Electrical Connections
17
2.3.5 EPO Input—Optional
The UPS has an Emergency Power Off (EPO) function that operates by a button on the control panel
and a dry contact. The EPO button is under a hinged, clear plastic shield.
The X2 slot, shown in Figure 9, is the EPO input interface. It is active when shorted from EPO-L to
EPO-H.
If an external Emergency Stop facility is required, it is connected terminals EPO-L to EPO-H of the
auxiliary terminal block (X2). It also is connected to the Normally Open remote stop switch between
these two terminals using shielded cable (see Figure 9 and Table 5). If this function is not used, ter-
minals EPO-L to EPO-H must be opened.
2.4 UPS Startup
The NX must be fully installed and commissioned before startup, and external power isolators must
be closed. Once those general conditions are met, the UPS may be started.
2.4.1 Startup Procedure
To start the UPS from a fully powered-down condition:
1. Open the UPS door to gain access to the main power switches.
2. Turn the rotary switch to TEST.
Table 5 EPO input contact relays
Position Name Description
J28.2 EPO_L Emergency Power Off Low
J28.4 EPO_H Emergency Power Off High
NOTE
The Emergency Stop action within the UPS shuts down the rectifier, inverter and static
bypass. It does not internally disconnect the input power supply.
!
WARNING
During this procedure the output terminals will become live.
If any load equipment is connected to the UPS output terminals, please check with the load
user and ascertain whether it is safe to apply power to the load. If the load is not ready to
receive power, then ensure that it is safely isolated from the UPS output terminals.
!
CAUTION
Do not operate the rotary switch too fast. Always wait at least three seconds when rotating
the switch from one position to another.
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