(under the class definition) Devices controlling the supply of heating fluid to an exchange or surface heater directly by means of a thermostat of the expanding solid type responsive to the temperature of the fluid heater.
SEE OR SEARCH THIS CLASS, SUBCLASS:
5, 43, 59+, 66, 96, and 101, for the type of thermostat used and control devices operated thereby.
33, for closed fluid heaters with similar controls.
93, for devices where flow is regulated by the temperature of the flowing fluid.
