Engineering guide
Galaxy VX alarms and mimic diagram LEDs
On a Galaxy VX the first clue is the mimic diagram: a red input, inverter or load LED narrows the fault to one stage of the power path. The message itself is in the active alarms list and the UPS log. Note both, keep the room and airflow clear, and call a technician for critical alarms, battery alarms and any loss of redundancy.
Key facts
- Red input LED: UIB open, or input out of tolerance
- Red load LED: UOB or SIB open, or output voltage out of tolerance
- Battery condition is poor: Capacity below 50%; replace batteries
- Restricted air flow: Critical; clogged filter or obstacle
- System locked in bypass operation: More than 10 transfers within 1 minute
Reading the red LEDs on the mimic diagram
The operation manual lists what each red LED can mean:
- Input LED red: the unit input breaker UIB is open, or the input is out of tolerance (waveform, voltage or frequency).
- Inverter LED red: the inverter is inoperable.
- Load LED red: UOB or SIB is open, or the output voltage is out of tolerance.
A red input LED during a utility disturbance is expected; a red inverter or load LED on a Galaxy VX with normal utility is a service call.
Two logs, two purposes
The VX keeps an NMC log (display and network activity) and a UPS log (system status and operation modes). For a fault, the UPS log is the one that matters: it shows the sequence of mode changes. Export or photograph it before anyone resets the system, because the order of events is often the diagnosis.
Battery and airflow alarms
- Battery condition is poor (warning): capacity is below 50%; the manual says the batteries should be replaced.
- Battery breakers tripped (event): the system tripped the battery breakers to stop a deep discharge. The manual's corrective action is closing them manually; have a technician confirm why they tripped first.
- Restricted air flow (critical): air flow is restricted, which the manual links to a clogged air filter or another obstacle.
- Fan inoperable (warning): one or more fans have stopped and fan redundancy is lost.
Large VX battery plants are usually replaced string by string. When a poor-condition alarm appears, battery blocks matched to the installed Schneider string can be quoted before the outage season, and the installation planned with a technician on site.
Load, input and redundancy alarms
- Input voltage out of tolerance (warning): mains input voltage is out of tolerance.
- Bypass voltage out of tolerance (warning): the bypass input is out of tolerance, so a requested bypass transfer is refused.
- Overload on installation (warning): the load exceeds 100% of the rated installation capacity; reduce load.
- Lost parallel redundancy (warning): the load is above the limit for the configured N+x redundancy; reduce load.
- System locked in bypass operation (critical): more than 10 transfers between inverter and bypass within 1 minute.
- System operation mode - Maintenance Bypass (warning): the load is on the maintenance bypass breaker MBB.
Lost redundancy does not drop the load, but it removes the margin the system was bought for; the N+1 and 2N guide explains the trade-off.
Safe checks and when to call
From the front of the unit, an operator can read the mimic LEDs and alarm list, record load percentage and mode, and check room temperature and that nothing blocks the air intakes. Everything else, including breakers, power cabinets and batteries, is technician work. For multi-cabinet systems, scheduled service on Schneider three-phase systems covers fans, filters and capacitors before they turn into alarms; see also three-phase UPS preventive maintenance.
Related pages
Common questions
What does a red load LED mean on a Galaxy VX?
The manual lists three causes: UOB open, SIB open, or output voltage out of tolerance. The load may not be fed normally, so call for service.
Why did my Galaxy VX trip its battery breakers?
The system trips them to prevent a deep discharge of the batteries. A technician should confirm the cause and the battery condition before they are closed again.
Is Restricted air flow serious?
Yes, the manual rates it critical. Check that nothing blocks the air intakes and book a filter and fan check.
What does Lost parallel redundancy mean?
The load is above what the configured N+x system can carry with one unit spare. Reduce the load or add capacity.
Which log should I send to the technician?
The UPS log, which records system status and operation modes. The NMC log covers display and network activity.
Sources, checked October 4, 2026:
- Schneider Electric, Galaxy VX UPS Operation, 990-5452N (7/2025), pp. 56, 59, 62, 63, 64, 65, 66, 67
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