evaporator not work properly

[climas]

In one cold room from my customer I involved in trouble with this cold room(i work tranport van for him).He tell me that evaporator freeze in short time and tell me to check defrost interval to controller,but after quickly check I notice this
1.evaporator circuit not freeze same ,two circuit freeze complete his coil others about 30-60% coil
2.liquid distributor complete in dry ice
3.sight glas full of liquid
4.MOST IMPORTANT crancase compressor I dont see oil only FOAM to the top of sight glass when stopped compressor I see oil in 1/2 sight glass
5.Suction line frosted no ice.Evaporator new Rivacold type with two fans
6.Evaporator capacity 6kw in delta t8 Danfoss valve tex2 oriffice no 4 !!!!!!!
7.Cold room is design for temp. 2-4 C
Does is possible that big oriffice cause this , and why in that case only two evaporator circuit refrigerated to the end of evapor.suction coil,and others dont do same thinks
I need members opinion about this
Regards

[RANGER1]

climas,
Probably need more information.
refrigerant type
pressures, suction & discharge
superheat
temp difference across evaporator
does evaporator have good airflow
door seal condition etc

Best start off with a frost free evaporaor before above is taken

[nike123]

Does is possible that big oriffice cause this , and why in that case only two evaporator circuit refrigerated to the end of evapor.suction coil,and others dont do same thinks
I need members opinion about this
Regards

You first need to check subcooling at each TXV is suficient (2K or more).
Than check air flow is as declared in evaporator documentation. Next, check superheat at each TXV. It should be about 65% of evaporator TD if subcooling is sufficient and air flow OK (cca 5K).

For correct check of subcooling you need access valve close enough before TXV, or you need to calculate pressure drop from high pressure measuring point to TXV, othervise your calculation of subcooling will be pretty wrong.

Also, measure air in and out temperature (DB and WB or RH) at each evaporator and post here all measured data separately for each evaporator.

Since I know well comisioning practice in our countries, I wuld first cliean TXV orifices and strainers from oxidation which came from pipes which are brazed without nitrogen blowing during brazing.

[climas]

Thanks for reply
This is only one evaporator and one refr.unit.When I go again I will measure, but for example superheat value be false,because the two or three section in evaporator who "works" give me maybe good superheat but fact is that other section in evaporator not feed properly.
I afraid for compressor I not see oil only foam that means we have liquid in crancase,body compressor is cold.Evaporator have good air flow,last time I have only termometer and see that liquid line temperature is 35C.Now we only talking what maybe be wrong in this refrigeration unit
Regards

[nike123]

OK, I wrongly taught that you speak of multiple evaporator set up.Nevertheless, proposed measurements should be done, for that single evaporator, in order to troubleshoot that problem.
Oversized orifice will cause haunting of TXV which will be visible as superheat oscillation when system get near design temperature and load is minimal.
Unequal feeding of evaporator circuit also could be (not necessary) by wrongly positioned distributor or unequal lengths of tubes feeding evaporator from distributor. Distributor should be pointed up to down for best distribution.
(http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/01/RI1CA152.pdfFeeding)http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/01/RI1CA152.pdf
Feeding tubes should also have same number of U turns of same diameter in order to have equal resistance to flow.
Check that equalisation line is fited to TXV.
TEX2 with orifice No 4 have around 9,7 to 11,3 kW of cooling capacity (in your working conditions) which is to big for evaporator of 6kW cooling capacity. You should try to fit orifice No 3 which has 6-7 kW of capacity.

[cold.man]

have you checked the liquid line solenoid valve? if the coil is always energised or if the is debris in the valave causing it to pass.
is the TX valve operating correctly?
if you have frosting on the suction line i would suggest there is liquid in the suction which will more than likley be causing your oil problem.
what defrost type is it, heater or hotgas, is the defrost working correctly?
i would make these checks first.