Brandon Loyd
Senior Member
Is it legal to trim strands from a wire that is oversized for voltage drop, to fit into the smaller lugs of a breaker?
Wire reduction
- Thread starter Brandon Loyd
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jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Nope. How would you comply with 310.11(A)(4)? What is the trimmed wire size?
John Valdes
Senior Member
- Location
- SC.
- Occupation
- Retired Electrician
Splitting hairs on that reference article? I do not think it applies.
OP......While I am fairly certain it is a violation, I am not sure what article makes it a violation. The one above clearly (IMO) is not the right one.
I just connect a smaller conductor to the larger conductor to connect/fit the device.
How about 110.14(A)
110.14 Electrical Connections.
(A) Terminals. Connection of conductors to terminal parts shall ensure a thoroughly good connection without damaging the conductors and shall be made by means of pressure connectors (including set-screw type), solder lugs, or splices to flexible leads. Connection by means of wire-binding screws or studs and nuts that have upturned lugs or the equivalent shall be permitted for 10 AWG or smaller conductors.
110.14 Electrical Connections.
(A) Terminals. Connection of conductors to terminal parts shall ensure a thoroughly good connection without damaging the conductors and shall be made by means of pressure connectors (including set-screw type), solder lugs, or splices to flexible leads. Connection by means of wire-binding screws or studs and nuts that have upturned lugs or the equivalent shall be permitted for 10 AWG or smaller conductors.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The only problem is how to determine how many strands are okay to cut. It is safer to just splice a smaller wire to the breaker.
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
NO ,NO and never
- Location
- Massachusetts
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Okay, if I cut two strands off a 4/0 conductor, what is my wire size and circular mil area. Ampacity is ?. The original marking no longer applies IMO.
(4) The AWG size or circular mil area.
renosteinke
Senior Member
- Location
- NE Arkansas
Doesn't Ilsco make crimp-on pieces for just this purpose?
This case seems to be a long insulated wire of correct CM and ampacity for its insulation
connected to a very short uninsulated "wire" or stub of reduced CM and reduced amp capacity.
But the stub is uninsulated so its ampacity is pretty high.
For a stub with a much reduced CM it would heat up, which may cause heating of the breaker terminal.
IMO unless there are mechanical reasons for not doing this, it sounds like some small reduction of CMs would be OK.
I guess then the crimp-on pieces do not reduce conductor cross section.
4/0 = 460 mils dia. = 460^2 CM = 211,600 CM.
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jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
handy10
Senior Member
- Location
- western suburbs, chicago
According to table 8, Chapt. 9 of NEC 08, a 4/0 conductor has 19 strands whose diameters are .106 in. If you cut two strands, the area of the conducting material would be reduced from 0.168 sq. in to 0.150 sq in., about an 11% reduction.
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
That makes no differance, you lost the ul listing by doing this. Fight it all you want but a good inspector will and should tag it every time.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
I do not think the ampacity of a conductor can be calculated that way.
handy10
Senior Member
- Location
- western suburbs, chicago
Note that I did not mention ampacity.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
True, you did not; however, when you trim you no longer have a circular mil area. An area approximation that also does not consider air gap between strands.
Only for the half inch or so at the end. You'd still have full cross section for the rest of the cable length.
These crimp-ons greatly reduce the cross section: half the dia. gives you 1/4th the cross section which is 4x the resistance per unit length. Once crimped this ratio will be slightly smaller.
I'd think then the rule is only for mechanical reasons.
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Jim W in Tampa
Senior Member
- Location
- Tampa Florida
The crimps have the one thing we need,U L listed
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