Diesel locomotive cable, or DLO, started life feeding traction motors on diesel-electric locomotives. The name stuck, but the cable moved on a long time ago. Today it's the default heavy-flex power cable for drill rigs, mines, shipyards, generator hookups, and battery banks, because the same qualities that survived a locomotive underframe survive just about everything else.
Construction and Ratings
DLO is a dual-layer cable: EPR (ethylene propylene rubber) insulation under a thermoset CPE jacket, over finely stranded tinned copper (Class I stranding). The two layers split the work. EPR handles the electrical stress and heat, and the CPE jacket takes the oil, sunlight, and abrasion.
| Voltage | 2000V (2kV) |
| Temperature | 90°C dry / 75°C wet; RHW-2 rated versions hold 90°C wet or dry |
| Conductor | Tinned copper, Class I fine stranding |
| Listings | UL RHH/RHW-2, CSA RW90 |
| Sizes | 14 AWG through 1111 MCM |
Because it carries a UL listing, DLO can be installed in conduit, cable tray, ducts, and troughs like any listed building conductor. Sizes 1/0 AWG and larger are typically tray-rated. That listing is a bigger deal than it sounds; it's the main thing separating DLO from lookalike cables that inspectors won't accept in fixed wiring.
Where It Gets Used
- Locomotives and transit: generator-to-traction-motor power, auxiliary circuits on rail cars
- Drill rigs: portable power and control on land and offshore rigs
- Marine: shipyard service and drilling platforms
- Industrial plants: motor leads, switchgear jumpers, power distribution where routing is tight
- Backup power: UPS battery strings, battery banks, generator leads
The common thread is vibration, movement, or tight bends, plus an environment with oil or weather in it. Anywhere a stiff building wire would be fighting you the whole install, DLO routes like rope.
DLO vs Welding Cable
The two get confused constantly because both are flexible, rubber-jacketed, and black. The differences that matter: DLO is rated 2000V to welding cable's 600V, uses tinned rather than bare copper, adds a second insulation layer, and carries a UL listing welding cable usually lacks. Welding cable belongs on welder secondary circuits; DLO can go in the raceway. The full breakdown is in our DLO vs welding cable comparison.
Terminating DLO
Fine stranding needs matching hardware. A standard mechanical lug sized for Class B stranding will not clamp Class I strands properly, and NEC 110.14 requires connectors listed for fine-stranded conductors. In practice:
- Use flex-rated compression lugs, ideally with a chamfered barrel entry
- Strip carefully; nicked strands on a fine-strand conductor add up fast
- Never fold or trim strands to force a fit in an undersized barrel
Get the termination right and DLO connections stay cool for decades. Get it wrong and the lug is the failure point, not the cable.
What It Costs
DLO runs more per foot than THHN or XHHW of the same gauge. Fine stranding, tinned copper, and two layers of thermoset compound cost more to make. You're buying service life in places that destroy cheaper cable, so the premium tends to pay for itself the first time you don't have to re-pull a run.
We stock UL-listed DLO across the size range, cut to length. Sizing a run? The DLO ampacity chart has free-air ratings by gauge, and our DLO spec sheet (PDF) has part numbers, dimensions, and weights for every size from 14 AWG to 1111 MCM. Browse the full transit and locomotive cable category for related products.
