cold room, freezing evaporator and pipework!!!???

[andrew20441]

Thanks for reading

Local company had installed a three cold rooms some 4 years ago. over the past 2 years the client has been suffering some ice formation in the negative room on the evaporator and also along the flow and return pipework......
the company then replaced all the pipe-work and not the insulation....the insulation. The problem still persists and the supply pipework outside is now frozen.

Even the cold room panels are sodden and i am afraid that the original problem was just a blocked condensate drain...can anyone help try to confirm this?
This puts extra load on the compressor and electrical systems and is evident as the conductors at the ATS are dis-colored and showing signs of excessive heat.
Here they also wrap the insulation so tightly that the insulation looses all its heat retention properties.....would this also be true to suggest?

Look forward to any feedback

Andrew

[andrew20441]

forgot to say....yes it could also be a defrost timer/heater problem....!!!

[lana]

Hi there,

First check the defrost. When defrosting, all the frost must disappear from the evaporator. If not, this will accumulate in time and will cause so many problems.
If the suction line is frosting check the superheat and see if you have liquid flood back. If there is no flood back then frosting could be due to low return gas temperature and you see air moisture as frost.

Cheers

[andrew20441]

hi...
so low temp on return...that means that it is not being dissapated through the evaporator....is that right??

And flood back is a result of what?

so would the insulation being wet exaggerate the freezing??

Regards

Andrew

[lana]

Hi,

When the evaporating temperature is below 0°C, say -20°C, having a normal superheat of 10k then suction gas temperature will be -10°C. This gas is cold and makes all the suction pipe to freeze the surrounding moisture. This freeze up depends completely on ambient air condition (DB/RH). When the evaporating temperature is lower, then things get worse. I had a double-stage system with evaporating temperature of -40°C and I had the same frosting problem on the suction pipe and on the accumulator, but it was not flood back. I must mention that this frost is more visible during winter than summer.

When frost is seen then the only way to know it's due to flood back is measuring the superheat.

Flood back means instead of gas, liquid refrigerant is returning to the compressor. The reasons are :
1- Wrong TEV nozzle (too big).
2- Incorrect TEV adjustment.
3- Burned out evaporator fan(s).
4- Evaporator too small.
5- TEV not functioning (stays open).
6- Overcharged system (specially cap tube systems).
7- Evaporator is blocked with frost.
7- Evaporator fans are rotating in the wrong direction.

I suggest that you check the visual problems first then measure the superheat.
Cheers

[smpsmp45]

I could guess that if the drain water pipes are not blocked & the problems is still there, it means the liquid is not getting evaporated properly. We had gone through this on one of our sites & finally it came out to that the Fan - It was a three fan unit - & one fan was not operational 7 was rotating in reverse due to other fans forces. So if one sees the fan from below it seems it is running. When that fan was found to be faulty & was replaced with proper rotation direction, things were perfect