5
ZB Series
Application guide
Field troubleshooting of the motor protection module
Cut-off the power supply of the control circuit, and bypass the
motor protection module. Remove the conductor of the control
circuit from M1 and M2 terminals of the module, and connect a
jumper wire to bypass the control circuit of the module. (Note:
thus far the motor protection module inside the compressor has
been bypassed, but this method can only be used to test the
module.)
Switch on the control circuit and the power supply of the module
again, and commission the compressor: if the compressor does
not operate when the module is by-passed, the fault is not in the
control system and the module. If the compressor operates
when by-passing the module, but fails to operate by connecting
the module again, the relay in the control circuit of the module is
undoubtedly cut-off. Now, the thermistors' series must be tested
in order to determine the reason why the relay in the control
circuit of the module is cut-off: either the internal temperature is
too high or elements in the control circuit are faulty.
Check the thermistors' series:
Cut-off the control circuit and the power supply of the module,
and remove the lead wire of the sensor from S1 and S2 terminals
of the module, and measure the resistance of the thermistor
series via the sensor by means of an ohmmeter. (Caution: use an
ohmmeter of 9V maximum resistance to check the series; the
sensor is sensitive and vulnerable; do not try to check the
electrical conductivity of the sensor by means of any non-
resistance tools; do not apply any external voltage to the sensor -
the compressor could be damaged and may even have to be
replaced.)
Diagnose resistance readings according to the following data:
- 150-2250: normal running range;
- 2750: the compressor superheats: rest the compressor for a
sufficiently long period to allow it to completely cool down;
- 0: the sensor has been short-circuited, change the compressor;
- : the sensor circuit is cut-off, change the compressor.
If the resistance readings are outside the range of normal values,
pull out the connector plug on the sensor and measure the
resistance at the sensor terminals. One can determine the reason
why the readings are not normal and establish whether the fault lies
with the connector or thermistor.
After compressor start or any module trip, the resistance of the
sensor series must be below the resetting point of the module
before it closes again. Its resetting value equals 2250-3000. If the
resistance of the sensor series is below 2250 and the compressor
cannot be put into operation through by-passing the control circuit,
it indicates solid-state module damage and should be exchanged.
During the test period, the voltage should be cut-off to prevent
short-circuit and accidents at the contacts. Whenever the circuit
breaker disconnects or trips, the module function should be
checked, to ensure that the module contacts haven't been bound.
(112 pages)
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