Operating Range; Motor Bearing Monitoring; Standstill Heating - Grundfos CUE Series Product Manual

Functions

Operating range

The area between the min. and max. speed is the
actual operating range of the pump.
The operating range can be changed by the user within
the area defined by the pump-dependent speed range.
For some pump families over synchronous operation
(max. speed above 100%) will be possible. This
requires an over-size motor to deliver the shaft power
required by the pump during over-synchronous opera-
tion.
Pump-dependent speed range
Min.
Actual operation
Min.
speed range
Min. speed adj. range
Max. speed adj. range
Fig. 27 Setting of the min. and max. speed in % of the
nominal speed of the pump
H
100 %
Max. curve
Min. curve
Pump-dependent
min. performance
Fig. 28 Operating range of the CUE

Motor bearing monitoring

This function is used to give an indication when it is time
to relubricate or change the motor bearings.
It shows these pieces of information:
• When to relubricate the motor bearings.
• How many times relubrication has been confirmed,
• When to replace the motor bearings.
Default function
The default function is based on the "mileage" of the
pump and takes into account if the pump has been run-
ning with reduced speed.
24
Nom.
Max.
Max.
Speed [%]
100%
Operating range
Q
Extended function
The bearing temperature is also included in the calcu-
lation.
The extended function requires an MCB 114 sensor
input module and Pt100/Pt1000 sensors measuring the
bearing temperature.
Monitoring of motor bearing temperatures
When temperature sensor 1 and 2 are used for meas-
uring the motor bearing temperature, a warning or an
alarm will be generated if the bearing temperature gets
too high.
Warnings and alarms are generated and reset using
hysteresis. See fig. 29.
Alarm limit
Warning limit
Normal
203 °F 212° F
(95 °C) (100 °C)
Fig. 29 Monitoring of bearing temperature with warning
and alarm limits

Standstill heating

This function pre-heats the motor during standstill in
order to avoid condensation within the motor.
When the pump is stopped by a stop command, a cur-
rent will be applied to the motor windings in order to
keep the temperature within the motor above the dew-
point temperature. No external heater is needed.
The pre-heating of the motor is especially important
when the motor is installed under these conditions:
• high humidity
• outdoor installation.
The consequences of condensed moisture within the
motor are for example corrosion damage to electrical
contacts and the bearings of the motor shaft.
Grundfos CUE
239 °F 248 °F
(115 °C) (120 °C)
Temperature