mtfallsmikey
Senior Member
Saw them at Lowe's yesterday.
Pre NEMA receptacle?
- Thread starter mbrooke
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mbrooke
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Maybe not then, but why does a keyless socket have a 250 volt rating? Why not 120 or 277?
IIRC, there was an NEC 10 amp limit for lighting ckts originally- this was likely because of circumstances surrounding the lack of conveinence recs/modern branch ckts in dwellings at that time- think of an iron plugged into an adapter screwed into a lamp with is plugged into adapter screwed in ceiling socket and all of that small conductor (cords) carrying that load- a lot of fires then. Eventually it was raised to 15a in the 1920s (makes sense b/c of the growing use of wall recs in new installations deeming all those adapter doohickeys/cords draped everywhere increasingly unnecessary) , but the old rule was still in effect for lighting ckts over 125v and stayed that why until the '50s- no clue why as it made no sense. (sorry to sound repetitive)
Its ok, Im just as puzzled.
al hildenbrand
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Maybe not then, but why does a keyless socket have a 250 volt rating? Why not 120 or 277?
Its ok, Im just as puzzled.
It's hard to imagine that the Tesla Westinghouse 1895 demonstration of useful horsepower (three phase AC motors) supplied from a generator eighty miles away (the Niagara Falls hydro electric plant) is only 120 years ago.
There were no "standards" to speak of, for AC power distribution at this proof-of-concept demonstration. . . all the AC standards followed.
I agree with User100's statement about the double tee slot receptacle in your photo. It has its roots in a manufacturer trying to get more market-share with a device that would receive both the standard parallel blade male cord plug as well as the competing male cord plug standard of two flat blades. Both were for 120 Volt loads.
The trap, in my opinion, is to try to understand the creation of materials standards through the lens of today's standards. Can't be done.
kwired
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Installed the receptacle or the adapter...maybe both? In most cases landing the ground lead to the plate screw was as effective as leaving it hanging, that screw was not bonded to any grounding source. I also have one of the screw shell adapters that I keep in the case with my circuit tracer.
I have a couple, they are still being sold. They are great for using a plug in breaker tracer sending unit to locate a lighting circuit breaker.
They are also UL approved.
If you are talking about the 250v/660w rating on some lamps, I think that's just the Max rating of the socket.
:thumbsup:.
mbrooke
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Why 250 when the light will only be applied on a 120 volts circuit?
JFletcher
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Other countries that use 230-250V power? Overkill in case it's accidentally connected to 240V here?
mbrooke
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My thinking, it could be connected to 240 volts in the real world. Which leads me to think this: those double T slot outlets could be used for either 120 or 240 applications.
fmtjfw
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Maybe not then, but why does a keyless socket have a 250 volt rating? Why not 120 or 277?
Its ok, Im just as puzzled.
because they make (made) 240V light bulbs. Often used in industrial locations.
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mbrooke
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kwired
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But, as said earlier, which equipment in the early 1900s used that other 250v/10a rating? Again, there were 2 competing 120v plug designs then, many other old 2 wire recs that accepted only parallel bade plugs (think of the modern, still listed 1-15r still used today for replacement purposes) had the same 125/15a -250/10a rating and remember the old code rule in effect until the '50s mentioned earlier too.
Back then, they would not have been that stupid to allow such an easily interchangeable device. There were 240v 20 amp devices that came along eventually (w/ markings like this: - |) and a 2-20 plug that mated with it, but the prongs were too large/far apart too fit the device in your op- the old timers who worked for Paulding, Arrow Hart, Hubbell etc knew what they were doing.
As said above by fmtjfw, it could be so that they could use that socket for industrial/commercial applications. I don't work either of those, but that to me is unlikely, as some of the fixtures w/ that rating probably couldn't/wouldn't be used for those areas. Could be just a determined maximum smoke point for the fixture, but only someone who is familiar w/ testing rating these fixtures would know for sure.
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kwired
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Most old houses I run into that still have an existing "220" outlet from many moons ago, always have a crowfoot style three wire receptacle that has a 125/250 volt rating on it. Seen these in buildings as new as 1965ish as the construction date - and often for window/thru the wall air conditioning units. Guessing they never truly used a neutral conductor in most appliances that got plugged into them but still grounded the appliance via the neutral terminal of that receptacle.
Also seen a lot of this particular receptacle on the farms for 240 volt equipment, though the 50 amp receptacle commonly used for household ranges is even more popular even if a 40/50 amp circuit isn't needed:roll:
Also seen a lot of this particular receptacle on the farms for 240 volt equipment, though the 50 amp receptacle commonly used for household ranges is even more popular even if a 40/50 amp circuit isn't needed:roll:
n1ist
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They do make 277V 100W A19 medium base bulbs; I use them for load-testing various products at work. Loading down 20A of 277V with bulbs gets quite toasty...
We also use 3 120V bulbs in series for testing 347V
We also use 3 120V bulbs in series for testing 347V
mbrooke
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What are the 277 volt lamp holder like?
n1ist
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Tough to find as most are rated at 250V max due to 210.6. I used Leviton L9878 which is rated at 600V.
/mike
drcampbell
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Your future's so bright, you'll need to wear shades.
I stumbled onto this curious item. I'm going to install it in a prominent place in my living room as an architectural/historical curiosity. (my house was built in 1927)
kwired
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I think I have run into those a time or two in the past.
Add: make sure you use a brass plate, and not one of the lightweight ones that are common today, to make it even more authentic.
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K8MHZ
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That's very cool!
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