Glossary 78
PDU
power distribution unit
PLC
programmable logic controller
power circuit
Conductors and components of branch and feeder circuits.
PPE
personal protective equipment
RU
rack units
structure
Enclosure of sufficient size to enable entry of personnel.
supplementary protector
A manually resettable device designed to open the circuit automatically on a predetermined value of time
versus current or voltage within an appliance or other electrical equipment. The protector can also be
provided manually to open or close the circuit. These devices can provide supplementary protection only.
UL
Underwriters Laboratory
UPS
uninterruptible power system
VESDA
very early smoke detection apparatus