Liebert STS2 - Manual (Page 126)

Specifications
118
14.2.4 Access
The STS2/PDU is designed so repairs and maintenance can be done from the front, side or top of the
unit. All components that may need repair or replacement during routine field maintenance are
safely accessed with the units in bypass without removing power from the unit. These components
include:
• All electronic PCB assemblies
• Power supply assemblies
• All control fuses
• All circuit breaker plug-in modules
• Fans
• SCRs
All power connections are designed to maintain proper connection torque over the lifetime of the unit
without any maintenance. The integrity of the connections can be checked via infrared scanning
safely from the front or top of the unit.
All other components including transformers, power cables and connections, circuit breaker bases,
etc., are replaceable from the front, rear or top of the unit, but this requires all power to be removed
from the unit for safety. Although routine re-torquing of the power connections is not required, if
maintenance of these connections is needed, complete removal of power is required from the unit for
safety reasons.
14.2.5 Circuit Breakers
The STS2/PDU is equipped with two input plug-in circuit breakers and five or six (if CB3A is used)
molded-case, plug-in, non-automatic circuit breakers. The breakers are UL listed for use up to
600VAC and CE marked. The plug-in feature of the breaker includes an interlock, which prevents the
breaker from being unplugged without being in the OFF (open) position.
Mechanical interlocks are provided on the breakers to prevent improper maintenance bypassing of
the solid-state switch. A bypass breaker cannot be closed unless the solid-state switch is connected to
the same input source and only one bypass breaker can be closed at a time. All breakers are equipped
with N.O. and N.C. auxiliary switches for monitoring of the breaker positions. The two solid-state
static switch input breakers are equipped with 48 VDC shunt trips to allow for control by the STS2/
PDU logic. See Tables 9 through 11.
14.2.6 Cable Entrance
Removable conduit termination plates are provided in the top and bottom of the STS2/PDU for termi-
nation of the two source input conduits or raceways and/or the output conduits or raceways. On units
with inline panelboards, output conduit or raceways are bottom exit only.
14.2.7 Doors
A removable key lock hinged front door provides access to the circuit breakers.
14.2.8 Color Graphical Display
The display is located in the front of the unit. Front panel display is an LCD touch screen display for
monitoring and configuring the unit. See Figure 57 for a drawing of the touch screen display.
!
WARNING
Lethal voltages exist inside the unit during normal operation. Only qualified service
personnel should perform maintenance on the Static Transfer Switch 2 Power Distribution
Unit.
The unit is supplied by more than one power source. The unit contains hazardous voltages if
any of the input sources is on, even when the unit is in bypass. To isolate the unit, turn off and
lock out all input power sources.
Verify that all input power sources are de-energized and locked out before making connections
inside unit.