DLO Ampacity Calculations for Permanent Installations

Written by By Paul Cardinal, P.E., Shell Exploration and Production

Excerpt from DLO for Permanent Installations paper

In safety conscious environments where even minor injuries must be documented, Diesel LOcomotive
(DLO) cable helps avoid the cuts, scrapes and bruises commonly seen when installing large diameter cable
in tight quarters. In addition to facilitating installation, properties required for railroad service, such as oil
resistance and limited vibration transmittal, translate well to standby generator applications.

Unfortunately, DLO has several hurdles to clear before acceptance in permanent installations by Authorities
Having Jurisdiction (AHJ). Neither “Diesel Locomotive” nor “DLO” is mentioned in the directory of the NEC.
Sizes, such as 535 kCMIL, are absent from NEC tables. DLO is flexible and NEC Article 400 governing
flexible cords and cables states that flexible cords and cables are not permitted as a substitute for the fixed
wiring of a structure.

Before dismissing DLO cable for permanent installations, however, a closer look is required at both the
cable and NEC. As shown in Fig. 1, DLO is UL listed as Type RHW-2. A quick look at the NEC reveals that
RHW-2 is found in Table 310.13(A) rather than with flexible cables in Table 400.4. By NEC definition, DLO is
a conductor for general wiring.