Configuring Your Neutraland Ground Connections 15
7.1 PreferredGrounding Configuration, 480 or 600 VAC Inputand Output, IsolatedPower Distribution Units, Wye-ConnectedService
Figure 3 Preferred Grounding Configuration, 480 or 600 VAC Input and Output
The most-common configuration of Series 600T UPS Multi-Module Systems is with 480 VAC
input, 480 VAC output, and a conne cted load consisting of multiple Power Distributi on Units
(PDUs) with isolation transformers in the PDUs to produce 208 VAC. For Canadian customers,
the UPS modules usually have 600 VAC input and output. The same principles apply if the con-
nected load is an isolation transformer feeding various load s. Figure 3 above shows a typical
installation. The Maintenance Bypass Switc hgear is shown separately for clarity, but is usually
containedwithin the System ControlCabinet (SCC).
Noticethat the UPS module inputand the system bypass inputare connected to a grounded-wye
service. In this configuration, the UP S module is not considered a separately derived s ource.
All ofthe UPS module output neutralsare solidly connected to theSCC neutral. The SCC neutral
is solidly connected to the building s ervice neutral, which is bonded to the gro unding conductor at
the service entranceequipment.
The isolation transformersin the PDUs can be considered separately derived sources. Therefore
the PDU neutrals should be bonded to the PDU grounding conductor and connected to a local
grounding electrode in compliance with NEC 25 0-26.
NOTE
Impedance-grounded w ye sources require an Isolated Neu tral Kit in
addition to the grounding and ne utral conductors shown above.