Engineering guide
XPC X90-2S alarm messages explained
The XPC X90-2S records each alarm in its LCD event list as Fault! or Warning! with a two-character code, such as Warning! <09> Overload warning or Fault! <43>Overload. Table 4-12 of the X90-2S User's Manual lists every code, and chapter 6 gives the solutions; the manual is clear that a user needs service personnel for most of them. The tables below group the codes by what they concern and separate the few an operator can act on.
Key facts
- Who handles most alarms: service personnel, per the manual
- Warning <33>: locked in bypass after overload 3 times in 30 min
- Fault <43>Overload: heavy overload causes the UPS to fault
- Warning <01> BATT open: battery not connected
Reading the X90-2S event list
Each entry starts with its class, Fault! or Warning!, then the code in angle brackets and a short text. Warning codes and fault codes are separate lists, so the same digits can mean different things: Warning <41> is Bypass Loss, Fault <41> is Over temp. Note the class, the code, the text and the time before anything is reset.
Input and bypass warnings
| Message on the display | What the manual says | What to do |
|---|---|---|
| Warning! <02> IP N loss | Input neutral loss. | Have an electrician check the input neutral. |
| Warning! <04> Line phase error | Input phase error, as stated. | Have the input phase sequence checked. |
| Warning! <06> Bypass FRE unstable | Bypass frequency unstable. | Check the bypass source; a generator may be feeding it. |
| Warning! <10> L1 IP fuse fail | L1 input fuse failed (L2, L3 alike as 11 and 12). | Call a technician. |
| Warning! <41> Bypass Loss | Bypass loss, as stated. | Check the bypass feeder breaker upstream. |
Overload messages
| Message on the display | What the manual says | What to do |
|---|---|---|
| Warning! <09> Overload warning | Overload warning. | Lower the load within UPS capacity. |
| Warning! Over Load | In Line mode, the load demands more power than the UPS can supply. | Lower the load within UPS capacity. |
| Warning! Over Load Fail | The UPS will transfer from Line mode to Bypass mode. | Lower the load; it is on bypass meanwhile. |
| Warning! <33> Lock BYP OL 3 times | Locked in bypass after overload 3 times in 30 min. | Remove the excess load before any return to Line mode. |
| Warning! <44> Redundancy Error | Redundancy error, as stated. | Check whether the load now exceeds the redundant capacity. |
| Fault! <43>Overload | Heavy overload causes the UPS to fault. | Reduce some load. |
On a 480 V frame running close to its rating, Warning <09> is the moment to shed load. Left alone, the sequence runs to Over Load Fail, a transfer to bypass, and after three overloads in 30 minutes a lock in bypass.
Battery messages
| Message on the display | What the manual says | What to do |
|---|---|---|
| Warning! <01> BATT open | Battery not connected. | The manual's first check is the battery breaker; have someone trained on the unit look. |
| Warning! <08> BATT low | Battery voltage is too low. | During an outage, prepare the loads for shutdown. |
| Warning! <3E> BATT VOL High | Battery voltage is too high. | Call service to check the nominal battery voltage setting. |
| Fault! <29>BATT fuse broken | Battery fuse open. | Call a technician. |
| Fault! <6F>BATT reversal | Battery polarity reversed. | Call a technician; do not restart. |
EPO, heat, fans and module locks
| Message on the display | What the manual says | What to do |
|---|---|---|
| Warning! <0B> EPO active | EPO active; the manual points to the pre-installed connector shorting X1.1 and X1.2. | Find what triggered the EPO; a loose connector can cause it. |
| Warning! <0A> Fan lock warning | A fan is locked. | Check from outside that nothing blocks the air path. |
| Warning! <0D> Over temperature | Over temperature. | Check the room temperature against the specification. |
| Fault! <41>Over temp | Over temperature fault. | Check the room cooling and clearance; or call service. |
| Warning! <3A> maintain is open | Cover of the maintenance switch is open. | Check whether maintenance is under way. |
| Warning! <48> Power module unlock | A power module is unlocked. | Call the technician who last worked on the frame. |
Faults that need a technician
| Message on the display | What the manual says | What to do |
|---|---|---|
| Fault! <01>Bus start fail | Bus soft start failed. | Call a technician. |
| Fault! Bus Soft Start Time Out | Rectifiers could not start: low DC bus voltage. | Turn off and restart once; if it fails again, call service. |
| Fault! <14>INV A out SC | Phase A output short circuited (15 to 19: other phases and line to line). | Call a technician. |
| Fault! <21>BATT SCR SC | Battery SCR short circuited. | Call a technician. |
| Fault! <25>In&out swop | Line wiring fault. | Have the wiring checked by an electrician. |
| Fault! <31>Par commu fail | Parallel communication failed. | Call a technician. |
| Fault! <61>BYP SCR SC | Bypass SCR short circuited. | Call a technician. |
| Fault! <77> ISO Over temp | Isolation transformer over temperature. | Call a technician; check the room cooling. |
Except for the single restart the manual allows after a soft start time-out, these are service calls. Keep the cabinet closed and the load where the UPS put it. The team that maintains XPC X90 systems reads the event list on site, and the three-phase UPS options page covers what fits when a frame is due for replacement rather than repair.
Related pages
Common questions
What does Fault! <43>Overload mean on an X90-2S?
A heavy overload caused the UPS to fault. Reduce some load before restarting.
What is Warning! <33> on the X90-2S?
The UPS is locked in bypass after three overloads in 30 minutes. Remove the excess load first.
Do warning and fault codes overlap?
They are separate lists. Warning <41> is Bypass Loss while Fault <41> is Over temp, so always note the class.
What does Warning! <0B> EPO active mean?
The emergency power off is active. The manual points to the pre-installed connector shorting X1.1 and X1.2.
Can I clear X90-2S faults myself?
Only a few: overloads by lowering the load, and one restart after a soft start time-out. The rest need service personnel.
Sources, checked October 4, 2026:
- Xtreme Power Conversion X90-2S User's Manual (Rev 2/29/24), chapter 6 Troubleshooting, pp. 79, 80, 79-80
- Xtreme Power Conversion X90-2S User's Manual (Rev 2/29/24), Table 4-12 Alarm List, p. 73-75
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