Inspector correction: main dwelling feeder is passing in the footprint of the house

[Alexis]

Hello,

Today I got a correction for something that I think is complete nonsense. I would appreciate your feedback:


My main conduit for the new 400A disconnect is passing throut the ceiling of the carport (he calles it "under the building") as it was requested by LADWP (Photos attached). He is trying to tell me to go around, on the side of the the building. Am I wrong here? The "code language" seems totally not applicable here?

The other violation he gave us is my 3in LB. I have 2 sets of 3/0 CU feeders coming down to the disconnect. In the LB it stated max 3x 250MCM. Does it then mean that we can't use any 3in LB for 400A services? As 1 set of 250MCM is too small and 2 sets of 3/0 too much.

Thank you so much for your feedback!

 

[infinity]

I don't see any conductors inside of the building so what's the issue?

 

[Elect117]

I would have said 110.26(E)(2)(C) - The water pipe is in the dedicated space + spill protection from the water pipe. It could also be sewer. I can't tell.

If you need a ladder to get to the meter LADWP will prob fail you. I have never seen them okay with a meter that is above 6'3".

I don't see it as inside the building.

If you take the area of 3x250 and subtract it by the area of 6x3/0 then the inspector is right. 314.28(C)(3). Basically, the area that the conduit body is listed for can not be exceeded.

 

[charlie b]

To be "under the building" the conductors would have to be below the carport's parking surface (i.e., in contact with dirt). I agree with you; this "violation" is nonsense.

 

[charlie b]

I would have said 110.26(E)(2)(C) - The water pipe is in the dedicated space. . . .

Meters are not included in the list of equipment that requires "dedicated space."

 

[infinity]

The other violation he gave us is my 3in LB. I have 2 sets of 3/0 CU feeders coming down to the disconnect. In the LB it stated max 3x 250MCM. Does it then mean that we can't use any 3in LB for 400A services? As 1 set of 250MCM is too small and 2 sets of 3/0 too much.

He's correct. Your conductor fill cannot exceed what's marked inside of the conduit body. You'll probably need some type of pull box if the POCO allows it ahead of the meters.

 

[Elect117]

Meters are not included in the list of equipment that requires "dedicated space."

I thought they might have something in those boxes that would require it. But now that you mention it, that is not likely.

 

[infinity]

I dont have my codebook but weren't meter enclosures added in the 2020 NEC?

 

[ptonsparky]

The utility would have clearance requirements for the meter.

 

[charlie b]

I dont have my codebook but weren't meter enclosures added in the 2020 NEC?

I will have to look it up later. But my belief is that the rule only includes components that might need room in the future for installation of more conduits.

 

[wwhitney]

The other violation he gave us is my 3in LB. I have 2 sets of 3/0 CU feeders coming down to the disconnect. In the LB it stated max 3x 250MCM.

The applicable code section is 314.28(A)(3), the last paragraph of which says:

"For other conductor sizes and combinations, the total cross-sectional area of the fill shall not exceed the cross-sectional area of the conductors specified in the marking, based on the type of conductor identified as part of the product listing."

The informational note after said the marking is based on XHHW insulation by default.

250 MCM XHHW conductors have a cross-sectional area including insulation of 251.9 mm² per Chapter 9 Table 5. If you are using XHHW, then 3/0 Cu conductors have a cross-sectional area of 170.5 mm². So if this is single phase and you have 4 of those for the ungrounded conductors, that leaves you with 3*251.9 - 4 *170.5 = 73.7 mm². The largest grounded conductor that would fit is #2 Cu XHHW (ok, that cheats by 0.24 mm²).

But Table 250.102(C)(1) says the minimum size grounded conductor when the ungrounded conductors have a combined area of 500 MCM is 1/0 Cu. So there's not enough room for even the minimum size grounded conductor. And using THWN-2 instead of XHHW insulation doesn't help.

On this one the inspector is correct.

Cheers, Wayne

 

[wwhitney]

I dont have my codebook but weren't meter enclosures added in the 2020 NEC?

No, not the 2020 NEC.

The 2023 NEC added "service equipment" to the list of equipment in 110.26(E), but meters don't meet the definition of "service equipment."

Cheers, Wayne

 

[Alexis]

Thank you all so much for your responses, this helps a lot!

I'm very surprised that standard 3in LB can't support 400A when utility ESR directly calling for it.. I also just thought that we could use 2 pairs of 2/0, since we can use derating for the feeders in res building, but I think we are still slightly over.

Maybe in this case I may try to go 4in LB and use reducing bushings.. and will try to argue my way of moving the conduit and loosing day of work and more money in materials (current wires will be too short) for a made up correction

 

[don_resqcapt19]

Thank you all so much for your responses, this helps a lot!

I'm very surprised that standard 3in LB can't support 400A when utility ESR directly calling for it.. I also just thought that we could use 2 pairs of 2/0, since we can use derating for the feeders in res building, but I think we are still slightly over.

Maybe in this case I may try to go 4in LB and use reducing bushings.. and will try to argue my way of moving the conduit and loosing day of work and more money in materials (current wires will be too short) for a made up correction

If the conductors are 4 AWG and larger and the conduit is anywhere near a 40% fill, a standard conduit body will almost never be suitable.
You can use a larger conduit body with reducers as you suggested or a mogul conduit body designed for the purpose.
I like the Reddot MALB series but they are pricey. MALB-8

 

[Alexis]

If the conductors are 4 AWG and larger and the conduit is anywhere near a 40% fill, a standard conduit body will almost never be suitable.
You can use a larger conduit body with reducers as you suggested or a mogul conduit body designed for the purpose.
I like the Reddot MALB series but they are pricey. MALB-8
View attachment 2573822

Thank you for the advice. My 3in conduit fill is only 17.19% (6x3/0) so far from getting close, so that is one of the things that surpriced me. I usually used my conduit fill calculator with thinking that LBs will be matching it..

 

[Todd0x1]

He's correct. Your conductor fill cannot exceed what's marked inside of the conduit body. You'll probably need some type of pull box if the POCO allows it ahead of the meters.

without having looked at a datasheet, would a mogul conduit body work?

 

[don_resqcapt19]

Thank you for the advice. My 3in conduit fill is only 17.19% (6x3/0) so far from getting close, so that is one of the things that surpriced me. I usually used my conduit fill calculator with thinking that LBs will be matching it..

I really should not have mentioned fill as the issue is based on the required 6x of the conduit size between the openings for a 90° pull.

The volume only comes in when converting from the conductors shown on the LB and the ones that you are installing. See post #11.

 

[Fred B]

Thank you for the advice. My 3in conduit fill is only 17.19% (6x3/0) so far from getting close, so that is one of the things that surpriced me. I usually used my conduit fill calculator with thinking that LBs will be matching it..

It's not just the volume fill but bend radius for the conductors.

 

[kwired]

Thank you all so much for your responses, this helps a lot!

I'm very surprised that standard 3in LB can't support 400A when utility ESR directly calling for it.. I also just thought that we could use 2 pairs of 2/0, since we can use derating for the feeders in res building, but I think we are still slightly over.

Maybe in this case I may try to go 4in LB and use reducing bushings.. and will try to argue my way of moving the conduit and loosing day of work and more money in materials (current wires will be too short) for a made up correction

I see no reason you can't use 2 sets of 2/0 copper in parallel with the 83% rule but they would need to be in separate raceways. The table(depending on which NEC applies) simply says 400 copper for 400 amps.

If all in one raceway the required ampacity adjustment won't let it work, you end up with adjusted ampacity of 156 per conductor times 2 gives you net of 312. The 83 percent allowed for 400 amps is 332.