Alpha Technologies Cordex HP CXRF 48-12kW - Manual (Page 23)

21 9400000-J0 Rev C
7.1 Grounding
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 a larger building. This acts as a system reference and as a low impedance path to the
ground for surges, transients, noise, etc. The MGB or FGB must have a direct low impedance path to the building
grounding system.
The cable from the power system to the MGB or FGB must be sized to provide sufficient ampacity to clear the
largest fuse or breaker on the power system, excluding the battery protection fuse or circuit breaker. 750 MCM
is recommended. This is the minimum requirement. Other factors including the length of the cable and special
grounding requirements of the load must also be factored in. The insulated cable must be equipped with two-
hole crimp type lugs and must not have any tight bends or kinks.
Table A — Typical ground reference conductor selection
Power system ampacity Ground reference conductor size
< 30A #10
30 – 100A #6-2
100 – 400A 0000
400 – 800A 350 MCM
> 800A 750 MCM
The power system frame must also be connected to the MGB or FGB. This is done for personnel safety and to
meet many telecom grounding requirements. Each bay must have its own frame or site ground connection. Refer
also to the customer connections drawing at the rear of the manual.
7.2 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 act as the disconnect device for the connected
module. Refer to the specifications for Alpha recommendations.
WARNING!
Ensure that the power at the AC service panel is off is switched off. Remove battery line
fuses or connections before attempting work on the wiring. Use a voltmeter to verify the
absence of a voltage. Clearly mark the correct polarity of the battery leads before start-
ing work on DC connections.
7. Wiring
This chapter provides cabling details and notes on cable sizing for DC applications using the Cordex 48-3.6kW,
4.0kW and 12kW modular switched mode rectifier systems.
Refer to the Safety section on page 5 for safety precautions.