Breaker lugs too small for wire?

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augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
Pins are my choice also, but the most common method I see is splicing on a pigtail that the breaker will accept.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
If you need to upsize the wire to 2/0 for the run because of its length, it is OK to reduce the size of the conductor for that six inches or so near the breaker? Is there less current flowing through the conductor near the breaker?
No, the whatever-length of the 2-0 will drop the voltage that that length of 2-0 will at the actual load current, and the 6" of #2 will drop the voltage that 6" of #2 wil at the same current. The current causes the voltage drop.

Remember, the breaker is sized to protect the #2 wire, so it won't suddenly become overloaded because there's a larger wire spliced to it. If someone mistakenly upsized the breaker for the larger wire, then you'd be correct.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
So your saying by reducing the wire size with a splice you would be in violation interesting.
Only if the breaker were sized larger than that required to protect the smaller wire.

This is similar to the mixed-wire-size discussion we had over the last couple of weeks.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
As long as the resistance of that 6 inches of smaller wire is less than the resistance of that whole run of 2/0, it doesn't matter.
The relative resistances are not relevant at all. What matters is that the smallest wire is protected.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Generally I try to avoid any splices in a panel, I think they look tacky and unprofessional. When I do a panel I like to leave it looking like a work of art.
Same here, but I do believe that form follows function, not the other way around. Make splices when you need to, just do them well first and pretty second.

I'm just wondering if I'm going to get any static from an inspector about it. It's been my experience that when it comes to dealing with any government officials you are at the mercy of their individual personalities with practically no consistency from one to the next.
First, you should get no static because this is compliant, done correctly. Consistency comes from communication and accurate code understanding. There are proper channels for challenging what you believe to be an improper ruling.

Second, inspectors usually appreciate being consulted when we're not sure about something. They're not the enemy, a lousy attitude is. Remember, the common goal is (or should be) a safe, compliant, well-performing installation.

Third, there is no reason for antagonism when dealing with an inspector. Speak respectfully, man to man, don't take his responses personally. If you disagree, then ask that the two of you consult his supervisor or head inspector together.

I just thought I would try to get a general consensus of what's acceptable or prohibited in this situation.
I'm sure we've covered that by now. :)
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Im not sure what is the difference between trimming the wire and putting a splice in your reducing the wire size to fit the lug .
Electrically, none, let's say. Legally, lots. Plus, it sure looks more unprofessional than splicing or pins.

What's a good reason for doing anything incorrectly? (Cheaper isn't a good reason.)
 

AV ELECTRIC

Senior Member
Only if the breaker were sized larger than that required to protect the smaller wire.

This is similar to the mixed-wire-size discussion we had over the last couple of weeks.

If the larger wire is used because of voltage drop and your reducing that wire size with a splice of some sort so it will fit in the lug are you not creating a problem by doing this or because of the short distance of the splice this will not affect the voltage
 

infinity

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Location
New Jersey
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Journeyman Electrician
If the larger wire is used because of voltage drop and your reducing that wire size with a splice of some sort so it will fit in the lug are you not creating a problem by doing this or because of the short distance of the splice this will not affect the voltage

Voltage drop is based on the resistance of the entire conductor length. It doesn't matter if you had a smaller conductor at the beginning, middle or end of the run. As long as the smaller condcutor is of adequate size splicing a small length of conductor on to allow it to fit into the lug is acceptable.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
If the larger wire is used because of voltage drop and your reducing that wire size with a splice of some sort so it will fit in the lug are you not creating a problem by doing this or because of the short distance of the splice this will not affect the voltage
The latter. The smaller size was adequate before the voltage-drop compensation was used, n'est pas?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
You missed what I was saying. AV ELECTRIC and infinity are speaking about my point in the post above mine.
I believe we're all in agreement. :) This says it all:
. . . the whatever-length of the 2-0 will drop the voltage that that length of 2-0 will at the actual load current, and the 6" of #2 will drop the voltage that 6" of #2 wil at the same current.
It's true that the relative location of each segment of the circuit doesn't matter, just as with extension cords. The voltage drops will add, just as in any series circuit.

Still, even knowing that, if I have to join extension cord of different sizes, there's just something inside me that makes me want the heaviest cord closest to the source.
 
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AV ELECTRIC

Senior Member
I believe we're all in agreement. :) This says it all:
It's true that the relative location of each segment of the circuit doesn't matter, just as with extension cords. The voltage drops will add, just as in any series circuit.

Still, even knowing that, if I have to join extension cord of different sizes, there's just something inside me that makes me want the heaviest cord closest to the source.

I feel the same way to
 

AV ELECTRIC

Senior Member
Voltage drop is based on the resistance of the entire conductor length. It doesn't matter if you had a smaller conductor at the beginning, middle or end of the run. As long as the smaller condcutor is of adequate size splicing a small length of conductor on to allow it to fit into the lug is acceptable.

Is there a reference in the code where this is allowed or can this be figured into the formula.In the past I special ordered a breaker with larger lugs .
 

augie47

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Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Is there a reference in the code where this is allowed or can this be figured into the formula.In the past I special ordered a breaker with larger lugs .
The only Code reference needed is 240.4. As long as the conductor is protected at it's ampacity, it meets Code.
You can use your standard voltage drop formulas. Say 40 amp breaker, #8 conductor 12" long spliced onto a 2/0.. Almost no voltage drop at the end of the #8. From the splice point you can figure the voltage drop on the remainder of the circuit
 

AV ELECTRIC

Senior Member
The only Code reference needed is 240.4. As long as the conductor is protected at it's ampacity, it meets Code.
You can use your standard voltage drop formulas. Say 40 amp breaker, #8 conductor 12" long spliced onto a 2/0.. Almost no voltage drop at the end of the #8. From the splice point you can figure the voltage drop on the remainder of the circuit

It just doesn't seem wright to splice a smaller wire at the source as Larry said but if the math says its good its good at least for this code cycle.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
It just doesn't seem wright to splice a smaller wire at the source as Larry said but if the math says its good its good at least for this code cycle.
It's just a #2-sized-wire circuit that has a larger conductor in a part of the run. The portion that is still #2 is not suddenly a problem.

I've runa 20a circuit in #12 to a J-box on an outside wall, extended it across a parking lot in #6, and then back to #12 at the far end.
 
I am curious about the best way to deal with this situation. Lets say you have a 125 Amp circuit and because of the length you end up with 2/0 copper wire. The 125 amp circuit breaker lugs are not big enough to accommodate wire that large. I've encountered jobs where someone has just trimmed off enough strands to make it fit but I don't think that would pass inspection. What would be the acceptable method for dealing with that?
Thanks

I've dealt with this problem before on the other end, eg. at the motor. I eventually needed to add a junction box to splice in the conductors rated for the overcurrent protection. (The motor JB just was waaaay too small to accomodate the oversized conductor due to the voltage drop adjustment.

Square "D" breaker lugs are notoriously undersized.
 

AV ELECTRIC

Senior Member
It's just a #2-sized-wire circuit that has a larger conductor in a part of the run. The portion that is still #2 is not suddenly a problem.

I've runa 20a circuit in #12 to a J-box on an outside wall, extended it across a parking lot in #6, and then back to #12 at the far end.

Well i guess there are limitations to what we can do with the material that is given maybe some day they will develop a super conductor that can provide a thousand amps in a wire the size of fishing line and one size would fit all but not today.
 

busman

Senior Member
Location
Northern Virginia
Occupation
Master Electrician / Electrical Engineer
I just did one of these. #10 wire on a 15A breaker for a 400' run to JB. Then change to #14 to wire lights and receptacles at stone wall. Fortunately, 15A breaker will take a #10 without adapter.

Mark
 

George Stolz

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Location
Windsor, CO NEC: 2017
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Service Manager
It just doesn't seem wright to splice a smaller wire at the source as Larry said but if the math says its good its good at least for this code cycle.
By saying "at least for this code cycle" you imply that you believe the option is something that should be removed for future codes. Why do you feel this way? It's a perfectly safe, compliant installation.
 
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