Surge suppressors

Robert G. Brown rgb at
Mon Oct 28 10:57:55 PST 2002

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.


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

More information about the Beowulf mailing list