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3.3.1. UPS System Power Wiring Preparation
NOTE
If installing a maintenance bypass, a minimum of two separate feeds with upstream
feeder breakers, or a single feed with two upstream feeder breakers, must be provided:
one for the UPS or rectier input breaker (if installed) and one for the maintenance bypass
input. DO NOT use a single feed or a single feeder breaker to supply both the UPS or
rectier input breaker and the maintenance bypass. If a bypass input breaker is installed
in the maintenance bypass and a single-feed UPS is being installed, a single feed to the
maintenance bypass is acceptable for supplying both the UPS and the bypass.
Read and understand the following notes while planning and performing the installation:
• Refer to national and local electrical codes for acceptable external wiring practices.
• To allow for future kVA upgrades (software and/or hardware), consider using conductors
sized for full bypass rating of the UPS.
• Material and labor for external wiring requirements are to be provided by designated
personnel.
• For external wiring, use 90°C copper wire. See the appropriate information in
Table 3-4
. Wire
sizes are based on using the specied breakers.
• If wire is run in an ambient temperature greater than 30°C, higher temperature wire and/or
larger size wire may be necessary.
• Specication is for copper wire with a 90°C rating.
4-wire system:
• The input uses three live wires and N wires, plus a grounding wire (protective grounding
conductor).the phases must be symmetrical about ground (from Y-type/Wye source) for
proper equipment operation.
• Support the load that needs to take N wire.
• If the neutral wire is disconnected, all phase wires should be disconnected at the same time.
3-wire system:
• The input uses three live wires and grounding wires (protective grounding conductors).
• Without the N-line, it does not support the load that requires the N-line.
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