Emerson SERIES 600T manual 10Installation Manual

LOCAL GROUNDING

ELECTRODE

PER NEC 250-30

GROUNDING

ELECTRODE

PER NEC 250-24

Figure 3. Preferred Grounding Configuration, 480 or 600 VAC input and 208 VAC output

7.3.Preferred Grounding Configuration, 480 or 600 VAC Input, 208VAC Output, and Isolated Bypass

Another configuration in this power range is the Single Module System with 480 or 600 VAC input, 208 VAC output, a Bypass Isolation Transformer and a connected load consisting of multiple distribution panelboards or switchboards. Figure 3 above shows a typical installation.

The Bypass Transformer provides isolation and steps down the voltage to the bypass inputs. The Bypass Transformer and the UPS module together constitute a separately derived system, since there is no direct electrical connection between the input (service entrance) circuit conductors and the output circuit conductors.

NOTE

The illustration above shows a wye- connected source, but the same grounding scheme would apply for a delta source at the service entrance.

The bonding of the neutral to the grounding conductor can theoretically be done at either the UPS module or the Bypass Transformer. However, we recommend bonding at the Bypass Transformer because the UPS module will sometimes be powered down for maintenance and its output transformer will be out of the circuit. The neutral should be bonded to ground and a local grounding electrode should be installed at the Bypass Transformer, per NEC 250-30.

Features of this configuration include:

•The UPS receives its bypass neutral from the Bypass Transformer

•The output is isolated from the input circuit conductors, and

•Some amount of common-mode noise attenu- ation can be obtained for sensitive loads if the UPS module and Bypass Transformer are located close to sensitive loads.

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