7.02-7: Penn Electric 1929 Automatic Pressure-Temperature Control

HHCC Accession No. 2006.038HHCC Classification Code: 7.02-7

An early, crude, hydraulic bellows actuated, FHP, single pole, snap action, refrigeration system, low-side pressure/temperature controller, in black cast iron enclosure, configured and levered much like a door lock of the period, appearing much more like the product of a locksmith than a new generation of early 20th century, automatic electric control engineers [incomplete assembly], Penn, circa 1929.

Image Gallery (3 Images)

7.02 Refrigerating and Air Conditioning Pressure and Temperature Controls - Commercial


Penn Electric


Penn Electric Switch Co. Des Moines Ida.


Type E

Serial No.:



4 x 4x 6 in h


3 lbs.




Education, and research quality, illustrating the design, engineering and construction of early, crude, automated refrigeration controller, by a relatively new comer entering the field. The controller appears here as an incomplete assembly, missing the hydraulic power element, among other things. The power element compensating spring is included, along with original lock nut for porcelain cable connector

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:

Hydraulic bellows operated Cast iron enclosure patterned after a typical door lock of the time


Heavy cast steel enclosure, and removable, steel cover plate all with black overcoat, cover plate secured with wing nut fastener, equipped with 3 bolt mounting

Special Features:

Handsome, etched brass name plate decorated in black enamel Full operating instructions and diagram on inside of cover plate


1HP single phase AC, 220 volts

Performance Characteristics:

Factory set 20 # closing, 10 # opening

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

The controller, although itself an incomplete assembly, when seen in the context of the offerings by other suppliers to the field [see the range of other artifacts of the period held by HHCC in the 7.02 series], helps to demonstrate the wide range of engineering design concepts being offered by the industry, as it experimented with the materials and know-how of the times to respond to potential market needs, and to grow the industry. This controller, much like the door lock, which seems to have inspired it, is a quintessential statement of serviceability. The cover plate, removable by means of a single wing nut, reveals the simplest of mechanical actions with levers and springs in door lock style. To further reinforce the strongly held value of maintainablility and serviceability the inside of the cover plate carries a still very readable account of the control and its operation, along with a full drawing of the control showing all operating components.

Industrial Significance:

The control admirably demonstrates the lengths original equipment manufactures of the times went to assist, often ill trained field installation and service personnel to understand and maintain the equipment.

Socio-economic Significance:
Socio-cultural Significance:

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

HHCC Storage Location:
Bibliographic References:

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