Moisture?

[lorano]

Right chaps thought id run this one past you.Recently changed compressor on a foster EMPROG600L upright freezer.Freezer has been running great for 2 weeks then over the weekend it 'broke down'.Went back to investigate today,stuck gauges on it pressure sitting around 120psi which i thought was fine,powered it back up pressure dropped to around 15psi then starting falling to around 5psi.I did doubt that there were any leaks but pressure tested anyway.Took pressure to around 350psi and monitored it for 2 hours where it fell by 5psi.checked the whole of the system for leaks with spray but was still doubtfull.Blew of the ofn and stuck it on a vac.When i shut the gauges off and switched off the pump i could actually watch the gauge go all the way back up to 0.This surely has to be moisture in the system right?Could it have ran for 2 weeks with moisture in it then run crap?If there was a leak that big i wouldve heard it never mind seen it:-).Any reply would be appreciated guys.

[install monkey]

ur pressure test of 350psi the 5psi change in pressure, was this during the stabilisation time or overall- did the ambient temperature change??
how long did u vac it for?
prob is moisture and possibly crap from brazing. final thought it could have a leak that only appears when its running and pipe temps change, usually re evaporation tray is prone to leaks and also the capillary if run in the suction lagging, weigh out the gas to see if its the same as charged

[r.bartlett]

are you vac'ing both side of the system or is there nitrogen in the high side still bleeding back

[1mikeefc1]

Is it leaking when on hot gas defrost? Also check the vapourising tray I've had the discharge line that runs through it leak there before.

[The Viking]

Hmm,
Pressure test with OFN indicates a drop...
Vacc after the system been flooded with OFN not only rising but goes back to atmospheric...

Me finks you got a leak mate.

How much refrigerant were you able to reclaim on your return visit compared to what you charged with after the compressor change?

[lorano]

I can only add pressure through the port on the compressor,the discharge line that runs through the drain pan was fine,the freezer is like brand new.I replaced the compressor,capillary and the copper spun drier at the same time.The old compressor was a none pumper and also the capillary was blocked.Why am I not hearing or seeing a leak when under pressure but when on a vac the pressure goes back up to 0psi?Vac'd out for around 20 minutes,I was being rushed out the building by a right nippy woman,tools and stuff everywhere but I had to leave:-(.

[1mikeefc1]

The capillary originally runs through the suction line have you brazed up each end of the old capillary when installing new capillary?

[monkey spanners]

Put a temporary T in the high side to see whats going on in both sides of the system, can pinch it and braze it up when not needed.

I'm thinking leak or blockage. How quick did it equalise when switching off?

[Tayters]

Not that it will help you now but on those integrals I've always been a bit partial to using the copper spun dryers with the access port on them. Saves all the wondering about equalising and handy to confirm partially blocked capillaries as I've always found you get a subcool reading around 8K if that's the case.

Did spend a while looking for a leak on a Foster once. Turned out me hose was perished!

[lorano]

I removed the old capillary totally.it did take a while to equalise out once powered down.

[lorano]

This freezer also has 2 solenoids on the system,I've only wee seen 1 solenoid which t's at the discharge line for hot gas defrost.The 2nd one sits after the condenser,the capillary line comes out this solenoid then goes into the evaporator.would there be a clear circuit when pressure testing when the system is powered down,would any solenoids be closed?

[monkey spanners]

You'd need a solenoid magnet to open the solenoid for proper vacuuming and pressure testing.

[lorano]

Right guys was back today,foster say the solenoid after the drier is to prevent migration of liquid,meaning to get a proper vac or pressure test you have to energise or open the valve.That would explain the happenings in my above posts.Vac'd out system and recharged again.System ran great but when temp got to around -10 the suction pressure started dropping.this was the problem I had at the start.Disconnected the capillary line from the evaporator coil and blew through,no problem,whole system clear.What would cause a drop like that.The capillary line and drier felt cold as if its back filling with liquid?!

[lorano]

Pressure at drier was 200psi,suction pressure was 15psi.

[1mikeefc1]

The circuit will only pressure test till the hot gas solenoid, if you've not picked a leak up pressure testing yet it sounds like its on the hot gas circuit.

[install monkey]

are ur gauge hoses sealing correctly??- tip use a schraeder core remover whilst vaccing, if ur torr gauge is the hrp dial type then check the rubber grommet on the back isnt leaking, also that your oil level is correct in ur vac pump and maybe changed recently.
could be moisture in ur drier, try vaccing for 2hrs and then ensure when u shut off ur vac pump the torr gauge only moves by say 1 torr(backdrop) and then doesnt move

[Tayters]

The capillary line and drier felt cold as if its back filling with liquid?!

This indicates a blockage in the drier, crud, moisture, whatever. When you say the pressure drops though, how far does it go? 15psi seems about right if you have R404A. Were the evap fans working and is the compressor the right one?

Cheers, Andy.

[chilliwilly]

Did you run the compressor for a few minutes to sweep the high side to the low side when the system was under vacuum?

The last couple of cabinets I have done pot changes on have give me the same trouble. As they only had low side ports, I didn't like using copper dryers with a high side port as you loose too much charge when removing the hose. I saw the system balance out on the low side when tightness tested it before removing the old pot and assumed there were no blockage. But only to find out after the new pot was fit and a satisfactory tightness test and vacked down to desired level, the reading crept back up towards atmosphere.

When I started to vack out again towards 400 mic, I swept the high side to the low side and there was a vast difference in pressure. So there had to be a blockage waiting to happen that had been caused by me sweeping the high side to the low. Even though I blew the pipework through in reverse before fitting the new pot.

Anyway, decided to remove the new pot, reversed flushed pipework from the suction side to the end of the capillary through twice with parraffin, which shifted all the sludge then with some flush I had left over from the last time which came through spotless. I didn't think I would have enough flush so I decided on parraffin, plus it was the only thing I could get at that time of night. And then did the same with the condensor, which was cleaner than expected.

Re brazed pot back into system with another dryer and system pulled down within 3 hours, swept high side to low side and there were no difference or increase in pressure to be concerned about. Unit now running sweet again giving no problems.

The old compressor that I removed did seem quite recent, and was pulling a vacuum as soon as it run, as it was a sub contract job I didn't ask any questions or make waves. But I found out later that the cost of repairing the cabinet was just under £700.00, and the cost of replacing it was £950.00. If it had been a direct customer, the repair wouldn't have been done, replacement would have been the best option, as it was only a Sadia.

There was a coil of capillary pipe deleivered to site with the compressor but no new dryer or flush, so the main contractor must have intended for me to change it, but not the dryer? But to be honest I have never replaced a capilllary that runs inside the low side, but have repaired sections of them. It looks like too much time and effort for what its worth, and I always feel that filler metal will be brought into the low side and eventually work its way through to the compressor?

[1mikeefc1]

15psi suction what temp was the cabinet and evap temp at his point? Also are you weighing in your gas as I have done many of these and weight on plate isn't reliable in my experience.

[1mikeefc1]

Sorry just re read cabinet was at -10. If it's only at this temp at 15psi it is still short of refrigerant. At temp it should be at this pressure but you are running it down with heat load to take out. Best guide line is to see t2(evap temp) if this is between 7 and 10 degrees lower than (t1) while in running and it's freezing back on the suction but not to the comp itself you won't be far off.

[lorano]

The hot gas circut feeds back into the evaporator coil on this unit,i dont think there is a leak but something not right within the system.This unit has ran fine for 2 weeks since the compressor was changed the all of a sudden its pulling almost into a vac(5psi).I'm leaning towards changing the drier even though i replaced it when doing the compressor.I dont go by the gas weight on the plate either as far to many times ive thought the system has a blockage but really its needed more charge.I usually watch the suction line to see if its sweating or icing back which is usually i good indicator of how much charge is in the system,to much to little.I left it running and told the staff to monitor it and if the temperature is high in the morning to call it back in.Been pretty frustrated with this job as everytime i go its in the afternoon and im on a time limit because staff want to go home which is no good as you guys will understand.

[lorano]

This indicates a blockage in the drier, crud, moisture, whatever. When you say the pressure drops though, how far does it go? 15psi seems about right if you have R404A. Were the evap fans working and is the compressor the right one?

Cheers, Andy.

Its alll of a sudden drops to around 5psi,but today it was going into a vac after running for 15 minutes and coming down to -10 degrees C.

[lorano]

Was back checking this freezer today after getting t running,everything seemed ok,staff said its been fine.The only thing i noticed that i thought wasnt right was the temperature of the discharge line felt too hot.Its quarter inch pipe and was reading around 55 degrees C on my infa red,is this right?

[install monkey]

discharge should be hot- liq line warm