Battery Connections | American Power Conversion MX28B1200 instruction

Rev 1

MX28B-1200+27V PRODUCT MANUAL

The AC input enclosure, located at the top rear of the MX28B housing, is provided with three pilot holes in the top for attaching external conduit (Figure 5-4), and three 1-inch conduits exiting the bottom for AC wire. AC wiring passing through the conduit will be routed through the access opening in the AC input enclosure into the wiring area where a safety ground bar and rectifier input terminal blocks are located. The terminal blocks are labeled as “L1” and “L2/N” for connection of the two AC wires (Figure 5-3). Each terminal block represents connections for all 4 rectifiers in the shelf.

The suggested wire size for L1, and L2 is #4 AWG rated at 105°C; however, the ambient temperature and number of wires in a conduit must also be considered in accordance with NEC requirements. Be sure to follow any local electrical wiring codes. Terminate the ground wire in the AC box at the top of the unit to the ground terminal block. Continue to run the remaining two wires into the individual conduits to each rectifier shelf. Connect them to L1, and L2 of the terminal block behind the access plate.

If the AC input power is provided from a three-phase distribution panel, the circuit breaker positions should be selected such that the load is balanced as much as possible.

Pilot holes (3)

Figure 5-4

5.3 Battery Connections

5.3.1Battery Disconnect

An external circuit breaker or fused disconnect (not supplied) is recommended in the positive 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 or fuse for a battery string should take into account maximum battery short circuit current and cable sizing.