Below is the text of an article from the November 1928 issue of the Frisco Employees Magazine. Did this system ever catch on with any railroad or rail car manufacturer?
To properly protect perishables-such as fruits and vegetables in transit during
the winter, there must be provision made for the temporary conversion of refrigerator cars to heater cars, or other cars having permanent heater apparatus must be used. Much work is being done along the lines of development of heaters and various types using live steam or employing alcohol, kerosene, coal, or charcoal as fuel have been used; some heat storage systems have also been devised.
One system of heating used with some success derives its heat from steam supplied by the locomotive; a steam duct leading from the locomotive passes under each car to a connection with piping in the interior. A thermostat automatically shuts off the steam when the interior reaches a predetermined temperature, and prevents the car from becoming overheated. This system eliminates the fire risk and the damage to the lading often resulting from the gases produced by combustion in those types of heaters using fuels. In a test of this system, made when the outside temperature varied 48 deg. F. -from 28 deg. F. to minus 20 deg. F.-the temperature inside of the car varied only 8 deg. F.-from 52 deg. to 60 deg. F.
Another steam heating system takes advantage of the heat absorbing and retentive properties of porous terra cotta. This system makes use of the same style of train pipe, valves, traps and hose that are used on passenger train equipment. The train pipe is located below the car floor; its lowest point is at the center of the car where an automatic trap provides an outlet for the water of condensation. At each end of the car a branch pipe extends to one side and passes up through the floor to a heat storage tank or reservoir-an iron cylinder about 8 inches in diameter and about 5 feet long-located in the space below the ice bunker. This cylinder is placed at an angle so that the water in condensation flows to the lower end and passes out through the branch pipe; an automatic air valve on the upper end controls the admission of steam. The reservoir is filled with specially made porous terra cotta bricks which have corrugated surfaces, and facilitate the passage of live steam from the locomotive--or a stationary boiler-to all parts of the reservoir. This insures the absorption of heat by the bricks which enables them to radiate heat for many hours after the steam supply
has been cut off-in one instance, with the outside temperature minus 18 deg. F., a sidetracked car retained, for twenty-four hours, sufficient heat to prevent freezing. A thermometer placed in sight from the outside of the car permits an easy check on the temperature inside of the car. The action is such as to cause a mild circulation of air in the car; the cool air sinks to the floor and is drawn toward the heater, the warm air passes upward and is diffused throughout the car from above.