Skip to content 
1.Why there is no response in the UPS when the mains power is turned on, The screen does not display and the fan does not work?
There are two reasons:
Firstly. The power supply board（SPS） is not working and cannot supply power to the UPS control system, causing the UPS to fail to start. Check the fuse input on the power supply board. If the fuse is fine, A new power board needs to be replaced.
Secondly. Low battery voltage: Some UPS' power supply boards are powered by batteries. When the battery's poor voltage is too low, the power supply board cannot start working. At this time, it is necessary to check and measure the battery voltage.
2.Why the UPS works normally in mains power mode, but it loses power when switched to battery mode?
There are two reasons:
Firstly. The battery voltage is too low to carry loads.
Secondly. It is necessary to confirm whether the charger is working properly.
3.why UPS Capacitor bulging or capacitor bursting?
Cause analysis: The capacitor voltage is too high; Or the capacitor is faulty.
Solution: Replace the UPS faulty capacitor and test whether the voltage across the capacitor exceeds the standard. If the voltage exceeds the standard, the relevant circuits need to be inspected and repaired.
4.Why the resistor of the UPS is burned out?
Cause analysis: Usually, a fault occurs in the circuit, causing excessive current to flow through the resistor, resulting in high power and overheating, leading to its burnout.
Solution: It is necessary to check where the abnormality in the circuit causes overcurrent. After identifying the problem, replace the resistor with a new one.
5.Why the UPS cannot be turned on when powered on or in battery mode?
Cause analysis: Commonly, it is due to abnormal boost or inverter circuits inside the UPS.
Solution: It is necessary to check whether there are any obvious abnormalities in the internal power board or replace the power board.
6.why the UPS fan does not rotate or rotates very slowly?
Cause analysis: It might be an abnormality in the fan power circuit or the fan is damaged
Solution: Replace the fan and confirm whether it has returned to normal. If the fan is still working abnormally, it is necessary to check and measure whether the power supply voltage to the fan is stable and meets the rated voltage of the fan. And repair the corresponding circuits.
7.why the UPS LCD display inverter output normally, but there is no output voltage. Or the inverter output of the UPS is normal, but there is no output when switching to the bypass ?
Solution: It is often the UPS output relay that is stuck. You can try knocking on the relay to see if it can return to normal. Or replace the relay.
8.Why The UPS reported a BUS boost fault?
Cause analysis: The internal wiring may be loose; Boost circuit damage - SCR, IGBT tube and corresponding drive circuit; The control board is faulty and the sampling control is abnormal.
Solution: Check the connection lines from the control board to the power board and the plug-in lines for each power connection. Inspect and repair power devices such as boost SCR or IGBT, as well as the corresponding drive circuits; Or repair and replace the control board.
9.why The UPS reports a bypass or phase sequence alarm for mains input ?
Cause analysis: Three-phase UPS, incorrect input phase sequence
Solution: Exchange any two live wires among A-B-C.
10.why UPS battery failure?
Reason: Battery aging or damage
Solution: Replace the battery.
11.When the mains power is on, an abnormal alarm for input to the mains power occurs.Why ?
Cause analysis: It might be that the input of the mains power is too low or too high. Abnormal mains power frequency; The mains power input fuse of the UPS was burned out. The front-end input circuit breaker tripped and was damaged.
Solution : Check the input circuit breaker, inspect the input lines. If the mains power is abnormal, it can be left untreated or the generator can be started to supply power. Replace the damaged circuit breaker, switch or fuse.
12.why During the operation of the UPS, it automatically switches to bypass and reports an overload fault. After the fault is cleared and the UPS is restarted, it works normally?
Cause analysis: Usually, the UPS is carrying instantaneous impact loads. When a certain part starts up, it will cause overload. After multiple overloads, the machine switches to bypass and reports an overload fault
Solution: Check for motor-type loads and remove those with excessive instantaneous start-up current.
13.Why UPS over-temperature fault?
Cause analysis: Abnormal fan; There is too much dust accumulated inside the machine. Excessively high ambient temperature UPS malfunction.
Solution : Replace the fan, clean the dust inside the UPS, keep the installation environment of the UPS well-ventilated, and check for UPS faults or replace the UPS.
14.why The UPS input fuse burns out ?
Cause analysis: Lightning strike or excessive input voltage at an instant caused the fuse to overcurrent and burn out.
Solution: Replace the input fuse of the same specification.
15.why UPS input filter MOV explosion ?
Cause analysis: The input voltage remained high for a long time or the instantaneous input lightning strike voltage was too high, resulting in the damage of the MOV.
Solution: Replace the MOV and check if there are any other defects in the circuit, or replace the circuit board.
16.why UPS Battery swelling due to overcharging?
Cause analysis: The charger is abnormal, the charging voltage output is too high, or the number of battery cells does not match the UPS Settings.
Solution: Replace the charging pad; Set the number of battery cells of the UPS to be consistent with the actual number of battery cells.
17.Why The UPS output voltage is too low or too high?
Cause analysis: Usually output overload; Abnormal load The UPS is faulty.
Solution: Check the load or replace the UPS.
18.Why The UPS is working properly, but the load is not working properly?
Cause analysis: It is usually due to poor grounding of the UPS, or improper connection of the neutral wire, or excessive voltage difference between zero and ground.
Solution: Check the UPS's zero connection and grounding, and ensure that the voltage difference between zero and ground is within 5V.
19.Why The three-phase UPS reports an input phase loss alarm ?
Cause analysis: The input voltage of one or two phases is abnormal, or the frequency is abnormal; Or there is a fault in the input fuse of a certain phase inside the UPS.
Solution: Check the input wiring, measure the input voltage and frequency to see if they are within the range required by the UPS. Check the input fuses inside the UPS and replace the defective ones.
