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06-20-2008, 09:55 AM #1
to blow or not to blow - that is the (burning) question
so now that the one circuit on this trane chiller is back up and running, I hacked apart the second burned out circuit. Man what a beautiful wreck (shawn mullins song for fans of ecelectic New Orleans/Austin music). The orange pink muck is still dripping out of the evaporator 3 hours after I cut out the old TEV and drier.
I put a tube on into a bucket and blew from 2000 to 1500 lbs. on my nitro tank and did get maybe two ounces, but the bottom of the pipe is still got a little meniscus(sp?) or arc of oil maybe a couple mm deep. If I want to blow continuously for a while to get whatever I can, I'm thinking I need to change over to an air compressor and then when I'm done I could flow some nitro through the system to displace air and then I'll be flowing nitro for brazing/soldering anyway, and then a triple evac.
Is it just plain a bad idea to introduce more than the atmospheric air I already have by cutting the thing apart since it has no isolation valves (of course it will have isolation valves when I get done with it), or would this be a reasonable way to flush a little bit more of the bad crap out before going over to reliance on my new suction bucket filter (with isolation valave and schrader taps for convenient monitoring and replacement of element).
Or is what I have done as 'sufficient' for getting the bulk of the junk out and you assume that a few mm coating on the bottom of evap pipes (don't really know about the condensor end, got maybe a few ounces gravity drip out of the high side and relatively little drip out of the liquid line side of the drier, not even an ounce) is the reason that you put the suction acid filter on in the first place. just get the damn thing together and let the filter do the work?
(I know if I had been really careful during compressor removal and if i could get specs for the original oil charge and assume that nothing changed during the last TEV replacement then I could theoretically dump out the compressor and assume that the extra pound I got in the refrigerant recovery tank over the normal r-22 charge is oil and then add all that up and subtract from original charge and I could actually estimate whether I have any 'quantity' left in the system but the compressor had no drain, so I had to yank this 90 or 100 lber out as is and I can't say I kept complete control of the oil charge during this maneuver so I'm flying bline, believeing that I got the vast majority but there is this ugly nuclear looking deposition that makes me nervous -- maybe I'm just nervous by disposition.)
06-20-2008, 10:01 AM #2Professional Member
- Join Date
- May 2007
I believe it was the forth day of refrigeration school we were told NEVER EVER EVER EVER use compressed air.
06-20-2008, 10:12 AM #3
never -ever ever ever drive a motorcar ever again
I admit, I've got something of the Mr. Toad character going on here and I'm pretty much convinced by your response and my intuition after typing that all out that what they taught in school was right, blast a little more nitro for fun and to reduce immediate profit but increase long run profit and get it going.
But when you get into a system that has no isolation, maybe you can keep it mostly from drawing in atmospheric moisture and contaminants by makeing sure you got atmostpheric nitrogen in there and then throwing plastic plugs in quickly after you cut it open and while preparing replacement piping, but I'm figuring that is the ideal that doesn't always occur. I figure you're going to get some atmosphere, i.e. air and attendant junk, in there so blowing with air followed immediately by blowing with nitrogen doesn't seem like the kind of pollution it might sound, but I'm not a tester of chaotic gas mixing or the possibility of pockets of moisture emerging if you don't watch the dewpoint during such an operation esp. that induced by the cooling of compressed air blowing.
Upon reflection, this seems to be the main problem. You need to run driers on your air compresor and cool the exhaust and get it to drip out in your tank rather than in your job. So with a small portable compressor, more headaches than its worth.
Answering my own questions again, proving not that I'm smart, but dense enough to ask in the first place. This is more like a psychology board than technicians, helps me get comfortable with what I know.
06-20-2008, 10:18 AM #4
that said what about a compatible solvent gas or liquid
So if air blowing is verboten, I've never seen any reference to a cleaning treatment used prior to reassembly rather than after. That is the thing that confuses me. I see aid treatments for use while the new compressor is already in service, but I would be most comfortable with some kind of recirc cleaner/machine similar to the recovery unit design to circulate some kind of gas or liquid that dissolves or removes the oil and acid and catches it in a filter/accumulator.
Tried and true seems to be get what you can out and then just plan on a number of quick filter changes. And to the extent that disciplined application of this regimen has long proven success I am not knocking it at all, but if you go on the threads about acid clean-up additives the disagreement about their utility indicates that in this area of clean-up thre is some disagreement about what constitutes proper approach and some concern that just throwing filters at it after the fact is less than perfect even if its all we've got at the moment.
sorry for the loggerheic discourse.
06-20-2008, 02:30 PM #5Regular Guest
- Join Date
- Dec 2003
Your local supply house should have RX11 flush kits. They are a little expensive but will help clean your system.
06-20-2008, 04:52 PM #6Member
- Join Date
- Dec 2005
- Rockhill South Carolina
From the looks of your post you may be too smart for this trade,to blow or not to blow thats what she said!
06-20-2008, 05:50 PM #7
Nothing a drum of R-11 won't cure.
Wait, did I say that, naw, that would be illeagle............I must be haveing a flashback to 1991..............ok, I'm back now, nevermind that statement..................hey, how come everything has trails all of a sudden??????
Seriously, they make chemicals to flush that crap out, I don't think I'd be using compressed air for anything related to a refrigeration circuit.
06-20-2008, 07:34 PM #8
right, i checked out the r[x]-11 [and man you can't afford a barrel of that crap] but the general protocol seems to be to put it in with the replacement compressor and then change all the filters I think, it was maybe a week ago I read the can.
If this is the stuff to do the job, by all means I'll put it to work. no penny wise and pound foolish here. what I can't figure out is why the protocol is to use your brand new compressor as the cleaning pump, why not a unit like the recovery machine that will circulate the rx11 along with nitro or ??? with some filters on the machine. Then once you've cleaned a bit, you braze in the compressor and off to the races.
I'm ready to take my medicine and will grab rx11 tomorrow on my way in and I have installed ball valves to isolate the filters so I can change them without complete charge removal. Or should I be throwing out the first load of r-22 I put in with that stuff?
PS - there is not such thing as too smart
[although there is such a thing as a too smartalec]
no such thing as too much fun
and no such thing as an EXTRA beer.
06-20-2008, 09:03 PM #9Regular Guest
- Join Date
- May 2007
add a suction dryer with a clean up core, liquid hh clean up cores, acid scavenger in oil sump and then plan to change the oil in a day or two. The rx11 flush works good as long as you get all of it out when you are done. good solevents make very thin oil. also before you start the new compressor, fix what killed the last one.
06-20-2008, 09:23 PM #10
what killed the last one?
got several candidates
age - 18 years
dirty condensor but I would have thought that would have shown up in cooling performance rather than compressor failure.
crankcase heater was factory wired to only run when the compressor was running. This seems kind of screwy to me. But this was orginally hardwired as the lead compressor so other than annual startup it might have been generally OK anyway. Also a help was that the install had the compressors at the sunny exposed end of the unit so they would have tended to be warmer generally. But I admit that I installed a 3-way switch in the control circuit 18 years ago so that we could switch lead compressor annually.
I keep forgetting to look at the wiring diagram but I am pretty sure that the originally designated lag circuit had the crankcase heater wired for constant on.
The circuit had been performing fine until failure so i don't believe there was any problem with the TEV which has been replaced once along with the dryer. There's no isolation so that would have involved recovery and recharge. I didn't do it, might have been on vacation. I don't even remember it happening and I have watched this unit throughout its life. I would have to check the fiscal records and maybe I could find a payment to one of the outside services to place the timing of this repair but I'm betting it would have beensummer of 2000 so I don't think I can really fault anything that was done.
The contactor didn't look great but it didn't look dead either. I'm replacing it anyway, along with a new TEV that is a virtual match to the OEM and the head replacements will then be the same for both circuits.
We weren't having any brownouts to speak of. But I haven't made a habit of amp testing the motors annually. I probably should to anticipate these events rather than deal with them in this worst case scenario.
open to other probably obvious thoughts I might have missed.
06-21-2008, 09:01 AM #11Regular Guest
- Join Date
- May 2007
had a severe burnout last year caused by a welded part winding start contactor, upon further investigation we found that stage controller was causing unit to cycle too often. however, the true cause of the failure was improper start up by untrained personel. They would just turn on the switch without verifying proper water flow, crankcase temp, condition of starters, etc. we found that they were running a chilled water pump and the stand by toghether and creating a flow loop that was wreaking havoc with the system.
we were not allowed to address the issues as we were only contracted to change the compreesor. when the second motor failed 2 weeks later due to flood back. we went over their heads and addressed the outstanding issues. 2 weeks ago we had a call for the same machine not cooling. We found that the crankshaft was broken. I asked her how they started the machine this season and she said flipped the switch. They are no longer our problem!!
they had us working on the B circuit and another conntractor servicing the A circuit.
06-23-2008, 10:00 AM #12
Our best results have been to remove the pressure switches, remove the cage to the expansion device and do a straight nitrogen [non-OSHA approved] blow. The hoses are 3000+ burst pressure so that is not a problem. The pressure switches are isolated so the High pressure blast does not recalibrate them. Put the system back together and do a couple of oil/dryer changes until the oil is non-acidic after a couple of days of operation.
06-23-2008, 11:20 AM #13
i chickened out
from the thousand lbs. plus nitrogen flush but I already had all valves and other junk removed so I probably would have gone for it if I saw your post first. It was only piping so maybe I should have just foregone the regulator and let at $20 b-tank lose on the thing. My main concern is any pockets of remaining rx-11 and that they might dilute the oil.
I think it worked pretty well at 150 lbs. opening and closing a ball valve temporarily affixed to the end of the open piping. (and with apologies to my original reaction to rx-11 suggestion. When I first looked in the clean-up aisle at the frig store I mistook rx-11 as an expensive version of one of the acid scavenging additives that you run in the new system, not as a flushing agent run while the system is open)
Got down to the pipes looking much better and when I was blowing 150 lbs. I never got completely rid of the fine pink orange spray blowing into the oil jug I had on the end of the line, but it got much more dilute and less and obvious cloud compared to when we started. So I ended up putting more or less a whole "B" can through this circuit after the rx-11 anyway, but just at a lower delivery pressure.
So now my last questions on burnout cleanup are, acid treatment or not? And is there such a thing as rx-11 scavenger to get any of the minor remnants of that solvent out of there.
I also heard from Copeland rep, Frank Russel, that HH filters are not acid clean-up specialties. This is a false assumption on my part. Rather they are for the burn remnants themselves and have activated charcoal for that (maybe the activated charcoal gets rx-11 too, i don't know) but in order to fit the charcoal in they take out acid scavenging alumina??, i.e. what-the-chemical, that sequesters acid. So I'm better to get a regular filter in there as soon as possible as it has better acid absorportion.
Once the clean-up is complete, he recommends a regular particle filter, pleated style, for the suction bucket and not leaving a dessicant filled element in the bucket as the resulting pressure drop can be harmful.