Refrigerating and Air Conditioning Pressure and Temperature Controls – Commercial
An early automatic temperature control for commercial refrigeration\r\napplications, employing a “silver dollar” style hydraulic power element, capillary tube sensor and bulb with liquid tight dealing gland; line-voltage, four pole open contact switch, mounted in heavy two-piece, screw assembled, cast enclosure with rubber sealing gasket, Tag Snapon, Circa 1928
One of a set of two controllers, demonstrating variations in design, engineering and application by the manufacturer, as well as the various effects of natural ageing in use, disuse, abuse and abandonment.
Features:
Brass, screw threaded, water tight sealing gland allowing immersion of temperature sensing bulb in liquid bath; “Silver dollar” style hydraulic power element; Cast enclosure overcoated with black paint
Technical Significance:
Representative of one of the broad range of approaches to the engineering, design and construction of temperature controllers being experimented with by “me too manufactures”. It was a period of rapid growth in what appeared to be an expanding, economically attractive market place
The heavy, open style, four pole switching marked the controller as able to handle larger HP applications than the mainstream of tilting mercury bulb controllers of the time – although current and HP ratings are not shown
The unusual attention given here to robust, waterproof [drip proof] construction and other design attributes is symptomatic of the period. It was one in which, in the absence of field-based experience and codified engineering data, manufactures tended, in many ways, to over design. The effects of progressive simplification can be seen in other controllers in the 7.02 series.
Industrial Significance:
See above