Ways an APC by Schneider Electric Double Online UPS Can Enter Bypass Mode

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Question:

What can Make a Single Phase APC Double Online UPS go to Bypass?

Product - Environment:
Double Online Topology based APC UPS units.

Answer:

There are two primary methods by which an APC by Schneider Electric Double Online UPS can switch to bypass mode. The exact process may vary depending on the specific model.

1. UPS Maintenance/Manual Bypass (Hard Bypass)

This method is initiated through physical interaction, requiring the end user to operate a breaker or rotary switch on the UPS itself. It is typically used during maintenance or testing.

For best practice, it is highly recommended to install an external Service/Maintenance Bypass Panel or Service Bypass Unit alongside the UPS. This ensures minimal downtime and simplifies replacement or servicing of the UPS. Check how a Service Bypass Panel is wired by clicking here.

The images below illustrate the location of the maintenance bypass switch on various APC by Schneider Electric models.

This is an image showing a LEGACY SURT single phase UPS Maintenance Bypass Switch The following image shows the MAINTENANCE BYPASS SWITCH/BREAKER of a Smart UPS Modular Ultra UPS

2. Internal Static/Automatic Bypass (Soft Bypass)

This feature is built into Double Online UPS units and can be activated manually through UPS control interfaces, such as a network management card, software, or the front display panel—depending on the model design.

The static bypass switch also engages automatically under certain conditions, such as:

- A system fault detected within the UPS
- Output instability caused by potential overloads

If the incoming power remains within the configured bypass range, the UPS will successfully transfer to bypass mode.

Modular UPS units like Symmetra™ and Smart-UPS Modular Ultra™ may exhibit additional soft bypass behaviors. For example, when transitioning from a hard bypass state - After the maintenance bypass switch is turned OFF, the UPS enters Temporary Bypass for approximately 10 seconds before returning to its previous operational state. This delay allows power modules to synchronize with the line cycle, reducing the risk of power distortion during reintegration.

If you have any clarifications and/or if you require assistance to troubleshoot your UPS, please feel free to contact us at 1-800-800-4272 or chat with our technical support representatives.