Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Service and Feeder Conductors
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## Aluminum is standard industry practice for large feeders and services; for sizes of 350 kcmil and above it delivers significant cost and weight savings with no performance penalty when AA-8000 alloy and listed AL/CU connectors are used and terminations are properly torqued. {note}
−## Specifying copper for large feeders without evaluating aluminum is a common and costly oversight; the design shall document the basis for a copper selection at 350 kcmil and above. {note}
+## Specifying copper for large feeders without evaluating aluminum is a common and costly oversight; the design shall document the basis for a copper selection at 350 kcmil and above.
## Conductors shall be copper or AA-8000 series aluminum alloy as scheduled for each feeder and service run.
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## Where a calculated conductor ampacity does not correspond to a standard overcurrent device rating, the next-higher standard device rating may be used in accordance with NEC 240.4(B) for devices rated 800 A and below.
−## The 80%-case default for a 200 A service or feeder is 4/0 AWG copper THHN/THWN-2 (230 A at the 75°C column) or 350 kcmil aluminum XHHW-2 (260 A at the 75°C column). {note}
+## The default for a 200 A service or feeder is 4/0 AWG copper THHN/THWN-2 (230 A at the 75°C column) or 350 kcmil aluminum XHHW-2 (260 A at the 75°C column). {note}
+## The feeder or service overcurrent device rating shall be specified, sized to the noncontinuous load plus 1.25 times the continuous load it serves.
+
```datasheet
label: Feeder or service rating (overcurrent device)
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## A reduced neutral is permissible for predominantly linear loads, but nonlinear loads such as variable-frequency drives and electronic equipment drive third-harmonic current that adds on the neutral and warrants a full-size or oversized neutral. {note}
−## Sizing a reduced neutral on a feeder that serves significant nonlinear load is a recurring error that produces neutral overheating; the harmonic content shall be evaluated before reducing the neutral. {note}
+## Sizing a reduced neutral on a feeder that serves significant nonlinear load is a recurring error that produces neutral overheating; the harmonic content shall be evaluated before reducing the neutral.
## The grounded (neutral) conductor shall be sized for the maximum unbalanced load calculated under NEC 220.61.
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## Paralleling distributes a single phase across two or more conductors per phase, and becomes the practical configuration for feeders of roughly 400 A and above where a single conductor would be unwieldy or unavailable. {note}
−## Parallel conductors are permitted only in sizes of 1/0 AWG and larger; conductors smaller than 1/0 AWG shall not be paralleled regardless of the load calculation. {note}
+## Parallel conductors are permitted only in sizes of 1/0 AWG and larger; conductors smaller than 1/0 AWG shall not be paralleled regardless of the load calculation.
−## For the parallel set to share current equally, all conductors of a given phase must be identical, and the same is required of the neutral set; any difference in length, material, or termination forces an unequal current split and localized overheating. {note}
+## For the parallel set to share current equally, all conductors of a given phase must be identical, and the same is required of the neutral set; any difference in length, material, or termination forces an unequal current split and localized overheating.
−## Specifying parallel conductors smaller than 1/0 AWG, or allowing unequal conductor lengths between parallel raceways, are recurring field problems that the specification shall foreclose explicitly. {note}
+## Specifying parallel conductors smaller than 1/0 AWG, or allowing unequal conductor lengths between parallel raceways, are recurring field problems that the specification shall foreclose explicitly.
## Conductors shall be paralleled only in sizes of 1/0 AWG and larger.
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## A direct aluminum-to-copper connection requires a connector listed and marked AL/CU; using a copper-only lug on an aluminum conductor causes a high-resistance joint that overheats and fails, and is a leading cause of service fires. {note}
−## Compression terminations must be made with the matching die and crimp count from the connector's listing; a connector crimped with the wrong die is not a listed termination. {note}
+## Compression terminations must be made with the matching die and crimp count from the connector's listing; a connector crimped with the wrong die is not a listed termination.
## Connectors and lugs shall be listed to UL 486A-486B and shall be marked for the conductor material on which they are used.
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## Compression connectors shall be installed with the die, crimp count, and tooling specified in the connector manufacturer's listing.
−## The conductor size selected for each termination shall fall within the listed conductor range of the lug; where it does not, an oversized-lug kit shall be specified rather than forcing the conductor into an undersized lug. {note}
+## The conductor size selected for each termination shall fall within the listed conductor range of the lug; where it does not, an oversized-lug kit shall be specified rather than forcing the conductor into an undersized lug.
```datasheet
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default: 0
```