Liebert 600T - Manual (Page 21)

Configuring Your Ground and Neutral Connections 15
7.3 Grounding Configuration, 480 or 600 VAC Input and Output, Delta Source or
Impedance-Grounded Wye
Figure 3 Preferred Grounding Configuration with Ungrounded Delta Source Input (top) and Corner-
Grounded Delta (bottom)
As previously mentioned, Series 600T UPS modules require a bypass input neutral for sensing
and monitoring. With a wye-connected input source, the installer should connect the building ser-
vice neutral to the module output neutral to achieve this. When the building service is delta-con-
nected, however, the installer must take special steps to ensure reliable UPS functioning.
If building service is ungrounded delta (and there is no intent to operate with one corner of the
delta grounded, either on purpose or accidentally), the UPS requires the Series 600T Artificial
Neutral Kit for proper operation. This kit uses a resistor network to create a reference point for
the bypass input. In this case, the UPS output neutral must be bonded to the UPS ground. See
Figure 5 above.
If the building service is corner-grounded delta or an impedance-grounded wye, the UPS requires
the Series 600T Isolated Neutral Kit. This kit uses control isolation transformers to create a refer-
ence point. For this application, the UPS output neutral must not be bonded to the UPS ground.
GROUNDING
ELECTRODE
PER NEC 250-24
GROUNDING
ELECTRODE
PER NEC 250-24
LOCAL
GROUNDING
ELECTRODE
PER NEC 250-30
LOCAL
GROUNDING
ELECTRODE
PER NEC 250-30
LOCAL
GROUNDING
ELECTRODE
PER NEC 250-30