12.11-3: Square D 1928 Safety Disconnect Switch

HHCC Accession No. 2006.118HHCC Classification Code: 12.11-3

A 1920’s automatic oil heating, safety, disconnect switch, in heavy steel, 4 pound enclosure, telling many stories around a master narrative, dominant in the times. The prospect of home electrification brought with it widespread concern for public safety with steps taken by authorities to help ensure safe practice and to ally unnecessary public apprehension, Square D, Circa 1928 [See also ID#230]

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12.11 Pressure Atomizing Oil Burner Equipment and Systems - Other Components and Parts


Square D


Square D Company Canada Ltd., Walkerville Ontario


Cat 96211

Serial No.:

Body no. U-127-27-W


6 x 4 x 8’ h


5 lbs.




Exhibit, education, and research quality, illustrating field electrical installation codes and practice, and the steps taken by electric utilities and equipment manufacturers to ally public fears over home electrification ‘ a necessary prerequisite for the development of a Canadian market place for automatic home heating equipment.

Patent Date/Number:

Name copyrighted 1922


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.

This particular safety switch was used on a residential heating system in York County [York Region], North of Toronto during the 1930’s.

Carries the official seal of the Hydro Electric Power Commission of Ontario, approval No. 634

Type and Design:

Heavy steel cabinet in black enamel Padlock style hinged cover Classic Square D profile with classic logo, a prominent symbol recognized throughout the industry through the 20th century Single throw side operated lever switch Twin fuses, making provision for fused neutral

Special Features:

Brass name plate, decorated in black with safety instructions Blue and white seal of the Hydro Electric Power Commission of Ontario, aproval No. 634 Original box connector Field installed dual knock out cover in galvanized sheet metal stock, screwed in place with 2 no 8-32 x ‘ inch machine screws, illustrates the adherence to the electrical code requirements of the day External # 8 solder lug affixed to the box, illustrates the grounding practice of the day in which much cable was not grounded and required a separate grounding network.

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

The danger of fire and electrocution were matters of wide spread public concern in the 1920’s through 30’s. Robustly designed equipment, evidence of government certification and equipment testing standards, as well as evidence of competent field practices and craftsmanship were all-important indicators intended to demonstrate due care, caution and respect for public safety.
Approved field practice, enforced by electrical inspectors, required that such panel boards be installed at the entrance to the furnace or boiler room within easy reach, allowing the homeowner full control and access, in order to shut down the system manually in the case of emergency [see ID#230]. The switch provides an example of the use of terminology in the description and specification of safety switches in the early years of home electrification technology. The device is described prominently on the cover as ‘single throw fused bottom’.
Of technological significance, in the history of emerging technology of home electrification , is this 120 volt, fused, disconnect switch designed with a fused neutral - a practice which would be rethought a few years later, and abandoned.

Industrial Significance:

The device tells the stories of the widespread apprehension over the coming of home electrification and the steps taken by the underwriters, regulators [codes and practices], electric utilities and equipment manufacturers to ally public fears over home electrification ‘ and in fact ensure public safety in an embryonic and rapidly developing field where there was little practical experience to draw on. The embryonic HVACR industry of the times was anxious to work with the electrical equipment manufacturers, regulators and underwriters in publishing re-assuring information on the many benefits and safety of home electrification, as well as educating the tradesmen of the day on electrical codes and safe practices. For these were seen as necessary prerequisites for the sale of automatic home heating equipment.

Socio-economic Significance:
Socio-cultural Significance:

Featured prominently on the switch, in large black letters on a white panel, an integral part of the design and styling of the switch are the ‘code words’ intended to ally public fears and instil confidence in public authorities and manufactures concerning the safety of the equipment and practices being followed: ‘Safety Switch’ ‘Makes Electricity Safe for Everyone’
Skilful managing of classic ‘approach avoidance’ psychological effect was major factors in shaping the market place of the day. There was a strong desire to partake of the many benefits of home electrification, which produced a strong psychological force of attraction. As duly demonstrated, the challenge was to reduce the avoidance factor to a manageable level, through a system of verbal cues and assurances.


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

HHCC Storage Location:
Bibliographic References:

Wiring Diagram ‘ Minneapolis Type R117-2 Protectorelay Models G and F Machines, Fess Oil Burner of Canada Ltd. Toronto and Montreal, Drwing No. 598, [Undated likely circa 1929]


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