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?