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3.4 Control Connections (MBS Arrangement Only)
Four control connections must be made between the Transformer Cabinet with MBS
arrangement and the UPS in order to provide backfeed protection, a required safety feature.
There is also a provision to provide Remote Emergency Power Off (REPO). REPO causes
the output breaker to trip, thereby removing power from the load. If the bypass path is
active, then REPO trips the bypass breaker, removing power from the load.
The wiring to these low voltage (“ELV”) connections must be kept separated from the
higher voltage wiring. Refer to
Figure 7
regarding the Low Voltage Terminal Block and to
the UPS manual that shows the connection point in the UPS.
3.4.1 Connections Between the Maintenance Bypass Switch and the UPS (MBS Arrangement
Only)
Since these wires affect the operation of the UPS, they should be protected. Running them
in conduit is recommended. It is also recommended that the wires are shielded twisted
pairs. Alpha 6010C is a shielded cable with three twisted pairs and is available from a
number of sources in various spool lengths.
Two pairs are required:
Pair 1 -- First wire from terminal 3 of the Low Voltage Connection Terminal Block (LVTB) of
the Transformer Cabinet with MBS arrangement to terminal 11 of the Remote Commands
and Alarms Connections on the UPS (RCA-UPS). Second wire from terminal 4 of LVTB to
terminal 12 of RCA-UPS.
Pair 2 – First wire from terminal 10 of LVTB to terminal 1 of RCA-UPS. Second wire from
terminal 11 of LVTB to terminal 2 of RCA-UPS.
Figure 7
is an electrical wiring schematic summarizing the connections to the Low Voltage
Connection Terminal Block.
The REPO switch connections are also shown. Please note that typically only one of the
REPO switch contacts is connected, depending on user preference, but both are shown to
illustrate the wiring. The normally open switch connects across terminals 5 and 6 while the
normally closed switch connects across terminals 8 and 9. Terminal 7 has a limited
amount of unregulated dc power available to power an LED lamp to permit the use of a
lighted switch for REPO. Contact Dual-Lite for details if you desire to use this feature. See
Section 3.4.3 Switch Settings (MBS Arrangement Only)
to properly configured the
Options Control Board in the Transformer Cabinet for the normally closed REPO switch to
work.
3.4.2 Terminal Strip Torque Requirements (MBS Arrangement Only)
The terminals on the Customer Low Voltage Connection Terminal Block must be torqued to
5.3 to 7.0 inch-lbs. The terminals on the Control Connections (on the UPS) must be torqued
to 4.4 inch-lbs.
