack Mount, Chassis Depth 5.5" I deal with large venues now and I need a distro. I acquired this distro, but need the feeder cable. Most of the venues have Cam hook ups. Can I get an L21-30 hubble to Cam lock cable? My system is. Mains Rack 3xEV P3000 Mon Rack 2xEV CP4000 2xEV Cp3000 Other then that I run two lines across the stage for the band gear. Thanks for the help!

The cable you're looking for looks something like this

If you want to work with real power, you need a real distro. Camlock is typically fed by breakers (or fuses) rated for at least 60A, more commonly 100A, 200A, or 400A. Any one of those will happily melt the 30A connector on your RacPac and the wire that fits into the L21-30 connector. You need a 30A breaker between the Camlock feed and your 30A distro.

 

[Brian jojade]

Re: Correct feeder cable for distro

The L21-30 is a 3 phase conductor. Your unit uses 6 20 amp circuits total. On the back of the unit, breaker 5 and breaker 6 use 2 dual outlets.

The L21-30 is 30 amps per leg, of which, each leg has 2 circuits with 20 amp breaker on each. There is no main breaker on the unit, so you MUST have an appropriate breaker upstream to prevent overload. You could pull 40 amps per leg without blowing a breaker on your distro.

For feeder cable, you could get by with 10/4 cable, but I'd suggest getting 8/4 instead. The cost is nearly the same, and if you have to make long runs, the voltage drop will be less. depending on the length of run you need, you might be best off making a few different lengths of cables so you can use the shortest possible length. Remember if you make one long cable, you CANNOT leave the unused portion coiled in the case, as that creates a fire hazard.

At the tie in, you will need a breaker box that has a triple 30 breaker. Here you can attach cam tails and then tie in as needed. Per code, if you are tying into a system with larger power rating than your distro of 30 amps, your 30 amp breaker has to be within 10 feet of your tie in.

 

[Rob Timmerman]

Re: Correct feeder cable for distro

Remember if you make one long cable, you CANNOT leave the unused portion coiled in the case, as that creates a fire hazard.

If your coiled cable is a fire hazard (exceeding the ignition temperature of comon combustibles), your wires are undersized. But yes, you do need to derate your cable based on ambient temperature, and wire coiled in a case will be warmer than that same wire in free air.

 

[Brian jojade]

Re: Correct feeder cable for distro

If your coiled cable is a fire hazard (exceeding the ignition temperature of comon combustibles), your wires are undersized. But yes, you do need to derate your cable based on ambient temperature, and wire coiled in a case will be warmer than that same wire in free air.

Having first hand experience in this, I will say that it is critical to not coil extension cords that are in use. I was at a show where we hooked a single 575 watt light up. All we had left was a 50' 12 gauge extension cord. We simply coiled the excess under the stage. Halfway through the show, there was that electrical 'hot' smell. Went and found that extension cord, and the cord was too hot to even touch.

No, it didn't start on fire that time, but imagine if the load were higher, and it started to melt the insulation. That would have created sparks as the wire shorted out, which would then have in turn, potentially caused a fire.

Trust me, I didn't believe it could happen either, until it did for me.

 

[Max Warasila]

Re: Correct feeder cable for distro

Having first hand experience in this, I will say that it is critical to not coil extension cords that are in use. I was at a show where we hooked a single 575 watt light up. All we had left was a 50' 12 gauge extension cord. We simply coiled the excess under the stage. Halfway through the show, there was that electrical 'hot' smell. Went and found that extension cord, and the cord was too hot to even touch.

No, it didn't start on fire that time, but imagine if the load were higher, and it started to melt the insulation. That would have created sparks as the wire shorted out, which would then have in turn, potentially caused a fire.

Trust me, I didn't believe it could happen either, until it did for me.

How tight were your coils? We regularly coil 12/3 SO with up to 1K loads regularly as theatrical electricians (though personally I prefer to run it back and forth if I can), and I haven't ever had an issue. The electricians this show decided to coil excess soca and I was concerned but so far there have been no issues, even under upwards of 4kw on the cable.

 

[Brian jojade]

Re: Correct feeder cable for distro

It was just a normal cable wrap thrown under the stage. Same thing I've done hundreds of times before. However, there was SOMETHING that caused the cable to heat up. I don't know if it was the proximity to the stage legs, proximity to some other power cord in the area, or some other magic that was happening. The point is, the fact that the wire was in a coil is a POTENTIAL hazard that one should be concerned about. I wish I would have been in a controlled environment to make this happen so I could pinpoint the exact cause. It only happened once, but one fire is all it takes to destroy your business.

 

[Rob Timmerman]

Re: Correct feeder cable for distro

It was just a normal cable wrap thrown under the stage. Same thing I've done hundreds of times before. However, there was SOMETHING that caused the cable to heat up. I don't know if it was the proximity to the stage legs, proximity to some other power cord in the area, or some other magic that was happening. The point is, the fact that the wire was in a coil is a POTENTIAL hazard that one should be concerned about. I wish I would have been in a controlled environment to make this happen so I could pinpoint the exact cause. It only happened once, but one fire is all it takes to destroy your business.

Any number of things could cause that to happen, including inadequate ventilation, magnetic coupling, or excessive current. And it's worth remembering that there are losses in wire that generate heat. A 100' length of 12/3 with 20A through it will dissipate about 120W of heat due to resistive losses alone. A single-phase run of 2/0 with 200A through it dissipates a touch over 600W. That heat has to go somewhere...

 

[Brian jojade]

Re: Correct feeder cable for distro

Ventilation wasn't an issue, nor was excess current. Again, under 1000 watts on a 12 gauge cable under a 2 foot stage shouldn't have made the cable even noticeably warm to the touch. Only the portion that was coiled was hot. The legs of the cable were cool to the touch. Had we been running a heavy load that caused the whole wire to get warm, I could explain the cable being warmer at the coil due to simple heat buildup, but this was different, for sure. Again, the cord got warm enough to 'smell' hot, which is significant cause for concern.

 

[Mark DeArman]

Re: Correct feeder cable for distro

Any number of things could cause that to happen, including inadequate ventilation, magnetic coupling, or excessive current. And it's worth remembering that there are losses in wire that generate heat. A 100' length of 12/3 with 20A through it will dissipate about 120W of heat due to resistive losses alone. A single-phase run of 2/0 with 200A through it dissipates a touch over 600W. That heat has to go somewhere...

It seems like the most obvious is a load fault ;-) Wires in an extension cord, in close proximity, the field is going to cancel? The only issue would be common mode noise coupling into the loop, correct?

EDIT: It seems this myth comes from auto-retracting cord reels which you find mounted on the walls in shops. In this case, you have cheap cables wrapped really tight on the drum. (Harbor Freight?) These products are normally labeled separately for wrapped and unwrapped so they can be UL listed. Cheap versions are most likely below the minimum bend radius for the wire on the inside of the spool. So you have stressed wire, tightly wrapped, with no ventilation. (Not to mention, how many times have I tugged on my drop light?) This is a little different than having 25' 12/3 SOW loosely coiled with with a 2ft radius on the floor.

Lots of talk about L21-30 up above breaking out into single phase circuits? Just remember the neutral is only rated at 30A.

 

[Tim McCulloch]

Re: Correct feeder cable for distro

The CamLok side of this will be the most expensive. The post up-thread about getting a 30 amp overcurrent protection device is spot on, too.

You'll need a Code-compliant way of getting 5 ea AWG #2 wires into a breaker box or fused disconnect switch with 30 amp fuses/breaker, and then either a direct termination to your #8 feeder to the L21-30 or you can install an L21-30 on the box so you can disconnect the load side feeder to pack it up while waiting on the house electrician.

Cooper (Crouse Hinds) e1016 CamLok connectors are about $22 each. I don't know what #2 type SC costs today, but you'll need 50 feed of it. Any of the "usual suspects" can build this for you - Motion Labs, Entertainment Metals, TMB, etc. Will be UL listed.

 

[Ian Appleby]

Re: Correct feeder cable for distro

The CamLok side of this will be the most expensive. The post up-thread about getting a 30 amp overcurrent protection device is spot on, too.

You'll need a Code-compliant way of getting 5 ea AWG #2 wires into a breaker box or fused disconnect switch with 30 amp fuses/breaker, and then either a direct termination to your #8 feeder to the L21-30 or you can install an L21-30 on the box so you can disconnect the load side feeder to pack it up while waiting on the house electrician.

Cooper (Crouse Hinds) e1016 CamLok connectors are about $22 each. I don't know what #2 type SC costs today, but you'll need 50 feed of it. Any of the "usual suspects" can build this for you - Motion Labs, Entertainment Metals, TMB, etc. Will be UL listed.

So so I believe really I need to get one of these: http://www.motionlabs.com/c-11-max-pac.aspx

If I get that then I just have to put a Rac Pac in each rack?

Or can I just put an L21-30 connector on to the rack and have it break out into Edison's in the rear of the rack?

I guess my really question is how much power do I need to run each rack and what kinda of connector do you guys recommended? I'd love to use power cons if possible?

I can only see my self adding one more rack with 2x EV P3000 and that's it. I don't plan on getting any bigger then that for a single show. At that point I hire in an their company to do the job.

 

[Rob Timmerman]

Re: Correct feeder cable for distro

So so I believe really I need to get one of these: http://www.motionlabs.com/c-11-max-pac.aspx

If I get that then I just have to put a Rac Pac in each rack?

Or can I just put an L21-30 connector on to the rack and have it break out into Edison's in the rear of the rack?

I guess my really question is how much power do I need to run each rack and what kinda of connector do you guys recommended? I'd love to use power cons if possible?

I can only see my self adding one more rack with 2x EV P3000 and that's it. I don't plan on getting any bigger then that for a single show. At that point I hire in an their company to do the job.

As far as connectors, I put together this list for reference.

 

[TJ Cornish]

Re: Correct feeder cable for distro

The L21-30 is a 3 phase conductor. Your unit uses 6 20 amp circuits total. On the back of the unit, breaker 5 and breaker 6 use 2 dual outlets.

The L21-30 is 30 amps per leg, of which, each leg has 2 circuits with 20 amp breaker on each. There is no main breaker on the unit, so you MUST have an appropriate breaker upstream to prevent overload. You could pull 40 amps per leg without blowing a breaker on your distro.

For feeder cable, you could get by with 10/4 cable, but I'd suggest getting 8/4 instead. The cost is nearly the same, and if you have to make long runs, the voltage drop will be less. depending on the length of run you need, you might be best off making a few different lengths of cables so you can use the shortest possible length. Remember if you make one long cable, you CANNOT leave the unused portion coiled in the case, as that creates a fire hazard.

At the tie in, you will need a breaker box that has a triple 30 breaker. Here you can attach cam tails and then tie in as needed. Per code, if you are tying into a system with larger power rating than your distro of 30 amps, your 30 amp breaker has to be within 10 feet of your tie in.

For a 3-phase application, you need 5-conductor wire, not 4-conductor. Code calls out #8 wire for 4 current carrying conductors at 30A, so the correct cable is 8/5 SOOW.

 

[TJ Cornish]

Re: Correct feeder cable for distro

So so I believe really I need to get one of these: http://www.motionlabs.com/c-11-max-pac.aspx

If I get that then I just have to put a Rac Pac in each rack?

Or can I just put an L21-30 connector on to the rack and have it break out into Edison's in the rear of the rack?

I guess my really question is how much power do I need to run each rack and what kinda of connector do you guys recommended? I'd love to use power cons if possible?

I can only see my self adding one more rack with 2x EV P3000 and that's it. I don't plan on getting any bigger then that for a single show. At that point I hire in an their company to do the job.

You cannot "just put an L21-30 connector on to the rack and have it break out into Edison's in the rear of the rack", because any time you step down in ampacity, you need to have a breaker rated to protect the downstream wiring. This is exactly what your rack PDU does.

Choosing the right distro system can be challenging. You need to figure out what power you will likely have available and balance that against what you would like to use. For example, what are you going to do if you run your gear at a venue that only has multiple Edison circuits? If it were me, I wouldn't permanently wire up your racks with rack distros until you really know what you're going to run into.

In your situation I would probably put your distro in one of the amp racks so you can use it when the circumstances work out, but I would leave the amp cords accessible so you can run them to regular outlets when you don't have heavy power.

If you always have 3-phase power available and you intend to grow, something like the MotionLabs Max-Pac unit would work, however I would prefer one of their regular distros that provides a variety of output options, including regular 120V/20A circuits.

 

[Rob Timmerman]

Re: Correct feeder cable for distro

For a 3-phase application, you need 5-conductor wire, not 4-conductor. Code calls out #8 wire for 4 current carrying conductors at 30A, so the correct cable is 8/5 SOOW.

Nope, not for flexible cables. For flexible cables, three current-carrying conductors of 8AWG are rated for 35A (neutral is not considered current-carrying if it only carries the unbalanced sum of the phase conductors and there are no appreciable harmonics). But for 4 current-carrying conductors (as is the case where you need to worry about harmonics), you need to reduce the current-carrying capacity to 80% of that, or 28A. Since 28<30, you need to step up a wire size to 6AWG. See tables 400.5(A)(1) and 400.5(A)(3) [unless things have changed since 2011, which is the latest version of the NEC I've got handy].

 

[TJ Cornish]

Re: Correct feeder cable for distro

Nope, not for flexible cables. For flexible cables, three current-carrying conductors of 8AWG are rated for 35A (neutral is not considered current-carrying if it only carries the unbalanced sum of the phase conductors and there are no appreciable harmonics). But for 4 current-carrying conductors (as is the case where you need to worry about harmonics), you need to reduce the current-carrying capacity to 80% of that, or 28A. Since 28<30, you need to step up a wire size to 6AWG. See tables 400.5(A)(1) and 400.5(A)(3) [unless things have changed since 2011, which is the latest version of the NEC I've got handy].

Rob,

NEC 400.5 is ambiguously written. The correction factor points to table 400.5(A)(1), which has two columns - A, and B, and which column to use for derating is not specified. 80% of column B for #8 wire is 32A. As you mention, 80% of column A is 28A. There are a couple points in the code where non-standard ampacities are allowable to be rounded up to the next standard breaker size.

I have never seen 6-5 SOOW used in an L21-30 application - that is pretty massive and inflexible cable. 8-5 SOOW is standard in my part of the world, and I'm happy to not see 10-5.

I think you are correct to the [intended] letter of the law, but as mentioned, it doesn't seem to be common practice, and in a similar vein, 6-4 SOOW is probably more common in a 50A two-phase application than the correct 4-4 SOOW.

 

[Rob Timmerman]

Re: Correct feeder cable for distro

NEC 400.5 is ambiguously written. The correction factor points to table 400.5(A)(1), which has two columns - A, and B, and which column to use for derating is not specified.

The text from 400.5(A) includes the following:

Where the number of current-carrying conductors exceeds three, the allowable ampacity or the ampacity of each conductor shall be reduced from the 3-conductor rating as shown in Table 400.5(A)(3).

(emphasis mine)

The footnote on table 400.5(A)(1) states that column A is for 3 current-carrying conductors, and column B is for 2 current-carrying conductors. So the derating is applied to column A.

But the ambiguity comes regarding the load type. An L21-30 feeding a colection of linear loads (such that the neutral only carries the imbalance between the phases, with no additional heating from triplen currents) only has 3 current-carrying conductors because the neutral doesn't count. So 8/5 is perfectly acceptable for general-purpose cable, but would be questionable for a dimmer rack.

 

[Barry Straub]

Re: Correct feeder cable for distro



Having first hand experience in this, I will say that it is critical to not coil extension cords that are in use. I was at a show where we hooked a single 575 watt light up. All we had left was a 50' 12 gauge extension cord. We simply coiled the excess under the stage. Halfway through the show, there was that electrical 'hot' smell. Went and found that extension cord, and the cord was too hot to even touch.

No, it didn't start on fire that time, but imagine if the load were higher, and it started to melt the insulation. That would have created sparks as the wire shorted out, which would then have in turn, potentially caused a fire.

Trust me, I didn't believe it could happen either, until it did for me.

Coiling up excess Edison and shoving it under the stage/ speaker shirt is common practice on a lot of the gigs I have worked. I suppose I should rethink doing this the next time is that correct? Or is it only with the smaller Gage Edison? If so when and at which gauge would this be safe?

 

[Tim McCulloch]

Coiling up excess Edison and shoving it under the stage/ speaker shirt is common practice on a lot of the gigs I have worked. I suppose I should rethink doing this the next time is that correct? Or is it only with the smaller Gage Edison? If so when and at which gauge would this be safe?

Hi Barry! The issue is one of *induction* and the heat it causes. This has nothing to do with the size of conductors.

Induction is why we figure-8 excess power cables, it tends to cancel out the induction.