It was 2 AM on a Sunday. Marcus, the senior facilities engineer for a mid-sized financial firm, got an automated alert: The Liebert Hipulse E—a 200kVA dual-conversion UPS protecting their trading floor—had switched to bypass mode.
Industrial UPS systems contain lethal DC and AC voltages. Before opening any equipment panels, adhere to strict safety measures.
| | Likely Cause | Recommended Action / Fix | | :--- | :--- | :--- | | INV. OFF | Inverter switched off or internal fault. | Check for other inverter alarms; seek service if fault persists. | | INV. OVERTEMPER. | Overheating due to poor ventilation. | Clean filters/fans, reduce ambient temp; load transfers to Bypass after 3 min. | | OVERLOAD PRESENT | Connected load exceeds 100%. | Reduce connected load immediately. | | RECT. OFF | Rectifier input failure or internal fault. | Check if Q1 is closed and input supply is normal. | | BATTERY: E.O.D. | Battery discharge beyond safe limit. | Initiate orderly shutdown; test/replace batteries. | | BYP. ABSENT | Bypass supply missing or failed. | Check if Q2 is closed and bypass input is stable. | | INV. UNSYNCHRONIZED | Bypass frequency out of acceptable range. | Check bypass source frequency; avoid switching off inverter. | | MANUAL BYPASS CLOSED | Load on unprotected maintenance bypass. | Follow procedure to transfer back to normal operation. | | BYP. SCR FAILURE | Static switch component failure. | Seek qualified assistance immediately. | | INV: PARALLEL ERROR | Incorrect load sharing in a parallel system. | Seek qualified assistance to investigate parallel board. | liebert hipulse d ups manual fix
Initial information to collect
Visually inspect air filters and verify room ambient temperature is kept between 20°C and 25°C (68°F to 77°F). It was 2 AM on a Sunday
When the HiPulse D encounters a fault, the liquid crystal display (LCD) panel or LED matrix flashes specific alarms. Identifying these codes is your first step to a manual fix. Common Alarm Reference Table Alarm Message / Code Likely Root Cause Immediate Action Commutation failure, blown IGBT, or blown DC fuses. Check inverter driving board and DC fuses. Rectifier Fault / Mains Abnormal
The Hipulse D’s default battery test is a "load step" test. It ramps the inverter to pull current from the batteries while still online. If the battery internal resistance is slightly high (but not dead), the voltage dips below the "Boost Charge Threshold," causing an auto-abort. Before opening any equipment panels, adhere to strict
For the other 80% of faults—phase errors, false SCR shorts, frozen screens, and PLL sync issues—the manual fixes detailed above will restore your Hipulse D to service. Always remember: the manual is a guide, but field experience is the real fix. Keep a digital copy of the Service Manual (Section 6: Troubleshooting) on your phone, and never reset an alarm without verifying the source.
Carefully measure the total string voltage at the DC breaker terminals to verify it matches the required DC bus specification. Clean any corroded terminals and tighten loose bolts using insulated torque wrenches. 2. Step-by-Step Manual Bypass Procedures
The is an industrial-grade UPS designed by Vertiv (formerly Emerson Network Power) for harsh environments like power plants and manufacturing. Common "Manual Fix" Procedures