Ice on the evaporator

[josua]

Good day all,
On board the vessel we have a one freezer and chiller room with one each fan/evaporator, they are using 2 Bitzer compressor (semi-hermetic) with R404a.

During normal operation there is ice on the freezer evaporator, compressor suction line and expansion valve, also the temp on the freezer room can’t reach -20 only can go till -14 max, especially if only the freezer solenoid valve open will be more ice. The suction press 1 bar and the discharge 17 bar, the evaporator fan working well with correct direction, when the two solenoid valve open (freezer & chiller) suction press 2 bar, discharge press 18 bar, temp compressor suction side -2 degree.

I try to completely defrost the freezer room and remove all the ice, after that I check the expansion valve filter strainer and clean, I’m also try to check and close all possibility hot air going inside the room as well as try to recharge but after I start the unit still the same problem appear.

We are using electric coil heating for defrost.

Before this unit was working well and freezer can reach -20, just yesterday the problem come.

So can you guys PLEASE help me with some advice to solve this problem? And please be gentle since I’m new on this kind of system.

if I miss something please tell me....
Thanks

[Joy]

Check Evap-pressure controler,
*Defrost time / Temperature, Minimum Time- Low defrost stop temperature set.
Defrost sensor -install in a proper place .Resistivity check)

Number of defrost/ day
Air leakage through door, Door open several time or keep open. Door gasket
Exp-Valve superheat
Liquid line solenoid slightly open at the defrost time.
/ Low air flow. Fresh air forcing through air shatter to deep freezer
Evaporator drainage block / No water in “U"tube.
Drainage heater check.
Check defrost heater.
Very low Set point
Evaporator fan on during defrost.
Defrost senser is near heater

[RANGER1]

You are on the right track , kind of .
1 bar = -30 C
2 bar = -20 C

De-ice freezer evaporator and check that you can see through it with say a torch , It must be 100 % clean .
Check all heaters are working while your at it , otherwise it will ice up again in near future .
Check door seals etc .
Check refrigerant levels , must have full sight glass .
With both freezer + chiller running ( assuming back pressure regulator in chiller suction ) suction pressure would have to be lower than 2 bar .
If cannot get suction lower investigate compessor/s .
Maybe not loading up if it has unloader
or should both machines run ?

[josua]

Thanks for the reply
Defrost 5 times a day with 15 minute
All heaters working good
Drainage good, door seal good, the fan stop during defrost, refrigerant full in side glass.
The evaporator it is clean, only when the system running ice start blocking the air flow..

it is possible to adjust the expansion valve manually..??(open & close)
how to check if the expansion v/v working good..??
it is ok the defrost time set 5 times a day (15 mnt)..???

[rizwankhan]

hi couple, evaporator is iced-up there are no problem expansionvalve. you check defrost time can be increase 15 to 25 mint and check thermal protector may possibility in short time cut out.first you check during defrost all ice melt or some is inside the evaporator,if there is ice after defrost,check timer timing and over heat thermister,

[josua]

Thanks Mr.Khan,

it is not to much 25 mnt ..??, how if only 20 mnt..??

[baycuclaudyu]

U say the evaporator is clean ,so dont need extra time becouse it is so much humidity in room the number of defrost times is not ok .Try to put in 4 h between defrost or, fallow after when defrost is stop what times it takes to have fully ice

[RANGER1]

Shortage of refrigerant can also cause evaporator to ice , usually end where distributor feeds into coil .

[Royal241]

I agree, short on ***** when both units are on, take a look at that

[prakash]

check for loss of refrigerant in the system, there might be leakage in system.

[baycuclaudyu]

Wen the system don t have ice on the evaporator , he say it is runing good at -20 and sight glass is full .So ,all the problems is coming to defrost times
.Is simple .

[Gary]

There should be an EPR valve on the chiller evap suction line. So, what's up with the suction rising when the chiller is working?

Either the EPR is non-existant or it is wide open.

[Bhagwan Harani]

Two differnt Equipments( In Uy case Freezer -20 &chiller -2) can not run on same compressor.
To maitain -20 Freezer Temp suction Temp sould be -25 Correspondig Pressure 1 Psig for R134a.
It seems Expansion is Bigger