Brand: AEC
Category: UPS
Document Type: Manual
Language: EN
Manual for IST7
Uploaded: April 20, 2026, 7:45 p.m.
UPS Operation Summary
The IST7 series UPS operates in four modes: Normal Mains, Battery, Bypass, and Maintenance Bypass. In Normal Mains mode, AC power is converted to DC by PFC and supplied to the inverter, providing stable power. In Battery mode, upon mains failure, the UPS switches to battery input, boosting voltage to power the inverter without interruption. If mains recover, it recharges the battery. Bypass mode is activated during system abnormalities like over-temperature or overload, where the inverter shuts down, and mains power bypasses to the load. Maintenance Bypass allows for safe maintenance by supplying power to the load while the UPS is offline.
Key operations include starting and shutting down the UPS, switching between modes, and managing emergency power off (EPO). The touch screen interface provides control and monitoring of running parameters, status, and historical events.
Troubleshooting and error codes
| NO | Abnormal phenomena | Possible reason |
|---|---|---|
| 1 | Mains normal, but UPS works in battery inverting status, the buzzer beeps intermittently. | Each connection point, socket of grid feed circuit is not so good, which causes the AC power supply input unblocked. |
| 2 | After installation, close breaker or switch of power supply, it will fuse the fuse or trip off. | The three-phase input wires are wrongly connected, such as neutral wire and ground wire or live wire and grounding (case) is wrongly connected or the three-phase output wire is wrongly connected. |
| 3 | After startup, the UPS outputs 220V AC power, but the UPS works in bypass status. | 1. The load it too large and exceed the rated output capacity of the UPS. It needs to reduce load or select a UPS with larger output capacity. 2. If it is temporary bypass caused by the impact of load startup, and it can recover to normal automatically, that is normal. |
| 4 | The UPS output normally after startup, but once turn on load, the UPS stop outputting immediately. | 1. The UPS is serious overload or the output circuit is short-circuit. It is necessary to reduce load to proper capacity or find the reason of short-circuit. Common reason is output socket is short circuit or input short circuit caused by device damage. 2. The load is not started according to the sequence from large power device to small power device. You should restart the UPS. After the UPS run stably, start the load according to the sequence from large power device to small power device. |
| 5 | The UPS work normally after startup, but some time later, the UPS shut down automatically. | At the status of battery supply power, the battery is runs out and system protects for battery under-voltage, the UPS shut down automatically. This phenomenon is normal. Once mains normal, system will start and charge battery automatically. Warning: if the battery stays in under-voltage status for long time, it will influence the battery service life. After battery under-voltage protection, if mains cannot recover in a long time, please disconnect the battery breaker to protect battery and restart the UPS and fully charge the battery once mains recovers. |
| 6 | After startup and work a period of time, buzzer long beeps and the touch screen shows battery low-voltage. | The mains voltage is too low, and the UPS works in battery inverting status, finally, the battery is under-voltage and causes under-voltage protection. |
| 7 | When there is mains, the UPS output normally, when there is no mains, the UPS is with no output. | 1. Battery fault or the battery group is serious damaged. 2. Charger fault. The battery cannot be charged and causes battery energy insufficient. 3. Battery wire is not well connected or the contact of wire terminal is not good. 4. Battery breaker is not closed. 5. After serious overload of UPS, the UPS is not restarted, which causes the UPS stay in bypass output status. |
| 8 | Buzzer long beeps, DC/AC indicator on, the UPS turns to bypass to supply power. | See the fault information on touch screen. |
| 9 | There is mains, but buzzer beeps intermittently. | The voltage or frequency of mains exceed the allowable range of the UPS. |
| 10 | At mains status, the UPS works normally, once power outage, the UPS works normally but load system halt. | The grounding is not so good and the float voltage between neutral wire and grounding wire is too large. |
| 11 | FAULT indicator of a power unit is on. | The power unit is fault, replace it in time. |