Pressure Atomizing Oil Burner Equipment and Systems – Room Temperature Thermostats
A room heating-cooling thermostat in the Honeywell classic round configuration popular throughout the latter 20th century; high style, gold plastic body, helical bimetal activated, low voltage, miniature mercury bulb switch, adjustable heat anticipator, with helical bimetal thermometer and heat-cool, fan on-off switch base, Type 87F, Honeywell, Circa 1975. [See also ID #220]
Technical Significance:
* Household temperature control technology, analogue and largely electro- mechanical and electro-magnetic in character, had reached its highest point of development by the mid 20th century, as represented here by the Honeywell T87F.
* The stage had been set for the progressive evolution of solid state, digital control HVACR control technology, which would soon dominate the field.
Industrial Significance:
* With the development of packaged mechanical cooling equipment for residential and commercial applications, the thermostat would become a multi-functional device, controlling room temperature during the heating cycle, as well as the cooling cycle and allowing switching between heating and cooling, in addition to the control of the air circulating fan on forced air systems. All this was to be accomplished within a single integrated device – to be popularly affordable and mass-produced.
* The miniaturized, single pole, double throw, mercury bulb switch required for cooling as well as heating was a masterpiece of design and mass production engineering, as was the entire configuration with small helical, bimetal, actuator and adjustable heat anticipator. It was executed in an attractive, moulded plastic, round, gold-colored format.
* A series of matching, optional, switch bases was provided by the manufacturer, in order to accommodate various switching functions, here heating/cooling on-off, fan on/automatic, part of the movement of equipment manufacturers to a comprehensive systems approach required of the times.
* The development of quiet, hermetic compressors in large capacities needed for home air conditioning applications, as well as the production and successful marketing of attractive packaged condensing units and evaporator coils for residential use contributed to the significant growth of the Canadian HVACR industry starting in the 1960’s