Danfoss EKE 1A User Manual page 77

Superheat controller, Type EKE 1A, 1B, 1C, 1D
ID Symptom
4 Liquid hammer in compres-
sor (noisy or unusual com-
pressor sound) and /or frost
on the suction line
5 Too Low superheat
6 High superheat
7 Too high or too low meas-
ured superheat
8 Measured Superheat is
higher than reference -
more than 5K for 5 - 10 min.
Measured Superheat is low-
er than reference - lower 3K
9 Fluctuating superheat
10 Negative superheat
© Danfoss | Climate Solutions | 2022.06
Possible cause/Reaction
Superheat reference set too low.
Superheat is too low.
Inaccurate SH measurement or slow response in S2 sen-
sors.
Refrigerant or pressure transmitter is not set correctly.
Min. SH parameter is too low set.
Valve Cannot Close fully.
Valve OD too large at start up.
Inaccurate superheat.
High-pressure drop-in suction line.
Valve is stuck at open.
Liquid returns to compressor.
Lack of sub-cooling.
Controller is not setup/tuned properly.
Wrong valve selected from the controller list or undersized
valve installed.
Seasonally high load condition or overloaded the system.
Wrong sensor type, refrigerant type, pressure transmitter
type and/or range.
Load condition has changed, and the superheat controller
is too slow to adapt to the change.
Compressor capacity has changed, and the superheat con-
troller is too slow to adapt to the change.
Missing valve capacity.
SH close parameter is disabled or not setup optimally.
Compressor capacity has changed, and the superheat con-
troller is act too aggressive to adapt to the change.
The S2 sensor not in good contact with the suction line.
Fast change in load and ambient condition.
Periodic flash gas at the valve inlet.
Aggressive gain Kp and Kp Te parameter.
Wrong sensor type, refrigerant type, pressure transmitter
type and range.
During start up suction pressure is low because of low Am-
bient temperature.
System is not running.
Solution
• Increase the SH reference by changing the SH min.
max. parameter.
• Make sure SH Close function is ON.
• Increase the values of SH close and SH min.
• Also check section "Too low superheat"
• Ensure that S2 sensor is secured on suction line.
• Insulate temperature sensor properly.
• Check the product installation guide section tempera-
ture sensor.
• Check the related parameters.
• Raise the min. SH parameter.
• Reduced the Valve OD or forced opening time at Start
up.
• Use P-control.
• Reduce Start OD.
• Mounting position of Temperature sensor. Place sensor
close to evaporator.
• Mounting position of the pressure transmitter. Place
the transmitter close to evaporator.
• Check the product installation guide section tempera-
ture sensor.
• Check valve installation.
• Check section Liquid hammering.
• Limit max opening degree of the valve setting in con-
troller.
• Check refrigeration system capacity and compare with
expansion valve capacity. Use proper valve size suitable
for the system.
• Check the controller superheat settings SH min, SH max
and sensors connected to it.
• Tune PID parameters in the controller.
• Check the right valve type and setting or use the ap-
propriate valve size for the needed condition.
• Check the heat exchanger for dirt's.
• Check superheat performance.
• Check the related setting and range.
• In case of offset in sensor or pressure transmitter, per-
form the sensor correction.
• Always use accurate pressure transmitter
• TN can be adjusted to 20% lower and Kp can be adjus-
ted to be 20% higher, monitor that the adjustment
doesn't make the valve OD and Pe/Te oscillate.
• Compensation for compressor change is done with
KpTe in this case KpTe can be adjusted to be 20% high-
er.
• 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.
• Enable the SH close function and set the setpoint 2K
below the reference.
• Compensation for compressor change is done with
KpTe in this case KpTe can be adjusted to be 20% lower.
• Check proper mounting of the temperature sensor.
• Wait for the stable condition and check again.
• Secure stable sub cooling
• Decrease gain in the controller, ex set SH Tn to be 20 %
higher and reduce Kp 20%, if still SH is fluctuating, re-
duce KpTe by 20%.
• Try with the higher SH reference.
• Check the related setting and range.
• Check the startup problem.
• Check the system.
BC398828796060en-000101 | 77