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 and extended capillary tube sensor; with 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 and engineering by the manufacturer, as well as the various effects of natural ageing in use, disuse, abuse and abandonment.
Features:
“Silver dollar” style hydraulic power element; original porcelain electrical box connector representative of practice in the period; original wiring harness, using an early form of twin, stranded wire, SJ cable; original two wire black backbite attachment cap; Cast enclosure overcoated with aluminium paint, employing a dispersion of aluminium particles in petroleum-based paint vehicle, new for the period.
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 ,water proof [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.
Other significant aspects of the controller include: “Silver dollar” style hydraulic power element; original porcelain electrical box connector representative of practice in the period; original wiring harness, using an early form of twin, stranded wire, SJ cable; original two wire black backbite attachment cap
Industrial Significance:
See above
