Refrigerating and Air Conditioning Pressure and Temperature Controls – Commercial
An early, commercial application, hydraulic bellows actuated, ambient temperature sensing, automatic temperature control; equipped with line voltage, tilting mercury tube switch and unusual rotary quick-make-and-break, manual on-off switch, for use in small food store, walk-in-refrigerators, Mercoid, 1930.
One of a matched set of similar Mercoid, early refrigeration system controllers, profiling a range of temperature/pressure control applications met by this pioneering manufacture, employing various design modifications made to same basic configuration. [See items ID # 153- 155]
Features:
Of special interest is the glass enclosed, mercury bulb switch, still in tact and operable. These are immensely fragile devices by definition and seldom have a long life, particularly after being taken out of service.
Unusual Danfield rotary quick-make-and-break, snop action, manual on-off switch, HEPC approved, with white porcelain base and black Bakelite cover and control knob,with handsome corporate logo.
Smith and Stone, with facilities in George town Ontario, 5 amp conduit fitting base for rotary switch
Large electrical junction box with 4 electrical connector knock-outs, representative of the wiring practice approved for commercial equipment of the period, which required heavy steel shielded twin conductor cable referred to as BX.
Technical Significance:
An exemplar of what is likely the first generation of wide spread, commercially manufactured and marketed pressure and temperature refrigeration controllers, popularly found in Canada.
The control, designed to mounted inside the refrigerated space, sensed the temperature through a copper sheathed bellows mechanism. A line voltage, manual on-off switch was attached for convenience. The rotary quick-make-and-break style was popular in the period, being extensively used on electrical stoves
The electrical switching properties of mercury had been discovered and the tilting mercury bulb would become the switching method of choice for much of the early 20th century for fractional HP applications. It was a period in which little empirical design data was available on alternating current switching. With an induction motor rating of up to 1 HP, and a split-phase rating of 1/4 HP this controller and most like it of the period was limited to fractional HP applications.
One of a matched set of similar Mercoid, early refrigeration system controllers, profiling a range of temperature/pressure control applications met by this pioneering manufacture, employing design modifications made to this basic configuration. This economic, robust configuration provided a platform readily adaptable to a wide range of commercial refrigeration field requirements [See items ID # 153- 155].
Industrial Significance:
A range of corporate names appear on the controls in the series, suggesting a range of corporate partnerships between Mercoid and other early players in the refrigeration control field: American Radiator Company; The Federal Gauge Company; Detroit Lubricator Company. The genre would give way within the decade to smaller, more sophisticated engineering approaches, yielding increasingly more precise refrigeration system control [See ID # 163 to 165].