Whats the difference between THHN-2 and THWN Cu. Wire, One in the same?

[stuartdmc]

We have a scenario here that we have an existing 200amp panel being feed with 4#3/0 THWN copper wire. We are upgrading the panel to a 400 amp panel, we are going to reuse the existing 200 amp feeders and simply add one additional 200 amp line to it, which will now become a paralleled 400 amp feeder to the new 400 amp panel.

The electrician ran the new line and pulled in 4#3/0 THHN-2 Copper wire.

My Question, Will THWN and THHN-2 comply with section 310-4 below?

PARALLEL FEEDERS SHALL COMPLY WITH NEC 310-4.
? BE THE SAME LENGTH
? HAVE THE SAME CONDUCTOR MATERIALS
? BE THE SAME SIZE IN CIRCULAR MILLS
? HAVE THE SAME INSULATION TYPE
? BE TERMINATED IN THE SAME MANNER

Thanks for your suggestions.

 

[infinity]

Where are you finding THHN-2? Did you mean THWN-2?

 

[Dennis Alwon]

As long as the existing wire has the same insulation and wire size you should be good. Why not just add a separate 200 amp panel and leave the other as is. This will not deal with parallel conductors and will not involve changing out a panel. I am also concerned about derating if the wires are in the same conduit.

If one is thwn and the other thwn-2 then there is a problem because one is rated 90C and the other 75C.

 

[stuartdmc]

Where are you finding THHN-2? Did you mean THWN-2?

Dry rated 90?C, Wet rated 75?C for THWN
Wet rated 90?C for THWN-2

 

[stuartdmc]

As long as the existing wire has the same insulation and wire size you should be good. Why not just add a separate 200 amp panel and leave the other as is. This will not deal with parallel conductors and will not involve changing out a panel. I am also concerned about derating if the wires are in the same conduit.

If one is thwn and the other thwn-2 then there is a problem because one is rated 90C and the other 75C.

The tenant wants 400 amp in their unit, the utility company will only provide the unit with one ponit of service which is a 400 amp service.
They ran (2) 2" conduits with 4#3/0 cu. in each to the new 400 amp panel.

 

[Dennis Alwon]

Dry rated 90?C, Wet rated 75?C for THWN
Wet rated 90?C for THWN-2

I don't see it as 90C. Thwn is rated 75?C for both dry and wet

 

[stuartdmc]

I don't see it as 90C. Thwn is rated 75?C for both dry and wet

http://www.abcwire.com/thhn-mtw-thhn2
see the attached link.

 

[rbalex]

What wasn?t clear to me is whether the second set of conductors is in the same or a separate raceway. Since California is still effectively on the 2008 NEC, 310.4(C) also comes into play if a separate raceway is used.

Whether THWN or THWN-2, I?d be much more concerned with how you determined the conductors were the same length than anything else. Only a few inches difference can severely affect the current divider between the conductors. Note: most, but not all, "old" THWN would have met the THWN-2 test critieria; the conductors just weren't tested and marked for it. Fundamentally, they are still both PVC insulated, nylon-jacketed conductors. If both are applied at a 75C rating, virtually nothing will be affected from that perspective.

 

[Dennis Alwon]

http://www.abcwire.com/thhn-mtw-thhn2
see the attached link.

Well I was going by the NEC so if the manufacturer rates it such and assuming it is not in a wet location then I do not see an issue. I am not sure what an inspector may say. It seems that the characteristics are not technically the same but for those conditions they are. Good question.

So is this what you have THHN/MTW/THHN-2 It is not even listed in the NEC

 

[rbalex]

Although it isn't absolutely true, almost every PVC insulated, Nylon-jacketed conductor in current US domestic production is multiple rated THHN-2/THWN-2/MTW. There's little eonomic justifcation for "losing" the "-2". The additional testing is minimal and they have virtually the same test requirements.

Some foreign manufacturers still only produce THHN/THWN or only THHN or THWN, but even most of them are beginning to fall in line with US domestic practice. It greatly expands their available US market for very little additional expense.

 

[Cow]

The wire he pulled in is also rated THWN, so I don't know what the problem is? I'd think the hardest part is rerunning another conduit right beside the old one so it's the same length, etc.