Danfoss APP Series User Manual page 62

Instruction
3. High torque on electric motor
Cause
3.1 Too high outlet pressure from pump
3.2 Pump starts against pressure
3.3 Constant torque
3.4 Water pump damage
44
6
Trouble shooting guide for APP and APP S 674 pumps
Remedy
3.1.1 Check fluid salinity.
3.1.2 Check temperature.
3.1.3 Check pressure drop across RO membrane.
3.2.1 Check that electric motor is correctly sized.
3.2.2 Check internal parts (see item 2.1).
3.2.3 Systems with more than one electric
motor installed:
Start motors simultaneously.
3.3.1 Please contact Danfoss High Pressure
Pumps sales office.
3.4.1 Dismantle pump and check for wear.
180R9267 / IOM APP 1.5-3.5 Appendices - v04 / 11.2013
06.2013
Comments
Pump conditions may change (more salt, lower
water temperature or scaling of RO membrane)
causing higher pressure, resulting in higher
motor torque.
Pumps run in parallel with cascade start, may
switch off the motor relay due to too high
torque caused by high outlet pressure.
If the electric motor is too small for the APP or
APP S 674 pump, it cannot provide sufficient
torque.
Too heavy damage in the pump will increase
friction causing a high torque (see item 6,
Typical signs of wear).