Operating instructions

Power and Control Wiring 13
5.0 POWER AND CONTROL WIRING
All power and control wiring should be installed by a qualified electrician. All power and control
wiring must comply with the NEC and applicable local codes. Unless otherwise labeled, use the rec-
ommended tightening torque as shown in Table 26 - Torque tightening, provided in 17.0 -
Maintenance on page 135.
The bus bars are accessible through the front of the STS 2, and are designed to allow one-handed
tightening.
Cables can be installed through the top or bottom of the unit through removable conduits plates.
See Figure 5 through Figure 10 in section 7.0 - Installation Drawings on page 23 for wiring
entrance locations.
Input wiring also can be installed under a raised floor to optional input junction boxes and cables,
when used.
5.1 Input And Output Power Connections
If the unit is furnished with input junction boxes, the input power connections are made to the
input power terminals located in the junction boxes. Input power cables, furnished with the input
junction boxes, are shipped unattached to the unit for connection between the junction boxes and
the bus bars provided inside the unit. Input junction box installation is discussed in 5.2 - Input
Junction Box Installation (Optional) on page 14.
If input junction boxes are not furnished, the input power connections are made to the bus bars
provided inside the unit. These bus bars are accessible through the front of the unit.
Output power connections also are made to the bus bars provided inside the unit. These bus bars
are accessible through the front of the unit. See Figure 14 on page 32 to Figure 19 on page 37 for
details on the bus bars.
The two input power feeds (sources) to the STS2 should be from two independent sources to avoid a
common source failure.
To ensure proper operation of the STS2, the two input sources must be the same nominal voltage
level and phase rotation.
For uninterrupted automatic transfer, the two input sources should be synchronized within 15
degrees.
The STS2 is designed for operation with 3 or 4-wire solidly grounded sources only.
For 4-wire operation, the common source neutral must be connected to the STS2. See Figure 3 on
page 14 for a typical one-line diagram. Refer to Figure 14 on page 32 to Figure 19 on page 37 for
electrical field connections on all units, with both single and dual output breakers.
!
WARNING
RISK OF ELECTRIC SHOCK
VERIFY THAT ALL INPUT POWER AND CONTROL CIRCUITS
ARE DE-ENERGIZED AND LOCKED OUT BEFORE MAKING
CONNECTIONS INSIDE UNIT.
!
CAUTION
RISK OF UNIT DAMAGE
THE INPUT SOURCES TO THE STATIC SWITCH MUST BE
GROUNDED-WYE SOURCES. INPUT SOURCES OTHER THAN
SOLIDLY GROUNDED-WYE SOURCES MAY CAUSE DAMAGE TO
THE SWITCH.