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 specification 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 configuration supports up to four UPS systems of the same kVA rating. Do not attempt to link more than four UPS
systems via parallel configuration.
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.
Note: Refer to section 4.3.6.2 steps 1 and 2 for information on configuring the UPS in parallel.
U PS1
UPS 1
A B C N A B C N
L1 L2 L3 N L1 L2 L3 N
U PS2
UPS 2
A B C N A B C N
L1 L2 L3 N L1 L2 L3 N
O ut put
I nput
Output
Input
32