On Thu, 14 Oct 2010 01:10:34 GMT, (Doug Miller)
wrote:

In article , wrote:
On Wed, 13 Oct 2010 02:49:40 GMT, (Doug Miller)
wrote:

In article , bud--
wrote:

Most of the thread uses 210.21. It says what you say above, which I
agree is odd.

No, it doesn't. Read Table 210.21(B)(3). The permitted receptacle ratings on a

15A circuit are "not over 15". On a 20A circuit, it's "15 or 20".

A while back I ran across 406.3-A which, IMHO, prohibits almost all 20A
single receptacles on a 15A circuit:

Never mind that. Table 210.21(B)(3) prohibits *all* 20A receptacles, single or

duplex, on a 15A circuit.

15/20A receptacles "shall be installed only on circuits of the voltage
class and current for which they are rated." This applies only to
"grounding-type" receptacles, so you presumably could put an ungrounded
20A single receptacle as the only receptacle on a 15A circuit (and only
in those cases where you can use an ungrounded receptacle). Oddness
remains, but is greatly limited.

No, you can't. 15A circuits may not have receptacles rated over 15A. Period.
There are no exceptions.

When you lookk at it logically - from an electrical point of view -
it would make more sense to allow a 20 amp receptacle on a 15 amp
circuit than the other way around. Look at it from this point of view.
A 20 amp receptacle ic designed to handle 20 amp loads - on a 15 amp
circuit it is protected to 15 amps. This is definitely safe as nothing
can operate above its rated or protected current .

No, it is not "definitely safe". It's of questionable safety at best

You obviously do not understand electrical theory any more than you
understand the code book.

You explain to me how a 20 amp receptacle on a 15 amp fused/protected
circuit is a safety issue.

Give it your best crack.

A 15 amp receptacle is designed for a 15 amp load and when installed
on a 20 amp circuit is protected at 20 amps and wired with wiring that
is rated at 20 amps. The receptacle is now the week link, and being
somewhat resistive in nature it is succeptible to overload damage if a
load plugged into it draws more than it's rated current - as it is
"protected" to a current higher than its rating.. This definitely has
the possibility of being unsafe as the receptacle can operate above
its rated current.

No, it can't, because any device that draws enough current to overload a 15A
circuit is not permitted to have a plug that will fit into a 15A receptacle.
It will have a plug that fits only into 20A receptacles. That's why a 20A
receptacle has a different configuration.
No, you are wrong. 100%
The fuse is their to prevent damage due to, and protect against FAULT
CURRENT. Any device, irregardless of it's rating, can draw excessive
current due to a FAULT. And a 15 amp plug fits a 20 amp receptacle.

By your logic, twisted as it is, all 15 amp receptacles on a
multi-branch circuit would have to be designed, built, and installed
in such a way that if anything was plugged into one receptacle drawing
close to 15 amps (or anything with a 15 amp plug, for that matter) ,
it would be impossible to plug anything else into any other receptacle
on the circuit.

That's not the way it works (thankfully), nor should it.

The "ring wiring" system used (at least untill recently) in brittain
and some parts of europe makes sense, with fused outlets. There is
also a proposed standard (smart home) that would have each plug
identify the rated current of the device and centrally monitor the
current draw, shutting the device down if current ratings are exceded
without shutting down anything else. This system uses RFID chips for
identity - and yes - it IS being worked on - I know one of the
engineers involved in the project.