For the inspectors out there.

[cowboyjwc]

How many of you have ever verified that paralleled conductors were the same length?

To tell you the truth I really haven't worried about it for years, until yesterday when a young electrician had all of the neutrals and grounds in one conduit and all of the phase conductors in the other.

When I told him that they were also supposed to be the same length, I got that deer in the headlights look.

 

[Dennis Alwon]

That install isn't legal even if they were the same length. Also as long as each parallel phase is the same then that is okay. All the phases don't need to be the same length as the other phases.

 

[infinity]

I would eyeball both ends on a short run, like transformer secondary conductors. On long runs that snake their way through a building it's nearly impossible to actually know if they're even close in length.

 

[cowboyjwc]

That install isn't legal even if they were the same length. Also as long as each parallel phase is the same then that is okay. All the phases don't need to be the same length as the other phases.

Sorry that part was being fixed. Yes they do, look at 310.4(B)(1)

Sorry, each phase must be the same length you are correct. Read your response to fast. I do that a lot.

 

[infinity]

Also as long as each parallel phase is the same then that is okay. All the phases don't need to be the same length as the other phases.

Sorry that part was being fixed. Yes they do, look at 310.4(B)(1)

I agree with Dennis, only the conductors of the same phase or neutral are required to be the same length. For example the parallel blacks could be 100', the reds 103', the blues 106' and the neutrals 115'. In many switchboards the neutrals are much longer because they're often landed at the bottom of the enclosure.

 

[Dennis Alwon]

Sorry that part was being fixed. Yes they do, look at 310.4(B)(1)

They only need to be the same length for each phase. Phase A paralleled conductors do not need to be the same length as phase B paralleled conductors. All those in "A" must be the same

 

[cowboyjwc]

They only need to be the same length for each phase. Phase A paralleled conductors do not need to be the same length as phase B paralleled conductors. All those in "A" must be the same

Yes I went back and corrected my answer before I saw the last two.

Oh and for those of you going "huh?" to my code section, in the 2011 it's 310.10(H)(1)

 

[texie]

As already said, on short runs give the eyeball check. On longer runs, while not practical to measure, at least the conduits are close together and following the same path. I've seen guys run 2 or more conduits going a completely different path.:happysad:

 

[John120/240]

I'm confused it happens a lot sometimes. Three conduits enter the bottom of the gear, left to

right one , two, three. The lugs are left & above #one conduit. So won't phase A,B, &C, be

longer in conduit # three than phase A B & C in conduit # one ?

 

[infinity]

I'm confused it happens a lot sometimes. Three conduits enter the bottom of the gear, left to

right one , two, three. The lugs are left & above #one conduit. So won't phase A,B, &C, be

longer in conduit # three than phase A B & C in conduit # one ?

It very well could be depending on the arrangement at the other end or if the installer made an effort to get them the same length.

 

[rcarroll]

How many of you have ever verified that paralleled conductors were the same length?
.

Interesting question!
Conductors are pulled in the same length.
EC cuts to fit into switchgear. POCO cuts to fit transformer lugs.
In 35 years I've never heard of a problem with parallel conductors not of the same length.
Have any of you?

 

[don_resqcapt19]

If the installation looks neat, and there are more than two conduits, then it is unlikely that the parallel conductors are of the same length

 

[kwired]

I'm confused it happens a lot sometimes. Three conduits enter the bottom of the gear, left to

right one , two, three. The lugs are left & above #one conduit. So won't phase A,B, &C, be

longer in conduit # three than phase A B & C in conduit # one ?

If you don't take care to ensure they are same lengths then yes they likely will not be same length.

Not only does code say each conductor of a parallel set be same length, it must also be size, type, etc. You should try to achieve same characteristics even if code did not say so. Having differences in characteristics is going to effect overall impedance of the conductors that make up the set. The one with the lowest impedance is the one that will carry the most current of the set, ideally you want them all the same so you don't end up with one that is significantly lower impedance and ends up carrying enough that it is overloaded. That situation kind of defeats the purpose of paralleling in the first place.

 

[kwired]

Interesting question!
Conductors are pulled in the same length.
EC cuts to fit into switchgear. POCO cuts to fit transformer lugs.
In 35 years I've never heard of a problem with parallel conductors not of the same length.
Have any of you?

I'm sure the longer the conductors are the more difference can be tolerated without too much negative effects. Quite often we see larger services, feeders, that are not necessarily loaded to 100% of the ampacity, so that may help prevent some failures that may otherwise happen if it was loaded hard and frequently.

 

[cowboyjwc]

I'm confused it happens a lot sometimes. Three conduits enter the bottom of the gear, left to

right one , two, three. The lugs are left & above #one conduit. So won't phase A,B, &C, be

longer in conduit # three than phase A B & C in conduit # one ?

Yes, that's where it gets tricky, according to the code, if you had three conduits and because of just the way it has to be with bends and such conduit one is 100' and two is 105' and three is 110', most of the wires would end up being 110' because wires of the same phase have to be the same length, so the black in conduit one and two has to be the same length as the black in conduit three.

 

[kwired]

Yes I went back and corrected my answer before I saw the last two.

Oh and for those of you going "huh?" to my code section, in the 2011 it's 310.10(H)(1)

You have the right code section - I was going to add that you can have all phase A in one conduit , B in another, .... IF it is underground in non metallic raceway, but am not finding that - did that allowance disappear?

 

[cowboyjwc]

Interesting question!
Conductors are pulled in the same length.
EC cuts to fit into switchgear. POCO cuts to fit transformer lugs.
In 35 years I've never heard of a problem with parallel conductors not of the same length.
Have any of you?

No I haven't, but this is where you get into the question of do I really follow the code all the time or only when it's convienent for me. Now others have explained why they should be the same length, so whether it's ever been a problem or not could just be a matter of luck.

 

[cowboyjwc]

You have the right code section - I was going to add that you can have all phase A in one conduit , B in another, .... IF it is underground in non metallic raceway, but am not finding that - did that allowance disappear?

No I saw it too, but I can't remember where it was right now and I'm off work. You guys have a great weekend.

 

[Dennis Alwon]

If I were doing parallel runs I would have my conductors measured out before they enter the conduits and then if any wire is cut from one I would cut the same amount on the other otherwise I would bend the excess inside the panel if possible.

 

[texie]

You have the right code section - I was going to add that you can have all phase A in one conduit , B in another, .... IF it is underground in non metallic raceway, but am not finding that - did that allowance disappear?

I think you are looking for 300.5(I) Exception 2.