Danfoss Electronic Expansion Valve Failure

[alireza]

Dear All,

Is there anybody who had experienced issue with Danfoss ETS valves in freezer room application ?

We have implemented ETS 12.5 with EKD-316 superheat controller for blast freezer.
The room is being cool down untill around -15 C. After 15 minutes the room temp. rise up.
The opening degree u24 is 100%, but there is no cooling in room and the superheat value u21 comes up. if the room is left in the same state for about 1 hour. The temp. increased from -15 C to 1 C and superheat reached from 10K to about 27K but u24 was 100%.

I can't recognize what is happened for ETS.

Any comment is appreciated;

Alireza

[Glenn Moore]

Hi Alireza
I know these valves and controller very well and have experienced similar problems with these valves. The ETS valve being of the stepper motor type can lose steps due to electrical noise in the circuit. Danfoss supply a noise filter called an AKA 211 Code no 084B2238 which connects between the controller and the stepper motor.
this device helps the stepper valve to operate with the correct steps calibration
Question 1
Have you an AKA211 filter fitted ?
Question 2
How long are the electrical cables between the EKD 316 and the ETS valve ?
Question 3
When the system stops on temperature does the volt free contacts D1 (Terminals 20 and 21 ) open circuit ?
Question 4
Have you Invertors fitted to any of the electrical motors on the plant ?


If the D1 contact does not open then the ETS valve can lose its step calibration , the EKD thinks that the valve is 100% open when in fact it is nearly closed. By opening the D1 contact the ETS/EKD recalibrates itself and may work OK for a few hours when the contact is closed, before it loses its calibration again due to electrical noise.
Please answer the questions above and if possible the parameter settings in the controller, and I will try to help you further
Kind Regards
Glenn

[alireza]

Dear Glenn,
Thanks for reply ;
Please find the answers as below
1)AKA 211 hasn't been installed
2)The cable length is about 7m from EKD to ets
3)When the system is off 21-22 is disconnected
4)No vfd has been installed in the plant, but there are more than 15 ets 6 are running in this plant without issue.

Thanks and regards,
Alireza

[Glenn Moore]

Hi Alireza
The ETS 6 valves are Unipolar stepper valves whereas the bigger ETS valves are all Bi-polar valves , so the output signal from the EKD for the 2 types of valve motors are different. This maybe why the 6's work and the 12.5 doesn't.
The other thing to check is that the cable from the EKD to the ETS valve is run in a separate 4 core cable just for the motor and not in a multi core cable with other power signals in the core. Also make sure there are no large power cables near the Stepper motor cable.
I always fit the AKA 211 Filter to these controls as standard as many times I have had to get customers to retrofit the filter to clear the problem. Check parameter No3 is set to 0
Kr Glenn

[alireza]

thanks for useful information about valve types;Honestly, I haven't been care of it.There is a separate 4 core cable from EKD to ETS, in a separate cable tray, far from high power cables. Fortunately, I have AKA 211 in stock that I will use it as my last bullet.
Do you think if there is any mechanical issue in ets or something that causes the valve to be stuck such as ice formation?
By the way, it's a blast freezer in -35 C room temp. and -40 to -45C evaporating and +50 condensing temperature(ets has been installed out of the room, 0.5 m far from distributor) .
Best Regards,
Alireza

[alireza]

thanks for useful information about valve types;Honestly, I haven't been care of it.There is a separate 4 core cable from EKD to ETS, in a separate cable tray, far from high power cables. Fortunately, I have AKA 211 in stock that I will use it as my last bullet.
Do you think if there is any mechanical issue in ets or something that causes the valve to be stuck such as ice formation?
By the way, it's a blast freezer in -35 C room temp. and -40 to -45C evaporating and +50 condensing temperature(ets has been installed out of the room, 0.5 m far from distributor) .
Best Regards,
Alireza

[Glenn Moore]

I had 3 separate plants where the standard ETS valve motors only lasted about 6 to 8 weeks before the stepper motor bearings failed due to a lack of oil circulating around the system. All 3 systems had coalescing oil seperators on them and the oil circulating was nearly zero, and the stepper motor bearings seized and jammed the motors , preventing the valve from opening and closing.
I solved the problem by replacing the Stepper motors with the Co2 version motors, which have ceramic bearings fitted as against standard roller bearings which are in the standard version ETS.
The Co2 version ETS valve motors all use ceramic bearings as Co2 is a poor oil carrying refrigerant and the standard motor would not last very long
I doubt if moisture is a problem as the orifice area is large, but you could always fit a replacement drier .
If you can please send the parameter settings so that I can check that they are Ok for your system
Does the valve work sometimes ? or not at all?
What do you do to get it working again .
I would fit the filter first and if that doesn't work replace the stepper motor
Glenn

[alireza]

Thanks for your perfect comments!
There are 2 paralleled double stage Bitzer compressors(S6F-30.2) with subcooler, feeding 2 blast freezers in one suction group.Once, 3 weeks after commissioning, I was called for service because warming up the rooms.Both ets 12.5 valves were fully closed.We tried to get back the valve to running by putting the valve in manual mode (O18=1) and playing with O45(% of manual opening degree in manual mode).
Also, we applied hot air and hitter it gently, it doesn't rerespond again.The last trick was to increase the suction pressure artificially and manually start of compressor.
After that, the valves got back to running.
Now, one of the valves are running, without issue.Another valve is working faulty as mentioned story.

[alireza]

Could you please advise which code of CO2 stepper me motor version can be replaced with standard ets 12.5(034G4210)motor?
Moreover, is that necessary to replace EKD-316(084B8040) with other controller?

[alireza]

Ekd-316 parameters:
N03=0, n04= 7, n05=90, n06=0, n09=7, n10=5,
n11=1.5, n15=14, n17=20, n18=5,
n19=0.3, n20=0.4, n21=1, n22=4,
n32=100, n44=30, o56=1, o30=19

[Glenn Moore]

Hi Alireza
The Co2 version Stepper Motor actuator is code no 034G2088

regarding the parameter settings please reset to the following :-
n03=0, n04=3, n05=120, n06=0, n09=7, n10=4, n11=1.8,
n15=0, n17=0, n19=0.3, n20=0.4, n21=2, n22=2, n32=100
n38=200, o30=19, o56=1, 061=2,

Check parameters o20 and o21 and pressure transducer code no and pressure range

Check pressure reading u25 with suction pressure gauge

The parameter n11 which is the MOP point which relates to the suction/evaporating pressure which is set at 1.5 Bar. The valve will not open at all if the suction pressure is higher than this pressure setting.

So try the new settings and make sure that the contact on the EKD D1 terminals 20 and 21 make when the compressor starts.If the suction pressure is higher than the n11 setting then the valve will stay closed until the compressor pulls the suction pressure below this pressure setting
Hope this works Glenn

[alireza]

I will change the settings and install a filter AKA 211 tomorrow morning. I will post the result in the evening.

Best regards,
Alireza

[alireza]

Hi,
Just I came back home. We installed the filter AKA 211. I wondered how much degrees of opening % was decreased after installing the filter and how does it improve the valve operation and room temp. We should wait until tomorrow to observe if the room temperature will be kept satisfactory or not.

Thanks for your help