Walk In Cooler Icing Up

[Royal241]

R 22, 40 suction, 220 high side (outdoor condenser, fan cycling), washed evaporator, blower motor turning the right way (within amperage and feels good). This is an existing cooler, 5 years old (no known issues). Not a pump down system, no defrost timer. Due to the nature of product, a defrost timer is not a good idea. System runs great, but after 10 minutes the coils start to freeze and the next day is full of ice. I replaced the expansion valve, same result, adjusted the valve, got better but I'm not happy. The old valve did not respond to adjustments and really thought this will solve it. The evaporator is 4000btu and the valve 1/2T, i think that 2 turns (close) will do, but, did I miss something? I usually don't ask for help, but a second opinion would be nice to have. I changed the thermostat also, didn't close at the right temp, but did maintain a 5 degree differential. Changing it was intended for the customer not to make the box too cold. What am I missing, did you guys come across something similar? Thanks for the time, cheers!

[sedgy]

hi royal 241,
your 40psi ? tells us that your freezer is evaporating at -8 c is this right for your product?
yes its quite normal at this temp to get frost on your evap, and also normal to have a de-frost system incorperated on the same , regards = sedgy,

[mbc]

What is your room temp.?
why you do not want to put timer on your system and do defrost with fans (if your room temp. is more than 4) or with elements ,

[chemi-cool]

Do you stop the compressor with low pressure device?
Do you have head pressure control?
Air entering when door is shot?

Why cant you use thermostat with natural defrost?

[kerrcell]

Can it be short of gas charge or faulty defrost heater/s ?

[mikeref]

Full evap. ice up, not gas issues. Seems your thermostat is not cycling off, so what has changed? Product load or a difference in the way the room is used. Someone leaving the door ajar, or your trying to run the room too cold. Pub coldrooms always a challenge when owner can change set temps. Thinks a fraction colder is no drama so, Tinker Tinker.... ICEUP! Help.. BTW, defrost timers are always a good idea on applications running close to 32F, 0C.

[ironmen]

hi Royal241,there is alot of factor that can cause a system to iceup,you need to go to the basic.maybe there is a service switch for the evap fan when they loading they turn it off and it stay off.what about the clearence between the fan coil and the goods.Is there any dust on your fan blade and causing lack of air flow.check your fan terminal maybe its stopping with faulty wire,terminal etc.what about moisture getting in the cabinet.open door,faulty door seal.Is the evaporator icecing up completly or half?Check those and then you will check the operation of it,system cycling,unbalance txv,liquid evaporating to early,etc.Goodluck men.

[Royal241]

Ok, this cooler has 3 independent units (evaporators and condensers). It turned out that someone switched the thermostat wirings. T1 was controlling condenser 2 and T2 controlling condenser 1. This problem was solved the next day, thank you for all other points.