Chapter 11 – ‘1+N System’ Liebert Hipulse E User Manual
Single or '1+N' UPS System
Page 11-10 (07/04)
11.2.5 Procedure for Switching the UPS system into normal operation from a Maintenance Bypass condition
- 1 + N Configuration (> two UPS's) or two UPS's with parallel power connection
It is assumed that the installation is complete (which includes also the maintenance bypass cabinet), the system has
been commissioned by authorized personnel and the external power isolators are closed. Study the reference
drawing provided in figure 4-8.
The process of transferring the load back to the UPS supply is the reverse of that described above.
1. Carefully read the messages displayed for the first UPS to make sure that the bypass supply is regular and
synchronised with the inverter in order to avoid short interruptions in the load supply.
2. Insert key (BP1) into the UPS and press INVERTER OFF button on the operator control panel (see Figure 8-2).
3. Place and rotate the key in the Castell key exchange box situated next to the switch panel of the external
maintenance bypass cabinet.
4. Repeat Steps 1 and 3 for all UPS.
5. Extract key BP2, insert it into the lock next to the UPS output isolator (Q4MBC) and turn it. Close the UPS output
isolator (Q4MBC). The external bypass line is now parallel with the bypass supply of the UPS's.
6. Open the external bypass isolator (Q5BYP). Extract key BP2.
7. Place and rotate the key (BP2) in the Castell key exchange box.
8. Remove the BP1 keys from the Castell key exchange box , and turn on the UPS inverters one at a time. The
system gradually reaches the ordinary operating status switching the load from the static bypass to the inverters.
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