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Proper Shutdown of a DPP UPS System with External Remote Manual Bypass Switch

Do you need to shut down your Digital ProcessPower (DPP) Uninterruptible Power Supply (UPS) system for some spring cleaning, maintenance or parts replacement? We have a step by step guide on how you can power down your DPP UPS system if it has an external Remote Manual Bypass Switch (RMBS) attached to it. These procedures will remove all power from the UPS system and allow you to work safely.

First, we will describe key indicators for normal operation and then explain the shutdown procedure.

Normal Operation

When your DPP UPS system is in normal operation there should be a few key indicators:
1. All the breakers on the front of the UPS should be closed.

2. On the display panel, the UPS Normal and In Sync indicators will be lit with green LED lights.

3. The display screen on the panel will show a line diagram with a bold line representing the power flow, including ‘Charger OK’ and ‘Inverter OK’ indications. This line goes all the way through to the static switch. The battery line is also in bold, indicating that the battery breaker is closed. The Float LED and Inverter to Load LED should both be on in green below the display screen.

Victor Voltage Tip:
Keep in mind our systems are customized specifically for each client, so your UPS display panel may show a different number of alarms and LEDs, feature different alarm types or have additional breakers. The main procedure will be the same as our below instructions, but you may have additional steps on the procedure plaque on the front of your system. It is important to always read the plaque and follow the procedures that are specified for that unit.

Safely Shutting Down
These ten steps correspond with our below shutdown video. Viewing the video will provide a visual reference and additional tips.


1. Press Bypass to Load Button – When you press it, the system will do a self-check and if everything is OK, it will transfer to Static Bypass. The Bypass to Load indicator on the display panel will now be lit with an amber LED light and the UPS Normal green LED has shifted to the red LED UPS Trouble indicator. The display screen will automatically change to the Alarm Status screen, which is showing an alarm called Bypass Supply in Load. This alarm means the bypass supply is now feeding the load circuits through the static switch internal to the UPS.

Victor Voltage Tip: The DPP system protects your load with a fail-safe feature where it will not allow the transfer if it detects there’s something wrong between the bypass and inverter.

2. Transfer RMBS to the Bypass to Load Position – In order to transfer, you want to make sure the unit is in sync. There’s a green LED on the RMBS unit that will indicate it is in sync. You can also make sure the UPS system Bypass to Load is indicated with the amber LED. Once you’ve confirmed they are in sync, you can move from the Normal Operation Position on the external RMBS to the Bypass to Load Position. At this point the bypass is now feeding power to the load circuits through the RMBS. 

Victor Voltage Tip: Remember the RMBS unit may be anywhere in the UPS system room, it may not be right beside your system. It tends to be on a wall where there was available space. Transfer the Inverter Enable Switch to the Off Position – Locate the Inverter Enable Switch and turn it to the Off Position.

3. Transfer the Inverter Enable Switch to the Off Position – Locate the Inverter Enable Switch and turn it to the Off Position. The Alarm Status screen will give two additional alarms: Inverter Low Voltage (Fast) and Inverter Failure. Click the Mimic button to return to the main screen and it will indicate Inverter Fail.

Victor Voltage Tip: When the Inverter Enable Switch is in the On Position, you will hear a constant high pitch noise, which indicates it is running. The noise will stop when switched to the Off Position.

4. Open the AC Input Breaker – Find the AC Input Breaker and turn to the Off Position. The Alarm Status screen shows the Charger Failure alarm. Returning to the main screen will show Charger Fail.

5. Open the Battery Input Breaker – Find the Battery Input Breaker and open it. The Alarm Status screen will show four new alarms: Low DC Voltage, Low DC Disconnect, Battery Breaker Open Alarm and DC too Low for Start.

Victor Voltage Tip: Clicking the Mimic button to return to the main screen will allow you to watch the DC Bus inside the system drop in Volts DC as the capacitors discharge.

6. Open the Bypass Input Breaker – Find the Bypass Input Breaker and open it.

Victor Voltage Tip: This is the point that scares people the most because the UPS system’s screen and fans turn off and they think their load circuits have now lost all power. The bypass supply is still supplying the load through the switch though. Everything on the load circuits is powered up and healthy.

At this point there is still voltage coming to the Battery Input Breaker from the battery, voltage coming to the AC Input Breaker from the 3-phase 480 Volt MCC bucket and bypass input voltage coming to the Bypass Input Breaker. All three sources need to be removed before work can safely be done on the system.

7. Remove the Bypass Power to the Bypass Input Breaker – Returning to the RMBS, move it to the third position, Isolated Bypass. This removes the voltage from the switch to the breaker.

8. Remove Power to the AC Input Breaker – Find the MCC Bucket and find the 3-phase 480 supply that supplies the AC Input to the rectifier. Open the bucket and put a Lockout/Tagout on that breaker.

9. Disconnect the Battery Input Breaker – Utilize the external battery disconnect on the battery. Open and Lockout/Tagout to remove the power.

10. Once you have removed all sources of power, everything in the UPS is completely Volt free aside from any alarm contacts you have from your DCS system. You will need to isolate any DCS power to alarm contacts within it before it is safe to work on.

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