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32
3. Installation and Wiring
3.14.2 Parallel System Requirements
A group of USP systems connected in parallel for capacity or redundancy behaves as one UPS system, but with the
advantage of higher reliability. In order to assure all connected UPS systems are utilized equally and compliant with
wiring codes, following these requirements:
1. All UPS systems must be of the same rating and be connected to the same bypass source.
2. The outputs of all the UPS systems must be connected to a common output bus.
3. The length and specication of power cables, including the bypass input cables and the UPS output cables, should be
the same. This facilitates load sharing when operating in bypass mode.
Parallel conguration supports up to four UPS systems of the same kVA rating. Do not attempt to link more than four
UPS systems via parallel conguration.
1. Install and wire the UPS system as shown in Figure 3-19.
2. When installing the parallel system, the length of input wires (L1, L2, L3, N) in one UPS must be equal to the input
wires of the other UPS. Likewise, the length of output wires (L1, L2, L3, N) must also be in equal length. If not, it will
cause unbalanced current on the output load.
3. Connect the input wiring of each UPS to an input breaker.
4. Connect all input breaker wiring to a main input breaker.
5. Connect the output wiring of each UPS to an output breaker.
6. Connect all output breakers to a main output breaker. This main output breaker will directly connect to the loads.
7.
If an external battery pack is used, each UPS must be connected to an independent battery pack or a common battery
pack.
A
B
C
N
A
B
C
N
A
B C
N
A
B
C
N
UPS1
UPS2
Out put I nput
Note: Refer to section 4.3.6.2 steps 1 and 2 for information on conguring the UPS in parallel.
UPS 1
Output Input
UPS 2
L1 L2 L3 N L1 L2 L3 N L1 L2 L3 N L1 L2 L3 N
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