Conduit fill (250kcmil)

J

Josabrock77

Member
OK, so I know this is a very very basic question but these inspectors have me in a rage. I have a 200 amp multifamily service. I have three 250 KCMIL aluminum XHHW conductors feeding a meter socket. Can someone please tell me what size schedule 40 PVC conduit/riser you can use that’s code compliant ? (The riser is about 14’ with a weatherhead) very basic I know!!!
After a couple responses I will explain more- I just want unbiased opinions !
 
This is what the inspector sent me!!! Which total blew my mind !!! 🤯

(From chief electrical inspector below)

aluminum XHHW appear to fit in 2" PVC since the total conductor area (≥1.026 in?) is less than 40% of the conduit area (≥1.316 in?).


However, Annex C is the governing reference for maximum number of conductors permitted in a given raceway. Annex C tables are based on tested dimensions and insulation tolerances, not just theoretical areas. In Annex C, Table C.11 (PVC Sch. 40, XHHW/XHHW-2), three (3)


× 250 kcmil AL conductors require a 3" raceway, not 2".


So while the math seems to work out on paper, the NEC requires us to use the Annex C values for compliance. That's why the installation must be in 3"
 
I would ask him what Table he is referencing.
2"is adequate even with Sch80.
 
Josabrock77 said:
This is what the inspector sent me!!! Which total blew my mind !!! 🤯

(From chief electrical inspector below)

aluminum XHHW appear to fit in 2" PVC since the total conductor area (≥1.026 in?) is less than 40% of the conduit area (≥1.316 in?).


However, Annex C is the governing reference for maximum number of conductors permitted in a given raceway. Annex C tables are based on tested dimensions and insulation tolerances, not just theoretical areas. In Annex C, Table C.11 (PVC Sch. 40, XHHW/XHHW-2), three (3)


× 250 kcmil AL conductors require a 3" raceway, not 2".


So while the math seems to work out on paper, the NEC requires us to use the Annex C values for compliance. That's why the installation must be in 3"
Click to expand...
You have a dopey inspector. Annex C is not part of the code. And he cannot even read the tables correctly.

C Conduit, Tubing, and Cable Tray Fill Tables for Conductors and Fixture Wires of the Same Size
This informative annex is not a part of the requirements of this NFPA document but is included for informational purposes only.
Click to expand...

Annex C.JPG
 
augie47 said:
I would ask him what Table he is referencing.
2"is adequate even with Sch80.
Click to expand...
He said annex C table C.11 !!! I just don’t understand what he’s looking at, maybe he has a plumbing code book(WTF) I was starting to think I was missing something or I was an idiot
 
It’s actually all 3 of the inspectors on a group chat- and they are adamant that I’m wrong and I need a 3”pvc, I’m sitting here reading the code then I did the math for the cross sectional area and still came out with 2”… I’m glad I’m not senile just yet
 
Josabrock77 said:
It’s actually all 3 of the inspectors on a group chat- and they are adamant that I’m wrong and I need a 3”pvc, I’m sitting here reading the code then I did the math for the cross sectional area and still came out with 2”… I’m glad I’m not senile just yet
Click to expand...
The fact that they're telling you that you have to use annex C is already an indication that they're way off base. Annex C is for informational purposes only is is not part of the code so no inspector should be quoting it as a code requirement.
 
Josabrock77 said:
However, Annex C is the governing reference for maximum number of conductors permitted in a given raceway. Annex C tables are based on tested dimensions and insulation tolerances, not just theoretical areas. In Annex C, Table C.11 (PVC Sch. 40, XHHW/XHHW-2), three (3)
Click to expand...
How does the clown think the Annex is a governing reference when it's not part of the code and as Infinity pointed out he can't even read the Tables in it. He also needs to read the title of the Annex and the commentary accompanying it.

Informative Annex C Conduit and Tubing Fill Tables for Conductors
and Fixture Wires of the Same Size
This informative annex is not a part of the requirements of this NFPA document but is
included for informational purposes only.
Click to expand...
 
Annex C only works if all conductors are same size as well.

If you had a reduced neutral which is a pretty common thing on service/feeders in this sort of application Annex C doesn't address mixed conductor sizes in the raceway.

It is simply a convenience thing should all conductors be the same size. Annex C wasn't always there. Before then you had to use chapter 9 tables to figure out raceway fill in all cases. I want to say they added Annex C in 1999 NEC?
 
kwired said:
Annex C wasn't always there. Before then you had to use chapter 9 tables to figure out raceway fill in all cases. I want to say they added Annex C in 1999 NEC?
Click to expand...
Prior to the 1996 NEC there were no tables for different types of raceways. The tables were based in the trade sizes of all of the raceways and specific conductor insulation types. Those tables go as far back as 1965 (the farthest back I checked).
 
infinity said:
Prior to the 1996 NEC there were no tables for different types of raceways. The tables were based in the trade sizes of all of the raceways and specific conductor insulation types. Those tables go as far back as 1965 (the farthest back I checked).
Click to expand...
Agree it was simple when all raceways of a given size could have the same fill.
 
Seven-Delta-FortyOne said:
If this is the riser with the weatherhead, serving the meter socket, it’s not even governed by the NEC, it’s a poco issue.
Click to expand...
That would only apply if the utility is responsible for installing and maintaining the riser. Some utilities around the country do that but most, including in CA the owner is responsible for installing and maintaining the riser. It must be installed to NEC requirements but the utility might have additional requirements for minimum sizing/support.
 
Josabrock77 said:
This is what the inspector sent me!!! Which total blew my mind !!! 🤯

(From chief electrical inspector below)

aluminum XHHW appear to fit in 2" PVC since the total conductor area (≥1.026 in?) is less than 40% of the conduit area (≥1.316 in?).


However, Annex C is the governing reference for maximum number of conductors permitted in a given raceway. Annex C tables are based on tested dimensions and insulation tolerances, not just theoretical areas. In Annex C, Table C.11 (PVC Sch. 40, XHHW/XHHW-2), three (3)


× 250 kcmil AL conductors require a 3" raceway, not 2".


So while the math seems to work out on paper, the NEC requires us to use the Annex C values for compliance. That's why the installation must be in 3"
Click to expand...
This kind of sounds like AI or a “AI influenced”response.
 
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