Intermodal temp control
The Heat King 430 provides temperature control for both rail and trailer applications. Its freeze-protection control is based on solid-state technology to avoid use of moving parts, and its controller is inside the unit enclosure for protection. A controller automatically starts the unit when coolant drops below 30 degrees. Return and supply air temperature sensors [...]
Source: http://www.truckersnews.com/intermodal-temp-control/