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Thread: a wet wet chiller
07-15-2004, 01:03 AM #1
hey commercial people.
i'm a young tech who mostly works on residential units, but today i started working on a 15 ton chiller. the evap froze and now there is water in the system. i have a new txv, 2 new solenoids, new sight glass, and an add-on suction line filter drier to install. i have high water cores that i will change in the first couple days as well as new filters for the liquid line filter drier.
i got about 2 gallons of water out of the old girl, but i don't think any made it up into the compressors (which set at the highest point of the chiller setup).
should i be changing out the oil? what are my chances of really getting this thing up and working again? i wish they would have thrown the damn thing out b/c this is one big job staring me in the face. i guess i change everything out and let the vac pump run for a week. i think every day i'll come back and pressurize it up with nitrogen and then start evacing again.
let me know what you think, and if you have any tid bits of info for me.
07-15-2004, 03:25 AM #2Professional Member
- Join Date
- Aug 2000
Your repair costs on a chiller that small will be more than the chiller is worth. Should have junked it IMO. A good evacuation, purging it wirh nitrogen, multiple oil and drier changes are about all you can do besides prey.
07-15-2004, 05:43 AM #3Member
- Join Date
- Mar 2003
i didn't see whre the chiller barrell or condenser barrell will be replaced. if you have water in the system then it came from one of these sources. why are you changing the solenoids and txv's are they bad. why the suction drier.
you need to install a new cooler or condenser which ever is leaking, install a changable shell and core drier in the liquid line with hi moisture driers, setup a foreline machine hookup vaccum pumps to it and pull vaccumm to 500 microns. also open up system at lowest point and any place that could trap water, drain as much as possible then purge with nitrogen then evacuate.
07-15-2004, 07:46 AM #4
i agree with absrbrtk, the chiller should have been replaced. the customer will have more money in the than a new chiller. keep evacuating til you can get it to at least 100 microns. do not run it if you cant get the vaucuum down. how did you discover water in system without any in compressor oil?
07-15-2004, 08:26 AM #5Professional Member
- Join Date
- Jun 2003
Before you start, your boss should be telling the customer that by the time all of the parts are purchased and the labor is tallied you will be very close to the price of a new package.
If you still have to fix it a few tips are:
Drill holes on all of the low points in the piping to drain standing water.
Isolate the compressors, drain the oil and evacuate them seperately.
Make or buy a cold trap to go between the system and your vacuum pump. It holds dry ice and condenses the water vapor before it hits your vacuum pump oil. Welch used to sell one, they still may, well worth getting in a clean up.
Before you start the vacuum pump(s) pressurize the system to about 20 PSIG with nitrogen for a minute and blow it off. At $5.00 for a large nitrgen cylinder it's worth doing about 4-6 cylinders.
You will need to babysit the vacuum pump for a while since the oil gets saturated very quickly early in the process.
I'm personally comfortable starting the system at 400 microns. Mineral oil starts to boil at about 250 microns.
If you do a good job you should be good with two compressor oil and drier changes. Use the Sporlan RCW/Gold cores.
After the system has run for a day or so, do an acid test to make sure there wasn't some standing water under a layer of oil.
Find out why the chiller barrel failed and fix it so it doesn't happen again!
Good luck, Roger
If you don't have the time to do it right the first time, when will you have the time to do it over?
07-15-2004, 07:41 PM #6
thanks for the replies. it's actually a 30 ton chiller that is split into 2 sections (each having 2 - 7.5 ton scroll compressors). the evap froze and cracked and that's why i have water in the system.
i'm replacing the solenoids and txv because they are at the lowest point and had standing water in them. the compressors on the other hand are at the high point and there was no standing water in them.
since the compressors are scrolls, it's gonna be a bugger getting the oil of of them and such.
i tallied the materials and it's gonna be about $3000 and the labor i figured at about 20 hours or so. this unit is only about 2 years old.
the deal is that there has been water in the system now for over 2 months. they only needed half of the 30 tons since it's not hot out, but now they could use to have the other 15 tons. i wish they had called me in sooner.
and why am i on this job? we are in a remote section of the country and i'm all you get unless you want to pay a company to come in from 2 hours away to wrench on it. but if i F it up, it could have been worth it for them. but i'm confident i'll get it done right. and i'm the boss, so i can't blame this job on anyone else
thanks for your replies,
07-15-2004, 07:58 PM #7
have you replaced the evap barrell? if you had water in it for 2 months and even if it didnt go to the compressor anything steel will be rust. the compressors will not last. 20 hours will not be enough to dehydrate the system and for the follow up visits to change driers
07-15-2004, 09:04 PM #8
Scrap the whole chiller, A 30 ton chiller will only be 20,000 or so and once you touch this chiller you will own it.You will be fighting rust and moisture related problems for the next 2-3 years.Also I wouldn't be so sure water didn't get to the compressors, oil change is a must(no brainer) but how can you be sure it didn't cycle even briefly when it got low on charge.Also if the water pressure becomes higher than the static pressure on the gas side it will move water into the refrigerant side no matter if the compressor is higher or not.I have been involved in jobs like that before and have learned that you won't be doing the owner any favours by doing it cheaply.You have him basically on the ropes so do what is right, new unit.
07-15-2004, 09:22 PM #9
I had a rack with water in it we had the damn thing on a large vac pupm with 2 belt drive pumps on it for 2 weeks before we got 400 microns, good luck!
Absolutely change oil and drill holes in ALL low spots and blow out with nitrogen.
07-15-2004, 09:24 PM #10
It sounds like you're in an area where you're the man and perhaps your customer is tight on money also however...all the advice you're getting is dead on. You will own this chiller. Standing water, scroll compressors which will make it difficult to change the oil, and you haven't mentioned what was done to the barrel. Was the evaporator repaired or replaced? Also, what kind of maintenance was done to this for this to be able to happen in the first place? I'm guilty of it all the time, feeling sorry for the customer and trying in any way to help them out, but they are counting on you as the professional to give them sound advice, even if it hurts. It sucks to replace a two year old chiller but that is what should be done. Have they even called their insurance agent and asked whether they may have coverage for such a thing?
07-15-2004, 09:31 PM #11Regular Guest
- Join Date
- Nov 2001
Two months with water inside. I agree there will be rust inside. I hope it turns out ok for you. I would expect a compressor failure in the VERY near future though. Even though the liquid water may have remained at a low point in the system, moisture VAPOR went everywhere in the system.
I've had a few experiences with evap cooled condensers getting leaks, and allowing a LOT of water in a system, from the roof above, down to the compressor and drier below, and see the water pour out on the floor when loosening the flare nuts on the drier. This is with supermarket work. I bought the large nitrogen cylinder, blew the system out with nitrogen every morning and afternoon and ran a vacuum pump 24 hours a day for a full 7 days until I got a good micron reading. I changed vac pump oil every morning and every afternoon.
Once the micron reading is good, don't just look at the micron reading and say, OK, it's good. Close the valves and shut down the pump, and make certain the micron reading stays low enough to be acceptable for at least an hour. Some job specs require the micron level hold for 1 hour, some for 5 hours, some for 24 hours. The smaller the system, the less crucial this is.
The acceptable level of microns is subject to opinion also. Bottom line: you want the micron level to be low enough to indicate no moisture. As you know, temperature and boiling points and pressures are related. From my experience, I've seen my vacuum pump pull down to a certain level and just stay in that range for several hours, such as 700 microns or another day maybe 850 microns. This tells me, that's the boiling point of the water at those conditions. Once it breaks below that level of 700 or 850, or whatever, the micron reading drops very quickly, indicating the moisture is removed. Except of course, the water trapped under the oil...after all, oil is lighter than water, and will sit on top of the water.
That being said. I have always been successful in my attempts to get the system operational again...but I've never experienced water remaining in a system for 2 months.
Can you change oil in those scroll compressors? I sure hope so. I'd drain the oil prior to evacuation, and add oil when finished evacuating.
From what we hear about polyolester oil, I suppose you really don't even need a vacuum pump. Just put some POE oil in, and it'll suck up all the moisture, then drain the oil and replace with the proper oil. Just a little dry humor in this last paragraph. I hope no newbies take me seriously on that point.
07-15-2004, 11:03 PM #12Regular Guest
- Join Date
- Aug 2003
Just like everyone else has said, replace the chiller. You estimated 20 hours... your way off. Also, you need to estimate 2 compressor replacements. You still havent told us if the chiller barrel has been replaced.
Just out of curiosity, how did the chiller barrel fail in the first place?
07-16-2004, 12:20 AM #13
sorry for not getting back to the forum more quickly.
the evap is a plate type evap that froze b/c the maintenance guy turned the LP safety and freeze stat way down to acheive a colder set point. his fault of course.
so i'm replacing the whole plate evap.
i guessed 20 hours thinking it will take me about 8 to change everything out, and then visits all week long to change the oil in the vac pump and blow through with nitrogen etc. (the manufacturing plant is 2 blocks from my house)
these compressors have 1/4 flare fittings towards the bottom of the compressor. i'm assuming that is for taking out oil and then pumping oil back in.
so i'm going to go ahead and change the oil in the compressor(maybe more than once?).
i didn't bid this job, and all i've done so far is rip apart everything and drain the water and start brazing the valves and solenoids back together.
i guess when i drain the oil i'll find out if there is water in the compressor and what shape the compressors are in.
again, thanks for your input, it is extremely helpfull