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Author Topic: #2 SC 200a feeder cable?  (Read 4347 times)

Jeffery Foster

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#2 SC 200a feeder cable?
« on: April 15, 2015, 05:34:59 pm »

Doing a quick forum search, I saw several references to people suggesting #2 cable for their single conductor feeder cables at a 200a distro. 
Isn't #2 rated at 190a? Or am I overlooking something silly?
Assume we are talking about 100' of it.
Thanks!
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Guy Holt

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Re: #2 SC 200a feeder cable?
« Reply #1 on: April 15, 2015, 05:41:38 pm »

Isn't #2 rated at 190a? Or am I overlooking something silly?

No you are not.  2 AWG SC cable is rated at 190A.  The typical over current protection used on film sets for #2 is 160A.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com
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Jeffery Foster

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Re: #2 SC 200a feeder cable?
« Reply #2 on: April 15, 2015, 09:11:53 pm »

Thank you, Guy.

So in choosing the correct feeder cable size, I would both; de-rate it depending on the terminal temperature rating (lugs, etc), as well as figure the acceptable and anticipated voltage drop?

I appreciate your information in this and other posts that you have contributed to.
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Ray Aberle

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Re: #2 SC 200a feeder cable?
« Reply #3 on: April 15, 2015, 11:40:54 pm »

Myself, and plenty of other people in my area, use #2 SC for distros-- unless you are running things Full Tilt Boogie, you will be OK. As always, your mileage may vary and exercise standard cautions in monitoring your gear-- but I have a huge pile of #2 and have never had a problem. Of course, I also don't ever even approach 100A/leg on things! (Remembering that the 190A/leg is per cable conductor…)

-Ray
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Kelcema Audio
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Jeffery Foster

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Re: #2 SC 200a feeder cable?
« Reply #4 on: April 16, 2015, 09:16:35 am »

Ray,

I appreciate your input. Have you ever had an inspector give your #2 cable a sideways look?

Myself, and plenty of other people in my area, use #2 SC for distros-- unless you are running things Full Tilt Boogie, you will be OK. As always, your mileage may vary and exercise standard cautions in monitoring your gear-- but I have a huge pile of #2 and have never had a problem. Of course, I also don't ever even approach 100A/leg on things! (Remembering that the 190A/leg is per cable conductor…)

-Ray
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TJ (Tom) Cornish

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Re: #2 SC 200a feeder cable?
« Reply #5 on: April 16, 2015, 09:24:32 am »

Doing a quick forum search, I saw several references to people suggesting #2 cable for their single conductor feeder cables at a 200a distro. 
Isn't #2 rated at 190a? Or am I overlooking something silly?
Assume we are talking about 100' of it.
Thanks!
Best practice is #2 for 100A, 2/0 for 200A, 4/0 for 400A.  Keep in mind that there are two issues:
- What the electrical inspector says
- The voltage drop at the end of your run

If you're running 100' of #2 wire even at 190A, you're going to have pretty significant voltage drop.  IMO fudging isn't worth it if you're that close to the edge.  On the other hand, if you're only using 100A worth of load you will likely be OK, however code says you need to use an in-line breaker at the source end of your run.  Something like this: http://motionlabs.com/c-30-breakered-disconnect.aspx
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Ray Aberle

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Re: #2 SC 200a feeder cable?
« Reply #6 on: April 16, 2015, 10:53:15 am »

Ray,

I appreciate your input. Have you ever had an inspector give your #2 cable a sideways look?

Nope. But, I'm only providing power for PA/FOH/backline, not lighting. Things change big time when you step that up. :) I also mostly do things that are coming right from my 45kW MQ -- and that's breakered at 110A/leg anyways, so I can never draw more then that.

The Big Boys of PA and power in our region do have plenty of 2/0 and 4/0 -- and for large festivals/spread out power distribution, I'll see 4/0 for large PA/lighting rigs, and 2/0 for vendor booth distro feeder. (then L21-20 twist from there to booth stringers)

-Ray
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Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)

Matthew Knischewsky

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Re: #2 SC 200a feeder cable?
« Reply #7 on: April 16, 2015, 01:44:12 pm »

Doing a quick forum search, I saw several references to people suggesting #2 cable for their single conductor feeder cables at a 200a distro. 
Isn't #2 rated at 190a? Or am I overlooking something silly?
Assume we are talking about 100' of it.
Thanks!

Around here (Ontario Canada) #2 used to be "passable" for 200amps. Yes, it's only rated for 190amps but you wouldn't get defected for using it. In the last couple of years the inspectors have started to look closer at this so usually we breaker #2 at 175 amps. We run #2 for up to 175A, 2/0 for 200A and 4/0 for 400A.
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Stephen Swaffer

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Re: #2 SC 200a feeder cable?
« Reply #8 on: April 17, 2015, 10:01:48 am »

Code allows the next larger standard breaker size (defined in code) on circuits under 800 amps.  Though actual "ampacity" involves temperature derating, derating for number of conductors in a cable/conduit, etc-its not usually the number listed in the table.

Unless there are other requirements for portable use that I am overlooking.  Whether or not that is appropriate involves other considerations as others have mentioned.
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Steve Swaffer

Jeffery Foster

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Re: #2 SC 200a feeder cable?
« Reply #9 on: April 17, 2015, 10:09:18 pm »

Stephen, I've always appreciated your contributions here.

Code allows the next larger standard breaker size (defined in code) on circuits under 800 amps.

Is this true? I had no idea.

FWIW, I just decided to bite the bullet and get 2/0 cable.  It's only money, right? And the live sound business will forever be profitable with no downturn, right?
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Guy Holt

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Re: #2 SC 200a feeder cable?
« Reply #10 on: April 18, 2015, 09:05:44 am »

Is this true? I had no idea.

Yes, but Article 530.18 "Overcurrent Protection (A) Stage Cables" of the NEC pertaining to “Motion Picture Studios and Similar Application” allow overcurrent protection to be up to 400 percent of the rated ampacity of the cable. The exact wording is a follows: “Stage cables for stage set lighting shall be protected by means of overcurrent devices set at not more than 400 percent of the ampacity given in the applicable tables of Articles 310 and 400.”  And, according to NEC Table 400.5(B) the rated ampacity of #2  90 degree SC cable is 190 Amp, which means that according to the NEC you could use up to a 760A breaker.  There is not a municipal inspector in the country that would countenance that. My point being that the NEC is a national code that a municipality can elect to adopt or not. It ultimately comes down to the Authority Having Jurisdiction and what they want you to do. The local electrical inspector has the final say, so it is worth finding out ahead of time what they want and don't bother trying to cite code to them.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com
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boburtz

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Re: #2 SC 200a feeder cable?
« Reply #11 on: April 18, 2015, 12:56:46 pm »

It's only money, right?
Unless you count the fun factor. 2/0 is WAY less fun to deal with than #2.
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Tim McCulloch

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Re: #2 SC 200a feeder cable?
« Reply #12 on: April 18, 2015, 01:16:49 pm »

Yes, but Article 530.18 "Overcurrent Protection (A) Stage Cables" of the NEC pertaining to “Motion Picture Studios and Similar Application” allow overcurrent protection to be up to 400 percent of the rated ampacity of the cable. The exact wording is a follows: “Stage cables for stage set lighting shall be protected by means of overcurrent devices set at not more than 400 percent of the ampacity given in the applicable tables of Articles 310 and 400.”  And, according to NEC Table 400.5(B) the rated ampacity of #2  90 degree SC cable is 190 Amp, which means that according to the NEC you could use up to a 760A breaker.  There is not a municipal inspector in the country that would countenance that. My point being that the NEC is a national code that a municipality can elect to adopt or not. It ultimately comes down to the Authority Having Jurisdiction and what they want you to do. The local electrical inspector has the final say, so it is worth finding out ahead of time what they want and don't bother trying to cite code to them.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com

Guy, what we're doing is almost 100% covered in 520 and 525.  The MP codes are much more lenient.
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Stephen Swaffer

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Re: #2 SC 200a feeder cable?
« Reply #13 on: April 20, 2015, 11:13:26 pm »

Code allows the next larger standard breaker size (defined in code) on circuits under 800 amps.

Since you asked,

This is true, but not for branch circuits feeding cord and plug connected loads.  So this would be true for a distro, since it would have OPCD for the branch circuits.  (Branch circuits, by definition, being the wiring after the last OCPD).  NEC 240.4 (B).  Standard fuse/breaker sizes are found in 240.6 (A).
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Steve Swaffer
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