ABB TLE Scalable Series Installation Manual page 32

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Note!
This UPS is only designed to operate in a wye-configured electrical system with a solidly grounded
neutral.
The UPS cannot be operated from a mid-point or end-point grounded delta supply source.
If the UPS is equipped with an input bypass transformer, the secondary of the transformer must be
wye-configured with neutral solidly grounded
If the Load requires a Neutral, a Bypass Source Neutral MUST BE PROVIDED.
If no Neutral Connection is available with the Bypass Input (3-wire input + ground) and the Load does not require
a Neutral, solidly connect the Output Neutral of the UPS to ground with a ground bonding jumper.
For single module applications install the ground bonding jumper directly at the UPS output.
Cable size for this connection shall be per National Electric Code and applicable local regulations, but not less
than AWG 1.
Attention!
With this configuration, Load can only be connected phase-phase.
Absolutely no Load Connection permitted to the Neutral of the output transformer.
DO NOT install both a source Neutral and a bonding jumper!
RPA Parallel System
In an RPA Parallel System configuration, it is most
important to connect the Neutrals of the UPS outputs
together.
The output distribution cabinet must contain a
Neutral Bus (see Fig .4.8.1-2).
If no Neutral Connection is available with the Bypass
Input (3-wire input + ground) and the Load does not
require a Neutral, solidly connect the Output Neutral
of the UPS to ground in the Output Distribution
Cabinet.
Wire Neutral Conductors from the UPS to the output
distribution cabinet (common point of connection)
and solidly connect to ground with a ground bonding
jumper.
Cable size for the ground bonding jumper shall be per National Electric Code and applicable local regulations, but
not less than the cable recommended for the ground.
Please consider the following when applying Ground Fault Circuit Interrupters (GFCIs) in 3-wire distribution:
• During transfers to and from bypass, circulating current may flow between the two AC sources (UPS Inverter
and Bypass Utility). In 3-wire distribution the current flows through the ground path. In order to prevent
tripping in such circumstances, proper adjustment of the GFCI is required. Particularly, the time delay should
be set to at least 300ms.
• With the Neutral to ground bonding jumper installed, the UPS ground current has been verified to be less than
or equal to 5% of the maximum rated input current of the unit in compliance with international safety
regulations. This shall be accounted for in GFCIs settings.
Note!
Failure to properly adjust the GFCI settings could compromise the power delivery to the critical
load!
TLE Scalable Series 40 to 150 UL S1
Fig. 4.8.1-2 RPA Parallel System
UPS Installation Guide / REV-B