Surge suppressors

Bob Drzyzgula bob at
Fri Nov 1 15:16:52 PST 2002

On Fri, Nov 01, 2002 at 04:52:13PM -0500, Robert G. Brown wrote:
> I'm trying to understand that.  Are they saying you can't use a
> 20A-rated receptacle on a 15A, 14Ga wire circuit?  I'd have thought it
> was the exact opposite, that it has to be at LEAST 15 (just like the 40
> A circuit needs a receptacle that is at LEAST 40).  

It isn't a capacity/rating issue, it's a plug-coding
issue. If a device is likely to require more current than
can be safely drawn from a standard 15A circuit, it is
supposed to have one of those plugs with one horizontal and
one vertical contact.  This prevents you from plugging it
into a 15A outlet, which doesn't have the provision for
that kind of plug.

> This is why I still just don't understand permitting a 15 A receptacle
> on a 20 A branch, where an 19 A sustained accidental overload (caused by
> e.g. a partial short circuit) could burn the receptacle without blowing
> the breaker.  I also don't understand the "not over" on the 15 A circuit
> rating for the same reason -- if 5 A receptacles existed and I used one
> on a 15 A circuit, I could critically overload it without blowing the
> breaker.  Whereas using a 20 A receptacle on a 15 A breaker, it just
> provides a greater margin of safety, the same as using 12 Ga wire for
> shorter runs than strictly necessary.
> Sigh.  Now I'm puzzled.  Any insight?

I belive that a "15A" outlet, e.g. a 5-15R, is designed to be able
to safely carry at least 20A. Again, it isn't a matter of what
will melt down the outlet's internal wiring, it's a matter of 
the hole pattern in the front of the outlet.

> BTW, did you find the code online (I'd love the URL) or do you have a
> paper copy.  IS the code online?

I believe that one has to pay for it; most people
buy interpretive/annotated versions from bookstores.


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