1. Why are the switches tripped off or failed to switch on frequently?
（2）Incorrect model selection of switches.
（3） Water pump sticking or short circuit inside motor.
（4） Aging circuit, short circuit, too small wires or phase failure.
Turn off power of the control system, measure motor with winding meter, and check if there is any short circuit of 3 phases or grounding (please note in the process of measurement: remove output terminal of the frequency converter to avoid damage to output module of the frequency converter): rotate the motor to check whether it is stuck or not; when necessary, replace the switch.
2. The contact noisy?
It is caused by uneven contacting of the contact, with sand or rust on the surface. Phase failure will be caused, and the contact, switch frequency conversion and other components are damaged.
Remove the load switch contacting the contact, manually switch on and off the contacts, after repeating many times, if the sound is not released, grind and level the armature or replace with new contacts.
3. Thermal relay tripped off frequently?
（2） Motor selection matching or not.
（3） Aging, main wire too mall or not.
Check model of the motor matches the thermal relay or not, and check the motor to ensure normal conditions. If the situations still exist, replace with new matching wires.
4. Abnormal engagement of contact or relay?
（1） Open circuit of coil and null coil.
（2） Damage of middle relay points.
Check the circuit, and replace with new relay points.
5. Frequency converter with fault frequently?
（1）Incorrect parameter setting;
（2） Aging of frequency converter
（3） Water pump overloading
（4） Phase failure
Reset the frequency converter, if the same fault occurs within a short time, the fault converter cannot work until the fault has been removed. Fault codes generated by the frequency converter have been recorded, and are solved by referring to the instruction manual. Fasten all the circuits, measure 3-phase current and check they are balanced or not. In case of damage to input terminal of the frequency converter by power supply phase failure or aging of the frequency converter, replace the frequency converter.
6. Input and output points of the control abnormal or not operated as usual?
（1）Input and output points of the control work frequently for a long time, and contacts inside the control are burnt down.
（2）Caused by strong current through the contacts.
（3） Program error or control burnt down.
Update program of the control, and change the burnt down input and output points to the spare contacts by software, and replace the control when necessary.
7. Unstable pressure with fluctuation?
（1） Parameters of the control are not well adjusted.
（2） Too low efficiency of water pump.
8. System sometimes failure, not operating as usual?
（1） Looseness of the circuit
（2） Component aging
Check circuit, fasten circuit, check components and change when necessary.