42
ENG
“EVD evolution” +030222041 - rel. 1.0 - 01.06.2008
PROBLEM
CAUSE
SOLUTION
In the start-up phase the
low pressure protection is
activated (only for units with
compressor on board)
The “Valve opening at start-up” parameter
is set too low
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.
The driver in pLAN or tLAN configura-
tion does not start control and the valve
remains closed
Check the pLAN / tLAN connections. Check that the pCO application connected to the
driver (where featured) correctly manages the driver start signal. Check that the driver
is NOT in stand-alone mode.
The driver in stand-alone configuration
does not start control and the valve
remains closed
Check the connection of the digital input. Check that when the control signal is sent
that the input is closed correctly. Check that the driver is in stand-alone mode.
LOP protection disabled
Set a LOP integration time greater than 0 s.
LOP protection ineffective
Make sure that the LOP protection threshold is at the required saturated evaporation
temperature (between the rated evaporation temperature of the unit and the corre-
sponding temperature at the calibration of the low pressure switch) and decrease the
value of the LOP integration time.
Solenoid blocked
Check that the solenoid opens correctly, check the electrical connections and the
operation of the relay.
Insufficient refrigerant
Check that there are no bubbles in the sight glass upstream of the expansion valve.
Check that the subcooling is suitable (greater than 5 °C); otherwise charge the circuit.
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 ope-
ning it completely. One complete opening must bring a decrease in the superheat and
vice-versa. If the movement is reversed, check the electrical connections.
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 closed
Use manual control after start-up to completely open the valve. If the superheat
remains high, check the electrical connections and/or replace the valve.
The unit switches off due
to low pressure during
control (only for units with
compressor on board)
LOP protection disabled
Set a LOP integration time greater than 0 s.
LOP protection ineffective
Make sure that the LOP protection threshold is at the required saturated evaporation
temperature (between the rated evaporation temperature of the unit and the corre-
sponding temperature at the calibration of the low pressure switch) and decrease the
value of the LOP integration time.
Solenoid blocked
Check that the solenoid opens correctly, check the electrical connections and the
operation of the control relay.
Insufficient refrigerant
Check that there are no bubbles of air in the liquid indicator upstream of the expansion
valve. Check that the subcooling is suitable (greater than 5 °C); otherwise charge the
circuit.
The valve is significantly undersized
Replace the valve with a larger equivalent.
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.
Valve stuck closed
Use manual control after start-up to completely open the valve. If the superheat
remains high, check the electrical connections and/or replace the valve.
The cabinet does not reach
the set temperature, despite
the value being opened to
the maximum (for multiple-
xed cabinets only)
Solenoid blocked
Check that the solenoid opens correctly, check the electrical connections and the
operation of the relay.
Insufficient refrigerant
Check that there are no bubbles of air in the liquid indicator upstream of the expansion
valve. Check that the subcooling is suitable (greater than 5 °C); otherwise charge the
circuit.
The valve is significantly undersized
Replace the valve with a larger equivalent.
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.
Valve stuck closed
Use manual control after start-up to completely open the valve. If the superheat
remains high, check the electrical connections and/or replace the valve.
The cabinet does not reach
the set temperature, and
the position of the valve is
always 0 (for multiplexed
cabinets only)
The driver in pLAN or tLAN configura-
tion does not start control and the valve
remains closed
Check the pLAN/tLAN connections. Check that the pCO application connected to the
driver (where featured) correctly manages the driver start signal. Check that the driver
is NOT in stand-alone mode.
The driver in stand-alone configuration
does not start control and the valve
remains closed
Check the connection of the digital input. Check that when the control signal is sent
that the input is closed correctly. Check that the driver is in stand-alone mode.
Tab. 10.a
