Liebert POWER PROTECTION STATIC TRANSFER SWITCH - Manual (Page 18)

Power and Control Wiring
10
The input and output power wire size should be based on the upstream overcurrent protection device,
observing the NEC and local codes.
The molded case switches contained in the STS2 are typically non-automatic circuit breakers that
rely on the upstream and/or load overcurrent protection. Upstream overcurrent protection should be
rated equal to or less than the rating of the STS2 molded case switches.
The STS2 input and output power and ground and neutral bus bars accommodate a wide range of
wire sizes. The STS2 bus bars accommodates standard 2 hole lugs.
5.2 Input Junction Box Installation (Optional)
The input junction box option is available to simplify input connections to the STS2. Two input junc-
tion boxes and the associated flexible 10 foot long (3 meter) input cables are provided with this option.
This option is available only with bottom cable entrance, typically when the unit is located on a raised
floor.
If the input junction boxes will be used, they either can be shipped with the unit or shipped in
advance to be installed during the rough-in stage of construction.
Locate the junction boxes a maximum of 8 feet (2.4 meters) from the planned location of the Static
Switch.
Due to a lack of clearance for the cables below the unit, the cables are also shipped loose from the unit
for installation at the site. The input cables connect from the input junction boxes to the input power
bus bars inside the STS2.
The standard configuration for the input junction boxes and cables is for 3-wire-plus-ground feeds. If
the input neutral is required, special 4-wire-plus-ground input cables and junction boxes are required.
See Figure 30 for wiring details.
For preparation purposes, the following tables provide the dimensions and wire sizes for the input
junction boxes.
Table 3 Input/output conduit plate specifications
Rating Max. number and size
100-250A 6 — 3" conduit
400-600A 9 — 4" conduit
800-1000A 12 — 4" conduits
Table 4 Input junction box dimensions
Switch Rating
Length
Inches (mm)
Width
Inches (mm)
Height
Inches (mm)
100 amp 16 (406) 14 (356) 6 (152)
250 to 600 amp 30 (762) 16 (406) 6 (152)
Table 5 Input junction box terminal wire size range
Switch Rating Power and Ground Lug Wire Range
100 amp #6 to #2/0 AWG
250 to 600 amp (2) #6 AWG to (2) 500 kcmil