Rick Christopherson
Senior Member
There is a manufacturing company that I do some contract engineering work for, and I discovered that they have decided to switch from the more-or-less ?industry standard? of #10/5 SJOW cord for their 20 amp, 3-ph extension cords and quad box cords (L21-20 ends), down to #12/5 cord. (Even though this is 120/208 wye, most loads are single-phase). This decision was driven by a non-engineer salesman before I began working with them.
As someone who has previously spent years on the ?usage side? of this type of equipment, I personally feel that this is not a good decision. I also believe that it is the cause for their unusually high concern for burnt neutrals. Prior to now, I have never heard of a burned neutral in this type of equipment, but that is because I have never encountered anything less than #10/5 either.
This non-engineering salesman has apparently convinced them that the reason they were getting product returned (warranty/repair) with burned neutrals was due to the added resistance from pigtail splices made into the neutral at each of the 3 quad box locations down the length of the quad box string (e.g. each splice was causing resistance). So now they are making a big deal about making non-spliced taps into the neutral (continuous, uninterrupted wire). Unless I am missing the bigger picture, this isn?t going to solve anything.
Even though we have no direct knowledge of how the equipment is finally used, it is pretty safe to say (from personal experience) that nonlinear loads can be quite common, and I have been on project sites where the load was entirely nonlinear.
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What I would like to do is put together a writeup summarizing my concern of using #12/5 for these cables. The nonlinear loads aspect is pretty straightforward and is substantiated from 400.5 (A) and 400.5 (B).
However, there is also the issue of voltage drop for the length of these cables. Each cable is about 100 feet, but it is very common to have runs that are several hundred feet, when put to use by the final user.
I have found a couple minor notes in the NEC regarding voltage drop, but nothing really concrete. Is anyone familiar with a citation or table from code that defines this with a little more vigor. Also, is there any other aspect I am overlooking?
As someone who has previously spent years on the ?usage side? of this type of equipment, I personally feel that this is not a good decision. I also believe that it is the cause for their unusually high concern for burnt neutrals. Prior to now, I have never heard of a burned neutral in this type of equipment, but that is because I have never encountered anything less than #10/5 either.
This non-engineering salesman has apparently convinced them that the reason they were getting product returned (warranty/repair) with burned neutrals was due to the added resistance from pigtail splices made into the neutral at each of the 3 quad box locations down the length of the quad box string (e.g. each splice was causing resistance). So now they are making a big deal about making non-spliced taps into the neutral (continuous, uninterrupted wire). Unless I am missing the bigger picture, this isn?t going to solve anything.
Even though we have no direct knowledge of how the equipment is finally used, it is pretty safe to say (from personal experience) that nonlinear loads can be quite common, and I have been on project sites where the load was entirely nonlinear.
================================
What I would like to do is put together a writeup summarizing my concern of using #12/5 for these cables. The nonlinear loads aspect is pretty straightforward and is substantiated from 400.5 (A) and 400.5 (B).
However, there is also the issue of voltage drop for the length of these cables. Each cable is about 100 feet, but it is very common to have runs that are several hundred feet, when put to use by the final user.
I have found a couple minor notes in the NEC regarding voltage drop, but nothing really concrete. Is anyone familiar with a citation or table from code that defines this with a little more vigor. Also, is there any other aspect I am overlooking?