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Have you ever known any one to trim strands from a conductor so it would fit a lug?
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 Post subject: Trimming strands from a conductor to fit lug?
PostPosted: Sun May 29, 2016 5:08 pm 
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Location: Scottsdale, Arizona
I had another question for this week but last week's discussion took an interesting twist so we'll follow up with it.

Have you ever known any one to trim strands from a conductor so it would fit a lug?

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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Mon May 30, 2016 4:34 am 
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Joined: Tue Nov 12, 2013 6:31 am
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Location: Port Huron, Michigan
We actually had an ugly installation earlier this year to avoid this. We ordered 750 MCM cable and compression lugs for an emergency repair to tie a transformer to a new section of distribution breakers. What we received from the supplier though was 777 MCM cable and 750 MCM lugs. We would have had to trim the cable back to fit it in the lugs. What we ended up doing instead though, was splitting the cable into two halves, and feeding each half into a 500 MCM mechanical lug.

Thankfully I got the proper size lugs in and we replaced the mess a few weeks ago.


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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Tue May 31, 2016 7:03 am 

Joined: Mon Nov 09, 2015 7:23 am
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Yes I have seen this done. However, it is strictly prohibited and definitely not a recommended practice. With that said, some expedient repairs may allow these type of practices on a very temporary basis due to incorrect components on hand.


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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Tue May 31, 2016 7:53 am 
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I have also seen the reverse, where a number of small wires (#14 or #12) were bundled together, crammed into a Crimp Lug, which was then hydraulically crimped. This was the solution of this Mfg. [assembly line "robot"] to the need to distribute power to a large number of motor contactors.
While the wires at the edge of this bundle were indeed tightly crimped and quite secure, the wires in the middle fell out when pulled on.


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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Tue May 31, 2016 8:39 am 
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I've seen both of the above described multiple times over (connections with vastly more cables than they are rated for, cables which are trimmed to fit in the lug). In fact I would say that when I do an inspection, at least 25% of my photos of installation inspections tend to be incorrect terminations. The third one that hasn't been mentioned for is all kinds of abuses of connectors such as stuffing multiple cables into a single cord grip or using some kind of connector such as a Myers hub instead of a cord grip. Inevitably with regard to the latter it provides easy entry for dirt and fluids going into the enclosure thus compromising the rating of the enclosure, as well as not preventing the wiring from getting ripped out of the box when invariably physical damage occurs at some point in the future, quite often as a result of maintenance activity. The result especially with medium voltage of course is that the likelihood of an arcing fault inside the box goes up dramatically.


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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Tue May 31, 2016 8:44 am 

Joined: Thu Sep 27, 2012 3:02 pm
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Location: Washington
I've seen many variations of this unholy practice, including trimming strands so that multiple cables can be crammed into a single lug and trying to stuff the hundred+ strand flexible cables into lugs designed for lower strand class lugs resulting in little strands hanging out of the lug then trimming the ones on the front. Another favorite is seeing a high strand class cable in a lug with a set screw that has augured right through the strands.


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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Wed Jun 01, 2016 4:06 pm 
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Joined: Fri Apr 15, 2011 7:43 am
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Location: Colorado
I actually have a project where we will probably be trimming the conductors due to wires being over sized for voltage drop. We are running over 1000' for a 480V panel and the wire is two sizes bigger. We are looking into reducing barrels - if we can find them.


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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Thu Jun 02, 2016 7:30 am 
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engrick wrote:
I actually have a project where we will probably be trimming the conductors due to wires being over sized for voltage drop. We are running over 1000' for a 480V panel and the wire is two sizes bigger. We are looking into reducing barrels - if we can find them.


Two easy choices. First one is land them onto a power distribution terminal block and then from there onto the actual terminals. A second method that I've used a lot is to purchase insulated two port terminals. They go by various names. Insultaps is one. Burndy and Polaris are two manufacturers. What you get is a two (actually as many as you need) port solid aluminum terminal block with antioxidant conductive grease preloaded into the holes. You can get them as "straight through" or "side-by-side" configuration. The latter fits best inside motor peckerheads. They are insulated already so they can just "hang" in space similar to using split bolts. Now the nice part though is that they are already totally insulated and the acceptable size ranges for a given size is enormous, like running from say #4 all the way to 500 MCM for a single block.

The original intended use for these is for utilities and installations where you have to connect together different size wires especially for long runs and even in buried applications where moisture is a problem at the vault. The reason I like them is because instead of taking about 30 minutes if you properly terminate a motor (vinyl, cambric, vinyl, rubber, vinyl), you can just shove the wires in, tighten the screws and you're done. And if you get a bottle of the conductive/moisture barrier gel/grease stuff you can reuse them, and you only need about 3 sizes to cover every motor in the NEMA MG-1 standard (1-500 HP). The only challenge is sometimes the peckerheads are a tight fit. Now this may not be to code but an electrician I knew years ago would stuff the remaining space in the peckerhead full of packing peanuts to eliminate problems with vibration rubbing the insulation off over time. This works with the "tape ball" approach too.


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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Wed Sep 07, 2016 3:39 pm 
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Did this at the power company I worked at in many cases where oversize secondary conductors were specified for voltage drop consideration (not ampacity). It was not a problem though I'm sure it would raise eyebrows of most inspectors.


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 Post subject: Re: Trimming strands from a conductor to fit lug?
PostPosted: Wed Sep 07, 2016 4:30 pm 
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Gary B wrote:
Did this at the power company I worked at in many cases where oversize secondary conductors were specified for voltage drop consideration (not ampacity). It was not a problem though I'm sure it would raise eyebrows of most inspectors.


So how did you determine whether or not the ampacity of the remaining conductors was adequate? How did you ensure that the connector worked correctly considering that the strand diameter and overall shape had changed from what it was originally intended to be?

Just playing devil's advocate here.


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