What Does This Error Mean?

CyberPower UPS in bypass mode means connected equipment is running directly from mains power with no battery protection or power conditioning. Bypass is triggered automatically when the UPS detects an overload, overheating, or an internal fault that prevents normal inverter operation.

Affected Models

CyberPower CP850PFCLCD
CyberPower CP1350PFCLCD
CyberPower CP1500AVRLCD
CyberPower OL1000RTXL2U
All CyberPower models with bypass capability

Common Causes

Overload — connected load exceeded UPS capacity, UPS bypassed to avoid shutdown
Overheating — thermal protection engaged bypass mode
Battery fault — battery too degraded for safe inverter operation
Inverter fault — internal failure preventing normal double-conversion or line-interactive operation
Manual bypass switch activated during maintenance and not returned to normal

How to Fix It

Check the display for a fault code.

In bypass mode, the CyberPower display usually shows a fault code or indicator alongside the bypass status. Note any code displayed and refer to the manual for its meaning. Common codes: overload, over temperature, battery fault.
Reduce the load immediately.

If overload triggered bypass, disconnect non-essential devices from the UPS immediately. After reducing load below 80% of capacity, press the power button to attempt to return to normal mode.
Allow the UPS to cool.

If the bypass was triggered by overheating, move the UPS to a well-ventilated area. Leave it connected to mains for 15–20 minutes with reduced load to allow the thermal protection to reset. Then attempt to restart in normal mode.
Check the battery health.

A severely degraded battery can trigger bypass as the UPS refuses to operate the inverter without a functional battery. Check the display for a battery fault indicator. If the battery is due for replacement (over 3–5 years), install a new one.
Restart the UPS.

After addressing the root cause (reduced load, cooling, or new battery), power off the UPS completely. Wait 30 seconds, then power on. The UPS should start in normal line-interactive or online mode. If it immediately returns to bypass, contact CyberPower support.

When to Call a Professional

If bypass cannot be cleared after resolving overload and temperature causes, and no manual bypass is active, the inverter circuit has likely failed. Contact CyberPower support.