Liebert 600T - Manual (Page 22)

16 Configuring Your Neutral and Ground Connections
7.2 Grounding Configuration, 480 or 600 VAC Input and Output, Delta Source
Figure 4 Grounding Configuration with Ungrounded Delta Source Input
As previously mentioned, Series 600T UPS systems require a bypass input neutral for sensing and
monitoring. With a wye-connected input source, the installer should always connected the building
service neutral to the System Control Cabinet (SCC) output neutral to achieve this. When the
building service is delta-connected, 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 SCC requires the Series 600T Artificial Neu-
tral Kit for proper operation. This kit uses a resistor network to create a reference point for the
bypass input. In this case, the SCC output neutral must be bonded to the SCC ground.
If the building service is corner-grounded delta or an Impedance-grounded wye, the SCC requires
the Isolated Neutral Kit, as do each of the UPS modules. This kit uses control isolation transform-
ers to create a reference point. For this application, the SCC output neutral must not be bonded to
the SCC ground.
NOTE
The Artificial Neutral Kit introduces a maximum current of 0.3 amps to
ground. Take care to ensure that this does not interfere with the operation of
any upstream ground-fault detection devices.