APC MX28B-1200, MX28B-2400 Battery Connections Battery Disconnect, Cable Sizing Considerations

Revision B MX28B-1200 PRODUCT MANUAL

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.

Battery Positive (+)

+

-

Battery Negative (-)

Figure 5-4 Battery Connections

***** 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.

5.4DC 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.

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