Alpha Technologies CXPS 48-1.2-225 48 Vdc - Manual (Page 27)

053-691-B1 Rev E Page 19 of 33
5 Wiring
This chapter provides cabling details and notes on cable sizing for DC applications.
WARNING Ensure that the power is removed by turning off rectifiers and removing battery line fuses
or connections before attempting work on the wiring connections. Use a voltmeter to verify the
absence of voltages. Clearly mark the correct polarity of the battery leads before working on DC
connections.
Refer to the Installation chapter for safety precautions and tools required.
5.1 Grounding
NOTE: This power system is suitable for installation as part of a Common Bonding Network (CBN) and is intended to be
used in a DC-C configuration (common DC return).
Connect the isolated power system battery return bus (BRB) to the building master ground bus (MGB) or floor
ground bus (FGB) in larger buildings. This acts as a system reference and a low impedance ground path for
surges, transients, noise, etc. The MGB or FGB should have a direct low impedance path to the building
grounding system.
Size the cable between the power system and the MGB or FGB so that there is sufficient ampacity to clear the
largest fuse or breaker on the power system, excluding the battery protection fuse or circuit breaker. This is the
minimum requirement. Other factors including length of cable and special grounding requirements of the load
must be factored in. The insulated cable should be equipped with two-hole crimp type lugs and should not have
any tight bends or kinks.
Power system ampacity Ground reference conductor size
< 30 A #10
30 – 100 A #6-2
100 – 400 A 0000
400 – 800 A 350 MCM
> 800 A 750 MCM
Table B–Typical ground reference conductor selection
5.1.1 Frame ground
The power system frame must also be connected to the MGB or FGB for safety reasons and to meet standard
Telco grounding requirements. Each bay must have its own frame or site ground connection. Refer to the
customer connections drawing at the rear of this manual.
The distribution center is grounded to the relay rack with screws/bonding washers, and then uses 35 mm
2
(#2 AWG) insulated cable to connect to the main grounding bus.
5.2 AC feeder protection/sizing
To maximize system reliability, each power module should be fed from a dedicated protection feeder breaker
located at the AC distribution panel. The feeder breaker can also be used as a disconnect device for the
connected module. Refer to the specifications at the front of this manual for Alpha recommendations.
5.3 AC input connections
CAUTION: AC input wires must be routed in flexible or rigid conduit as far away as possible from DC
power wires to minimize EMI disturbances.
Ensure that all modules are removed from the shelf. Refer to customer connections drawing. The shelf
incorporates IEC plug connections, which require line cords with C19R type receptacles. See ordering information
for available cords.