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I started this as a new thread so this procedure wouldn't get lost in lynn rodenmayer's post of 7/14/04. I think it is important to understand. On a Copeland refrigerant cooled compressor the following can be used to determine piston blow by.
The oil check valve is NOT spring loaded. It is either a free floating ball or flat disc operated by the direction of oil flow. Any higher pressure in the crankcase is bad news, the ½ pound would be correct, and yes a ½ pound would be difficult to see.
To check; put a gauge on the crankcase and another on the suction service valve. Let's say they both read 20psi. Start closing the SUCTION service valve. When the pressures begin to drop (pumping down), now close the suction slowing and watch both gauges. They should pull down together, all the way down, how ever far it will go.
Let's say at 5psi the crankcase doesn't drop any more and the suction pulls lower. That is the point (5psi) where the crankcase pressure is overcoming the internal VENT valve and the oil check valve will now close. The check valve closes because of the reverse flow of oil direction.
[Edited by basser on 08-09-2004 at 08:43 AM]
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In some Copeland models there is hole (always open) that provides a vent between the crankcase and motor. It is high on the firewall, and does not equalize oil level, only pressure.
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That hole is your crankcase vent. The oil check valve is located directly below it under the center bearing. The same procedure can be used to check these compressors also.
Call me 2813.
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No contradiction intended- just meant to add there may be a gas vent with no check valve. There must be a vent of some sort as the oil check may be under oil on both sides and not allow gas to vent.
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To Basser and ECT
OK for a blowby test we throttle the suction and watch for a difference in psi between suction valve and crankcase. How much is maximum psi differential recommended by Copeland indicating replacement?
I have also wondered how many gallons or what percentage of crankcase oil capacity actually goes out of the compressor and has to be returned through the system on say an average new 5 hp as I understand that a high percentage of oil to refrigerant raises the refrigerant boiling point also
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If the crankcase is any amount higher then the suction, that is bad news. (That is where the ½ psi comes from.)That indicates blowby around the piston and the result will be an oil safety control trip. This is why you want to zero out your gauges as close as you possibliy can and use two low side gauges because of the smaller scale.
As far as the circulation rate of the oil, it is approximately 1%. What ever amount of oil leaves the compressor must be returned. If the compressor pumps out more then is returning, that means you have excess oil out in the sytem somewhere. It will probably end up in the evaporator. Now your system may not achieve the desired temperature. If enough oil logs out in the system you starve the compressor and again the result should be an oil safety trip.
System oil capacity depends on the length of runs (piping).
After original start up be certain the compressor oil level is satisfactory. Semi-hermetics will have a sight glass.
Raising the boiling point. Theoretically your point is probably true, because the refrigerant would have to boil through the oil. I really doubt if you could notice the difference. Think of oil in an evap. The oil reduces heat transfer and that is one reason you will reduce performance.
Hope this helps.
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Hello Basser.A while ago I went on a call.Oil safety was tripping.Barely seeing through sight glass the oil was very low.By the way this was a 17 door frozen food case.I believe it was 7.5 HP copelamatic.408a.Hot gas defrost.I added about a gallon of c3 oil given to me by my boss.couldn`t change the level.Then I ended up opening the 4 balanced port expansion valves all the way ,because they were starving the evaporator.Eventough it improved the situation dramatically I couldn`t read the temp.at the outlets of evaporators it was still high.So I concluded the excess oil in the system was hindering the heat transfer in the evaporator.I didn`t change the TXVs yet ( I think my boss ordered them and it takes time to get them after I opposed to install regular TXVs)Costumor is ok with 0*F for now.I am still apprehensive even if I put new TXVs that I may have oil problem.with the info I could provide anything you could suggest?
thanks.
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You might want to start a new thread, altan.
This would be a good case to discuss.
Do you have all of the particulars, such as pressures, temps, etc?
I'll start off by saying that "barely seeing through the sightglass" is a bad situation that is easily remedied, by depressurizing the crankcase, removing the 3 bolts that hold the glass on, and wiping the inside of the sightglass with a rag dampened with Virginia #10 solvent, then reinstalling it. It would also behoove you at that time to remove and clean the oil sump strainer, and, if so equipped, the Sentronic sensor. A fresh charge of oil could then be added to 1/2 sightglass, and you start anew. Top it off with drier replacement, and you're on your way to Happytown.
One more thing, if you added an entire gallon of oil to a 7.5 HP Cope, you most certainly should've seen a significant change in oil level!
Now, you say opened the TXVs all the way up. Let me ask you this:
Did you pull and inspect/clean the TXV inlet strainers before doing this? This should be done before any TXV adjustment is ever made, on a case that is starving for refrigerant. Often, the system crap (That you saw staining the oil sightglass on that pump) collects in these 100 mesh strainers, and restrict the flow of refrigerant. Opening the superheat stem all the way sometimes fools you into thinking you've made it better, but you didn't...
Those TXVs need a solid column of liquid at their inlets to operate properly. Clogged strainers prevent a solid column of liquid from entering the valve inlet.
It would take a quantity of oil on a rather grand scale to oil log 38' of low temp evaps!
I'm talking many gallons. Also, oil logging with hot gas defrost cases is relatively rare.
I will say that I prefer a synthetic alkylate (Alkylbenzene) like Zerol 200TD with the HCFCs, but often we just have to deal with what we're handed...
[Edited by condenseddave on 09-18-2004 at 10:39 PM]
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Originally posted by condenseddave
You might want to start a new thread, altan.
This would be a good case to discuss.
Do you have all of the particulars, such as pressures, temps, etc?
[Edited by condenseddave on 09-18-2004 at 10:39 PM]
408a.head 265-270 psi,water outlet 83*F valve all the way open.,back 16-18 psi,box; two sections 0-5*F,one section 16-18*F,one section 25-30*F couldn`t take the stem cap off to open valve, was leaking too strong.
didn`t check the strainers because didn`t wanna warm the box more it was fully loaded.but on a balanced port txv thought because it responded to adjustment might not be the strainer?didn`t wanna mingle with sight glass was affraid could crack it.definately this job needs more than me but I am the only one to steer this ship in this water.
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ALWAYS check the strainers before you make an adjustment.
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99% of the time adjusting the TXV will only confuse the situation. It should be the absolute last resort. TXV’s are one of the most reliable devices in refrigeration. When they do start having problems, adjusting them won’t help.
A Diamond is just a piece of coal, that made good under pressure!
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Never walk away from a wide open TXV!
You have a problem many of us have lost alot of sleep over before and I hope your customer stays with you until it's fixed.
If you have a dirty sightglass you have dirty screens too it's showing you what's inside the system.
Valve salesmen told me when balanced port came out they had tighter clearances than standard valves and required a finer screen and I have had those screens rupture and fill the valve with crap and stop it from working.I do not sell balanced port valves for this reason. You will find none on my truck. I have had many plugged or ruptured screens after retrofitting to the new refrigerants. I would never open up a valve and walk away as it might blow the crap out at midnight and flood the compressor. Some cases even come with a C-083 ahead of the strainer because of this fine screen or they request added filters. Assuming this system was changed from 502 the 408a or the oil may have a higher detergent action and washed a truck load of crap lose into the screens. I have watched a 1/2 ton valve frost a 10 hp when coming out of defrost because someone left it open and walked away.Always check the txv screen and change the main driers before setting superheat
Do you have pressure limiting power elements? I'm guessing you do on a freezer or just low temp elements with a CPR
Sometimes a mop power element will starve the coil if the compressor can't pump the correct amount and if and when the valve comes out of mop range (if you have opened the valve wide open) it will immediately flood the comp so you put another compressor on and it will destroy another and another. Check the compressor capacity against Copeland charts. Read Basser's post and check for blowby. In the past I have taken out over three gallons of excess oil out of 5/7hp comps that other serivce men had addded trying to keep oil in the crankcase. You can't correct blowby by adding oil and if you put a new comp on you will need to remove the excess oil before you leave and I would change the TXV's too and check the superheat at case design temp only.
Well I should throw another what if in here. What if different refigerants have been mixed in the system? I have seen multiple compressor failures running 50% 502 and 22 after liquid lines got cross piped on a med/low temp rack they fixed the mistake but left the mixture in the system for financial reasons and that was when gas was cheap and the replacement comps were under warranty.
If they have mixed they will never admit it due to EPA laws.
It happens and maybe more than we think about. Some mechanics are tempted to top off to help the customer but how many times can you top off and maintain correct superheat?
If your customer stays with you through this hang on to him he's a good one.
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Subcooling Measurment would have helped to see if she even had the ability to provide TXV with a good column. A superheat measurment would tell you if your oil was logging in coil. Starving. How do you know whats going on with out a superheat measurment.
Never add oil till your reasonably sure that it left the building.
You just caused even more problems by cranking on those txvs and adding oil.
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Time for the Dutch Uncle talk.
Originally posted by altan
didn`t check the strainers because didn`t wanna warm the box more it was fully loaded.
LAME-OOOOOOOO. You had the time and access to open the stems. It would 've taken five extra minutes to check the screens! A degree or ten more ouldn't have hurt at all, especially if you would've fixed it right the first time, and left there with the cases at 10 below! You're cutting corners, and that's what's got those cases running warm now.
Originally posted by altan
but on a balanced port txv thought because it responded to adjustment might not be the strainer?
Absolutely 100% incorrect. It's just a TXV. Forget about the porting, it doesn't make any difference at all when the cases are down.
Originally posted by altan
didn`t wanna mingle with sight glass was affraid could crack it.
Trust me, son, you ain't as tough as that sightglass. And you still don't know what the oil level is. My guess is that it's way high. Like holy sh!t high. Like bust up a valve plate if any makes it back high. Again, not slowing down and checking basic, seemingly minor things is called cutting corners, and it's causing you, your boss. and that customer unnecessary grief.
Originally posted by altan
definately this job needs more than me but I am the only one to steer this ship in this water.
Bullshit. It easier than you think. Print this out, go back there on a slow morning, (plan to spend the better part of a day there) and take this with you and follow the list, in order. Just do everything I tell you.
Altan's list of things to do:
[list][*]Left to right, write down each case temp and the time.[*]Have the store personell empty out the lefthand corner of each case, so you can get to the valves.
{While they're working on that...}[*]Go to the condensing unit, and install your gauges on the compressor, including an extra lowside gauge on the oil pump. Write down the pressures and the time.[*]Valve off the HOT GAS DEFROST LINE before the solenoid valve, before you do anything else. Does the suction pressure change????????Write it down, yes or no. If yes, write down the new suction pressure. If yes, also, that's a problem, but we'll address that later.[*]Close off the compressor Suction Service Valve, and run the compressor down to atmospheric. Pull your LS gauge off the SSV to make sure it's actually at atmospheric.[*]Get something to catch the oil in, and put it beneath the drain hole of the compressor. (Discus it's the lower left front port.)[*]Remove the two bolts holding the port cover on, you might need to smack the oval cover with a wrench to get it loose. Catch the spring. The spring is critical. NEVER run one without that spring. Oil might come out at this point, but it might NOT. Don't be alarmed if it doesn't. If the oil sump screen doesn't come out on it's own, use two flat blade screwdrivers to pull it out. (Just put them both inside the screen, then pull the handles apart, and pull towards you with a slight twisting motion.[*]Drain all the oil out.[*]Clean the screen with brake cleaner, wipe off the spring, scrape the gasket off.[*]Using a new gasket, reinstall the screen, spring, and cover.[*]Pull the sightglass off the side (Or front, if it's on the front.) by removing the three 1/4-20 bolts. Don't lose them. You might need to smack the glass with a wrench to get IT loose, just like the oval oil drain cover. REMEMBER, that glass is sturdier than you are. Just try not to drop it six feet onto concrete. Save the gasket. You'll need that, too. Clean the inside of the glass with brake cleaner and paper towels, until you can see clearly through it. (No "ghost line" should be left on it.) [*]Reinstall the sightglass, using the old gasket and bolts. This doesn't require superhuman strength, BTW. Just tighten the bolts evenly.[*]If the oil fail control is a 'SENTRONIC', remove the sensor from the side of the oil pump.[*]Spray down the part of the sensor that goes inside the compressor with brake cleaner, make sure that the little O-ring is in place and not damaged, then reinstall the sensor.
Remember, take your time, and work thoroughly, not quickly.
[*]Put your gauge back on the SSV, and put your vacuum pump on the low side of the compressor, and get your air out.[*]After your vacuum is done, pump in fresh oil (Whatever poisin you choose, 408a can use any refrigerant oil...) to 1/2 sightglass. [*]Open up your SSV and start the compressor. Let it stabilize. Leave the Hot gas isolation valve closed for now.[*]Check the comressor against it's published curve. (You'll need the compressor model number, and your Copeland wholesaler can get it for you. If you don't have a Copeland wholesaler nearby, get me the model number, and I'll scan the curve and post it for you.)[*]Check the efficiency like Basser described, even if the the compressor is at it's curve.[*]Go wash your hands, dirtbag.
[*]Let it pull the cases down a little, only because it seems to worry you so much. 
[*]Take a breather. Admire your clean sightglass and nice net oil pressure.
[*]Now, pump the system down into the receiver.[*]Replace the liquid line filter-drier before going any further. If there is a suction line filter, either remove it or replace it now.[*]Go out to the cases, start left to right, remove each one of the TXV inlet strainers, and spray them out with brake cleaner. They should be 100% free of debris when they go back in. (A 'little' dirt is too much.)[*]Put the screens back in and tighten them.[*]Pull the superheat adjustment caps, turn the valves back in, (all the way.) counting the number of full turns that it takes to get back to 100% closed. [*]Now turn the stems out, exactly one half the number of turns it took to close them up in the last step. [*]Put the caps back on the valves.[*]Use a flashilight and a mirror, and look at the liquid lines in the case, as someone else mentioned, sometimes you'll find small filter-driers in each case. If they're there, remove them, and braze in the appropriate size copper tube in their place. (Remember, this lineup is going to work when you leave. Don't skip this step. Don't be afraid to get them to pull more product, either, if necessary to get to the filter-driers and anything else, like bad fan motors.)[*]Make sure all of the TXV bulbs are tight.[*]Go back to the compressor room, and evacute your system.[*]Start it back up.[*]Make sure that the liquid line sightglass is full, within a minute or two after startup.[*]Strap a thermometer probe on the suction line next to the suction service valve.[*]Record your suction, discharge, net oil, and liquid line pressures, and case temps and the time, shortly after startup.[*]Once the case fans start going again, and the temp is dropping, check the superheat at the SSV. Write it down, along with the time, and the other pressures, and anything else you think is important, and want to remember.[*]Keep an eye on the compressor oil level, you don't want to go past 3/4 sightglass. [*]Once the case discharge air temps drop off a bit, you can check the individual evaporator superheats. Set them between 8 and 4 degrees for now.
[list]
Now, there is more, but I think this will get you down to temp, and will prevent further grief.
Also, print out the next post I make, I'll tell you what to take with you when you go do this, to make sure you're prepared to do this.
DO NOT let this list of things to do intimidate you. It's easy, I do it all the time. You just need to deal with it, that's all.
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When you go to this store, take the following items:
- Fresh refrigerant oil. (Get at least two gallons, just in case.)
- New filter-driers, or cores, for the condensing unit.
- 3 or 4 cans of CRC brake cleaner.
- Something to drain oil into, I use el-cheapo oil plastic oil pans from the Auto Zone.
- A five gallon gas can with a cap, to get the old oil back to the shop.
- At least two copper couplings of the size of the liquid lines, and a couple feet of copper to remove any in-case filter-driers.
- Multi-meter and amp clamp.
- Spare small, oval service valve gaskets. The kind you use on K body service valves. (For the oil drain port cover.)
- Compressor curve sheet for that compressor.
- Spare set of gauges.
- Accurate digital thermometer, and some foam tape to check superheat.
- Spare vacuum pump oil.
- Your normal service hand tools.
- A PT chart for 408A.
- The printed out copy of this entire thread, and printed out copies of the following links.
http://www.sporlan.com/10-143.pdf
http://www.sporlan.com/10-11.pdf
http://www.sporlan.com/10-135.pdf
Now, if that Hot gas solenoid in the last post (Remember the Hot gas solenoid?? Did I ever tell you to open it's isolation valve? ) was causing the suction pressure to rise, then it must be serviced. Hopefully it's a Sporlan valve, as they're easy to service.
I'll help you with that, if need be, once you tell me what model number it is, whether it's an actual three way valve, or a combination of solenoids opening and closing to get hot gas.
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Re: When you go to this store, take the following items:
Originally posted by condenseddave
- Fresh refrigerant oil. (Get at least two gallons, just in case.)
- New filter-driers, or cores, for the condensing unit.
- 3 or 4 cans of CRC brake cleaner.
- Something to drain oil into, I use el-cheapo oil plastic oil pans from the Auto Zone.
- A five gallon gas can with a cap, to get the old oil back to the shop.
- At least two copper couplings of the size of the liquid lines, and a couple feet of copper to remove any in-case filter-driers.
- Multi-meter and amp clamp.
- Spare small, oval service valve gaskets. The kind you use on K body service valves. (For the oil drain port cover.)
- Compressor curve sheet for that compressor.
- Spare set of gauges.
- Accurate digital thermometer, and some foam tape to check superheat.
- Spare vacuum pump oil.
- Your normal service hand tools.
- A PT chart for 408A.
- The printed out copy of this entire thread, and printed out copies of the following links.
http://www.sporlan.com/10-143.pdf
http://www.sporlan.com/10-11.pdf
http://www.sporlan.com/10-135.pdf
Now, if that Hot gas solenoid in the last post (Remember the Hot gas solenoid?? Did I ever tell you to open it's isolation valve? ) was causing the suction pressure to rise, then it must be serviced. Hopefully it's a Sporlan valve, as they're easy to service.
I'll help you with that, if need be, once you tell me what model number it is, whether it's an actual three way valve, or a combination of solenoids opening and closing to get hot gas.
MASTER,I will finally go buy the printer I `ve been neglecting.As far as those pdf files;I hate them.in the past I downloaded whatever I had to, still can not open one of them.
also if all the oil I put before does not come out what then.I couldn`t open one of the valves` cap it was leaking too strong so I have to change a valve anyway.And I think my boss would not bother with cleaning the strainers and the sight glass he will have me replace them all.hot gas valve I will definately make sure wheather its leaking or not.its been two weeks we didn`t get a call from this one.this costumer worships me.he thinks I know what I am doing!
any comment about the head pressure being 265-270 psi?water outlet 83*F.I don`t believe there`s overcharge..and if I replace the TXVs what if I don`t use balanced port?would the 270psi head pressure give trouble?One more detail I forgot to mention;3 of the TXVs are 1.5 ton one of them turned out to be 2.5 ton...
thanks for your time and info.
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The pdfs are easy.
Right click on them, then choose "Save target as", and put it in your "my documents" folder, or someplace else that you can find them. They open easier there than over the 'net.
Make sure you have adobe aacrobat reader version 6.
Sporlan used to have "winzip" files. Maybe those were the ones you were having trouble with???
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The high head isn't ultra high. That's around 117 degrees condensing, which is higher than I like, but with a water cooled condenser, and the valve full open, then you get what you get until you feel like tearing into cleaning water cooled condensers...
Cleaning the screens is MUCH easier than changing the valves out. If you pump these down, then that leaking one won't be a problem.
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Altan, sorry for not getting back sooner but I've been out of touch for a few weeks (vacation and fishing). You have recieved allot of excellant advise here follow it and you will be fine.
One question I still have is the oil you added to the compressor, where and how did you put it in? "IF" you added it through the suction it may never reach the crankcase if the crankcase is indeed pressurized. Clean the glass and watch the level in it when you shut the compressor off. If you added the oil directly into the crankcase then you should have raised the oil level. Like stated above, a gallon of oil is allot of oil.
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Originally posted by basser
Altan, sorry for not getting back sooner but I've been out of touch for a few weeks (vacation and fishing). You have recieved allot of excellant advise here follow it and you will be fine.
One question I still have is the oil you added to the compressor, where and how did you put it in? "IF" you added it through the suction it may never reach the crankcase if the crankcase is indeed pressurized. Clean the glass and watch the level in it when you shut the compressor off. If you added the oil directly into the crankcase then you should have raised the oil level. Like stated above, a gallon of oil is allot of oil.
yes indeed I added it through the suction and I thought I made a mistake but still couldn`t figure out how come it didn`t end up in the crankcase.
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