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Rockwell Automation Publication 1512A-UM101B-EN-P - December 2021
Appendix A ArcShield Unit Information
ArcShield Design
ArcShield units typically include a pressure relief vent on the roof of the
structure (some incoming units may not have a pressure relief vent if top cable
entry is required). Under arc flash conditions the pressure relief vent will open
allowing hazardous flames and gases to exit the enclosure via plenum or
chimney system. The low voltage panel area is sealed to prevent flames and
gases from entering; however, suitable personal protective equipment (PPE)
must be used whenever working on live circuits.
Exhaust Systems: Chimney
or Plenum Option
Plenum Information
A plenum can be provided for each unit, and is to be field-mounted on the top
of the unit structure (some incoming units may not have a plenum if top cable
entry is required). The purpose of the plenum is to direct the hazardous flames
and gases away from the top of the arc resistant enclosure. Unit plenums are
secured to the top of the unit structure and to adjacent plenums, creating a
continuous conduit for release of the arc flash energy. See
for
plenum installation instructions.
Each plenum based, ArcShield line-up includes a plenum exhaust piece that
extends beyond either the left or right ends of the line-up. The other end of the
plenums is capped with an end cover. Extensions can be added to the plenum
to allow the arc flash energy to be directed further away from the ArcShield
line-up to an area where safe venting of the plasma gases can occur.
Figure 58 - Elements of ArcShield Plenum
