40 NFS2-640/E Installation Manual — P/N 52741:P2 7/10/14
Installation UL Power-limited Wiring Requirements
3.11 UL Power-limited Wiring Requirements
Power-limited and nonpower-limited circuit wiring must remain separated in the cabinet. All
power-limited circuit wiring must remain at least 0.25 inches (6.35 mm) from any nonpower-
limited circuit wiring. All power-limited and nonpower-limited circuit wiring must enter and exit
the cabinet through different knockout and or conduits. To maintain separation, group non-power
limited modules together, i.e., group modules on the same side of the enclosure or in separate rows.
Figure 3.23 shows one configuration that meets these UL requirements. The first two rows of
modules are configured with at least a 0.25 inch (6.35 mm) separation between power-limited and
nonpower-limited wiring; AC and battery wiring is routed away from power-limited wiring.
320-2-640-PWRLMTWIR-ISO2.wmf
Figure 3.23 Typical Wiring for UL Power-limited Wiring Requirements
(Shown with relays as connected to power-limited modules)
NOTE: AC and battery wiring are not power-limited. Maintain at least 0.25 inches (6.35 mm)
between power-limited and non power-limited circuit wiring. Install tie wraps and adhesive squares
to secure the wiring. Use a power-limited source for relay output on terminals TB8 – TB11.
See Figure 2.2, “CPU2-640/CPU2-640E and Power-Supply: Wiring Connections” on page 14 to
identify power-limited and non-powerlimited circuits.
NOTE: Drawing is not to scale; proportions and angles are exaggerated to show wire-placement
more clearly.
NOTE: If additional knockouts are added to the backbox, proper separation of power-limited and
nonpower-limited wiring should be maintained.
Power-limited Circuits*
Nonpower-
limited
circuits
To cabinet-mounted battery
(nonpower-limited)
Power-
limited
circuits
NPL
NPL
Maintain vertical
separation where
circuits appear to
“cross”
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