larger wire for voltage drop

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var

Member
Theres a circuit pulling 24 amps and is about 400 feet long.
The wire size gets increased to #4 copper to reduce resistance and voltage drop.
Now the wire will not fit into the breaker so here is my questions.

1)If several strands are removed from the wire to fit on the breaker would the strands that are cut in the wire be of no use in reducing resistance even tho they are in contact with all the other strands tightly wrapped in insulation.

2)If no strands are cut on the #4 and Butt splices are used to reduce the wire down to a size that will fit on the breaker will there be less resistance in the circuit than if the strands are cut?

All thoughts welcome:)
 

iwire

Moderator
Staff member
Location
Massachusetts
Never cut the strands of a conductor if for no other reason then it screams 'hack'.

You can splice on a smaller conductor as long as the smaller conductor is still above the ampacity of the breaker and the load being placed n it.

10' of 'normal' size wire at the end of 400' of up sized wire will not effect voltage drop enough to worry about, do the calculations and you can prove it.
 

Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Theres a circuit pulling 24 amps and is about 400 feet long.
The wire size gets increased to #4 copper to reduce resistance and voltage drop.
Don't forget to increase the EGC based on 250.122(B). Sorry I had to do that. :smile:
 

Besoeker

Senior Member
Location
UK
Theres a circuit pulling 24 amps and is about 400 feet long.
The wire size gets increased to #4 copper to reduce resistance and voltage drop.
Now the wire will not fit into the breaker so here is my questions.

1)If several strands are removed from the wire to fit on the breaker would the strands that are cut in the wire be of no use in reducing resistance even tho they are in contact with all the other strands tightly wrapped in insulation.

2)If no strands are cut on the #4 and Butt splices are used to reduce the wire down to a size that will fit on the breaker will there be less resistance in the circuit than if the strands are cut?

All thoughts welcome:)
I'm with the others here. Don't cut any strands out.
We often come across issues where the conductors are too large or numerous to fit on to breaker terminals. There are various solutions. One is to "extend" the terminals. Here's one we did earlier.

 

elohr46

Senior Member
Location
square one
I'm with the others here. Don't cut any strands out.
We often come across issues where the conductors are too large or numerous to fit on to breaker terminals. There are various solutions. One is to "extend" the terminals. Here's one we did earlier.
Wow, sorry, but I don't like that conversion one bit. Would 4 barrel lugs been a better choice?
 
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var

Member
There wasnt an answer to the question 1.
The reason I asked the question was I came across this situation.
I measured voltage drop at the customers equipment, I then repaired the cut strands and spliced a piece of #8 to land on the breaker, "I understand that I was lowering resistance and that a small section wouldnt matter".
My thought was that the strands being cut werent being used in the larger cable to lower resistance because they werent connected at both ends.
So I made the splices, fired up the equipment and there was no difference in the voltage at the equipment at all.
The customer then informed me it was a waste of time and money to do that.
I explained my reasoning but he didnt really care.
I'm just trying to understand how the cut strands still lowered resistance even tho they werent connected.
 

charlie b

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Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
I do not understand the situation you encountered, nor your repair, nor the test you did after your repair. But I will try to answer your first question.

I am sure that you know that if you put two resistors in series, the total resistance gets higher, and is equal to the sum of the two resistances. If you put five identical resistors in series, then the total resistance is equal to five times the value of any one of them. If you make a series connection of resistors that are of different values, then you simply add up the individual values to get the total resistance.

A long conductor can be regarded as a series connection of small resistors. Consider a 1 foot long section of #4 bare copper wire. It has some value of resistance. Now consider a 100 foot long section of the same wire. It is essentially a series connection of 100 resistors, each having the value of resistance as your initial 1 foot section, and the total resistance is 100 times the value of the 1 foot section. If you tie together (good luck on getting good connections here, but stay with me, and let’s pretend you can do this with zero extra resistance at the connection points) 100 sections of 1 foot long bare wires of varying AWG sizes, then the total resistance will be the sum of the resistances of the one hundred individual pieces.

In your example, you have 399 feet plus 11 inches of #4 wire in series with a 1/2 inch section of #4 wire that has been trimmed down and placed into a lug on one end, plus another 1/2 inch section of #4 wire that has been trimmed down and placed into a lug on the other end. This is a total of three resistors in series, and the total resistance is the sum of the three individual resistances. The resistance per unit length of the trimmed down sections at either end is higher than the resistance per unit length of the long section. But the total resistance of the 399+ foot long piece in the middle has not been altered by what was done at either end.

Does this answer your question?

By the way, welcome to the forum.
 
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var

Member
Thanks Charlie,
Yes, that makes things a bit more clearer now.
My customer had a piece of equipment that would not run at lower than 230 volts.
A contractor came and upsized the wire for voltage drop but then trimmed the ends to fit under the lugs at disco and at the breaker.
I told the customer that it shouldnt have been done like that and it would lower the resistance of the run to remove the trimmed #4 ends and splice a #8 smaller piece on the #4 ends untrimmed with butt splices and that we should gain a couple volts in doing so.
I measured the voltage at the equipment at full load amps before I removed the trimmed pieces and after I made the repair with #8 wire at the disco and breaker and there was no difference.
I guess I didnt understand how the trimmed strands would count as lowering the resistance when they were not connected at either end, but they must count because they are wrapped tightly with the other strands and held tight by the insulation.
 

iwire

Moderator
Staff member
Location
Massachusetts
I guess I didnt understand how the trimmed strands would count as lowering the resistance when they were not connected at either end, but they must count because they are wrapped tightly with the other strands and held tight by the insulation.
That is correct, just because they are not connected by the terminal the cut strands still function.

In my opinion you corrected a code violation.
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
I measured the voltage at the equipment at full load amps before I removed the trimmed pieces and after I made the repair with #8 wire at the disco and breaker and there was no difference.
There really was no hope that this would solve the problem. As you can now see, you have a 400 foot long wire and you are changing the resistance of only an inch or two of its length. You need to replace the entire wire with a larger size, in order to have a measurable impact on voltage drop.
 

StephenSDH

Senior Member
Location
Allentown, PA
You could consider a transformer before/after to boost the voltage and reduce voltage drop. With your current scenario there is not much you can do besides replacing the wire or changing the voltage.
 

Besoeker

Senior Member
Location
UK
How are those extensions made that you can bolt through for support? They look like solid CU but I'm guessing they can't be unless they're bolted to something non-conductive.
They are solid Cu, but as cycotcskir has noted, there are red barrel insulators on the supports.
 

cycotcskir

Senior Member
Besoeker,

Have you thought about putting the insulator on the other end of the rod (next to the bar) and securing it with a bolt? There would be no "hot" rod and also no rod sticking out past the bar, just the bolt head.

Just a thought.

I do see that the rod is coated, though
 

Besoeker

Senior Member
Location
UK
Besoeker,

Have you thought about putting the insulator on the other end of the rod (next to the bar) and securing it with a bolt? There would be no "hot" rod and also no rod sticking out past the bar, just the bolt head.

Just a thought.

I do see that the rod is coated, though
Yes, there is merit in what you suggest.
In fact, in retrospect, an insulator at both ends might not have been a bad idea
That said, the panel cover operates a microswitch that is in the shunt trip circuit of the breaker so you can't get in with the output side live.
Additionally, everything inside the panel was shrouded to IP2x or better to prevent accidental contact. IP2x is Ingress Protection against solid objects greater than 12mm (just under 0.5 inch). Basically, you can't stick you finger through it to touch anything live.
It's a common specification used here (UK) for the internals of electrical panels.
 

cycotcskir

Senior Member
It's a common specification used here (UK) for the internals of electrical panels.

UK... didn't see that. So do you guys use the NEC over there? I think that I would assume that you do since you are on this forum. My wife wants to move over there (Ireland or Scotland). Maybe I have a chance of getting work if they follow the NEC :roll:

The shunt seems like a good idea, I don't see much of that around here, though. Most equipment that I have worked with had a way to open while hot.

I think that 2 insulators could be considered wasteful, but definitely not harmful; only because if the first one does it's job then the second one isn't helping the cause.

It's a nice looking install.
 
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PetrosA

Senior Member
They are solid Cu, but as cycotcskir has noted, there are red barrel insulators on the supports.
Ahh the joys of being slightly red/green color blind ;). I think what cycotcskir (psychotic skier?) had in mind was mounting the barrel insulators to the copper, rather than to the back plate, one per rod.
 
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