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Electrical Connections—UPS
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3.2.9 Protective Devices
For safety, it is necessary to install circuit breakers in the input AC supply external to the UPS
system. Given that every installation has its own characteristics, this section provides guidelines for
qualified installation engineers with knowledge of operating practices, regulatory standards and the
equipment to be installed.
UPS Rectifier and Bypass Input Supply
• Protection from excessive overcurrents and short circuits in power supply input
External overcurrent protection for the AC output circuit is to be provided. See 11.4 - UPS Elec-
trical Characteristics and Table 47 for overload capacity.
A breaker is used for internal battery circuit overcurrent protection. When an external battery
supply is used, overcurrent protection for the battery circuit is to be provided by the customer.
• Dual Input Single Source
When wiring the UPS with dual inputs but with a single input source, the Rectifier input and the
Bypass input must be protected separately. Size the breakers according to the input currents
shown in Table 41.
Fuses
The Liebert APM’s main input and bypass input busbars are equipped with fuses (six locations; see
Figure 33). The type is Bussman 170M4465, rated at 550A and 700V.
System Output
When using an external distribution panel for load distribution, the output neutral and input neutral
must be separated at the input to the UPS.
3.2.10 Cabling Procedure
Once the equipment has been positioned and secured for operation, and the battery and ground lugs
have been connected (see 3.2.6 - Cable Connections), connect the power cables as described below.
(Study the reference drawing in 6.0 - Installation Drawings.)
1. Verify that all incoming high and low voltage power circuits are de-energized and locked out or
tagged out before installing cables or making any electrical connections.
2. Remove the right side panel to gain easier access to the connections busbars.
3. Connect the safety ground and any easier bonding ground bus cables to the copper ground busbar
located in the middle of the Liebert
®
APM
™
below the Input and Bypass connections. All cabinets
in the UPS system must be connected to the user’s ground connection.
4. Identify and make power connections with incoming cables according to Steps 5 through 8.
Common Input Connections
5. For common bypass and main inputs, connect the AC input supply cables to the UPS input
terminals (A2-B2-C2-N1) and tighten the connections to 240lb-in. (27N-m) (M10 Bolt). Ensure
correct phase rotation.
!
CAUTION
The operations described in this section must be performed by authorized electricians or
qualified technical personnel. If you have any difficulties, contact your local Emerson
representative or Liebert Services.
NOTE
Hydraulic pressure pliers, combinative tools and piston ring pliers should be used to connect
AC wiring.
NOTE
The grounding and neutral bonding arrangement must comply with the National Electrical
Code and all applicable local codes.
NOTE
For common bypass and main inputs, the AC input cables must be connected to the bypass
terminal (A2-B2-C2-N1) but not the main input terminal (A2-B2-C2).