PEPCO No. 43

The PEPCO No. 43 was built by Heisler Locomotive Works and purchased new by the Potomac Electric Power Company, or “PEPCO,” in 1938. It is a rare type of “fireless” – or “thermos-bottle” – steam locomotive. These engines had no fuel-burning fireboxes to generate energy; instead, they had to “recharge” at large steam plants. During these recharging periods, the locomotive’s boiler was filled with “superheated water” that had been pressurized to reach temperatures of about 400 degrees F. When the boiler was filled to about ½ or ¾ capacity, the superheated water was “charged” with 250 psi of steam. For the PEPCO No. 43, the entire process would take just about 10 minutes.  

Once the locomotive was charged, the steam in the boiler pushed the engine forward. When the steam was gone, the pressure within the boiler dropped, causing the superheated water to boil and generate more steam. A fully charged thermos-bottle locomotive could only operate like this for a few hours on a single charge. This meant that all fireless locomotives had to operate within a short distance of their “home” stations. Thermos-bottle locomotives may be considered an early form of green technology: while fuel-burning steam engines emit hazardous smoke exhaust, fireless locomotives only emit steam vapor. 

Most fireless locomotives in the United States were used to push loaded coal cars around large-scale utility stations, like those owned by PEPCO. Because they were used for such specialized tasks, very few fireless locomotives were ever made. Heisler Locomotive Works only produced 50, and that was more than any other manufacturer in the nation.   

From 1938 to 1978, the No. 43 was used to haul coal, first at the Buzzard Point Power Station in Washington, DC, and then at the Potomac River Power Station in Alexandira, VA. At some point during its 40 years with the power company, the locomotive was renumbered as the PEPCO No. 1. Though the No. 1 was still in good condition when it retired in 1978, it was not strong enough to pull the newer, heavier coal hoppers of the late-1970s.