Vintage American outlet

[bgadow]

That's what I couldn't figure out, why would you design it so that lower-amp appliances couldn't be plugged in?

[jeyurkon]

One could guess, but this is only a guess. Extension cords and long power cords. The devices were seldom fused so the lines had to be able to handle up to what the circuit is fused for. If the 15 amp device was malfuntioning it could draw 20amps and overheat the cord. At some point they then decided that the risk was minimal and more likely to cause people to try to circumvent it.

This probably wasn't a local code issue, but they can be weird too. In one town here they decided it was a good idea to try to balance the load in homes by splitting the outlets and have the top outlet be on a different phase than the bottom. I plugged in a multiple outlet surge suppressor that used both the top and bottom outlets in parallel. The only problem is that the potential between the two live sides was now 220VAC yielding pretty impressive results when the suppressor shorted them.

John

[electroking]

Originally Posted by jeyurkon

One could guess, but this is only a guess. Extension cords and long power cords. The devices were seldom fused so the lines had to be able to handle up to what the circuit is fused for. If the 15 amp device was malfuntioning it could draw 20amps and overheat the cord. At some point they then decided that the risk was minimal and more likely to cause people to try to circumvent it.

This probably wasn't a local code issue, but they can be weird too. In one town here they decided it was a good idea to try to balance the load in homes by splitting the outlets and have the top outlet be on a different phase than the bottom. I plugged in a multiple outlet surge suppressor that used both the top and bottom outlets in parallel. The only problem is that the potential between the two live sides was now 220VAC yielding pretty impressive results when the suppressor shorted them.

John

In Canada kitchen countertop outlets must be wired that way, to allow
plugging in two high power appliances.

[wa2ise]

Seems that these crowfoot connectors have existed as far back as 1916, as seen at the US Patent office http://patft.uspto.gov/netahtml/PTO/srchnum.htm, look for patent number 1179728 (type this number in the search box, and on the next screen click "images" and look at figures 3 and 4.