12.11-10: Hotstream 1935 Automatic Draft Stabalizer

HHCC Accession No. 2006.116HHCC Classification Code: 12.11-10

Employed to automatically bypassing air up the chimney, this automatic draft stabalizer, for use on home heating systems fired with coal, fuel oil or gas was equipped with cast iron frame with sheet metal boot. The brake-formed, pivoted damper blade is decorated in handsome red, wrinkled finish, with balancing weight affixed to a travelling screw, which is manually adjusted with a rotating knurled hand wheel, Draft-O-Stat, circa 1935.

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




Hotstream Heater Co, Cleveland, Ohio



Serial No.:

8 in. round X 6 in long


4 lbs.




Exhibit, education, and research quality, illustrating the engineering and construction of early automatic chimney draft stabalizers, essential to the new world of automated home heating in Canada, as it evolved in the early 1930’s

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:

An automatic chimney draft stabalizer, designed for automatically fired coal, fuel oil or gas home heating systems; Operating on the air bypass principle Cast iron frame Sheet metal boot for mounting on 7 or 8 inch stacks, Brake formed, pivoted bypass damper blade, Counter balancing weight affixed to a travelling screw, Manually adjusted with a rotating knurled hand wheel

Special Features:

Equipped with gold lettering


Handsome red, wrinkled finish Needle point pivot damper mounts Original installation instruction sheet

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

The introduction of automation for home heating systems in Canada brought with it a range of engineering and operational challenges, which were often unexpected. A largely unanticipated requirement, in the early years, was the need for an over-the-fire automatic draft control. The performance, safety and efficiency of automated combustion was dependent on reasonably stable draft ‘ not too high not too low. It was a period in which heating systems operated on conventional chimneys, which would produce a great range of draft conditions, depending on height, flue size, wind strength, direction and so forth. The simple, weighted, pivoted, bypass damper blade system opened to allow excess air [beyond what was required for clean combustion] to pass up the chimney, rather than be drawn over the fire. The system was ideal for the heating applications of the period, which were predominantly of the ‘conversion’ type in which existing furnaces and boilers, operating on conventional chimneys were converted from manual to automated combustion The device, in various configurations, would become the standard of the industry for home heating systems, through to the introduction of forced draft and induced draft combustion in the latter part of the 20th century.

Industrial Significance:

With increasing sophistication in system design came the need for greater precision in the setting of draft regulators. The draft gauge and combustion efficiency test kit would become an essential tools in the installers and service technicians tool box [see Collection Group 12.12] An exemplary ‘Cadillac’ version of the draft stabilizer, this device by Draft-O-Stat, decorated in black, red and gold, would soon appear in much lower cost versions, as the pressure for cost reduction and market forces began to be key factors in the development of automatic home heating equipment.

Socio-economic Significance:
Socio-cultural Significance:

The automatic, air bypass draft stabalizer would become a marker of the times, seen and heard on heating systems across the country. Part of the culture, the householder would become accustomed to the heating system coming on and off, with the whirr of the burner mechanism, a bump announcing that combustion had begun, and then the bang of the draft regulator repositioning itself as flue gasses began to roar up the chimney.


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

HHCC Storage Location:
Bibliographic References:

Domestic Draft-O-Stat Instruction Sheet, Form 25-II-DOS-9-35, The Holstream Heater Company, Cleveland Ohio,


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