My Heating plus Air Conditioning companions plus I dedicatedly worked together to invent cooling plus heating units for trains of all types for years.
Most trains have an individual furnace for each part of the train.These old school gas furnaces are a lot like a huge portable space furnace that takes a super long time to heat up a single train cart.
I once rode a train in mid Winter season plus was beyond disappointed at how slow the huge portable space furnace heater up the damn train. I asked a few of my Heating plus Air Conditioning friends to come over after that to my furnace plus AC shop plus help myself and others develop something new. The people I was with and I took apart an old portable space furnace plus tried to decide if we could make a better portable space furnace that would heat up a train faster, however to no avail. Instead, we decided to completely scrap the method of a different portable space furnace plus try out a style of hydronic heating that could heat the whole entire train with 1 single furnace. The people I was with and I would install a seriously huge water boiler to the train caboose that attached to the rest of the train through heavy duty water lines. This would enable the whole train to be heated with 1 hydronic oil furnace plus it worked. The people I was with and I sold our first train hydronic oil furnace to a company who was in desperate need of a new furnace for his train. When the hydronic furnace heated the train way better plus more efficient than any other furnace they had ever had seen before.