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View Full Version : Copeland Oil Migration/Pressure Troubles



daddyfixit
17-04-2008, 01:57 PM
Split 2 stage AC mix-n-match system.
York M# K2ES12A25A (10 ton, 2 5 ton ckts.) Air handler.
Trenton M# T050M8-HT4A-BA ref. condenser on stg 1.
Trenton M#TEA051H*-HT4A-BA ref. condenser on stg 2.

Both have been over charged with oil. Pulled abt 1 gallon out of stg 1 and it is still filling up. Superheat is quite low and oil pressure before and after the oil pump change was about 12-15 psi. I even checked the mesh screen in the oil sump - clean.

There is a 17 foot rise and about a 25 foot run to the line-sets. 1 1/8" suction and 1/2" liquid lines. 1 ft drop then a 9 ft run, then Oil trap at the floor level, then at 14 ft a 15 foot horizontal run, another oil trap for a 3 foot rise throught the roof, an inverted trap on the roof, then 7 feet to the unit.

I've increased the deadband on the T-stat to 5deg to allow the unit to run longer.

:mad:Aaaarrrrggggg..... What am I missing?

powell
17-04-2008, 04:21 PM
Hello daddyfixit,

You state that the compressors have been overcharged with oil and that you are removing oil as it fills the crank. It seems you're solving the problem.

Are you having other problems? Trips on the lube oil control maybe. 12 - 15 psi net oil pressure is lower than nornal but usually okay.

You also stated these were two 5 ton units. Thats pretty small units for a Copeland semi-hermetic compressor, unless they're older units.

Regards...........Powell

daddyfixit
17-04-2008, 06:28 PM
Powell...Hi and thanks for your input.

Yes, I am fixing the problem, however, the unit still tripps out on low oil pressure. Copeland tech site says it should be 20-60 PSI. Roof access for this customer requires 2-man access. Quite costly to keep resetting the OPC. Besides, there is still a problem, otherwise it wouldn't trip.

What would cause the oil to be saturated with refrigerant? My superheat just before the compressor is only 2-4 deg F sometimes. The TXV was replaced abt 4 mo. ago and set for 12-16 deg SSH at the bulb. When looking in the compressor sight-glass, there is minor to no bubbling under the fluid level with foam on top of the fluid. Seems normal enough, but that low SSH

daddyfixit
17-04-2008, 06:32 PM
Another question. Is there a component in the copeland that could be creating the low oil pressure? One individual told me there is a check valve in the compressor that might cause it. I, however, have never heard of this before. The pump is new and the mesh sump screen is clean.

powell
17-04-2008, 10:00 PM
Which model Copeland do you have?

US Iceman
17-04-2008, 10:49 PM
My superheat just before the compressor is only 2-4 deg F sometimes. The TXV was replaced abt 4 mo. ago and set for 12-16 deg SSH at the bulb.


You just answered your own question. If you are reading 2-4° of superheat AT the compressor you essentially have no superheat in the suction vapor.

Any liquid entering the compressor lowers the oil viscosity therefore the oil pump will not produce sufficient oil pressure. The downside is the oil pump will experience increased wear also (besides what happens to the compressor).

I suggest you start looking at the evaporator, fans, etc to see what is going on there.

bill1983
17-04-2008, 11:24 PM
i was going to suggest the same thing iceman, the reason you're pulling oil out is that previous techs have probably just added oil to relieve the problem without solving it. the biggest question is why is the superheat so low? check air handler operation and condition, how old is the plant? is it in good condition or are heat transfer surfaces crudded up. does airflow seen normal, are filters blocked, does fan run at full speed, etc? check tev superheat after confirming airflow. oil pressure is low due to liquid causing oil to foam and so reduce oil pressure due to reduced amount of oil being pumped. increase superheat to a max of 20 or check manufacturers spec for correct figure.
last thought for this post, is there liquid injection fitted to compressor and how is it controlled?
have fun!

US Iceman
18-04-2008, 01:20 AM
There is a 17 foot rise and about a 25 foot run to the line-sets. 1 1/8" suction and 1/2" liquid lines. 1 ft drop then a 9 ft run, then Oil trap at the floor level, then at 14 ft a 15 foot horizontal run, another oil trap for a 3 foot rise through the roof, an inverted trap on the roof, then 7 feet to the unit.


I have a question.... Is the suction riser the same diameter for the entire pipe run?

If so, the gas velocity may be low enough where the oil separates and runs down back into the evaporator (during normal operation, whatever that might be).



I've increased the deadband on the T-stat to 5deg to allow the unit to run longer.


This might be why the oil is now returning also. Food for thought.;)

daddyfixit
18-04-2008, 04:56 AM
:)Wow. I go off to work and ... great ideas and thoughts. Let's see...

:rolleyes:Powell...
The compressor is M# 2DC3-050ETFD
S# CCG0113853

US Iceman...
Yes, the superheat was one of the first things I started to tackle. The evap is fine, I did change the TXV, and had a rough time adjusting it.:( My Service manager thought there might be oil at the sensor bulb location causing the difficulty. Last checked, the SSH at the bulb was varying 12 to 16 deg F. ( About a month ago) On the roof it was less. Weird. Maybe things changed at the evap too, though. Next chance I get I'll check both again, real close. I couldn't check both at the same time. 2 man roof access.
I don't think it's liquid ref coming back - but ref saturated oil instead, maybe boiling off in the suction line before the 1 foot rise to the suction inlet. It may be a viscosity issue -- but the oil isn't boiling or even bubbling much. Not saturated in the compressor.
Oh, and US Iceman... I did remove the lower oil trap and there was no oil there. Shows that the oil is able to climb back without sliding back down. :confused:I was shocked to see that. 1 1/8 suction line all the way - trap at bottom, before going through the roof, and an inverted trap after roof penetration. It works.

bill1983... I'm beginning to like your idea of increasing the SSH. I believe part of the problem is due to the low load in the winter months. Increasing the SSH would decrease the evap efficiency(slightly) and increase the compressor run time. I did change the T-Stat to a programmable and have increased the dead band to 5 deg. (stg1 75-on, 70-off, stg 2 76-on, 71-off.) Stage 2 was also overcharged with oil but hasn't had the troubles that stage 1 has had. SSH has been better. No oil pres tripping. Haven't checked the oil pres. even, hmmm. I've been concentrating on ckt 1 soo much -- I forgot to compare the oil pres with ckt 2 (?I think?) :o(Note to self: check ckt 2 oil pressure asap).

My service manager thinks the compressor might have minor bearing damage from previous flooding back and that's why the oil pres is so low. Once I balance the oil level and get the SSH up - I think we're gonna let 'er ride until we're forced to do something. :eek:

I hate not knowing for sure tho.

Thanks again for the inputs. Great thought stimulation.:D This sure beats bouncing ideas off my wife. The looks she gives me sometimes.... it's as if she hadn't heard a word I said.:confused:


:)Wish you the best.....

US Iceman
18-04-2008, 05:52 AM
...but the oil isn't boiling or even bubbling much.


Don't go by that. I have seen compressor site glasses that looked relatively normal and flooding back like crazy.

If it's liquid causing the issue you can quickly check it. Measure the discharge superheat on the compressor or the actual discharge temperature. If liquid is coming into the compressor either of these will be very low.

If you are only getting 2-4° of superheat at the compressor suction then liquid is either:

overfeeding from the evaporator
accumulating in the suction line and then traveling in slugs up the riserDoes the evaporator have a pump cycle on it?

SteinarN
18-04-2008, 10:19 AM
Does the evaporator have a pump cycle on it?

Was thinking on the same. Does it have a LL solenoid valve closing when the compressor stops?

RANGER1
18-04-2008, 12:24 PM
Sometimes, if eaporator has a liguid line/suction heat exchanger it can leak internally causing floodback at compressor but s/heat o.k at evap.
Check s/heat at tx bulb and suction pipe out of evaporator ,or downstream of liq/suc h/exchanger if evap has heat /exchanger

daddyfixit
18-04-2008, 12:53 PM
G-mornin' folks,

More great thoughts....:D


Don't go by that. I have seen compressor site glasses that looked relatively normal and flooding back like crazy.

If it's liquid causing the issue you can quickly check it. Measure the discharge superheat on the compressor or the actual discharge temperature. If liquid is coming into the compressor either of these will be very low.

If you are only getting 2-4° of superheat at the compressor suction then liquid is either:

overfeeding from the evaporator
accumulating in the suction line and then traveling in slugs up the riserDoes the evaporator have a pump cycle on it?

US Iceman... Yes, the unit does pump down to shut off. LPC is set for 10psig off - 30 psig on. That was why I replaced the TXV several months ago. I thought it was overfeeding. The solenoid valve used to be on the roof. I moved it to the evap just after the LL service ball valve to reduce the pump down cycle. It was not only pumping down the evap, but also the LL through the TXV. I think this was a big part of the early "low oil troubles" that led to the "add oil to fix it" idea someone else had.:rolleyes: Which led to ..... :confused: and here we are. Almost done - I hope.:o

The plant is a paper mill and is quite warm inside (just plain HOT in the summer). Only the last 10 feet or so are exposed to the frigid Maine winters.

RANGER1.... Good thought! Sorry, no suction-line heat exchanger though.



Wish you the best....