RTAC Compressor Noise

[martinfd1975]

Hi guys... I have an 09 model RTAC200 that is giving me a hard time. Compressor 2 squeals when unloaded, but not all the time. It'll be running smooth, and out of the blue make this loud whining noise, which it will do over and over again. Once the chiller loads up over 50% this goes away, but the compressor is still noticeably louder than the other circuit, or second chiller. In this circuit, I have had to change the refrigerant liquid level sensor twice, first one went bad and the factory sent me a bad replacement. I have also had to clean the strainer in the oil scavenging line 4 times. I am wondering if the oil filter needs to be replaced. Oil level is fine.. I do have a low discharge superheat at all load levels though. Also, the compressor is sweating almost all the way through. That makes me think I have a bad shaft seal and liquid is bypassing, or lack of oil to make the seal between the male and female screws. The machine does not trip out for any reason. What do you guys think?

Here's a vid of the noise...

[jayguy]

you need to get a handle on the liquid refrigerant coming back to the compressor...if not, you may be buying a new compressor. then you can get the oil in the right place and hopefully that will quiet the noise down.

[Trane Tech NYC]

First has the refrigerant charge been weighed in after any repairs?

Has anyone added any refrigerant?

[martinfd1975]

I have the returning liquid taken care of temporarily. It won't stay this way, but I have my sweat line where it should be. I simply backed down my liquid level setpoint, I know not the best idea, but I am not flooding my compressor anymore. The only repairs that have been done was the liquid level sensor and refrigerant was transferred to the condenser except a little bit which I recovered and pumped back in with my recovery unit. None was lost, or added. I am seriously considering pulling the charge out of that circuit to get a weight and re-charge... While I have the refrigerant out, I need to go ahead and drain the oil charge and re-charge with fresh, changing the oil filter and quite possibly the master oil valve. I don't know, I have been on the phone with tech support and they can't help me figure this out and I am at whits end here... In Kestrel View, I have backed my liquid level setpoint down to -.3 in order to get my sweat line right on my chiller.

[jayguy]

...While I have the refrigerant out, I need to go ahead and drain the oil charge and re-charge with fresh, changing the oil filter and quite possibly the master oil valve....

1. no
2. yes
3. no

refrigerant weighing, sure.
getting liquid level under control, sure.

[R123]

Hi guys... I have an 09 model RTAC200 that is giving me a hard time. Compressor 2 squeals when unloaded, but not all the time. It'll be running smooth, and out of the blue make this loud whining noise, which it will do over and over again. Once the chiller loads up over 50% this goes away, but the compressor is still noticeably louder than the other circuit, or second chiller. In this circuit, I have had to change the refrigerant liquid level sensor twice, first one went bad and the factory sent me a bad replacement. I have also had to clean the strainer in the oil scavenging line 4 times. I am wondering if the oil filter needs to be replaced. Oil level is fine.. I do have a low discharge superheat at all load levels though. Also, the compressor is sweating almost all the way through. That makes me think I have a bad shaft seal and liquid is bypassing, or lack of oil to make the seal between the male and female screws. The machine does not trip out for any reason. What do you guys think?

Here's a vid of the noise...

Everything your describing points to a clogged scavenger line and oil not returning to the oil separator. The low discharge superheat indicates an oil logged evaporator.

[jayguy]

...I have also had to clean the strainer in the oil scavenging line 4 times. ...

i missed this line the first time...cleaning that strainer should only need to be done once (if ever) unless there is an issue like a cmpressor failure or something. what was in the strainer? the lack of oil and the strainer filling up may indicate that you already have damage to the rotors which means that you are going to be installing a new compressor soon. a vibration analysis on the compressor should be performed.

[R123]

I've had a few machines that continually clogged the strainer when the chiller was brand new due to construction debris that was left in the chiller from the factory. It was a metal substance that kinda looked like steel wool packed in the strainer. We consulted with Pueblo and ended up putting a flare liquid line filter drier in the line along with a 3/8 ball valve (with schreader port) to easily isolate it. The debris eventually filtered out.

[martinfd1975]

Thank you all for the input... R123, I have cleaned the strainer in the scavenging line multiple times, the first couple times it was in horrible shape, but the last couple it wasn't so bad... In the summer, the line does sweat all the way back to the compressor, even when the strainer was stopped up, so I don't use that as an indicator of anything... I am going to get on this in a couple days when the inspection is over... As for now, that circuit is locked out..

[Screwit]

Might be worth installing a sight glass in the oil return/scavenger line

[Gear-Drive Guru]

Low discharge superheated indicates liquid carryover. Problem is the unit is fitted with a falling film evaporator and it is impossible to get a liquid carryover from the evaporator and therefore where is the excessive liquid coming from? Is the water circuit piped correctly, in at the top and out at the bottom? What happens during the off cycle? I have seen the compressor ice during the off cycle and this causes a whole new set of problems. When does the unit suffer low discharge temperatures? Full load, part load??? A noisy compressor is a good indication that you have an oil problem. The RTAC uses thick casing and oil to reduce the compressor noises. It is possible the oil filter is partially blocked. Has the pressure drop across the filter been measured?

[R123]

Low discharge superheated indicates liquid carryover. Problem is the unit is fitted with a falling film evaporator and it is impossible to get a liquid carryover from the evaporator and therefore where is the excessive liquid coming from? Is the water circuit piped correctly, in at the top and out at the bottom? What happens during the off cycle? I have seen the compressor ice during the off cycle and this causes a whole new set of problems. When does the unit suffer low discharge temperatures? Full load, part load??? A noisy compressor is a good indication that you have an oil problem. The RTAC uses thick casing and oil to reduce the compressor noises. It is possible the oil filter is partially blocked. Has the pressure drop across the filter been measured?

It is quite possible to get liquid carryover from the evaperator. I have seen it many times. If the evaporator is oil logged, the oil/refrigerant mixture entering the top of the evaperator in the distributor will foam up and the foam will be sucked up into the suction ell. This will cause 0 degrees discharge superheat.

[Gear-Drive Guru]

If the evaporator is oil logged then the oil mixed with the refrigerant will be at the bottom of the evaporator where the refrigerant is pooled. If the liquid entering the evaporator has that much oil in it then the oil separators are doing nothing or the unit has been overcharged with oil. The oil separator is efficient as the load increases but does not preform well at part load but does still separate. Has oil ever been added to the chiller?

[martinfd1975]

If the evaporator is oil logged then the oil mixed with the refrigerant will be at the bottom of the evaporator where the refrigerant is pooled. If the liquid entering the evaporator has that much oil in it then the oil separators are doing nothing or the unit has been overcharged with oil. The oil separator is efficient as the load increases but does not preform well at part load but does still separate. Has oil ever been added to the chiller?

This chiller has never had oil added to it... Considering the amount of gunk that I have pulled out of the strainer in the oil scavenger line, I am going to check for a clog at both ends of it... I actually have a co-worker coming tomorrow to help me figure this out, he has worked for Trane for 42 years, so I am sure we will get it figured out... I'm a new guy with Trane, only 3 years now so he will once again get me straightened out... His role, considering his tenure, is training now... I appreciate all the input guys and I will definitely post the results of tomorrow's testing...

[FixItRight]

There is a lot still needed like the evap approach with a unit that is oil logged it will have a high evap approach.Also it is a waste of time to pull the charge just go by superheat. Also the master oil valve is more than likely ok when they fail 90%of the time they shut the unit down on oil flow fast. You can check your acceptable pressure ratio to tell if the oil filter is good but if it was bad the chiller goes off on intermediate oil pressure most of the time.

[FixItRight]

There is a lot still needed like the evap approach with a unit that is oil logged it will have a high evap approach.Also it is a waste of time to pull the charge just go by superheat. Also the master oil valve is more than likely ok when they fail 90%of the time they shut the unit down on oil flow fast. You can check your acceptable pressure ratio to tell if the oil filter is good but if it was bad the chiller goes off on intermediate oil pressure most of the time.

I meant to say charge by subcooling not superheat.

[R123]

I've been working on these machines since they first came out over 10 years ago and I've worked on hundreds of them. I stand by what I stated in my previous posts as I've dealt with this exact problem many times. The oil seperators are not 100 % efficient, so if your scavanger line is clogged, your evap will eventually get oil logged and you WILL get liquid carry over. This vintage is the RTAC Plus which has the evaporator with the internal liquid vapor seperator. They are very susceptible of foaming and liquid carry over when they become oil logged. On this vintage, the oil seperator is more efficient at part load. So, if your evaporator is oil logged, you run the circuit fully UNLOADED to return the oil to the seperator after you get the scavanger line cleared out.

[martinfd1975]

Agreed R123.... unfortunately my problem isn't oil related... It's mechanical within the compressor. Evaporator approach is 3 * at 80% load, oil separator level is 7", oil scavenging line is not stopped up, oil pressure is great, oil filter has a good dp. We are going to refer to the service e bulletins to see if this has been addressed yet and go from there... I appreciate the advice you guys have given me...


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[jayguy]

...oil pressure is great, oil filter has a good dp...

what is 'great oil pressure'? what number does an oil filter have when it has a 'good dp'?

technical help requires technical numbers. you if need help, you are no longer allowed to make decisions about what is 'good' or 'bad'. you need to post everything. sometimes an 'acceptable' number is actually 'unacceptable' if certain other conditions are present.

do you have glycol (type and percentage) or water? and what is your actual flow rate or actual pressure drop? and what is the design? something is starting to hit me kind of funny about this job.

[martinfd1975]

Actually, as stated above, I had my co-worker (Trane tech for 42 years) at my location Thursday. That is why I made the statements that I did. As far as not having the right to make decisions, even when the senior level techs come to my location, I still make the decisions based on the info they give me. My last post was actually made to say that I wanted to close this discussion.. thank you all for the helpful input.

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