Eev reaction time too long

[samux12]

Hello fellas,

My company is manufacturing brine/water heat pumps.
To ensure proper refrigerant volume to evaporator we are using Danfoss ETS6 electronic expansion valves. Controller - Danfoss MCX061V with integrated EEV controller.

As we all know EEV ensures precise Superheat of refrigerant before getting to the compressor.

Yesterday one customer complained for us that heat pump is working very inefficiently. When we made the examination of that heat pump we noticed that ETS6 reaction time of reaching the desire Superheat value is very long. It takes almost about 30 minutes when the superheat drops from 20K to 10K, and the setpoint value - 6K didn't reach at all.
First of all I thought that heat pump is starving from low refrigerant volume, but when i turned EEV to manual control I could set 6K superheat very easily, and after that the system is working under designed condition.

Working conditions is listed below:
Return/supply water - 30C/36C
Return/supply brine - 5C/2C

Condensation temp - +48C
Evaporation temp - -6C
Superheat - 13K (after 20 minutes from starting of heat pump)

After EEV manual setting:
Return/supply water - 30C/36C
Return/supply brine - 5C/2C
Condensation temp - 39C
Evaporation temp - 0C
Superheat - 6K

Can anybody tell me, why EEV is reacting so slow?
Do all EEVs are working the same?
IF not, whose fault is for that. Maybe something wrong is for Danfoss MCX 061V controler?

[Brian_UK]

Have you checked the PID settings of the valve

[samux12]

No I don't.
Tell me, how I can do that. Is it some parameter that could be changed, or it is set by manufacturer and I couldn't do nothing.

[NoNickName]

Please note we are having the same issues with ETS6 valves, because they are not manufactured by Danfoss, but are Saginomiya rebranded, and are very badly interfaced with danish-made Danfoss drivers. A slow valve may be caused by a wrong PID setting (as Brian suggested) or a wrong number of parametrised steps of the stepping motor.
Make sure you have the latest firmware available of the EXV driver, as they recently introduced some bugfixes for the ETS6.
To setup the parameters of the EXD you need a MMIMYK remote display or modbus interfacing software.

[chemi-cool]

Try these, works fine with Dixell controls.

http://www.emersonclimate.com/en-US/products/valves/expansion_valves/Pages/electronic_expansion_valve.aspx