Grundfos CRN-H MAGdrive, Installation And Operating Instructions Manual

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Eng
lish (US)
22
9. Fault finding the product
The table above is not exhaustive for the faults and observations possible. Please contact your local Grundfos company in case of
questions or in case of fault situations not described.
Observation Description Possible causes
1. The available differential
pressure is lower than
anticipated.
The pump is operating, it builds
up a differential pressure > 3 psi
(0.2 bar), but it is unable to build
up a differential pressure to the
anticipated level. a) The direction of rotation is wrong.
b) Insufficient pressure drop in pipe system.
c) Pump performance reduced due to vapor bubbles (gas) in
inlet.
d) Pressure drop in outlet pipe, fittings and check valve.
e) The speed is too low (variable-frequency operation).
f)
The pump is filled with oil (low temperature, especially in NH
3
systems).
g) Electrical failure (working on only two phases).
h) Mechanical failure (noise is heard).
2. The available differential
pressure is higher than
anticipated.
The pump is operating, but it
builds up a differential pressure
much higher than anticipated. a) The outlet stop valve is closed.
b) The pipe system to evaporators is blocked, and the bypass
does not open (similar to no refrigeration demand).
3. The pump cuts out due to
low differential pressure.
The pump is operating, but cuts
out due to low differential
pressure. Restarting gives similar
result. a) Setting for minimum differential pressure is too high for the
system.
b) The pump performance is reduced due to vapor bubbles (gas)
in inlet.
c) Defective differential pressure switch or transmitter.
4. The pump cuts out due to
too high current power
consumption (motor
protection).
The pump is operating, but the
motor protection switches it off. a) The speed is too high.
b) The flow rate is too high.
c) Too much oil in refrigerant (low temperature).
d) Electrical failure (short-circuiting of windings).
e) Mechanical failure (mechanical wear).
5. Noise. The pump is operating, but an
unexpected noise is heard. a) Cavitation.
b) The inlet filter is blocked.
c) Inadequate lubrication of bearings (strong mechanical noise
and vibrations).
d) Variable-frequency operation (high pitch noise).
e) Mechanical failure (grinding noise).
6. Leakage. If the pump is operating, it must
be stopped. a) Leakage from pipe connections.
b) Leakage from seal.