compressor icing up.

[dunny123]

Hi,i went to a 3door bench fridge about 3week ago,the condenssor was extremely blocked,and compressor red hot.I cleaned condenssor best i could,and advised to leave off over nite to allow comp to cool.Its worked ok till today.When i arrived the suction line into comp was iced up,also comp a bit.I reclaimed all the gas R404a,and vaced out system.I wanted to start from scrach to be 100% the blend was right.the sytem didnt hold a vac,it crept up slowly,im pritty confident it hasnt a leak,as it has held its pressure ok.Is it the compressor that is passing gas?Thanks for your time?

[nike123]

Hi,i went to a 3door bench fridge about 3week ago,the condenssor was extremely blocked,and compressor red hot.I cleaned condenssor best i could,and advised to leave off over nite to allow comp to cool.Its worked ok till today.When i arrived the suction line into comp was iced up,also comp a bit.I reclaimed all the gas R404a,and vaced out system.I wanted to start from scrach to be 100% the blend was right.the sytem didnt hold a vac,it crept up slowly,im pritty confident it hasnt a leak,as it has held its pressure ok.Is it the compressor that is passing gas?Thanks for your time?

Could be that your hoses have a leak.

[icecube51]

what was the reason for the blockage ??? was is inside or outside ?? did you checkt the other components , magnetic valve, TEV ,filter/dryer ???


Ice

[dunny123]

Im 100% my hoses arnt leaking.The top of the compressor was even icing up,very strange.In thinking the compressor is nacked,and passing gas?

[dunny123]

I mean blocked with grease,not a blockage in the system.Its a small bench fridge,and is on a cappilary.No other companants on it.The compressor was very cold,even when running,and starting to ice on the top,and also round the suction pipe.Never had this before.

[philfridge]

Evaporator coil may be iced up causing floodback .Evaporator fans may not be running. System is overcharged . Check all these ok.

[dunny123]

Checked all these,all fine.There is only a shrader on the suction,and when i vaced it out it didnt hold a vac,the pressure slowly went up,whould it do this if,like i suspect the compressor is passing,and the seals have gone inside?

[powell]

You probably have a restricted capillary tubing due to the oil breaking down from the extreme heat.

The system will need a good clean up if this is the case. If it's a semi-hermetic compressor you could inspect the compressor.

[philfridge]

If you pulled a vac and it did not hold then you have a leak . The compressor will vac both sides from the suction line this is normal.

[nike123]

the sytem didnt hold a vac,it crept up slowly,im pritty confident it hasnt a leak,as it has held its pressure ok.Is it the compressor that is passing gas?

Does this mean that you are sure that system does not have a leak, because you make a leak test with nitrogen?

If you have blockage, maybe you did not recovered all of refrigerant, and when you vacuuming it, could be that refrigerant coming from that blocked part of system.

[casstrig]

You didnt mention the condition of the evap,a bottle cooler with a capillary tube or ax valve will have a thermostat sensing the temperature of the suction line to stop liquide reaching the compressor,was the coil fully frosted,if so your controle is the trouble or the bulb is not atached.Please give more information also pressures.

[nike123]

You probably have a restricted capillary tubing due to the oil breaking down from the extreme heat.
If capillary is restricted then compressor should not getting liquid floodback.
It could be wrong refrigerant, overcharge or evaporator not getting enough air (blocked with something, fan defective).

[nevgee]

Come on guys ....
I don't know what a bench fridge is but...
Compressor is icing up ..this is not a capillary block!

If the guy is not able to hold a vacuum ...does this mean he has a leak? Of course he has a leak or there is something else at fault.
If the compressor is icing up does this suggest he has a VERY low superheat?

Low sureheat suggests what?

Too much refrigerant coming back ..perhaps... then why would that be?


Is this system a capillary or tev?

[wambat]

Hi,i went to a 3door bench fridge about 3week ago,the condenssor was extremely blocked,and compressor red hot.I cleaned condenssor best i could,and advised to leave off over nite to allow comp to cool.Its worked ok till today.When i arrived the suction line into comp was iced up,also comp a bit.I reclaimed all the gas R404a,and vaced out system.I wanted to start from scrach to be 100% the blend was right.the sytem didnt hold a vac,it crept up slowly,im pritty confident it hasnt a leak,as it has held its pressure ok.Is it the compressor that is passing gas?Thanks for your time?

There is one interesting point I would like to bring out, and that is, when the condenser becomes overloaded and the pressures go very high, you have another controlling factor. At this point of high loading not all the refrigerant is condensed and some vapors enter
the cap tube as gas pockets. These gas pockets further restrict the refrigerant flow without affecting the head pressureand the compressor can get very hot. However, it kinds of protects the compressor from flooding Now after you clean the condenser and the system started to work more efficiently you would develop a condition as you describe, where you are feeding too much refrigerant because of higher subcooling thereby reducing the bubble length. When you recharge make sure you check both the hi side and the low side with a set of gauges.
To best describe describe the cap tube operation is to say that the low side gauge will react almost the same as if you had a thermostatic expansion valve. In other words the longer the unit runs the colder the evaporator, and the low side gauge will react
accordingly. The evaporator must maintain its full working capacity throughout the cycle. No frost should appear on the suction line during the cycle or on the start up. The
strainer should always be slightly warmer than room temperature and the condenser should be hot at the top and gradually change to the temperature of the strainer.

[fridgey]

To me it sounds overcharged or the capillary is to large in bore size. Has it been replaced? Is there a specified refrigerant and charge on the fridge if so what is it? You say R404a, are you sure its not R134a? Charging with the wrong refrigerant can cause the same problems you're experiencing.
What are your operating pressures? I would suggest fitting a high side access valve.
As for it not holding vac, the compressor and oil are more than likely cold from the flood back, the refrigerant is getting trapped in the oil and it slowly boiling off causing the pressure to rise.

[dunny123]

Yeh 100% its r404a,itresting point you made at the end,makes sence.

[dunny123]

Iv been back there today,and the evap is slightly iced up today,but not at the cappilary,suggesting it isnt a blockage in the cappilary.Maybe i was too quick at saying the evap wasent iced up when i charged it.Although the finse wasnt iced the pipes may have already formed a bit of ice on them.And ofcourse the evap has flooded causing liquid floodback.
What im going to do is switch off over night to allow comp to cool,evap to defrost,and start from scratch.Im confident it hasnt a blockage,leak,or fans broke.I will keep you informed,thanks for your time guys,great advise.

[philfridge]

Maybe i was too quick at saying the evap wasent iced up when i charged it.


;) Here to help

[icecube51]

as Einstein joust to say "simplify-simplify " , and i always say, when you don't find it straight away , and keep turning for a wile, go back to the basics, they always help. ;)

Ice

[chemi-cool]

Iteresting post, may I add someting?

Compressor icing up is only from one reaon > liquid refrigerant is boiling in the suction line or in the compressor.My conclusion, too much refrigerant or the wrong gas is used.
There was not a word about head pressure or amp drawing.
Cap tube canot be adjuted so thats good news.

I would suggest to replace the 404 with 134 and give it a try, slowly charge and ballance the system and always check head pressure.

[dunny123]

Hi guys iv been back to the job today,after cabinet has been switched off for 24hrs.There was far 2much gas in the system.What threw me off this conclusion is i was assured by the manager i was the only person to work on the fridge,and id never put gas in it.Iv found out today by the chef that someone else came last week,and obviously put gas in,Im fuming...
When i fit gauges before,it was showing it was evaporating about -5,which is about rite for a fridge set at +3.Although i cheched evap wasnt iced up,i musnt have looked properly at the pipes behind the finse. There must have been frost forming on the pipes,this caused my gauges to look like the gas pressures were right.Faulse reading,becouse of evp ice.Anyway the most important thing is the fridge is now working great,and the gas pressures are spot on,the suction pipe is slightly sweating back.Lovely.
Many thanks to you all,great advice to a young improver.Thanks for your time.:)

[nike123]

Anyway the most important thing is the fridge is now working great,and the gas pressures are spot on,the suction pipe is slightly sweating back.Lovely.
Many thanks to you all,great advice to a young improver.Thanks for your time.:)

First law of service in refrigeration (and many other disciplines) is that you don't account much to what user or your boss said about history (or behaviour) of unit. Always aproach with assumption that someone else was before you there, and start with your own observations and what are they saying is only something to think in distance.
Start with basics and go further as your measurements and observations directs. Their observations could be both, misleading and directing, but your instruments and knowledge is what you need to follow.;)

[icecube51]

they ask us why we charge so much, and mi answer is, because we are doing 3 jobs at once.:o
the first is detective,(determine whats happened), second is shrink ,(see if what they tell you is through) and last but not least engineer, (to fix what is broken.) don't underestimate the power of a client.;)


Ice

[acb]

Hi mate, I know this happened a few days ago and im a bit late with thr post, but you still have a blocked drier caused by the dirty condenser. when cooler was off to allow comp to cool, this allowed the refrigerant to fully equalise in the system, and why it gradually started rise in temp again. why did the other fridge guy add more refrigerant to chiller? probably because when he put his guages on the service valve it was reading low and decided to top it up by forcing liquid through the drier resulting in suction line icing up. Hope that didnt sound to arrogant.

regards