Carel E2V S0 Series - Troubleshooting

Code +030220811- rel. 1.0 – 26.04.2007
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10. Troubleshooting
The following table lists a series of situations of malfunctions that may occur when starting and operating the driver
and the electronic valve. These cover the more common problems and provide an initial response to help resolve
the fault.
PROBLEM CAUSE SOLUTION
The probe does not measure correct
values
Check that the pressure and the temperature measured are correct
and that the probe position is correct. Check that the minimum
and maximum pressure parameters for the pressure transducer set
on the driver correspond to the range of the pressure probe
installed. Check the correct probe electrical connections.
The superheat value
measured is incorrect
The type of refrigerant set is incorrect Check and correct the type of refrigerant parameter.
The type of valve set is incorrect Check and correct the type of valve parameter.
The valve is connected incorrectly
(rotates in reverse) and is open
Check the movement of the valve by placing it in manual control
and closing or opening it completely. One complete opening must
bring a decrease in the superheat and vice-versa. If the movement
is reversed, check the electrical connections.
The superheat set point is too low
Increase the superheat set point. Initially set it to 12 °C and check
that there is no longer return of liquid. Then gradually reduce the
set point, always making sure there is no return of liquid.
Low superheat protection ineffective
If the superheat remains low for too long with the valve that is
slow to close, increase the low superheat threshold and/or
decrease the low superheat integration time. Initially set the
threshold 3 °C below the superheat set point, with an integration
time of 3-4 seconds. Then gradually lower the low superheat
threshold and increase the low superheat integration time,
checking that there is no return of liquid in any operating
conditions.
Stator broken or connected
incorrectly
Disconnect the stator from the valve and the cable and measure
the resistance of the windings using an ordinary tester.
The resistance of both should be around 36 ohms. Otherwise
replace the stator. Finally, check the electrical connections of the
cable to the driver (see paragraph 5.1).
Valve stuck open
Check if the superheating is always low (<2 °C) with the valve
position permanently at 0 steps. If so, set the valve to manual
control and close it completely. If the superheat is always low,
check the electrical connections and/or replace the valve.
Liquid returns to the
compressor during
operating
The “valve opening at start-up”
parameter is too high on many
showcases in which the control set
point is often reached
(for
multiplexed showcases only)
Decrease the value of the “Valve opening at start-up” parameter
on all the utilities, making sure that there are no repercussions on
the control temperature.
The pause in control after defrosting
is too short
(for MasterCase,
MasterCase 2 and mpxPRO only)
Increase the value of the “valve control delay after defrosting”
parameter.
The superheat measured by the
driver after defrosting and before
reaching operating conditions is very
low for a few minutes
Check that the LowSH threshold is greater than the superheat
value measured and that the corresponding protection is activated
(integration time > 0sec). If necessary, decrease the value of the
integration time.
The superheat measured by the
driver does not reach low values, but
there is still return of liquid to the
compressor rack
Set more reactive parameters to bring forward the closing of the
valve: increase the proportional factor to 30, increase the
integration time to 250 sec and increase the derivative time to 10
sec.
Many showcases defrosting at the
same time
Stagger the start defrost times. If this is not possible, if the
conditions in the previous two points are not present, increase the
superheat set point and the LowSH thresholds by at least 2 °C on
the showcases involved.
Liquid returns to the
compressor only after
defrosting (
for
multiplexed
showcases only)
The valve is significantly oversized Replace the valve with a smaller equivalent.
Liquid returns to the
compressor only
when starting the
controller (after being
OFF)
The “valve opening at start-up”
parameter is set too high
Check the calculation in reference to the ratio between the rated
cooling capacity of the evaporator and the capacity of the valve; if
necessary, lower the value.
control