Conductor Set

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bhc

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Hello, I have a simple question...when replacing existing motors with larger motors, and you can reuse the existing conductors but need to add a set or two to meet the ampacity, does the Code require the new sets to match the size of the existing set of conductors, or can the new set be smaller, but large enough to meet the required ampacity? Thanks in advance.
 
bhc said:
Yessir
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Technically, if you are able to convince the inspector that the new cables are identical in length, material, size, and physical route (including raceway type), then there does not seem to be any prohibition in the code.
The fact that the old conductors may be un-inspectable may persuade the inspector not to approve the new parallel set.
 
I think 310.10(H)(2) makes it an issue.

(1) Be the same length.
(2) Consist of the same conductor material.
(3) Be the same size in circular mil area.
(4) Have the same insulation type.
(5) Be terminated in the same manner.
 
GoldDigger said:
Technically, if you are able to convince the inspector that the new cables are identical in length, material, size, and physical route (including raceway type), then there does not seem to be any prohibition in the code.
The fact that the old conductors may be un-inspectable may persuade the inspector not to approve the new parallel set.
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Where is physical route in the NEC?
 
jumper said:
Why? I am not being a smart aleck. Real question.
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The physical aspects of the sets must be identical.
Electrically that means at a bare minimum that the number of conductors per raceway must match, and the ferrous/non-ferrous nature of the raceway must match.
Beyond those obvious distinctions, it seems hard to draw the line anywhere short of identical types and fill values.
 
GoldDigger said:
The physical aspects of the sets must be identical.
Electrically that means at a bare minimum that the number of conductors per raceway must match, and the ferrous/non-ferrous nature of the raceway must match.
Beyond those obvious distinctions, it seems hard to draw the line anywhere short of identical types and fill values.
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What if you have one set made of the older variant of pure THHN, and another set made out of the current product that is dual rated THHN/THWN-2? And you are only counting on the THHN rating of each.
 
The conductors need to be as close as possible to the same length. You would want to pull the conductors out, layout new next to the old, and cut to the same length.

We have a question on how critical it was for conductors to be the same length some years ago, it was surprising to me how critical it was, basically as close as you can measure...
 
Carultch said:
What if you have one set made of the older variant of pure THHN, and another set made out of the current product that is dual rated THHN/THWN-2? And you are only counting on the THHN rating of each.
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I wouldn't think that would make any difference as long as the voltage rating of all insulation is sufficient. The parallel sets rules concern the electrical characteristics of the wires and I don't think THHN vs. THHH/THWN-2 is a player.
 
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