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11.4 Grounding Wire
Be sure to ground the UPS as specified.
Using the UPS without a proper ground will deteriorate the
insulation and may cause electric shock due to leakage currents.
The resistance to ground should be 10Ω or less.
A grounding bus is provided on the inside of the each unit. The bus is located on the front at the bottom of
the UPS units. For the 250/300kVA unit, it is located on the top left. See chapter 7 “Dimensions and
Weight” for bus location detailed.
It is recommended that 2 AWG (or 38mm
2
) or larger cable be used for the grounding wire. The wire shall
be fed through an opening at the bottom, or through a hole on a knockout plate (250/300kVA only). See
Figure 11.5 for knockout plate detail. Only one of 2 ground buses on top and at bottom shall be
connected to the ground for 250/300kVA.
The cable end must have Amp terminal of 1/2” (12mm) diameter hole to tighten with ground bus inside
the UPS, as the ground bus has 33/64” (13mm) screw hole.
The Amp terminal and ground bus shall be tightened with a 7/16” (10mm) diameter screw.
Figure 11.6 - Earth Ground Wiring.
WARNING
< 100~225kVA >
2AWG (38mm
2
)
Ground bus
12mm or 1/2”
Terminal
Feed
Through
Opening
10mm or 7/16”
Screw
To the facility
Earth ground
< 250/300kVA >
Through knockout plate
On top (Recommended)
10mm
OR
7/16”
Screw
Another way
For grounding
Note:
Only one top or bottom should
be connected to ground.