Moisture

[Abe]

Have a 4 hp Prestcold Unit, subsequent engineers working on this unit have "allowed" moisture and air ingress into system. Despite installing filters, one just before expansion valve, system goes into deep vacuum each time.

Unit is a L400/0062 Prestcold running on Iceon R69
Has a Oil Seperator, oil is a muddy brown colour. System has had leaks in the past, system operates on pump down, and pressure switch cuts at 14 inches vacuum !! Horror Horror

Ive reset pressure switch to cut out at 5psig

No wonder it has been sucking in air all this time.

It has been suggested I replace all the oil, change oil seperator, change receiver tank, and replace Evaporator blower, and this shouls solve problem.

[Abe]

Marc,

Thanks for your advice.

Hope your dad enjoyed his trip up north, with gales and we have got snow this morning.

Next time youre up, be sure to bring your dad up with you.

I want him to enjoy a nice curry to warm him up and shake off the winter blues.

Once again, thanks, speak soon

Aiyub

[Gary]

Why do you believe the problem is moisture? Is the oil separator working?

[Abe]

When I apply warmth to the expansion valve I hear a "whoosh" and rushing sound as the built up gas surges as the ice plug I presume thats there melts.

But the problem doesnt stop there. There is another area of built up pressure, I think at the filter drier, located just after the receiver.

Filter is cold to the touch.

After I opened up the TXV , this second "rush" of gas came sweeping by. Am I supposed to assume that the restriction was at the filter. Its a monstor big Sporlan valve, 1/2" pipe size.

Or, is it something more sinister.................at the AC&R oil separator

I dont know.........

But Im ready to change oil..........

[Gary]

At low temps, oil can become very thick and act a lot like moisture. As the metering device warms, the oil thins out and passes through.

This is common in cap tube cascade systems, but not impossible in TXV systems. It is much more likely if someone has added oil along the way. In addition, some refrigerants are not very good at carrying the oil.

The tearing out of the hair is also a common symptom of oil problems.

Is there a moisture indicator in the sightglass?

[Abe]

Gary

The sight glass is very old with no moisture indicator and the glass looks a dirty brown shade.

The temperature around these parts is around -6 C at the moment, the condensing unit is located near an open field, we had gale force winds gusting last week, and I worked Thursday night and all day Friday outside with the wind smacking into me.

Hence, ( I want to tear my hair out)

System has a back up unit, albeit smaller capacity, and this unit failed as well. Fortunately I sorted that one out, problem with the heat exchanger , blocked up, walls collapsed presumably.

My engineer, is of course "on leave" I cant afford to pay him exhorbitant overtime this time of year, so yours truly was on call.

And, this "service contract, I took it on just before Christmas, at the time I was rubbing my hands with glee, but now Im not too sure, Customers had his monies worth, I saved an awful lot of stock, hope he appreciates it.

Hope this cold weather spell ends soon, I have to get back to sort the the whole thing out, enginneer is back tomorrow..........

Im thinking..............I have just the job for him!!!!!
I say with my "evil eye""" and a sly grin

That will teach him !!!! He Heeeeeee

[Gary]

Happy New Year, Aiyub!!

I always recommend moisture indicators, especially on low temp systems.

The dirty brown shade in the glass might be another indication of dirty brown oil getting past the separator.

Then there is the second surge through the drier. If it were ice plugged, why would it surge through without being warmed? If it is at a low point, it may provide a gathering point for oil after the TXV plugs. Then it could push the oil through when the TXV is unplugged.

A temporary "fix" might be to change to ester oil, as it tends to flow much better at low temps, and the dirty stuff needs to be changed anyway. Don't be too surprised if the oil level rises as the excess is swept back to the compressor. You should change it several times.

But the separator should be replaced ASAP.

Passing the job to your engineer sounds like a great idea, but be sure to let us know how it works out.

[Gary]

Happy New Year, Marc!!

These are all very good points, and I fully agree.

To expand on this a bit, as I understand it, the high discharge temp (caused by high inlet superheat), cooks the oil giving it a muddy brown appearance, which then transfers to the glass.

[Prof Sporlan]

To expand on this a bit, as I understand it, the high discharge temp (caused by high inlet superheat), cooks the oil giving it a muddy brown appearance, which then transfers to the glass.

This is the usual case. When a dirty sightglass is observed on a refrigeration unit, the first order of business should be to replace the oil, and not simply rely on filter-drier changes to clean it up. And then consider replacing the sightglass. You should be able to save some of your hair this way...

The POE reacts with the moisture to form a substance of bloody consistancy but waxy in appearance, this reaks havoc at the TEV and distributor.

POE oil in the presence of moisture will hydrolyze to form a carboxylic acid, an organic acid which can damage the system. As a result, it is a good idea to use a filter-drier with some acid capacity when using POE oil.

The waxy substances found in a refrigeration system using POE oil are more likely due to the fact that POE oil is an extremely effective solvent, far better than mineral or AB oil. Waxy substances present in the refrigeration tubing and compressor from manufacture will often not be bothered by mineral or AB oils, while POE oils will more likely to remove these substances. These waxes will flow in solution with the refrigerant and oil, and will precipitate out at the TEV port. Unfortunately, standard filter-driers are not effective in removing wax. Filter-driers which contain activated charcoal, however, (e.g., Sporlan "HH" filter-driers), are effective in removing wax.

Wax can also be effectively removed by disassembling the TEV and cleaning it.... though it may do little to save what remaining hair you have on your head...

[Abe]

Marc,

Thanks for the Trouble Shooting Data Collection sheet.
I have printed it and will fill it out and complete it "NEXT WEEK"

Why next week, you may ask?

Well, I was ready, prepared to carry out the operation this weekend.

But remember, I mentioned the freezer room has a standby system in place, which was repaired as well.

Well, customer is quite happy that room is "working" and holding temperature, so he wants me to "delay" the job for a while.

ie: he wants to delay parting with his cash by pushing the job away.......to another date

Dont come this week he says, theres snow on the ground, and its cold, Come next week

How thoughtful, how kind..........

But wait, if that standby system breaks down tomorrow.......you can stand on your head and whistle thru your.............XXXX
before you get me out there in the middle of the night!!!

[Abe]

Just so I organise myself for the job,

How do I read/get measurements for the following:

Saturated condensing temperature
Do I read this off my pressure guage hooked up at the receiver end?

Saturated evaporating tem
Again, I presume I read this off my gauges pressure/temp chart


COOLING MEDIUM SUPPLY TEMP

I presume thats evaporator fans, supply temp is the temp of air entering the evaporator, or is it leaving the coil?


I think I understand the rest
Thanks in advance

[Abe]

I stripped the unit this weekend. I found an oily "sludge" contaminating the condenser right up to the filter. The oil seperator has obviously not being doing its job. System has had a ****tail of refrigerants added to compound the problem. I found bottles of 502. 69. 49, you name it , littered near the unit.

I decided that changing oil to sort out "moisture" prob was not the answer. I wont get rid of the "oil lining" covering the liquid pipe right up from compressor to filter and beyond.

I am going to replace all pipes and recondition compressor with new oil.

[Abe]

Hello Marc,

Ive got the flu, banging headache, sneezes, runny nose, and just want to lie in bed all propped up with some fluffy pillows with the central heater on, and probably pretend to be very very ill so "nurse" the missus can run up the stairs and attend to my cries everynow and then and bring up steaming mugs of lemon and honey and lemsip!!

And whilst in bed I can think of this blasted job at the ice cream factory, methinks the oil seperator didnt fullfill its job, ie: retain the oil and return it to the compressor sump.

I found traces of this oily substance beyond the seperator, and I think this is what is blocking up the system, and moisture too.

So to make things squeaky clean again, be a good idea to change the liquid line, new filter , new sight glass, also found the solonoid valve leaking, so that goes as well, refill compressor sump with new ester oil, charge with Isceon 69 and keep my fingers crossed.

But will have to wait until I get/feel better. Winter is dragging on and Im dreaming of a holiday, somewhere warm, like Durban where all my relations have been holidaying over Xmas, Wild Coast more precise.

But not sure about Durbs, its not I believe the same, so will have to think of someplace else. Got my house keys last week, so got the move to the new place to think about too, theres boxes everywhere, and packing, and wife browsing the MFI catalogue for a new kitchen

Ok, Im losing it............I blame it on the Lemsip!!!

[Abe]

Sorry,

If I had been paying attention...........like I should have done, all the ANSWERS are there already in your earlier postings

I should have been more attentive.......so thanks once again for all the help I got on this one

Dankie

[Jim Rushforth]

Have you tried the triple evacuation method ? I have a leaflet on how it is done - would you like one ?

[Abe]

thanks

Abe

[Brian_UK]

Now, now Aiyub, control yourself

Everyone should know how to do a triple evacuation and with a double salko I believe it's worth 7/10

[Jim Rushforth]

Hi Again Abe,

Couldn't get the file through as a .doc so am sending it to you
as a j.peg

Cheers - Jim

[Abe]

Jim

Would you mind sending the *.doc file to my e mail address
Look it up on my details

Thanks

[Jim Rushforth]

Hi Abe

Cannot contact you by e-mail - there is no access to your mail
address.

Did you receive the two-page file sent in jpeg format and the
text notes ????

Cheers - Jim

[herefishy]

Is the problem resolved?


I was wondering - DEEP VACUUM. What micron level have you brought it down to, and I assume you have no rise on a shut in? that would eliminate moisture if your down to 150-300 mic's and it it holds, indicating no ongoing evaporation of moisture as long as your not evacuating in an extremely cold ambient.

The sysmptom regarding TEV observation sounds like moisture

[Gary]

Triple Evacuation Procedure

1. Evacuate the system (from both sides if possible) to 1000 microns.

2. Break the vacuum (from the discharge access if possible) with dry nitrogen to slightly above atmospheric pressure.

3. Evacuate the system (opening the low side access first) to 500 microns.

4. Break the vacuum (from the discharge access if possible) with system refrigerant to slightly above atmospheric pressure.

5. Evacuate the system (opening the low side access first) to 500 microns or less.

6. Charge the system.

[Gary]

Some may find my procedure a little unorthodox. Here is the reasoning behind it:

When a system is evacuated, approximately 10% of the old refrigerant is still in the system. Breaking the vacuum from the discharge port forces the old stuff through the system towards the suction line. If you then start the evacuation at the suction port, you will pull a higher percentage of old residual gas out.

Breaking the vacuum with dry nitrogen is a BIG time saver, because the compressor oil will not absorb the nitrogen. The second evacuation will be very fast.

[Abe]

The system was very contaminated, the pressure switches were set to cut the unit on pump down in a vacuum setting, 15 inches

The system had leaks, it had been sucking in air every time it went into pump down.

Oil was sludged, the oil seperator didnt work. System was 15 years old.

I took everything out and dumped the lot, including the evaporator

Have fitted a new system in. Everything running well at -25 C

Ok, I know, its like cheating, but as the medical profession puts it, delaying death wasnt the answer, the quality of life for that old system was not there, so I let it die, or more accurately I practiced Euthanasia on it!!!

Thats all folks, and thanks a lot, I learnt a lot on that job with all the input I received.

[herefishy]

I don't think that's cheating.... It's one thing to know how to fix it all and it's the same to recognize whether there is any value in doing it!

I would say the (customer) could not realize any better value than the service that you rendered. Was it a hard sell?

[frank]

I like the quote " delaying death wasn't the answer"

[pdproductions]

Have you tried a 'dryer' on the system? In case you dont know what this is, it is a piece of tubing that attatches to the bottom of the evaporator right at the capillary tube. This piece is specifically designed for removing moisture from the sealed system when the system is opened (letting moisture in)...The trick to this piece of equipment, is that it has to be replaced EVERY time the sealed system is opened. So, if you install one now, then have sealed system work later, you need to install a new one at that time.

[brookbank]

ive found that when engineers say a system is full of moisture, it is usually the oil waxing in the system.
Shell SD oil seems to be a lot better at low temperatures than Clavus 32 on R22 or when the discharge temperature is high
change the oil.also check the suction superheat as this will raise discharge temperatures to a point that will kill oil

the way i check a seperator is to disconnect the oil return and run it into a container, with the system running you should see a trickle of oil returning and no gas (honest)

also if you let the seperator cool down and start the system back up, you can feel a temperature drop where the oil level is as the top of the seperator heats up and the oil stays cool

[4petes]

I work for a very large commercial refrigeration contractor doing 90%supermarkets. just be done with it pull charge vacume unit change oil add gas and driers. had a store employee try to deice a low temp tub with a screwdriver hE punched A hole in coil sucked into vacume. major pain pulled 600 #refrigerant after trying to clean up system for over two weeks YOUR KILLING YOUR CUSTOMER WITH LABOR HE JUST WANTS IT TAKEN CARE OF. NEVER A COMPLAINT AFTER THIS WORK was done. what is head psi ? and does it equate to what the outlet of the condenser tube feels like. if it is cool but running high hp then you have non condensibles.

[soma pencil]

Hi I am soma , i am a new member.

i would like to say hello to all the member in this forums.