Figure 1.3 Warning Label
Back feed protection can also be implemented by means of coil-based system controlled by UPS itself through output dry
contact triggered in case of back feed. Output dry contacts are configurable.
WARNING! High earth leakage current: Earth connection is critical before connecting the input supply
(including both mains supply and battery). This equipment is installed with an EMC filter. Earth leakage
current is less than 3000 mA. Transient and steady state earth leakage currents, which m ay occur when the
equipment is started, should be taken in to account in the selection of instantaneous RCCBs or RCD devices.
RCCB which is sensitive to unidirectional DC pulse (class A) and insensitive to transient state current pulse
must be selected. Note also that the earth leakage currents of the load will be carried by the RCCBs or RCDs.
The equipment must be earthed in accordance with the local electrical code of practice.
WARNING! The selection of the upstream distribution protection equipment of the UPS shall be selected in
accordance with the details and shall comply with the local electrical regulations.
WARNING! Back feeding protection
This UPS is fitted with a dry contact closure signal for use with an external automatic disconnect device
(supplied by others) to protect against back feeding voltage into the incoming terminal through the rectifier
or bypass static switch circuit. A label must be added at all external incoming primary supply disconnect
device to warn service personnel that the circuit is connected to a UPS. The text of the label has the following
meaning: Risk of voltage back feed! Isolate the UPS, then check for hazardous voltage between all terminals
including the protective earth before working on this circuit.
1.6 Operation
NOTE: Do not disconnect the grounding/earthing conductor cable on the UPS or the building wiring terminals under
any circumstance.
NOTE: The UPS system features its own, internal current source (batteries). The UPS output sockets or output
terminal blocks may be electrically live even if the UPS system is not connected to the building mains/live wires. (only
for standard models)
NOTE: Press the “OFF” button and then disconnect the mains/live wires to fully disconnect the UPS system.
1 Important Safety Instructions Proprietary and Confidential ©2024 Vertiv Group Corp. 5
Vertiv™ Liebert® MTP Online UPS User Manual 20-40-80kVA
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