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Revision B MX28B-1200 PRODUCT MANUAL
MX28B-1200/2400 17
5.3 Battery Connections
5.3.1 Battery Disconnect
An external circuit breaker (not supplied) is required in the negative line (located at the battery
end) to protect the cables from the battery to the MX28B dc power plant. The power plant can
monitor auxiliary contacts from this breaker. Selection of a circuit breaker for a battery string
should take into account maximum battery short circuit current and cable sizing.
5.3.2 Cable Sizing Considerations
The battery cable(s) should be sized
sufficiently large to limit the voltage drop from
the MX28B dc power plant to the battery
during charging per system design
requirements. The cable(s) must also carry the
full load current during battery operation. If
assistance is required to determine the
necessary cables for the application, contact
your sales representative or APC.
5.3.3 Connecting the Cables
The battery cable connections are located at the
top rear of the unit as shown in Figure 5-4.
The battery positive (return bus) and battery
negative (-48V bus) buses each provide four
sets of 3/8”-16 holes on a double pattern one-
inch and 1 ¾-inch centers for connecting two-
hole battery cable lugs. Connect the battery
cables as applicable using 3/8”-16 bolts (not
provided) and tighten them with a torque
wrench to 200 in-lbs.
***** CAUTION *****
Make certain that the battery polarity is correct when making connections to the Model
MX28B dc power plant. Incorrect connection could cause severe equipment damage.
5.4 DC SYSTEM GROUNDING
THE POSITIVE LOAD CONNECTION (RETURN BUS) FOR THE POWER PLANT
MUST BE CONNECTED TO THE FACILITY MASTER STATION GROUND. THE
CONNECTION SHOULD BE MADE ON THE RETURN BUS IN THE BASE UNIT
DISTRIBUTION AREA. DETAILS FOR THIS CONNECTION SHOULD BE
PROVIDED IN THE SITE ELECTRICAL GROUNDING PLANS.
+
-
Battery Positive (+)
Battery Negative (-)
Figure 5-4 Battery Connections