Surge suppressors

[Robert G. Brown]

On Mon, 28 Oct 2002, Steve Gaudet wrote:

> You might want to reconsider how you have your UPS plugged into your surge
> strips.  Your current configuration is not wired correctly.  The UPS has
> surge built in and nothing should be between it and the power source.
> Coming out of the UPS is a surge protector.  Therefore, all you need is
> cheap power strips with no surge in it.
> 
> Of course it will work but it is against National Electrical Code.  Any kind
> of inspector can fine you for this configuration.  Keep in mind that all
> UPS's have surge protection built into them.  The correct scenario would be
> to plug PDU's into the UPS for receptacle distribution.  PDU's do not have
> any surge protection built into them.

This is the second or third time I've heard this little-known bit of the
NEC cited (that one cannot plug surge strips into surge strips).  Being
the curious sort, I wonder why this is the case (that is, what is the
hazard avoided by not doing this).  I can't offhand see why plugging a
surge protector into a surge protector would do anything but provide one
with marginally greater surge protection and three de facto overcurrent
circuit breakers in the circuit instead of two.

Anybody know?  I like to understand this sort of thing, and not just
avoid it because an inspector would fine me.

   rgb

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu