Trimming down feeder wire strands

[porkchop]

So I'd like to get everyone's ideas on cutting copper out of bare end tails to make them fit an install. I know this is a rather touchy topic, but I don't think we've covered it before.

To a newbie this may sound like a rumor or horror story, but pretty much every pro that does tie-ins knows that at some time you'll be put in a situation where cutting some but not all of the copper from tails is an option, and you might be tempted to think it's a good one, be it to put 4/0 tails in 2/0 cams, to make a lug fit, or to make very rough and frayed tails fit.

So here's my basic question to stir up conversation. Is it acceptable to cut out copper and why do you say that? If yes, are there any extra precautions you take to ensure cutting the minimum necessary? If no, what is your response to the normal bosses excuses (we don't draw that much being the first to come to my mind)?

To keep this neutral for a few posts I'll wait to post my opinion.

 

[coldnorth57]

http://www.controlbooth.com/forums/lighting-electrics/25419-feeder-tails.html

we have talked this one through once or twice

 

[porkchop]

Not really the same topic there. That's assuming your tails fit if you have a fresh connection. What if it's 8am on a Saturday. All the rental shops are closed. The show is that night. You're running power and the show has 4/0 tails and the house only has 2/0 lugs to tie-in to?

 

[ptero]

Are you talking about removing some of the copper strands from the stripped end? Thus reducing the diameter of the stripped end? That's a different twist on the noted discussion. That one seems to be about successively chopping feeder lengths shorter and shorter with freshly stripping ends as sometimes necessary when working with bare ends.

No answers, sorry. Just trying to clarify the discussion. I'd assume downgrading limits on loading but it may just be by seat of the pants. Anyone?

edit: OP/porkchop slipped in... good example.

 

[derekleffew]

...What if it's 8am on a Saturday. All the rental shops are closed. The show is that night. You're running power and the show has 4/0 tails and the house only has 2/0 lugs to tie-in to?

1. 2011 NEC 110.14(A) doesn't care when the show is. Nor does the electrical inspector/AHJ.
2. The only acceptable alternatives are to replace the lugs with a larger size, or use an approved adapter. From CPM AL/CU PIN :
   

   Rated for full ampacity of incoming conductor.

   
3. If the lugs are sized for 2/0 AND your current draw is less than the 2/0 rating, you might argue that the 4/0 is over-sized to begin with. But you'd likely lose.

 

[porkchop]

They make adapters? I never knew.

 

[avkid]

They make adapters? I never knew.

That makes two of us.
Interesting device that is.

 

[Footer]

Seen it done, however, it can easily be avoided. I know your not the one who writes your rider, however, I have seen riders stating that the show travels with cams and 4/0 tails. If the venue is not capable of tieing in 4/0 tails that the promoter is responsible for providing sufficient tails. Granted, that was one rider out of many that mention nothing, but its out there.

I'm also with derek on this one... while 4/0 feeder is the industry standard, if your not loading it up why are you carrying the weight anyway? If a venue installed a 2/0 disconnect, odds are it is not going to supply enough power anyway. Once again, correctly sized cable for the right purpose. Also, very rough and frayed tails should be cut back and re-stripped every time. I'm still amazed at how many venues that have bare ends that don't have tails. Hell, I have a set of tails, 4 sets of turn arounds, and I don't even have bare ends anywhere in the venue!

And another link for reducers: http://www.greaves-usa.com/pdf/ReduceR Color Sheet.pdf

 

[mstaylor]

Is it proper, no, is it done, all the time. I never knew about the reducers either. May have to add some to my bag of tricks. I work with a sound/light company and they carry 4/0 tails in all their rigs but 1/0 feeder for their sound.

 

[porkchop]

Is it proper, no, is it done, all the time.

Exactly why I brought it up

 

[STEVETERRY]

1. 2011 NEC 110.14(A) doesn't care when the show is. Nor does the electrical inspector/AHJ.
2. The only acceptable alternatives are to replace the lugs with a larger size, or use an approved adapter. From CPM AL/CU PIN :
   
   
   
3. If the lugs are sized for 2/0 AND your current draw is less than the 2/0 rating, you might argue that the 4/0 is over-sized to begin with. But you'd likely lose.

Err.....not exactly.

The Ilsco adapter you show has one purpose only: to convert an aluminum conductor to a smaller gauge copper conductor of the same ampacity so that it can terminate to a smaller lug. Its female barrel comes pre-filled with deoxidizing compound that is meant to be used with AL conductors only.

It's a neat tool (good for feeding Sensor racks with big fat AL conductors that won't otherwise fit the lugs), but it cannot be used on portable feeders because:

A. Such feeders don't come in Aluminum
B. The device is not rated for copper on the input sleeve, especially with class K stranding, which is what we use in portable feeders

So, this takes us back to the OP's question: should you cut strands from feeder to make it fit in a smaller lug, especially if you are not using the full rated ampacity of the cable?

Answer: NO!

How can you determine the allowable number of strands to cut? You can't.

To solve this problem,carry a set of E1016 tie-ins made with 2/0 cable. Voila! Problem solved, since E1016 connectors from #2AWG to 4/0 AWG are intermateable. Incidentally, this is one of the primary reasons that the NEC requires qualified personnel to install single conductor feeder systems. That's because the installer needs to know all about cable ampacity for a given application, since connectors for a wide variety of ampacities can plug together.

And for another story, I'll tell you just how hard it was and how many years it took to get UL and the NEC to accept that approach!

Finally, a quiz for everyone: when would it be useful (or necessary) to use 4/0 type SCE conductors for only a 200 amp load normally served by 2/0?

ST

 

[JD]

My vote would be on extended runs. (using 4/0 for 200 amps)

 

[STEVETERRY]

My vote would be on extended runs. (using 4/0 for 200 amps)

Precisely!

One of our primary tools for dealing with voltage drop on long runs is to upsize the feeder cable. Intermateable Cam connectors let us do this with ease.

ST

 

[porkchop]

Footer's link is to all copper reducers and I think there's a good chance I'll be buying some next time I'm stateside.

Now that I've mentioned this I'll give a little more detail on the situation that brought this up. I'm out of the US in a less than first world country. Shipping is almost impossible, local good are questionable at best, and the show was sent down here poorly stocked in my opinion. Local voltage is 220/380 it goes into a variable step down transformer and it's my job to make sure it comes out as close as possible to 120/208. The show has 4/0 tails because every show the company owns has 4/0 tails, but the draw is notably less than 200 amps at 120/208. This means at the disconnect we're drawing less than 100 amps. We go to tie in and all that's available is a 200 amp service that only takes 2/0 lugs. The show owns 4/0 and 2/0 removable lugs. What would you do?

Side note: this already happened, the situation was dealt with, and I'm comfortable with the outcome. Just wanted to throw the situation into conversation to see what people would have done.

 

[JD]

Footer's link is to all copper reducers and I think there's a good chance I'll be buying some next time I'm stateside.

Don't know about the reduction part, but if the come in a 1:1 ratio, they look like a great way to straighen out the stranding issue on SCE tails. Not sure how long they would last, but might be intresting.

 

[derekleffew]

...Finally, a quiz for everyone: when would it be useful (or necessary) to use 4/0 type SCE conductors for only a 200 amp load normally served by 2/0?

My vote would be on extended runs. ...

And here I was wondering what the duration of the engagement had to do with anything.

Footer's link is to all copper reducers and I think there's a good chance I'll be buying some next time I'm stateside. ...

Don't do it. While the Greaves document does say "copper conductor" ...

STEP-DOWN COMPRESSION ADAPTER PLUGS
• All-copper compression adapters
• For reliable termination of Class B copper conductor
• Use where oversized cable is used to reduce voltage drop on log runs
• Use where neutrals are upsized for power quality
• Narrow profile often allows use in place of offset adapters on multi-wire terminals
• Fits into mechanical set-screw type connectors in panels, transformers, machinery
• Current rating is per the plug size
• Fabricated of wrought copper with plug of Class B copper conductor
• Insulating covers are provided

...it also mentions "Class B", TWICE. Class B stranding uses fewer, thicker wires than Class K Stranding. The termination must match the stranding. Also, installation of either the Ilsco or Greaves requires a crimper and specific die, which is sure to be upwards of $200.
-----
As to your current situation, when not in North America, you're not bound by the NEC, but let's not make this thread about how electrical work is performed in less than first world countries. There are already plenty of sites on the Internet for that.

 

[STEVETERRY]

And here I was wondering what the duration of the engagement had to do with anything.

Don't do it. While the Greaves document does say "copper conductor" ...
...it also mentions "Class B", TWICE. Class B stranding uses fewer, thicker wires than Class K Stranding. The termination must match the stranding. Also, installation of either the Ilsco or Greaves requires a crimper and specific die, which is sure to be upwards of $200.
-----
As to your current situation, when not in North America, you're not bound by the NEC, but let's not make this thread about how electrical work is performed in less than first world countries. There are already plenty of sites on the Internet for that.

What he said.

ST

 

[avkid]

A used hydraulic crimper and good die had can be had for around $150.
That said, using it correctly is not child's play.