Input/Output Over Current Protection And Wire Sizing; Battery Connection; Input Grounding Systems - ABB MegaFlex 1000 UL S1 Installation Manual

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4.8.2 Input/output over current protection and wire sizing

Wiring must be sized according to UPS power rating.
Sizing of Circuit Breakers and cables for Input Utility, Output Load and Battery must meet the requirements of
local and national electrical code and any other local regulation that may apply.
Utility Voltage, Frequency, Short Circuit Current, Load Voltage, Frequency, Current and Battery data (cells
number, floating voltage, autonomy) must be within UPS rating. This must be verified prior installation.
Avoid running the input cables in parallel with the output cables to prevent them from noise induction.
The connection of the Battery to the UPS must be protected with breakers or similar devices according to
technical specifications and in accordance with local standards.
Power cables must run into dedicated conduits. Signal and RPA cables shall not share routing with power cables.
Note!
If you use ELCB breaker (Earth Limiting Circuit Breaker) to protect the input connections, consider
the high leakage current generated by the noise suppression capacitors.
If these ELCB breakers are strictly necessary, we suggest using the largest type suitable for non-
linear current and for delayed operations.
To ensure the Circuit Selectivity in case of Short- Circuit in the Load equipment, special care must be taken in
choosing the Circuit Breaker ratings installed in the output distribution circuits.
Due to the relatively low short-circuit capability of the UPS Inverter, a short-circuit in the Load will cause an
immediate transfer to Utility.
The largest breaker in the output distribution should be at least 1.6 time smaller than breaker supplying Bypass
line.
If Circuit Selectivity is required while the Load is fed from the Inverter (Bypass Utility not available), the Largest
Circuit Breaker should be rated at no more than 20% of the UPS Output Current Rating.
Note!
The delivery and installation of breakers and input/output connections of the UPS are at the
customer's expense, unless agreed otherwise.

4.8.3 Battery connection

Remote Battery cabinet is external and not provided with UPS.
Battery poles must be insulated from ground (floating). Center-tapping is not allowed.
Battery cabinet's ground must be connected to UPS ground.
UPS internal protections can cope short circuit fault currents from 8 kA to 100 kA.
Make sure Battery overall short circuit capacity falls into this range.

4.8.4 Input grounding systems

Megaflex 1000 to 1600 UL UPS is compatible with the following grounding systems:
480V, 3-phase, 3-wire grounded or 480V, 3-phase, 3-wire ungrounded and 480V, 3-phase, 3-wire ungrounded high
resistance ground. Equipment connected to UPS shall meet the grounding system intended.
As defined by NFPA 70 Article 250, grounding detectors and cautionary marking shall be provided to operate in
ungrounded systems.
Under no circumstances neutral bonding shall be pulled to UPS: only phase-to-phase balanced loads are allowed.
When UPS operates in VFI mode, grounding on the AC input is delivered to the AC output circuit (non-separately
derived system). During temporary Battery operation, the output is always ungrounded.
MegaFlex 1000 to 1600 UPS Installation Guide / REV-A