Preferred Grounding Configuration, 480 Or 600 Vac Input, 208Vac Output; Figure 3. Preferred Grounding Configuration, 480 Or 600 Vac Input And 208 Vac Output - Liebert Series 600T Installation Manual

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.
10
LOCAL GROUNDING
ELECTRODE
PER NEC 250-30
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.
Installation Manual