Emerson NX manual 2.5.6 1+N System Transfer load from UPS to Bypass

Operation

2.5.5Maintenance Bypass Load Transfers-Single Module System: If Load is on Maintenance Bypass

1.Verify that the module’s rectifier is On and in bypass mode. See 2.5.1 - Startup—Single Module System for the startup sequence.

2.Close the Bypass Input Breaker (BIB) or verify that it is closed. This breaker is external to the UPS; it may be in the Maintenance Bypass Cabinet.

3.Close the UPS Backfeed Breaker (BFB). Refer to 2.5.1 - Startup—Single Module System.

4.If using a key interlock system,

a.Depress the key-release unit push button.

b.Turn the key and remove it from the key-release unit.

NOTE

The UPS system is now locked in bypass and cannot be retransferred to the inverter until the key is returned.

c.Insert the key into the lock for the Maintenance Isolation Breaker (MIB);

d.Retract the bolt.

5.Close the Maintenance Isolation Breaker (MIB).

NOTICE

Risk of improper operation sequence. Can cause equipment damage.

Failure to close the Maintenance Isolation Breaker (MIB) will interrupt power to the load.

6.Open the Maintenance Bypass Breaker (MBB). Load is now on UPS Internal Bypass.

7.If using a key interlock system,

a.Remove the key from the lock for the Maintenance Bypass Breaker (MBB) to lock it open.

b.Reinsert the key into the solenoid.

8.The UPS system may now be transferred from bypass to UPS (see 2.5.3 - Load Transfer and Retransfer-Single Module System).

2.5.61+N System: Transfer load from UPS to Bypass

1.On each module, press the “Stop Inverter” button on touchscreen.

NOTE

The inverters will stay online until the Stop inverter button is pressed on the last module.

2.This will transfer the UPS system to bypass.

3.If transferring to a wrap-around Maintenance Bypass

a.If using a key interlock system,

1.The “OK to transfer” lamp on the key-release unit will light.

2.Depress the key-release unit push button.

3.Turn the key and remove it from the key-release unit.

4.Insert the key into the lock for the Maintenance Bypass Breaker (MBB).

5.Retract the bolt.

b.Close the Maintenance Bypass Breaker (MBB).

c.Open the Maintenance Isolation Breaker (MIB). The UPS system is now isolated from the critical load and the load is now on Maintenance Bypass.

d.If using a key interlock system:

1.Remove the key from the lock for the Maintenance Isolation Breaker (MIB).

2.Replace the key into the solenoid.

21 Liebert®NX™