Paul,
I think you have nailed it!
Most likely the term was developed from purchased power from the Edison Company which used DC systems, and before the Niagra Dam AC power Plant project by Tesla and Westinghouse proved AC's benefits - leading to the exclusive use of AC power systems.
As mentioned, Thomas Edison was reluctant to accept the use of AC, and promoted the use of DC. This probably was from envy and jealousness of Tesla's acceptance by Edison's rival, George Westinghouse!
Also, while Tesla worked for Edison Labs, he described the same thing about using AC instead of DC for system power, as he did to his Electrical Engineering Professor in College.
As what resulted from the MSEE Professor, Edison reacted the same way!
" Are You Crazy!!??, AC CAN NOT BE USED FOR ANYTHING PRACTACLE!!!"
[gee, I wonder if they were right?
]
Ok, enough with the Ancient History report
The term "Edison Circuit" may have been in some reference to circuits connected to Electro-Chemical cells.
The "Edison-Lelande" cell was a commonly used "Wet" cell, modeled from the famous "Leclanche Cell" experimental models.
The circuits made up in Edison Labs would have certainly included 3 wire DC circuits, made up by using two Edison Cells in Series, with a "Center Tap" between the two cells.
It's just a guess of mine that the term may have originated from this, but became familiar to the Edison Power Company's commonly used multiwire DC circuits.
FYI, and for more trivia
, the 3 wire DC system can be derived from the following setups:
<OL TYPE=1>
[*] From two Cells connected in Series, "Center Tap" made between the Cells,
[*] From two Batteries connected in Series, "Center Tap" made between the Batteries,
[*] From One "3-wire" DC Generator, which has a "Center Tap" between two Field Coils,
[*] From two individual 2-wire DC Generators connected in Series, and a "Center Tap" made between the two Generators,
[*] From a "Combination" of a 2-wire DC Generator connected in Parallel with two Batteries or Cells, which are connected in Series with each other - and deriving the "Neutral" [proper term here!] from a "Center Tap" between the two Batteries or Cells.
</OL>
If these seem nearly impossible to invision, posted schematics can help unmask these obsolete systems.
I use the term "Obsolete" as to the extensive use of DC for consumer power systems [how the consumer buys Kilowatt Hours].
3-wire DC power supplies are far from being obsolete!
DC Power supplies for the PC you are using right now, have a 3-wire output.
Sorry to throw this DC stuff into a thread about Heater/Fan/Light combo's!
Just felt the urge again
Nurse Diesel Is Coming To Get Me!Scott SET