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UPS alarm triage: what to do in the first hour

When a UPS alarms, the first job is to find out whether the load is still protected, not to silence the buzzer. The display says which state the UPS is in, and each state has its own first move. Save the event log before any reset, reduce the load if it is overloaded, and call for service.

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Key facts

  • On battery: input lost; the runtime is now counting down
  • On bypass: mains power to the load, only while the input stays within limits (APC)[1]
  • Low battery: a SmartOnline unit warns when less than 3 minutes of runtime remain[2]
  • Overload: above the rating; after a limited period the UPS transfers to bypass (Delta manual)[3]
  • Battery replace: the batteries are weak and need replacing (Delta manual)[4]
  • Output short circuit: the UPS shuts down with no output voltage (Delta manual)[5]
  • Red alarm light (Eaton 93PS): an alarm is active or normal operation has stopped; call service[6]

The first ten minutes

  1. Check the load: is the critical equipment still powered, and from what (inverter, battery or bypass)?
  2. Read the display and save the log: photograph the screen and download the event log before anyone presses reset. A reset clears the message, not the cause.
  3. If on battery: check whether the generator has started. If there is no generator, start an orderly shutdown of the least critical systems to stretch the runtime.
  4. If overloaded: unplug or shut down non-critical loads to bring the UPS back under its rating, as Delta’s manual advises [7].
  5. If on bypass: keep changes to a minimum. The load has no protection until the UPS returns to normal operation.

The first hour

  • Call for service with the model, the alarm text and the log; it saves a diagnostic trip.
  • Note when the alarm started and what else happened at that time: a utility blip, a generator test, new equipment added, a hot afternoon.
  • Do not cycle the UPS off and on to see if the alarm clears. On some faults that drops the load.
  • If a battery alarm appears with a swollen, hot or leaking battery, keep people away from it and ventilate the room.

What the common alarms usually point to

Alarm Usual causes
On battery, input normal input breaker tripped, input out of tolerance, rectifier fault
On bypass overload, inverter fault, manual transfer left in place
Overload new equipment added, failed redundant power supply, load imbalance
Battery replace or failure aged or warm batteries, a failed block, a loose connection
Fault internal failure: fan, power module, board or capacitor

Standards cited

  • Manufacturer user manuals (Delta Amplon N series quoted)

Common questions

What does it mean when a UPS goes to bypass?

The load is being fed straight from the input, with no protection. On many units an overload moves the UPS to bypass after a limited period [3]; an internal fault can do the same.

Should I reset a UPS alarm?

Not before saving the event log and finding the cause. A reset clears the message, not the problem, and the log is what the technician needs.

What does the battery replace alarm mean?

That the UPS has found the batteries weak and is asking for them to be replaced [4]. Until they are, runtime during an outage may be much shorter than expected.

My UPS is beeping on battery. What should I do?

Check whether the input power has failed and whether the generator has started. If not, begin an orderly shutdown of non-critical systems and call for service.

Sources

  1. Schneider Electric, Smart-UPS On-Line SRT2200XLA/SRT3000XLA Operation Manual, operation mode icons
  2. Eaton (Tripp Lite), Tripp Lite by Eaton SmartOnline SU750-SU3000RTXLCD2U Owner's Manual 614-21325 Rev 05, section 4.7 (PDF p. 36)
  3. Delta Electronics, Delta UPS Amplon Family N Series 1/2/3 kVA User Manual, indicator 10, Overload
  4. Delta Electronics, Delta UPS Amplon Family N Series 1/2/3 kVA User Manual, indicator 9
  5. Delta Electronics, Delta UPS Amplon Family N Series 1/2/3 kVA User Manual, section 4, short circuit
  6. Eaton, Eaton 91PS/93PS UPS 8-40 kW User's and Installation Guide, P-164000493 rev 006, p. 110, section 8.3.1
  7. Delta Electronics, Delta UPS Amplon Family N Series 1/2/3 kVA User Manual, section 4, overload

Updated