Eutectic tank mystery

[Venus1]

Help needed. I am not refrigeration savvy. My new Ozefridge (I'm in Australia) works poorly. It is an electric driven compressor with a eutectic tank in the fridge cabinet.
My local fridge guy is helpful, and trying more gas - so far to no avail. There is some cooling, but nowhere near enough (12 hours continuous running gives eutectic temp -7, but would have given -21 when new, a few months ago).
The observation that has me stumped is: the eutectic tank has ice on its outside surface, as you would expect, but unlike previously, the ice is only on the top quarter of the tank. (The brine in the tank has freezing point of -5). When the fridge was working properly, the ice would form evenly over the tank's surface as you would expect. I'm pretty sure sure the tank is full (no sign of leaks of the green brine).
Question: any ideas on why the ice now forms only on the top part of the tank, and how it might give a clew as to why the fridge is not performing properly?
I hope this makes sense. I have tried to be concise....
Thanks in advance for help.

 

[Bilgediver]

Have you spoken to Ozefridge?

 

[vyv_cox]

There is a guide as to levels of refrigerant and the appearance of various components in the system on my website. Might be worth consulting.

 

[Venus1]

Have you spoken to Ozefridge?

I will talk to Ozefridge. It's tricky though because I have my local fridge guy working on it (so far unsuccessfully), and I don't want to go behind his back..

 

[Venus1]

There is a guide as to levels of refrigerant and the appearance of various components in the system on my website. Might be worth consulting.

Thanks Viv, I have checked your excellent site. It refers to a capillary system. Does the advice on refrigerant charge checking apply equally to a eutectic system? Pardon my ignorance.

 

[Bilgediver]

Thanks Viv, I have checked your excellent site. It refers to a capillary system. Does the advice on refrigerant charge checking apply equally to a eutectic system? Pardon my ignorance.

No the Eutectic system has the complication of eutectic medium in a tank and this adds extra problems in diagnostics. Your problem appears to be that the eutectic medium in the tank is not performing correctly It should pass through from a fluid stage to a frozen state at a precise temperature according to its specific make up for the application. If the eutectic tank is not showing frost all over this may indicate the fluid has ceased circulating within the tank and has become frozen prematurely. Heaven knows what could cause this . Each eutectic tank is filled with a fluid to suite a service and yours seems to think it is a fridge and not a freezer!!!!!

 

[Venus1]

No the Eutectic system has the complication of eutectic medium in a tank and this adds extra problems in diagnostics. Your problem appears to be that the eutectic medium in the tank is not performing correctly It should pass through from a fluid stage to a frozen state at a precise temperature according to its specific make up for the application. If the eutectic tank is not showing frost all over this may indicate the fluid has ceased circulating within the tank and has become frozen prematurely. Heaven knows what could cause this . Each eutectic tank is filled with a fluid to suite a service and yours seems to think it is a fridge and not a freezer!!!!!

Thanks Bilgediver, yes it is a mystery. The fluid in the eutectic tank (can't recall it's name, but it freezes at -5) has been the same for 2 years, and was working fine until a month ago, and the tank is full (no leaks). Still, you have made me wonder whether it's not evenly distributed somehow - but with a full tank I can't see how this can be.

 

[Bilgediver]

Is there any chance someone topped it up ???

 

[Venus1]

UPDATE: PROBLEM SOLVED
It turns out there was a blockage (oil?) in the capillary inside the eutectic tank. This was diagnosed by the refrigeration technician using his pressure gauges. 12 hours of pumping nitrogen through the low pressure side (ie the capillary through the tank) seemed to unblock it, and the fridge is now running normally. Brine down to -18'C. (I now wonder whether getting it so cold increases the chance of a blockage, but that's for another day. ) FYI
PS. I still don't know why only the top quarter of the eutectic tank iced over, but with a normally running fridge, I'm not going to worry about that. It probably related to the blockage..)