Surge suppressors

Jim Lux James.P.Lux at jpl.nasa.gov
Fri Nov 1 13:48:53 EST 2002


At 08:59 AM 11/1/2002 -0800, you wrote:

> > I'm not sure what this means.  15A "plug"?  Either this is horribly
> > dangerous and a code violation or irrelevant -- if you use a 20A
> > breaker, everything in your circuit downstream had better be rated for
> > 20A or be fused for lower current operation so you can't start a fire
> > and not blow the (or a) breaker first.
>
>You're absolutely right.
>
>The room is wired correctly - I misidentifed the plug types.
>The wire molding is darkish gray and runs along the wall beneath
>the table surfaces - so there isn't a lot of light or contrast.
>Inspected up close with a flashlight the receptacles are clearly
>5-20R.  Oddly, even knowing this, looking at them with normal room
>light from 8 feet out they still look like 5-15Rs to me.

Actually, the code (2002 version, and it's been that way for a while) 
allows 15A receptacles on a 20A branch circuit.

NEC 210.21 (B) (3) Receptacle Ratings
Where connected to a branch circuit supplying two or more receptacles or 
outlets, recptacle ratings shall conform to the values listed in Table 
220.21(B)(3)...

The table shows the following

Circuit Rating/Receptacle rating
15/not over 15
20/15 or 20
30/30
40/40 or 50
50/50

For what it's worth, an earlier section (B)(2) is also of interest
(B)(2) Total Cord-and-Plug-Connected Load
Where connected to a branch circuit supplying two or more receptacles or 
outlets, a receptacle shall not supply a total cord-and-plug-connected load 
in excess of the maximum specified in table ...

circuit rating/recep rating/max load
15 or 20/15/12
20/20/16
30/30/24


I think you need to calculate load by summing the "nameplate" current for 
the devices, not by measuring the actual current drawn, but I can't find 
that section off hand..



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