Tripping Of The Differential Protection; The Pump Unit Runs At Maximum Speed Without Stopping; Only One Pump Unit Is Running; There Is Demand For Water But The Pump Unit Does Not Start - Xylem LOWARA SMB /SVE Series Installation, Operation And Maintenance Manual

7.10 Tripping of the differential protection

Cause
Damaged motor
Power cable of the motor faulty or
worn
Differential switch not compliant
with the specifications
Differential current too high

7.11 The pump unit runs at maximum speed without stopping

Cause
Pressure setpoint not suitable for
the system (the value is higher than
the pressure that the pump unit can
deliver)
Sensor not connected or damaged

7.12 Only one pump unit is running

Cause
The pump units have different
settings

7.13 There is demand for water but the pump unit does not start

Cause
The setpoint is set at zero
Remedy
Replace the motor
Replace the cable
Replace the differential switch
Contact a qualified technician to have the electrical system modified
Remedy
Set the new setpoint according to the performance of the pump unit
Check the hydraulic and electrical connection of the sensor
Remedy
1. Check setting of the frequency converter
2. Check the serial connection between the two frequency converters
Remedy
1. Check setting of the frequency converter
2. Set the setpoint
en – Original instructions
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