Refrigerant jumping evaporator

[Cary]

Can anyone explain the problem I'm experiencing with an aged near stuffed Muller evaporator.The system has started icing up the suction line and compressor,when I first saw it I thought easy, frosted evaporator but no such luck.
The evaporator is frosting at the TX Valve equal frosting over the distributer and first runs on the evaporator and then no more frost until it reappears at a point where the liquid pipe enters the heat exchange section on the suction line, it continues out an ices over the compressor.
The sight glass shows a great deal of vapour.
System is running on SP34 drop in with a suction pressure around 170kpa and high side pressure around 750kpa.
I have tried changing the TX to no avail. Done a leak survey, unable to locate a leak and so i added some refrigerant in an attempt to get a liquid state at the sight glass .
I can not understand why the system is showing opposite symptoms of vapour in the sight glass and icing the compressor.
Need to return to the job tomorrow so Id be glad to hear of any suggestions

[NH3LVR]

I would bet that you have a leak in the heat exchange section. This allows the liquid to enter the suction line without going through the evaporator.
You probably do not have valves to isolate the heat exchanger, so you might have to cut the liquid line on both sides and pressure test it.

[ConDor]

Without a doubt a broken heat exchanger

[monkey spanners]

Busted heat exchanger for me too.
Had a tev leak into the equalising line and do something similar, but i see you have replaced this.
Intersesting condesing unit you have there, makes going to work worthwhile when you find something like this.

Cheers Jon

[old gas bottle]

yep ,same hear,try cutting the liquid line pipes off and joining them together,not forgetting to seal the other ends, should do the joby,

[sylvester]

condition when suction pressure drops too low that frosting occur.Please check if system has no leak considering that Tx valve has been replaced.check if discharge pressure is too high else refrigerant is blocked.
If disccharge pressure is low and suction pressure is low then possible leak; else lack of refrigerant

[paul_h]

condition when suction pressure drops too low that frosting occur.Please check if system has no leak considering that Tx valve has been replaced.check if discharge pressure is too high else refrigerant is blocked.
If disccharge pressure is low and suction pressure is low then possible leak; else lack of refrigerant

Have you read what's above? NH3LVR was spot on the money, not much liquid in the evap, heaps in the suction line after the evap. Even the OP said liquid was bypassing the evap and that there is in fact a heat exchanger, where the frost line actually starts.

edit: sorry man, I don't want to bug you on your first post, so don't be too discouraged. I don't want to step on any toes here, but it looks like you replied without reading anything here. The pressures were given in the OP, and everyone's advice here before you was good. Your reply makes no sense here.

[Cary]

Yes you were correct it was hole in the liquid line in the heat exchanger causing the refrigerant to take the easy way back to the compressor.
I did consider this when I first went to the job but then over analysed the situation thinking what could possibly cause a leak inside the heat exchanger,but thanks to your replies and the shortage of any other possibilites I went ahead with the bypass.
The patient is now operating within the correct temperature range although as you can see from the back view it really showing its age.
The butcher is in a rented premise and niether he nor the landlord want to splash out and actually improve the situation it just wire and bailing twine to keep the system limping along.
Is it just me or does everyone get can't you just fix it , it used to work fine for Grandad.
Any way thank you very much for your replies it makes it much easier to consider the way others would approach a problem

[The MG Pony]

Just give it a good therough cleaning and a pat on the back and it'll be fine! I adore thoughs older compressors, I even got one here at home

[monkey spanners]

Chopped this out today due to the poor quality brazing. thought i'd cut it in half to see how it worked.

Jon

[US Iceman]

Now that you have cut it apart how are you going to put it back together?

[monkey spanners]

Didn't think of that lol, too late now!