# Acceptable error margin on a parallel wire run on a transformer



## frenchelectrican

Tesla_Fusion said:


> Ive been arguing with my fellow electrician about what is the acceptable error margin lenght wise on a parallel run to a transformer .
> Anyone know what and/where i could find that awnser?
> I work in canada, so if you are able to give me exactly where to find that awnser that would be awesome thanks


I will reply in both engish and French.

Pour les conducteurs parallèles de la marge d'erreur en fonction du type de conducteur et les matériaux utilisés et étant la longueur du conducteur lui-même, si bien que la réponse varie un peu.

Ainsi., C'est ma réponse courte et douce là-bas. mais si vous voulez plus de détails vous pouvez chercher dans votre carnet d'trouver les réponses dedans.


For the parallel conductors the margin of error will depending on the type of conductor and materials it being used and the length of the conductor itself as well so the answer will varies a bit.

So., that is my short and sweet answer there. but if you need more details you may look up in your book to find the answer there.

Merci,
Marc


----------



## 360max

...there is no acceptable difference for paralleled conductors , 310.4(B)(1) states they must *be the same length*.


post script; just realized you are from Canada


----------



## KDC

Code here in canada is the same. Parallelled conductors must be identical in type, size, length etc.


----------



## erics37

frenchelectrican said:


> I will reply in both engish and French.


:laughing::laughing::laughing::thumbup::thumbup:


----------



## frenchelectrican

erics37 said:


> :laughing::laughing::laughing::thumbup::thumbup:


I figured that you will laugh a little but ya know moi,,,

Merci,
Marc


----------



## BBQ

KDC said:


> Code here in canada is the same. Parallelled conductors must be identical in type, size, length etc.


So just like in the US none of the installations are compliant. :jester:


----------



## Tesla_Fusion

BBQ said:


> So just like in the US none of the installations are compliant. :jester:


Exactly it is impossible to have the same lenght!

Ill try to find the article in the cnd code


----------



## Tesla_Fusion

So it is impossible to comply to the electrical code book?


----------



## erics37

Tesla_Fusion said:


> So it is impossible to comply to the electrical code book?


It's difficult. I think what BBQ is implying is that there probably isn't an installation anywhere that has paralleled conductors the exact same length. No one is that perfect :laughing: So to answer your question, a few inches difference probably won't have any ill effect


----------



## BBQ

Tesla_Fusion said:


> So it is impossible to comply to the electrical code book?


It is impossible for anyone to make conductors the same length.

The code should provide a tolerance or range.


----------



## ponyboy

BBQ said:


> It is impossible for anyone to make conductors the same length.
> 
> The code should provide a tolerance or range.


And like I've said before- it is YOUR responsibility to make them as close as possible. A tolerance is not a hack it for free card


----------



## BBQ

ponyboy said:


> And like I've said before- it is YOUR responsibility to make them as close as possible. A tolerance is not a hack it for free card


It is not within anyone's ability to comply.

Inspectors could fail every parallel job due to the current wording.


----------



## ponyboy

BBQ said:


> It is not within anyone's ability to comply.
> 
> Inspectors could fail every parallel job due to the current wording.


I agree. What I'm saying is hopefully people aren't using the obscure wording to justify doing crappy parallel installs. All we can do is the best we can


----------



## stuiec

ponyboy said:


> And like I've said before- it is YOUR responsibility to make them as close as possible. A tolerance is not a hack it for free card


 
This is an interesting proposition.......A back page (or two depending on province or state), with tear-out coupon style 'one free hack', or 'get out of inspection free' cards. Someone ought to print some up, and try em out on the next free wheelin' inspector they encounter.........just watch his face as you remove it from the code book before his disbeleivin eyes :laughing:.


----------



## gottspeed

You measure the longer run of the two and order both the same length. Then have a JB or trough to bunch up the slack in the shorter run. Its only a couple of feet...


----------



## don_resqcapt19

ponyboy said:


> I agree. What I'm saying is hopefully people aren't using the obscure wording to justify doing crappy parallel installs. All we can do is the best we can


Actually it is the neat looking parallel installations that are likely a code violation. The crappy looking installations probably look that way because they tried to keep the lengths matched.


----------



## Pete m.

BBQ said:


> Inspectors could fail every parallel job due to the current wording.


I agree and have just started rejecting every parallel installation I come across due to the current wording in the NEC.

I figure I'll keep it up until the current verbiage is changed.

Pete

p.s. I am not serious about the above in the least, but if I were one of "those guys" I certainly could.


----------



## ponyboy

don_resqcapt19 said:


> Actually it is the neat looking parallel installations that are likely a code violation. The crappy looking installations probably look that way because they tried to keep the lengths matched.


I think the same thing every time I see one of those picture perfect terminations and you just know its wrong.


----------



## hardworkingstiff

Thinking and planning really counts here. Someone mentioned 2 conductors per set, but, think about when you might have 8 conductors per set.

Sometimes simple things like burying a conduit a few inches deeper, or routing one or two with some extra sweep, or or or, can make a huge difference when it comes to getting the conductors the same length.


----------



## Mshea

Simple 2 cable or raceway installs are easiest but a micro ohm meter or a TDR can reduce length errors to less than %1. That said is even 1% acceptable? not literally it won't. Never mind the wire length it is pretty hard to get 2 connectors to have the same connection resistance.


----------



## htneighbors

Canadian Code
*12-108 Conductors in parallel​*​​​​(see Appendix B)​
(1) Conductors of similar conductivity in sizes No. 1/0 AWG copper or aluminum and larger shall be permitted
in parallel, provided that they are
(a) free of splices throughout the total length;
(b) the same circular mil area;
(c) the same type of insulation;
*(d) the same length*; and
(e) terminated in the same manner.
(2) The orientation of single-conductor cables in parallel, with respect to each other and to those in other
phases, shall be such as to minimize the difference in inductive reactance and the unequal division of
current.
(3) Conductors of similar conductivity in sizes smaller than No. 1/0 AWG copper shall be permitted in parallel
to supply control power to indicating instruments and devices, contactors, relays, solenoids, and similar
control devices, provided that
(a) they are contained within one cable;
(b) the ampacity of each individual conductor is sufficient to carry the entire load current shared by the
parallel conductors; and
(c) the overcurrent protection is such that the ampacity of each individual conductor will not be
exceeded if one or more of the parallel conductors becomes inadvertently disconnected.
(4) Where parallel conductors include grounded circuit conductors, each parallel set shall have a separate
grounded circuit conductor.
(5) Where the size of neutral conductors is reduced in conformance with Rule 4-022, neutral conductors
smaller than No. 1/0 AWG shall be permitted in circuits run in parallel, provided that they are installed in​conformance with the requirements of Subrule (1)(a), (b), (c), (d), and (e).


----------



## BBQ

gottspeed said:


> You measure the longer run of the two and order both the same length. Then have a JB or trough to bunch up the slack in the shorter run. Its only a couple of feet...


The supply houses around me are not that accurate.


----------



## thegoldenboy

BBQ said:


> The supply houses around me are not that accurate.


Ask for a cut of 380' and it can be + or - 20'.


----------



## ponyboy

thegoldenboy said:


> Ask for a cut of 380' and it can be + or - 20'.





BBQ said:


> The supply houses around me are not that accurate.


if its not too big a pain in the ass I like to order the quantity in one piece and make my own cuts. its not too bad with shorter runs and smaller conductors


----------



## Cletis

erics37 said:


> It's difficult. I think what BBQ is implying is that there probably isn't an installation anywhere that has paralleled conductors the exact same length. No one is that perfect :laughing: So to answer your question, *a few inches difference probably won't have any ill effect*


Tell that to a drunk female. Anyhow, I think as the distance changes the resistance and impedance changes logarythmically creating skin effect imbalances and harmonic distortions in 3 phase systems


----------



## mikestew

I worked on an oilfield job where it was defined that a tolerance up to 3% was acceptable. I don't think I would lose sleep over a few extra inches at each termination point on longer runs.


----------



## glen1971

I did a job in Saskatchewan and they were 15' long and the foreman made me string out the wires and tape one to the next to make sure that all 8 were the same length and cut nothing off.. The breaker end had NO room for slack, so all the slack was left in the 36" x 36" cabinet outside..


----------



## Fredman

Just completed a gen run that had 6 conductors per phase in two 4" pipes. Nothing like trying to line up 18 curly cuts of 3/0 240' long on a sidewalk. We had to end up with at least a few inches of difference. 

Now I can sleep knowing I'm not the only one and the install wont explode like an atomic bomb. ... :laughing:


----------



## don_resqcapt19

You can do a calculation based on the lengths of the conductors to get an idea of the current division between the sets, but there are other factors that can change the impedance of the paths at least as much as a small difference in lengths. 
The calculation would be:

C1=(total current/ ((1/L1) + (1/L2) + (1/L3))) * (1/L1))

C1= equals current in set #1
L1 = length set 1
L2 = length set 2
L3 = length set 3
(can be expanded to any number of parallel runs)


----------



## BBQ

Fredman said:


> Just completed a gen run that had 6 conductors per phase in two 4" pipes. Nothing like trying to line up 18 curly cuts of 3/0 240' long on a sidewalk. We had to end up with at least a few inches of difference.
> 
> Now I can sleep knowing I'm not the only one and the install wont explode like an atomic bomb. ... :laughing:


Keep in mind that group 'A' does not have to be the same length as groups B & C etc.

Only the conductors of the same phase have or neutral have to be the same. 

In other words you only had to deal with 6 at a time. 


Also, who planed that, six sets of 3/0 seems odd to me? Why not 3 sets of 500 or 600 etc?


----------



## hardworkingstiff

BBQ said:


> Also, who planed that, six sets of 3/0 seems odd to me? Why not 3 sets of 500 or 600 etc?


Probably someone looking at materials only. You get more allowed amps per pound of copper with smaller wire than you do with larger wire. Working 3/0 is a lot easier than 500 or 600. The only downside I see is number of physical connections.


----------



## BBQ

hardworkingstiff said:


> Probably someone looking at materials only. You get more allowed amps per pound of copper with smaller wire than you do with larger wire.


For sure and when I was planning some large PV installations multiple sets of 3/0 would save money as the raceways where very easy to install. They were just laying on sleepers across a roof.

But once you need to start running the conduits in areas that require bending the labor will quickly creep up on you. 

Not to mention six pull set ups takes a lot longer than three. 

It strikes me that someone may not have a tugger.


----------



## hardworkingstiff

BBQ said:


> For sure and when I was planning some large PV installations multiple sets of 3/0 would save money as the raceways where very easy to install. They were just laying on sleepers across a roof.
> 
> But once you need to start running the conduits in areas that require bending the labor will quickly creep up on you.
> 
> Not to mention six pull set ups takes a lot longer than three.
> 
> It strikes me that someone may not have a tugger.


I would stuff 2 sets of 3/0 in one conduit where I'd only put 1 set of 500 or 600 in a conduit. So, IMO, the pulls are not that much different (other than the 3/0 being sooooo much easier to manipulate, :laughing: , yes, I'm old.

I agree that if you don't have a tugger, forget 500's.


----------



## sbrn33

BBQ said:


> Also, who planed that, six sets of 3/0 seems odd to me? Why not 3 sets of 500 or 600 etc?


Probably someone that doesn't have a bender for anything larger than 2 inch.


----------



## Fredman

BBQ said:


> Keep in mind that group 'A' does not have to be the same length as groups B & C etc.
> 
> *Yup paralleled conductors not phases* :laughing:
> 
> Only the conductors of the same phase have or neutral have to be the same.
> 
> In other words you only had to deal with 6 at a time.
> 
> *I phrased it like we did all 18 at once. It was 6 at a time. *
> 
> Also, who planed that, six sets of 3/0 seems odd to me? Why not 3 sets of 500 or 600 etc?
> *
> The company owner. (Not me) He thought easier to deal with. *


****


----------



## Fredman

BBQ said:


> For sure and when I was planning some large PV installations multiple sets of 3/0 would save money as the raceways where very easy to install. They were just laying on sleepers across a roof.
> 
> But once you need to start running the conduits in areas that require bending the labor will quickly creep up on you.
> 
> Not to mention six pull set ups takes a lot longer than three.
> 
> *It strikes me that someone may not have a tugger*.


What makes you think that? I'd love to watch someone pull those 9 conductors up overhead thru 240' of pipe with 360 in bends using muscle alone. :laughing: :thumbup:


----------



## Fredman

sbrn33 said:


> Probably someone that doesn't have a bender for anything larger than 2 inch.


Grasshopper, you assume much. Some local union boys threw up the pipe not me. And when I say threw up, 




















Oh never mind. :laughing::laughing:


----------



## don_resqcapt19

Fredman said:


> Grasshopper, you assume much. Some local union boys threw up the pipe not me. And when I say threw up,
> ...


Half of the members of every group preform in the lower half of their group.


----------

