You've hit upon a common point of confusion in electrical codes and standards. Let's break it down: Southwire's DLO (Diesel Locomotive) Cable

Southwire, as a manufacturer, provides specifications for their cable based on their testing and design. Their 90°C ampacity rating for 2/0 DLO is 300 amps.

NFPA 79 Table 12.5.1

NFPA 79 (Electrical Standard for Industrial Machinery) provides a table of ampacities for various conductors at different temperature ratings. This table is intended as a general guide for wiring industrial machinery.Here's the core concept:

Manufacturer's specifications can often supersede general code tables if they are more restrictive or provide more detailed information.Here's how to approach this situation


Is it DLO Cable? The crucial question is whether you're specifically using DLO cable. DLO cable has a specific construction and application (originally for diesel locomotives, but now used in other high-flex, high-current applications). Table 12.5.1 is a general ampacity table and might not be specifically for DLO cable.2. Application Matters

Consider the actual application. Is the cable being used within an industrial machine and falling under the scope of NFPA 79? If so, NFPA 79 becomes very important.3.

NEC Applicability

While NFPA 79 is specific to industrial machinery, the National Electrical Code (NEC) also plays a role. The NEC generally requires you to follow the most restrictive of the manufacturer's specifications, listing, or the code tables. If the NEC requires you to follow NFPA 79 for this installation, then NFPA 79 controls.4.

Engineering Judgement & Documentation

Document, document, document! If you choose to use the manufacturer's higher ampacity rating, you must have sound engineering justification and documentation. This should include: The specific Southwire DLO cable part number. A statement that you're following the manufacturer's published specifications. Justification for why the application is suitable for DLO cable and why the manufacturer's ampacity is appropriate. Verification that all other applicable code requirements (overcurrent protection, derating for ambient temperature, number of conductors in a raceway, etc.) are being met.5.

AHJ Approval

It's always best practice to discuss this with the Authority Having Jurisdiction (AHJ, often the electrical inspector). Explain your reasoning and provide your documentation. They have the final say on whether your installation meets code.

In Summary



It is possible to use the manufacturer's higher ampacity rating for Southwire DLO cable (300 amps for 2/0) if you can justify it based on the manufacturer's specifications and the application. However, you must be sure that all other code requirements are met, that the application is suitable for DLO cable, and that you have proper documentation and AHJ approval. If there is any doubt or if the application isn't clearly suited for DLO cable, it's safer and easier to follow the more conservative ampacity from NFPA 79 Table 12.5.
1.Therefore, you might* be able to specify the Southwire cable and use the manufacturer's rating, but you need to do your homework, document everything, and get approval. If you are risk adverse or have not had a prior review from the AHJ, I would recommend using the lower amperage from Table 12.5.
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