Engineering guide
XPC E91 fault and warning codes
The XPC E91 shows two kinds of codes on its LCD: warning codes, such as 09 Overload or 0B EPO enable, and fault codes, such as 43 Over load, where the UPS has shut down. The E91 User's Manual lists both in sections 3-7 and 3-8, and its troubleshooting table explains the common ones. Remove excess load for overloads and short circuits on the output; for other fault codes, the manual says a UPS internal fault has occurred and the dealer must be contacted.
Key facts
- Warning 33: locked in bypass after overload 3 times in 30 minutes
- Fault 43 Over load: UPS overloaded too long, becomes a fault and shuts down
- Faults 14 to 19: short circuit on the UPS output
- Warning 0B EPO enable: EPO function activated
Warning codes and fault codes
A warning code is a condition the UPS is reporting while it keeps running. A fault code is shown when the UPS has tripped; the manual says the code shows on the LCD and the alarm beeps continuously. The same digits can mean different things in the two lists: warning 01 is Battery unconnected, fault 01 is Bus start failure. Note which list the code came from, the code and the time.
Warning codes
| Code | Message on the display | What the manual says | What to do |
|---|---|---|---|
| 01 | Battery unconnected | The external or internal battery is not correctly connected. | Have a technician check the battery connections. |
| 02 | IP Neutral loss | The input neutral is lost. | Have an electrician check the input neutral connection. |
| 04 | IP phase abnormal | Input phase abnormal. | Check the upstream supply; call if it persists. |
| 05 | Bypass phase abnormal | Bypass phase abnormal. | Check the bypass supply. |
| 08 | Low battery | Low battery. | Prepare the loads for shutdown if the outage continues. |
| 09 | Overload | The UPS is overloaded. | Remove excess loads from the UPS output. |
| 0A | Fan failure | A fan is locked or not working, or the UPS temperature is too high. | Check room temperature and vents; call for the fans. |
| 0B | EPO enable | The EPO function is activated. | Find what triggered the EPO; the circuit must be closed again by someone trained. |
| 0D | Over temperature | Over temperature. | Check the room cooling and that vents are clear. |
| 0E | Charger failure | Charger failure. | Call a technician. |
| 33 | Locked in bypass after overload 3 times in 30 minutes | Three overloads in 30 minutes locked the UPS in bypass. | Remove excess load first; the restart is a shutdown and restart of the UPS. |
| 3A | Cover of maintain switch is open | The maintenance switch cover is open. | Check whether maintenance is under way. |
| 3E | Battery voltage too high | Battery voltage too high. | Call a technician. |
Warning 33 is the one to watch after repeated overloads: the UPS has locked itself in bypass, so the load is on raw utility power until the overload is removed and the UPS is restarted.
Fault codes
| Code | Message on the display | What the manual says | What to do |
|---|---|---|---|
| 43 | Over load | The UPS was overloaded too long, became a fault and shut down. | Remove excess loads, then restart. |
| 14-19 | Inverter output short circuited | A short circuit on the UPS output shut the UPS down. | Have an electrician check the output wiring and the connected devices. |
| 41 | Over temperature | Over temperature fault. | Check the room cooling; call a technician. |
| 25 | Line wiring fault | Line wiring fault. | Have an electrician check the input wiring. |
| 6F | Battery polarity reverse | Battery polarity reversed. | Call a technician; do not restart. |
| 01, 02, 03 | Bus start failure, Bus over, Bus under | DC bus faults. | Call a technician. |
| 06 | Converter over current | Converter overcurrent. | Call a technician. |
| 12 | High inverter voltage | Inverter voltage too high. | Call a technician. |
| 31 | Parallel communication failure | Parallel communication lost. | Call a technician. |
| 77 | LCD & MCU communication failure | Display and controller communication lost. | Call a technician. |
For any fault code not covered by the troubleshooting table, the manual's answer is that a UPS internal fault has occurred. Keep the cabinet closed and call a technician.
When the code points to the battery
Low battery runtime and repeated 01 or 3E warnings usually mean the internal string needs testing. Our XPC service crews commission and maintain E91 units, and the battery replacement service covers the internal string and external battery cabinets alike.
Related pages
Common questions
What does fault code 43 mean on an XPC E91?
The UPS was overloaded for too long, became a fault and shut down. Remove excess loads and restart it.
What do E91 fault codes 14 to 19 mean?
The UPS shut down because of a short circuit on its output. The output wiring and connected devices need checking.
What is warning code 0B on the E91?
EPO enable: the emergency power off function is activated.
What is warning code 33?
The UPS is locked in bypass after three overloads in 30 minutes.
What if the E91 shows a fault code that is not in the troubleshooting table?
The manual says a UPS internal fault has occurred. Call a technician.
Sources, checked October 4, 2026:
- Xtreme Power Conversion E91 User's Manual, section 3-7 Fault Code, p. 47
- Xtreme Power Conversion E91 User's Manual, section 3-8 Warning Code, p. 48
- Xtreme Power Conversion E91 User's Manual, section 4 Trouble Shooting, p. 49
Send us the details
Fill this in and your own mail client opens with everything already written out. Nothing is sent from this site.
Brand names are trademarks of their owners and are used only to identify the equipment we service. We are not the manufacturer and are not affiliated with it.