RTAA 90 Oil Fault Help!

[_knight_]

I have a Trane RTAA0904XJ01A3C0BG that has circuit 1 continuously tripping due to "Oil System Fault-ckt 1". Now, there has been no recent repairs done to this circuit which could have brought in any contaminates, and the refrigerant charge is good. I'll be going in later to check oil level, but I know the oil filter on this system is generally oversized and shouldn't need replaced regularly (per the mfg), and there doesn't appear to be any leaks on this particular circuit (or even a history of leaks for that matter). Do any of you chiller pro's have any insight as to what a common cause is. I know this chiller verifies proper oil charge by means of the oil temp at the separator and the saturated condenser temp, and I believe it faults after 30 mins if there is lower than a 4 degree difference. What could cause this fault or restriction?

[Octopus]

Fans staging properly?
Are all of your sensors reading accurately?
What's your SH/SC
Do you have a operating Log?

[Freightshaker]

Fans staging properly?
Are all of your sensors reading accurately?
What's your SH/SC
Do you have a operating Log?

I second that check your condenser fan motors.

[_knight_]

Fans staging properly?
Are all of your sensors reading accurately?
What's your SH/SC
Do you have a operating Log?

I'll start with checking that this evening, I was there last week which is why I knew the charge (at that time) was good. However, I just had received emails regarding the faults it was logging, which is what prompted the question. So this could be an issue with condensing temperatures and not so much an oil restriction?

[Freightshaker]

High cond. Pres. Causes a high enough oil differential to trip it. A lot of times one fan falls out and knocks multiple fans out.

[Nuclrchiller]

A search of this site will show numerous threads on this subject. This is not an oil DP switch function. It's usually caused by carry over, or over feeding refrigerant to the evaporator. Check the compressor discharge temp. And look at the temperature sensors that are used to control the EXV. That would be the saturated evaporator refrigerant temperature sensor and the compressor suction temperature sensor. And perform the test on the EXV.

[Freightshaker]

A search of this site will show numerous threads on this subject. This is not an oil DP switch function. It's usually caused by carry over, or over feeding refrigerant to the evaporator. Check the compressor discharge temp. And look at the temperature sensors that are used to control the EXV. That would be the saturated evaporator refrigerant temperature sensor and the compressor suction temperature sensor. And perform the test on the EXV.

The 125's and lower don't do what i was reffering to do they.

[Nuclrchiller]

Correct, Freightshaker. It's easy to get them confused. I've done it myself. And I ain't gonna promise that I won't do it again!

[Tommy knocker]

Sensors being off can cause it. Plugged oil filter could possibly cause it, holding oil in cooler. Never had this fault on the baby screws I take care of so let us know what you come up with.

[Freightshaker]

I'm good at that. Checked a manual after you said that and got to thinking about it. I don't think I have been around a RTAA under 125. Have a safe day NC.
Keep us updated OP.

[Octopus]

Don't forget to check the accuracy of those sensors and DO NOT check that SH and SC with readings from the panel use your own manifold and thermocouple.

[_knight_]

An update will be coming in the next couple of hours. Thanks for all the advice it's pointing me in the right direction.
I also noticed a post earlier where someone was talking about sweating LL canisters on these units possibly caused by bad EEV's. Coincidentally enough this unit does the same when not running (several hours after shutdown is when I noticed it.) So the EEV will definitely be looked at and tested once on site.

[_knight_]

Update: unit is now online, both circuits are running. Here are the readings for circuit 1 (the circuit that has been tripping on 'oil failure').
Compressor RLA average=91%
Entering oil temp=125* (actual reading 121*)
Evap Pressure=68 (confirmed)
Cond Pressure=251 (actual reading 233 at LL)
Compressor suction temp=48* (actual reading 52*)
Evap temp=40*
Saturated condenser temp=117* (confirmed)

SH: 14ish
SC: 9ish

Those were the readings.

I ran an EEV test, and it appeared to operate fine, upon opening I saw refrigerant flow in the sight glass, upon closing it stopped.
Now something odd I haven't heard before was happening, shortly after the chiller started up, on circuit 1 I was hearing a very very high pitched buzzing sound (almost not noticeable), happening for about 5 seconds every 20 seconds or so. Not sure if this info will help anyone but I couldn't pinpoint where it was coming from, just that it sounded to be coming from the two unloader solenoids on the male side?

[B1978]

I pulled this from a thread from 2010,

"assuming the oil temperature sensors are correct...you need to look at the saturated evap temp and compressor temp sensors. if they are wrong, then you could flood back (the compressor won't care), however, you will be putting liquid refrigerant into the oil separator. as the liquid boils off, it pre-cools the oil before going into the oil cooler portion of the condensor. this makes the oil temp colder than the saturated condensing temperature...which is the reason for the diagnostic." -JayGuy

[_knight_]

I checked my other circuit (circuit 2) and I am running almost identical pressure/temperatures, the one thing that is different on circuit 2 is the entering oil temp is 140* with a 117* sat. cond temp. Now that seems to me like that would be the one tripping.
I'm also noticing both compressors sweating badly, and both sight glasses are now flashing, when previously they had not been.
Now I don't believe I'm flooding back because I have 14* superheat. Or am I possibly.
Thanks for the reply B1978

[jayguy]

...I'm also noticing both compressors sweating badly, and both sight glasses are now flashing, when previously they had not been.
Now I don't believe I'm flooding back because I have 14* superheat. Or am I possibly.
Thanks for the reply B1978

sweating compressors are not necessarily a good or bad sign...way too much information is needed to determine if it is good or bad in your case. however, your 14F superheat...where is that? suction superheat or discharge superheat? this unit is designed to have 4F suction superheat and unless you have a temperature probe in the suction line refrigerant stream, you really can't accurately determine if the compressor suction temperature sensor is accurate or not. check your discharge superheat...it should be between 25F and 50F in pretty much all cases. you will be at the lower end of the discharge superheat as the compressor loads up.

[milkyway]

Look jay , found ya!! Good job! B1978'found ya

[_knight_]

sweating compressors are not necessarily a good or bad sign...way too much information is needed to determine if it is good or bad in your case. however, your 14F superheat...where is that? suction superheat or discharge superheat? this unit is designed to have 4F suction superheat

The 14 degrees superheat was suction superheat.
I didn't notice any issues with floodback or with improper EEV function, circuit 1 sensors appeared to be reading accurately and the system never did fault during my time checking everything.
There was one bad condenser fan motor, but that was on circuit 2 side. I didn't notice anything major.
The customer did mention that the compressors were replaced a few years ago, should I go ahead and replace the oil filters, or at least check there for restriction?
Not quite sure where to go from this point.

[Nuclrchiller]

The 14 degrees superheat was suction superheat.

That was determined using "your" measurements, right? It looks as though the chiller is indicating suction superheat is 8 F. As Jay says, check discharge superheat. How did you measure compressor suction temperature? If suction superheat is truly 8 F, that is too high. It should be 4 F, as Jay mentioned, although it may "float" a little under changing conditions.

[_knight_]

That was determined using "your" measurements, right? It looks as though the chiller is indicating suction superheat is 8 F. As Jay says, check discharge superheat. How did you measure compressor suction temperature? If suction superheat is truly 8 F, that is too high. It should be 4 F, as Jay mentioned, although it may "float" a little under changing conditions.

Yes, 14 was my measurement. 8 is what the system was saying, and it was staying pretty constant at that. I haven't checked the discharge superheat.
Now I'm getting mixed signals now on whether my issue is the EEV over feeding, under charged, oil restriction, or what. Because the oil fault issue I'm having is due to a 4 degree deviation from the oil entering temp and the condensers saturated temp for 30 mins or more (apparently).
Are the things I'm chasing after helping me get closer to finding THAT issue or are we talking another problem here? I know you all are giving me good advice on what to check, but ultimately I want to get in your head (as scary as it might be) to know the issues we are looking into, and why we are looking into them in reference to the fault I'm having.....sorry for the ignorance here, but my work on these rtaa's has been limited. Thanks for all the replies up til now, it is furthering my understanding on this system.