Product Overview

© Danfoss | DCS | 2019.04
Data sheet | Superheat controller type EKE 1A, EKE 1B, EKE 1C
DKRCC.PD.RS0.A4.02 | 67
ID Symptom Possible cause / Reaction Solution
6 High superheat Lack of sub-cooling. • Limit max opening degree of the valve setting in controller.
• Check refrigeration system capacity and compare with expansion
valve capacity. Use proper valve size suitable for the system.
Controller is not setup/tuned properly. • Check the controller superheat settings SH min., max. and sensors
connected to it.
• Tune PID parameters in the controller.
Wrong valve selected from the controller list or
undersized valve installed.
• Check the right valve type and setting or use the appropriate valve
size for the needed condition.
Seasonally high load condition or overloaded
the system.
• Check the heat exchanger for dirt’s.
• Check superheat performance.
7 Too high or too low
measured superheat
Wrong sensor type, refrigerant type,
pressure transmitter type and/or range.
• Check the related setting and range.
• In case of oset in sensor or pressure transmitter, perform the
sensor correction.
• Always use accurate pressure transmitter
8 a. Measured Superheat
is higher than reference
- more than 5K for
5 - 10 min.
Load condition has changed and the superheat
controller is too slow to adapt to the change.
• TN can be adjusted to 20% lower and Kp can be adjusted to be
20% higher, monitor that the adjustment don’t make the valve OD
and Pe/Te oscillate.
Compressor capacity has changed and the
superheat controller is too slow to adapt to the
change.
• Compensation for compressor change is done with KpTe in this
case KpTe can be adjusted to be 20% higher.
Missing valve capacity. • Check if valve OD is close to 100 %, if so the valve is missing
capacity , check if sub cooling is OK.
• System might have loss charge.
b. Measured Superheat
is lower than reference -
lower 3K
SH close parameter is disabled or not setup
optimally.
• Enable the SH close function and set the setpoint 2K below the
reference.
Compressor capacity has changed and the
superheat controller is act too aggressive to
adapt to the change.
• Compensation for compressor change is done with KpTe in this
case KpTe can be adjusted to be 20% lower.
9 Fluctuating superheat The S2 sensor not in good contact with the
suction line.
• Check proper mounting of the temperature sensor.
Fast change in load and ambient condition. • Wait for the stable condition and check again.
Periodic ash gas at the valve inlet. • Secure stable sub cooling.
Aggressive gain Kp and Kp Te parameter. • Decrease gain in the controller, ex set SH Tn to be 20 % higher and
reduce Kp 20%, if still SH is uctuating, reduce KpTe by 20%.
• Try with the higher SH reference.
10 Negative superheat Wrong sensor type, refrigerant type, pressure
transmitter type and range.
• Check the related setting and range.
During start up suction pressure is low
because of low Ambient temperature.
• Check the startup problem.
System is not running. • Check the system.
11 Superheat outside the
dened range or does
not reached the setpoint
Wrong valve selected or its valve parameter. • Check the right valve type and its setting.
Loss of refrigerant in the system. • Charge the system with appropriate refrigerant capacity.
• Check for leakage in the system.
Expansion valve too small. • Replace with larger valve if necessary.
• Check the selected valve in the controller valve list.
Step loss in the valve. • Drive the stepper valve with the recommended Speed.
• Too high or too low speed could result in loss step in the valve.
• For the user dened valves, check the other valve settings such as
current, duty cycle, holding current and other relevant parameter.
• Use overdrive features to mitigate the loss steps. Use the correct
overdriving values with respect to the used value.
• Wrong dened valve type or its setting.
• Longer cables mounted than specied for the controller.
• Separate Valve cable from other high power cables and do not
bundle the cables.
• Blockage in the valve or high friction in the valve.
• MOPD exceeded than specied in the valve specication.