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chillyblue
18-01-2009, 11:23 AM
Hi guys

I seem to be finding lots of problems with cappillaries blocking, systems mainly operating with R404a (new type refrigerants with poly oil).
i have several questions

1 how do you know what is blocking the cappillary, could it be moisture or oil or other contaminenets, what clues should i look for. If it is water then i know it's a case of vaumming and drier/ gas changes, but what would you do if it's oil and how would you know if it's oil.

2 how do you know where the blockage is ??

3 what process do you all suggest for resolving the problem?

4 is everybody using a nitrogen bleed when brazing ??

I have had systems that have blocked, i have changed the cappillary (supplied by manufacutrer) drier, vacumed system and recharged with new refrigerant. The system virtually blocked again within 2 hours, what would you do??.

I've had systems block because the condenser fan has failed. Why??

You only seem to have to look at a cappillary the wrong way and it blocks, LOL.

I can't remeber having all these problems with old mineral oil systems.

CB

Tesla
19-01-2009, 06:47 AM
Hi Chillyblu
I do remember having these probs on old r22 systems. The capp. blocked up with a coke/charcol type substance from running too hot usually by a blocked condenser which burns out the compressor. As a standard we would replace comp., capp., and bigger drier. Not sure about the new refrigerants - it's been a decade since working on refrigeration units. Best method zi know to locate blockage is a temp drop just after blockage. When the oil runs too hot it breaks down into other chemicals including water and acids. And most didn't use nitro but I did.

nicolacozma
19-01-2009, 10:43 PM
Hi guys

I seem to be finding lots of problems with cappillaries blocking, systems mainly operating with R404a (new type refrigerants with poly oil).
i have several questions

1 how do you know what is blocking the cappillary, could it be moisture or oil or other contaminenets, what clues should i look for. If it is water then i know it's a case of vaumming and drier/ gas changes, but what would you do if it's oil and how would you know if it's oil.

2 how do you know where the blockage is ??

3 what process do you all suggest for resolving the problem?

4 is everybody using a nitrogen bleed when brazing ??

I have had systems that have blocked, i have changed the cappillary (supplied by manufacutrer) drier, vacumed system and recharged with new refrigerant. The system virtually blocked again within 2 hours, what would you do??.

I've had systems block because the condenser fan has failed. Why??

You only seem to have to look at a cappillary the wrong way and it blocks, LOL.

I can't remeber having all these problems with old mineral oil systems.

CB

1. In case of cappillary tube blockage the system will go slightly or deeply into vacuum. If you heat up the cappillary line and the vacuum level start to decrease, means that the blockage is generated by moisture. To be sure in this case is better to make a hole in the bottom of the accumulator in order to try to evacuate the water. Close the hole and then make vacumming. At the same time you can heat up the crankcase of the compressor with an electrical resistance.

2. Temperature difference method (more than 2~3K)over devices could be a sign that there is blackage.
If the above method could not be used then try to measure the pressure step by step.

3. Moisture problem: vacumming method.
Dirty oil: compressor replacement and flushing all the refrigerant system with cleaning product.

4. You have to use nitrogen during bazing, otherwise you can have all the problem listed above.

Even if you change the cappillary tube, the dirty oil from compressor cranckase could block again next time the new cappillary tube.

good look
Nicola

chillyblue
20-01-2009, 09:40 PM
Thanks Nicola

"Even if you change the cappillary tube, the dirty oil from compressor cranckase could block again next time the new cappillary tube".

Do you know of any way of avoiding this or at least limiting the chance of it happening??

CB

nike123
20-01-2009, 09:45 PM
Thanks Nicola

"Even if you change the cappillary tube, the dirty oil from compressor cranckase could block again next time the new cappillary tube".

Do you know of any way of avoiding this or at least limiting the chance of it happening??

CB

Over sized liquid line filter drier.

nicolacozma
20-01-2009, 10:30 PM
As I specify at point 3 in order to be sure, you have to change the compressor and to clean all the refrigerant circuit with specific cleaning product and to replace the liquid line filter. Of course this is an expensive solution.

As nike123 said you can try his solution, it`s cheaper.

chillyblue
20-01-2009, 10:52 PM
Thanks, i'll bear that in mind!!

CB

dooda
21-01-2009, 12:47 AM
When a condenser fan motor fails you have very high discharge pressures, this can cause the drier to break down into a very fine powder which can pass through the gauze filter blocking the capillary. Always use good quality driers. If a system has had a leak sealer added to the system this can cause blocked capillary's.

Tesla
21-01-2009, 07:21 AM
Hi Nicola
It's Tesla (ironic), to clean the systen thoroughly we used to use r11(big no no now days) but there are other refrigerants/solvents available to liquid flush a system to clean it - flush both ways, leaktest with nitro, then deep vacume ensures no callbacks and a reliable service job
Thanks

chillyblue
21-01-2009, 09:57 PM
Just been searching previous posts and found this, just wondered if anyone else has tried it and what the general thoughts of doing this are??

I don't know if WD40 contains anything that may cause problems in a refrigeration circuit??


Don't you just love 134a, It's the best thing since sliced bread !!

As stated above waxes capilery tubes wonderfully.
A tip for what it's worth, braze a piece of 1/4 copper to the end of the capilery about 6" long with a 1/4 fitting on the end, spray some wd40 into the copper pipe, connect line to nitrogen bottle and blast away, don't forget to remove sution line from compressor, not that I think the small amount of wd40 will do any harm to compressor. Nomally clears capilery of most junk

Good luck

Mr Cool

nike123
21-01-2009, 10:07 PM
I don't know if WD40 contains anything that may cause problems in a refrigeration circuit??


Where did you found that WD 40 could be used to deal with refrigerant system?

chillyblue
21-01-2009, 10:17 PM
Hi Nike

In the quote posted by mr Cool!!

nike123
22-01-2009, 07:14 AM
Hi Nike

In the quote posted by mr Cool!!

Sorry, I must be blinded by first sentence.;)

First law of refrigeration: inside system is allowed only refrigerant and oil. Everything else is contaminant.

jeff /lpool
22-01-2009, 10:39 AM
We came across this problem a few years ago....the size of the cappilary and drier is key to solving this problem...on larger commercial systems you need to increase the size on the drier (053 minimum- good quality!)
If your capp. is too small, it can frost back to the drier and have the same effect as moisture and cause a blockage in the system.
I personally would swerve it whenever possible on commercial...when the ambient increases this seems to be when the problems start. For the extra few quid, i would always go for an expansion valve / sight glass & drier.

chillyblue
22-01-2009, 06:44 PM
Whats if any is the disadvantage of a larger bore cappillary??

CB

munya72002
23-01-2009, 08:18 PM
maybe the system had a compressor burn out so u need to remove the compressor, drain the oil, clean it with nitrogen, put new compressor oil. you also need to clean the sytem with nitrogen put a new capillary tube and a bigger filter drier (3/8 inch), then you evacuate the system for about an hour. finally you recharge it and the restart

chillyblue
24-01-2009, 09:05 AM
I've never drained and recharged a hermetically sealed compressor.
Do yopu just pour the oil out of the suction port??, measuring the quantity and refill the same way??

CB

Harrison
01-02-2009, 11:18 AM
I've never drained and recharged a hermetically sealed compressor.
Do yopu just pour the oil out of the suction port??, measuring the quantity and refill the same way??

CB
yeah thats right, but you may want to check the oil volume with specs just to be sure.

Deniver45
01-01-2011, 10:18 AM
I see this is an old question and don't know how I found it; but figured I would reply anyway.

These new refrigerants use the poly-ester oil or POE oil which is actually acid based.

When the customer does not keep the condenser clean = it over heats. It causes the oil in the compressor to seperate. IF you arrive at one medium temp unit and the condenser is clogged, the unit not cooling, BUT heat is still present at the condenser, then you have a good chance of acid cleaning the condenser, checking your head and suction and you might get her down cold again.

BUT if there is no heat present at the condenser, then there is a good chance of blockage. Only your head pressure will confirm that.

On these cap tube systems with the POE oil, the oil seperates into an acid / waxy substance and that's why IF U ONLY replace the cap tube; then within 20 minutes it could be blocked again. I have seen this acid eat a hole right through the cap tube from the inside out!

One SHOULD always use 2 to 3 lbs pressure of dry nitrogen to braze............. pull the shraders of course so the nitrogen displaces the O2 and you wont get the carbon build up. The last one I did, I did in such a way that the nitrogen flowed right through the access ports. That way I had 0 PSI at my solder or braze joints. It also helps to cool after the joints are brazed in.

1. You MUST change the oil in the compressor, wether it be with an oil pump or a compressor removal ( empty the oil upside down), remember 5% will remain in the compressor and that = a larger dryer to catch the remaining "wax" in there. Remember to add additional refrigerant w a larger dryer.

2. A can of flush before the new dryer is put in place or in the line.

3. The cap tube must be replaced too after you flush the system. Depending on the configuration, you may have to leave the old cap in there untill flushing is complete.

4. IF it has a small accumulator in the box, you SHOULD drill a small hole through the bottom of it while you flush, then seal it back up ( braze) after the flush as some of the "waxy substance" can get trapped in the accumulator and all will be for nothing.

5. On some of these like the prep tables like the ones made by "TROOH" ( I wont name any manufacturer's here !), they are NOTORIOUS for this problem with 134a in there.

6. Many times the customer does not want to pay $1000 for a repair like this. SO YOU may want to cut a few corners to save HIM money. BUT it COULD cost you your reputation............ and you might have to do it over the right way anyway.

7. In the end a 500 vacuum is a MUST to remove the last non-condensables, like moisture, flush.

8. ALSO, you COULD remove the cap tube altogether, FLUSH as good as possible, and run a TXV in the place of the cap tube., but many times, there is no room for a larger copper line then the cap tube especially where it goes into the evaporator as they carm everything in the corner there on some of these prep tables and reach in's,

Hope this helps!

acb
02-01-2011, 12:36 PM
hi chilly, ive found this does only happen with 404a 134a cappilliaries, if you suspect a cappilliarie is blocked, remove refrigerant, with pliers snap the cap line off the drier and look at the end of it, if its blocked you can see a 'skin' round the inside of the cap line, if so i suggest, carefully removing the cap line in 1" sections and keep checking the end, sometimes only the start of the cap line is blocked, if this proves fruitless and you dont have the right cap line to hand to replace, ive found that you can just use one of those 1/4 cap connection lines you get with the flare nuts on just remove the flare nuts and weyhay.

DrFreezeMD
02-01-2011, 07:02 PM
Read some good advice here. If the cappillary tube has restricted, you can bet it was because of a compressor that was running hot because of possible blocked air flow at condenser coil. The Oil doesn't necessarily have to turn black for this to happen. A slight break down in the oil can clog driers and cap tubes. Especially the cheap copper spun driers that are so prevalent on new units. But if the drier has done its job hopefully the Cap tube will not be restricted. The advice of cutting off an inch at a time from the cap tube was good advice and sometimes this works. I personally use a small oil pump to pump the oil out of a hermetically sealed compressor. It takes a little doing but most of the time I am successful. Make sure you know how much oil the compressor uses and judge from there. I usually finish the job with a good oversize drier. Oh yes do not forget to blow system out with nitrogen or use a cleaning agent from Mainstream Engineering.:cool: