Emerson 60HZ, 480V user manual 2.1.2UPS Input Configuration, 2.1.3Cabling Guidelines

Electrical Connections

2.1.2UPS Input Configuration

Figure 3 illustrates the Liebert NX in a split bypass (dual-input) configuration. In this configuration the Static Bypass and the Maintenance Bypass lines are supplied from a separate feed from the Main input. Both sources must be protected externally with properly sized protective devices. By default, the unit ships with internal links installed between the bypass input and main input (Single Input configuration). To wire the unit as a dual input UPS, remove the links and wire the bypass to the input bus bars, then wire the Main input directly to CB1 (see Figure 4).

Figure 3 Single module block diagram—dual input configuration

3-Phase	Internal Maintenance Bypass
3W + Gnd

3-Phase	Static Bypass
3W + Gnd

AC Input	Rectifier	Inverter
		Converter
	UPS Cabinet
	2W + Gnd

3-Phase

3W + Gnd

AC Output

Battery Cabinet

2.1.3Cabling Guidelines

The following are guidelines only and are superseded by local regulations and codes of practice where applicable. Use wiring rated at 75°C or greater.

1.The ground conductor should be sized in accordance with the input overcurrent protection device data in Table 8. The ground cable connecting the UPS to the main ground system must follow the most direct route possible. Control wiring and power wiring must be run in separate conduit.

Output and input cables must be run in separate conduit.

2.Consider using paralleled smaller cables for heavy currents—this can ease installation.

3.When sizing battery cables, a maximum voltage drop of 4VDC is permissible at the current ratings in UPS terminal. For terminal connection sizing, see Table 8.

4.In most installations, especially parallel multi-module systems, the load equipment is connected to a distribution network of individually protected busbars fed by the UPS output, rather than connected directly to the UPS itself. When this is the case, the UPS output cables can be rated to suit the individual distribution network demands rather than being fully load-rated.

NOTE

If more load is added to the distribution panel, the unit’s cabling must be resized.

5.When laying power cables, do not form coils; this will help avoid increasing formation of electromagnetic interference.

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