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In Reply to: RE: All true in the perfect world of today. posted by jea48 on February 11, 2017 at 08:45:55
All true in the perfect world of today
IIRC, fuses were being used in telegraphy by the 1870s and in electrical circuits by the early 20th century. IMHO, far from being of today's perfect world, they're pretty much obsolete but that's another topic.
But what about two wire power cord and plug vintage audio equipment made before the polarized plug?
Can't off-hand comment on old kit or US rules. IIRC, UK regulations have stipulated 3-pin plugs for pretty much everything other than lighting circuits since the 1930s except for what we now call 'double insulated' devices. (What domestic users did was of course a different matter.)
In the event of an overload the fuse is still in series with the load and will blow if the load exceeds the ampere rating of the fuse
The fuse will blow (sooner or later, often considerably later) but, if the fuse is in the neutral line, the circuit remains live and thus possibly hazardous, esp if the earthing is poor.
With a 3 wire power cord . . . it could prove dangerous to the user . . . if the AC power polarity is reversed ahead of the fuse on equipment where the safety equipment ground from the wall receptacle is used.
You're right - but isn't that where I came in?
What about the incorrectly wired wall receptacle where the hot and neutral wires are reversed?
Competent electricians do not reverse polarities for well understood reasons. Incompetent electricians can be lethal.
What about the aftermarket power cord that has the hot and neutral reversed at the female IEC connector? This is more common than you would expect.
I've never bought an audio-style after-market power cord but if I did and found it was wired incorrectly I'd make the mother of a fuss.
D
Follow Ups:
Can't off-hand comment on old kit or US rules. IIRC, UK regulations have stipulated 3-pin plugs for pretty much everything other than lighting circuits since the 1930s except for what we now call 'double insulated' devices. (What domestic users did was of course a different matter.)
Interesting to lean that all the mass produced audio equipment manufactured in the 1970s for sale in the UK had a 3 wire cord and 3 wire grounding type plug.
Marantz, Pioneer, Sansui, Kenwood, NAD, Nakamichi, Teac, Technics, AKAI, JVC, you name it, sold in the USA and Canada came with a 2 wire power cord and plug.
Edits: 02/11/17 02/11/17
Interesting to lean that all the mass produced audio equipment manufactured in the 1970s for sale in the UK had a 3 wire cord and 3 wire grounding type plug.
I never suggested such kit came with a 3-wire cord or a "3 wire grounding type plug" (whatever that is). I wonder if you know what "double insulated" means.
In fairness, your confusion may have arisen because appliances sold in the UK with two-wire cords do nowadays come with a three-pin plug though the "earth" pin is unconnected and typically plastic. There are valid reasons for that but they are not relevant here; I'd hate to add to your muddle.
The rest of your post was not worth the effect to respond.
If, as I assume, you meant "effort", I know how you feel.
D
Ryelands said:
I never suggested such kit came with a 3-wire cord or a "3 wire grounding type plug" (whatever that is).
Really?
Ryelands said:
Can't off-hand comment on old kit or US rules. IIRC, UK regulations have stipulated 3-pin plugs for pretty much everything other than lighting circuits since the 1930s except for what we now call 'double insulated' devices. (What domestic users did was of course a different matter.)
A 3 wire type grounding plug is a plug that has 2 line prongs and a safety equipment ground prong/pin. In the case of a standard NEMA 5-15P 120V 15 amp plug a straight blade for the HOT, a straight blade for the neutral, and a round pin for the safety equipment ground. A wider neutral blade is not needed on a 3 wire plug because the ground prong/pin keys the plug so it will only plug into the mating receptacle in one direction.
Ryelands said:
I wonder if you know what "double insulated" means.
As matter of fact I do. And I also know double insulated power wiring for audio as well as video equipment did not exist in the 1970s, let alone earlier.
Ryelands said:
In fairness, your confusion may have arisen because appliances sold in the UK with two-wire cords do nowadays come with a three-pin plug though the "earth" pin is unconnected and typically plastic. There are valid reasons for that but they are not relevant here; I'd hate to add to your muddle.
LOL, fairness?
I would imagine the dummy ground pin is there so the plug can only be plugged in only in one direction. It's used to maintain plug to receptacle polarity orientation.
In the USA we don't waste the extra money on dummy ground pins. UL, NEMA, NEC, dictates 2 wire plugs must be polarized. They will only plug into a mating polarized receptacle in one direction. The neutral blade is slightly wider than the hot blade. In the USA it is against electrical safety standards as well as codes to install a 3 wire grounding type plug on a 2 wire cord. It's an electrical safety thing.
//
jea48 deleted from post prior to Ryelands response:
The rest of your post was not worth the effect to respond.
Ryelands said:
If, as I assume, you meant "effort", I know how you feel.
No, I doubt if you do.
Hind sites 20/20. I should have left it in the original message.
Best regards.
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