7.02-5: Frigidaire 1937 Automatic Pressure Control

HHCC Accession No. 2006.036HHCC Classification Code: 7.02-5

Hydraulic bellows actuated, automatic pressure control for mid 20th century, commercial refrigeration applications, with dual high-low pressure functions, for control of low-side temperature and high pressure cut-out, a new generation thermal motor overload protection and manual reset, Frigidaire, Circa 1937:

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7.02 Refrigerating and Air Conditioning Pressure and Temperature Controls - Commercial




Frigidaire, Div of General Motors Corp, Dayton Ohio.


type YD, Model LPH

Serial No.:



6 x 3x 5 in. h, plus capillary lines


10 lbs.




Exhibition, education, and research quality, illustrating the design, engineering and construction of an early mid 20th century, sophisticated, dual pressure, refrigeration system control, with motor over load protector.

Patent Date/Number:

From York County (York Region) Ontario, once a rich agricultural hinterlands, attracting early settlement in the last years of the 18th century. Located on the north slopes of the Oak Ridges Moraine, within 20 miles of Toronto, the County would also attract early ex-urban development, to be come a wealthy market place for the emerging household and consumer technologies of the early and mid 20th century.

This artifact was discovered in the 1950’s in the used stock of T. H. Oliver, Refrigeration and Electric Sales and Service, Aurora, Ontario, an early worker in the field of agricultural, industrial and consumer technology.

Type and Design:

Compact, dual high and low pressure bellows with short extended capillary lines


Enclosed in a heavy, 1/16 “heavy steel, deep draw casing with similar style cover, the control has a formed base in 1/8 “ steel plate designed for bolting directly to Frigidaire condensing units of the period.

Special Features:

Original cable connectors and refrigerant tube fittings illustrating the trade practices of the period

Performance Characteristics:
Control and Regulation:
Targeted Market Segment:
Consumer Acceptance:
Market Price:
Technological Significance:

It was the mid 1930’s and the refrigeration and air conditioning industry was a buss with the promise of a post depression and pre WWW II period. As a marker, a new generation of well-integrated and carefully engineered refrigeration condensing units, readily adapted to a wide range of field applications was in production at Frigidaire - reflecting the market optimism of the period. According to Frigidaire’s installation and service manual No. SER,-405, for products manufactured prior to 1937, the YD series of controls had just been put on the market. With new engineering and manufacturing know-how, the control was designed and built to performs the 3 functions of low side operating temperature/pressure, high side pressure protection and motor overload cut-out, using spring compensated bellows and overload heater coil with manual reset. With the market optimism of the time, the control series was produced in a wide range of models, covering various functional combinations for installation on all Frigidaire condensing units. Included were low and high pressure, as well as temperature sensing bulbs, all with various lengths of capillary line, plus a range of motor overload, trip, heater coils from 1 to 15 amperes.

Industrial Significance:

The control stands as a marker of significantly changing times in the Canadian refrigeration and air conditioning industry and the consumer market place that motivated and sustained it Creating and responding to market forces for automated refrigeration and air conditioning systems, pressure control technology evolved rapidly in the late 1930’s. Better engineering data, new materials and new more precise manufacturing methods all helped the industry to respond to thye now vastly changing times. Engineers were learning how to combine multiple functions within the same control device - low side operating pressure, high side safety cut-out and automatic motor over load protection.

Socio-economic Significance:

The era of the chain food store was at hand. It would move the bulk of food retailing from the family run food stores to larger corporate, commercial operations. Much of the automated control technology of the pre and post WWW II was shaped by this significant marketing trend.

Socio-cultural Significance:

G. Leslie Oliver, The T. H. Oliver HVACR Collection

HHCC Storage Location:
Bibliographic References:

see Frigidaire Installation and Service Manual, SER.-405

  • See exhibit programs for CMX02 and CMX04

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