Robert G. Brown
rgb at phy.duke.edu
Mon Oct 28 13:57:55 EST 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 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
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