Liebert POWER PROTECTION STATIC TRANSFER SWITCH manual Input Junction Box Installation Optional

Power and Control Wiring

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.

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

5.2Input 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 4	Input junction box dimensions
		Length	Width	Height
Switch Rating		Inches (mm)	Inches (mm)	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

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