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7. Turn off S7 (ON-OFF) and after a few seconds turn it on again. UPS wilt start running again.

8. When “INVERTER START” message appears on the front panel turn on S5 (Battery) into “1”.

Perform the same procedure given above for all UPS units. Make sure that all the units have the

same operating mode but different UPS numbers.

9. Turn on S4 (AC Output) switches of all UPSs one by one. Now the parallel UPS system is ready to supply

the critical load.

5.3.2 Power Off

After turning off all the loads connected to the Parallel UPS System output, apply the following procedure to

all the UPS units in the parallel system.

1. Turn off S4 (AC Output) into “0” position.

2. Turn off S7 (ON/OFF Switch) into “0” position.

3. Turn off S5 (Battery) into “0” position.

4. Turn off S2 (Bypass) into “0” position.

5. Turn off S1 (AC Input) into “0” position.

This is a complete power off condition and both RECTIFIER and INVERTER are not operating in this case.

5.3.3 Switching the Parallel UPS System into Maintenance Bypass Mode

(uninterrupted transfer)

1. Switch S6 (static bypass switch for parallel UPSs) of either one of the UPS units into “STATIC BYPASS”

position.

2. See that the red-colored by-pass LEDs (L4) on the front panels of all UPSs are turned on.

(Static Bypass Operation)

3. Turn on S3 switches (maintenance bypass) of all UPSs in the parallel system.

4. Turn off S4 switches (AC Output) of all UPS units.

5. Turn off S1 (AC Input) and S2 (Bypass) switches of all UPSs.

6. Turn off S5 (Battery) switches off all the UPS units in the parallel system.

Now all the UPS units which are connected in parallel are completely turned off and the load is

supplied by the common Bypass supply via the Maintenance Bypass Switches of all the UPSs.

5.3.4 Switching the Parallel UPS system into Normal Operation From a Maintenance Bypass

Power Down Condition. (uninterrupted transfer)

With the S6 switches (static bypass) of at least one of the UPSs, in “STATIC BYPASS” position, turn on

all the units as follows:

1. Turn on S1 (AC Input) switches into “1” position.

2. Turn on S2 (Bypass) switches into “1” position.

3. Turn on S4 (AC Output) switches into “1” position.

4. Turn on S7 (ON-OFF) switches into “1” position.

5. When “MAINT SWITCH ON” message appears on LCD, turn off S3 (Maintenance bypass) switches of all

UPSs.

6. Turn on S5 (Battery) into “1” position.

7. Bring S6 (static bypass) switches of all UPS units back to “NORMAL” position.

inform DSP User Manual

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