Conduit Fill and conductors question

[Plano12345]

Hi all.

I have a 4" PVC Sch 40 in my design. This conduit run, with a few ground boxes, is approximately 600 feet before conductors go their separate ways.

In the 4" PVC, I am powering roadway equipment using a 120/240 service. Inside the 4" PVC, I have 18 conductors (mix of xhhw, neutral, and grounding). The area for all wires is about 3.75 square inches, which is about a 30% fill.

I know the NEC allows up to a 40% fill for 3+ conductors, but should I be looking to use a second conduit to make things easier on construction?

 

[infinity]

Have you factored in derating with your 18 conductors?

 

[Plano12345]

Have you factored in derating with your 18 conductors?

Yes. After 50% derating (between 10 and 20 CCC), I cover all circuit breakers.

 

[infinity]

What size conductors? Straight pull or multiple pulling points?

 

[Plano12345]

What size conductors? Straight pull or multiple pulling points?

Not sure on pull. Each circuit has a single device, ranging in distance from device to service at 500 feet to 1 mile. Ground boxes spaced appropriately every 500' or when a device is near. Assuming multiple pulling.

When all these conductors are together, the distance is about 500 or 600 feet with 4 total ground boxes from service to split. Conduit is crossing at an intersection.

Sizes:

4-#6
4-#4
2-#2
2-#1/0
2-#3/0
4-#350 kcmil

Conductors larger due to distance from service. The design area only had one service location within a mile of certain devices.

 

[augie47]

I would opt for additional conduit(s) taking "multiple pulls" and the cost of PVC vs labor into account.

 

[Fulthrotl]

Not sure on pull. Each circuit has a single device, ranging in distance from device to service at 500 feet to 1 mile. Ground boxes spaced appropriately every 500' or when a device is near. Assuming multiple pulling.

When all these conductors are together, the distance is about 500 or 600 feet with 4 total ground boxes from service to split. Conduit is crossing at an intersection.

Sizes:

4-#6
4-#4
2-#2
2-#1/0
2-#3/0
4-#350 kcmil

Conductors larger due to distance from service. The design area only had one service location within a mile of certain devices.

i'm guessing that the increase in size due to voltage drop far exceeds the derating value,
so there is no incentive to use multiple conduits as a way to escape the derating.

i've learned that 500' spools of wire, anymore, are ALWAYS short a little bit. ALWAYS.
used to be they were a bit longer, but that is so.... outmoded a concept, giving you what you pay for.

don't go past 475' between pull points on 500' spools. it will be a sub optimal experience.

use simpull, or equal. don't even consider doing it with anything else. you want to be able to pull this dry.

and make sure to tape a lock of your hair to the prints. whoever gets stuck pulling this will want it for the
voodoo doll they will make of you.

 

[pjholguin]

Hello,
Down South, most of our supply houses will not ship a spool wire straight from the manufacturer. They are required to spool out all wire orders to insure correct footage. We once had a pull that was ~900', they sent 1000' spools...well they were short and didn't find this out till we were close to the end of pull. Let's just say it was a long week, and many angry people...last time that happened. :happysad:

Next, I would propose using two conduits sized correctly...and separate the large conductors from the small(they tend to tangle). The bonus is you have future expansion room if necessary. Just my humble option.

Best to luck,
PJHolguin

i'm guessing that the increase in size due to voltage drop far exceeds the derating value,
so there is no incentive to use multiple conduits as a way to escape the derating.

i've learned that 500' spools of wire, anymore, are ALWAYS short a little bit. ALWAYS.
used to be they were a bit longer, but that is so.... outmoded a concept, giving you what you pay for.

don't go past 475' between pull points on 500' spools. it will be a sub optimal experience.

use simpull, or equal. don't even consider doing it with anything else. you want to be able to pull this dry.

and make sure to tape a lock of your hair to the prints. whoever gets stuck pulling this will want it for the
voodoo doll they will make of you.

 

[fmtjfw]

Consider using paralleled conductors for the larder sizes, it may save you money and pulling tension.

 

[cadpoint]

JMO
Be ready for a RFI, at bid. EC's will question you doing this. I would lay out 3 sets of Sched. 40
(be sure to spec Sched 80 on the up - maybe even ridge if soil or enviromental is a concern).

I'd add another 1" PVC (independant) everywhere for security or telephone/data - FA...

Once the earth is open it's not that much more to add pipes.

 

[Plano12345]

Follow Up:

I have a meeting with construction and the company installing the wiring on Thursday morning. This project is more of a design/build variety. Nothing has been installed (and won't for a few months) so there is plenty of room to build what is needed.

We will discuss the sitaution then and I can adjust the plans with whatever conduit is necessary. This meeting will save any RFIs.

Thanks for the help. My knowledge is in design and not construction, so I'm learning all I can. Greatly appreciated.

 

[kingpb]

somebody better be doing a pulling tension/sidewall pressure calc and checking jam ratio.

If there's a 90 on either end, better make them rigid steel conduit. The rope when pulling will cut right through the PVC conduit.

 

[GoldDigger]

Make that "if there is a 90 on the end where pulling"? Once the pull rope is past an entrance 90 there is no chance of cutting it.

Tapatalk!

 

[kingpb]

Make that "if there is a 90 on the end where pulling"? Once the pull rope is past an entrance 90 there is no chance of cutting it.

Tapatalk!

A valuable point... :thumbsup:

 

[don_resqcapt19]

...
4-#6
4-#4
2-#2
2-#1/0
2-#3/0
4-#350 kcmil
...

I would never consider making a pull with those combinations of conductors if there are any 90s in the run. I would be fine with a straight pull, but not with bends.

 

[Plano12345]

I would never consider making a pull with those combinations of conductors if there are any 90s in the run. I would be fine with a straight pull, but not with bends.

It's a straight pull until the first set of devices and some of the wires make right angles and branch off from there. Again, thanks for the information as all previous experience is in design with no one providing feedback via the construction side. This has been great information. What's obvious for many wasn't obvious for me at first glance except my gut.