Results 1 to 41 of 41
  1. #1
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Bitzer CSH8561-125Y oil sight glass



    I posted on http://www.megaupload.com/?d=AR1DNT54 a movie o 7 minutes (+/- 35 MB) of an oil sight glass of a running CSH8561 Bitzer screw

    You will see the machine at startup in partial load then running full load and going back again in partial load before shutting down.
    You will also hear the reverse running when shutting down.

    In +/- 2 to 2.5 months, 2 compressors burned (one winding) Chiller was then +/- 2.5 years old.
    Their was no mechanical wear (pictures taken at Bitzer Germany after opening 1 compressor)
    See pictures.
    They're mounted in a monobloc chiller of +/- 1MW. (3 screws)

    In the compressor was only 9 l oil instead of the 16 recommended by the chiller manufacturer (or 22 l as stated in the Bitzer manual)

    After you've seen the movie, can someone tell me where the oil is going? It's a compact screw.



    Does someone have an idea how much oil there is in the sump while running in partial load?
    Or how much will is needed before shutting down in alarm.

    You also see the oil coming back when running full load.
    The circuit is very short, suction of perhaps 2 meter (6 feet)
    Tube and shell evaporator with 2 equal circuits.
    No economizer.

    Can we assume that the motors burned when running in partial load or when shutting down or starting up because there's only 9 l in the sump?

    They were originally protected with a INT69, the 2 new compressors came with A SE-B2 and SE-E1 and recently changed by Bitzer with the brand new a SE-C1.
    Does someone had in the recent past specific problems with one of these Kriwan types?

    I would like to hear your opinion about the fact that the machines are only protected with the Kriwan's (so no overload relay)
    Attached Images Attached Images
    Last edited by Peter_1; 17-11-2008 at 09:54 PM.


    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  2. #2
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    This is the link to the Kriwan pdf
    http://www.bitzer.co.kr/public_html/...f/st-120-1.pdf and
    http://www.bitzer.de/download/downlo...N=st-600-2.pdf -
    The file of the new SE-C1 isn't published yet on the Bitzer site but this is the link of the pdf
    http://www.megaupload.com/?d=TODP38EY
    Any help is much appreciated.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  3. #3
    Join Date
    Jun 2001
    Location
    N.Ireland
    Age
    50
    Posts
    1,632
    Rep Power
    24

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by Peter_1 View Post
    I posted on http://www.megaupload.com/?d=AR1DNT54 a movie o 7 minutes (+/- 35 MB) of an oil sight glass of a running CSH8561 Bitzer screw

    You will see the machine at startup in partial load then running full load and going back again in partial load before shutting down.
    You will also hear the reverse running when shutting down.

    In +/- 2 to 2.5 months, 2 compressors burned (one winding) Chiller was then +/- 2.5 years old.
    Their was no mechanical wear (pictures taken at Bitzer Germany after opening 1 compressor)
    See pictures.
    They're mounted in a monobloc chiller of +/- 1MW. (3 screws)

    In the compressor was only 9 l oil instead of the 16 recommended by the chiller manufacturer (or 22 l as stated in the Bitzer manual)

    After you've seen the movie, can someone tell me where the oil is going? It's a compact screw.



    Does someone have an idea how much oil there is in the sump while running in partial load?
    Or how much will is needed before shutting down in alarm.

    You also see the oil coming back when running full load.
    The circuit is very short, suction of perhaps 2 meter (6 feet)
    Tube and shell evaporator with 2 equal circuits.
    No economizer.

    Can we assume that the motors burned when running in partial load or when shutting down or starting up because there's only 9 l in the sump?

    They were originally protected with a INT69, the 2 new compressors came with A SE-B2 and SE-E1 and recently changed by Bitzer with the brand new a SE-C1.
    Does someone had in the recent past specific problems with one of these Kriwan types?

    I would like to hear your opinion about the fact that the machines are only protected with the Kriwan's (so no overload relay)
    Hello Peter

    so the screw is OK mechanically

    with oil surging like that I would expect the bearings to fail.

    Burnt motor windings. We have a site that has burnt out some motors, the electricity supply company checked the voltage and insist it is within tolerance, but the controller on the compressor tells me otherwise.

    My guess would be under voltage.

    My advise would be to fit voltage and current monitoring and a set of electronic overloads.

    Kind Regards Andy
    If you can't fix it leave it that no one else will:rolleyes:

  4. #4
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    Peter,

    Here are some ideas to consider...

    If the compressor starts, goes to full load, and then shuts off in 7 minutes I do not think that is enough time for good oil return to occur.

    Another point is; the short run-times may not allow good motor cooling (too many hot starts per hour?).

    On the shell and tube evaporator; is it one common refrigerant circuit or multiple separate circuits?

    If the power quality is OK, then this looks like a system design problem...
    If all else fails, ask for help.


  5. #5
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    As you can expect, this is something difficult.
    The claim will be something in the region of 50,.000 Euros of +/- 60,000 $.
    The electricity company did extensive measuring for a long period and everything was within specs.
    Bitzer say you may start 8 times/hour, so +/- 7 minutes between to starts. So this is OK.
    The chiller manufacturer measured this and came to 2.5 starts /hours.
    The oil separator and oil reservoir is bolted on the compressor itself. This is something very specific for these compact screws.
    The evaporator has 2 independent circuits with each their own inner circuit if this is what you mean USIceman.

    System design problem: what are you thinking?

    The bearings were OK and were inspected by Bitzer in the presence of some peoples.
    The surging of the oil, I think that this is something normal for these screws. All 3 are doing the same.

    AnNdy, the electronic controller that said that the power wasn't OK, do you remember the type of it?
    We had here the same problem with the Kriwans delivered with the new compressors. The sometimes tripped more than once a day but you can't know on what fault with these Kriwans (phase sequence or unbalance at start-up, too high discharge or too high oiltemperature, too high winding temperature...)
    They changed to the new SE-C1 and all the problems were gone at once.
    Are the problems gone or are they still there but does the new Kriwan doesn' t see them?
    Or was the previous Kriwan too sensitive?
    A new type will have normally not the faults of the old ones, it's an improved version.
    There are also several LED's now on th Kriwan to indicate on what type of alarm the Kriwan tripped.

    The whole factory is connected on their own high-voltage transformer and everything is controlled.
    In this factory are at least hundred of very sensitive bio-technologial machines located without problems of power supply.

    What can be th reason Bitzer recommends that the cos-phi may not be higher than 92% or 93%?
    Last edited by Peter_1; 18-11-2008 at 07:55 AM.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  6. #6
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    Hi Peter.

    The reason I asked about the evaporator is I have seen some DX chillers that have one refrigerant circuit but have two compressors. During part load the gas velocity through the chiller is not high enough to return oil and the evaporator begins to fill with oil.

    This is why I thought of a system design problem:

    In the compressor was only 9 l oil instead of the 16 recommended by the chiller manufacturer (or 22 l as stated in the Bitzer manual)
    If the oil system was properly charged with oil when the system was started, then the oil should return if the system is designed properly. That is why I asked about the evaporator.

    From what you have described I doubt the problem is with the Bitzer screws. I thought they built very good compressors.

    Sometimes on a screw compressor if they start with low discharge pressure the gas velocity through the separator is so high the oil is blown out of the separator. The oil has to be returned as you know. If the run time is not long enough, sufficient oil may not return. As you say, part of the oil returns but maybe not enough before the compressor shuts down again.

    Bitzer should be able to tell you something about the burned windings by the way they look. I do not remember the different types of burn patterns anymore that show when various types of problems occur. If it was phase-imbalance or something else someone should know what the burned windings were caused by.

    Another thing is the power quality. Was this checked when the compressors were loaded? Was the power OK at the terminals of the motor? Where and when did they check it?

    I had one compressor that burned up several times and found bad contacts on a new starter. The resistance on one set of contacts was high enough to change the power at the motor terminals, which caused the motor to run hot (the contacts too).

    The black boxes may pick this up and show a trip condition but monitoring equipment on the line side of the starter may not show this.
    Last edited by US Iceman; 18-11-2008 at 01:22 AM. Reason: spelling
    If all else fails, ask for help.


  7. #7
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    Peter,

    One more question...


    What can be th reason Bitzer recommends that the cos-phi may not be higher than 92% or 93%?
    What is cos-phi?
    If all else fails, ask for help.


  8. #8
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by US Iceman View Post
    Peter,

    One more question...



    What is cos-phi?
    Power factor!

  9. #9
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    I deliberately didn't gave all the information because I wanted to ask neutral non- suggestive questions so that I would see if you came to the same answers as I did.

    Concerning the burnt windings and the problem I face: I suspect Bitzer they don't give all the information I need and ask because the chiller manufacturer is a huge client for them.
    There's a change that they both know more and tell this to each other but not to outsiders.

    Fact was that the contacts of the original relays were welded together. This is of course extremely important.
    The manufacturer says that the relays were properly selected by Schneider/Télémécanique. They were not selected according the specs of Bitzer - much smaller - but this was done again after a 'special' agreement between Bitzer and the OEM client.
    Bitzer advises to select at - if I remember well- 120% of full load. We had something of 60% of full load.

    There's also something strange with the Kriwan's.
    We now already had 3 different Kriwan's in one machine.
    The original ones were apparently INT69 which are made for pistons compressors if I'm right.
    Those delivered with the new ones for replacement generated or false alarms or detected something that the other types doesn't see.

    Has someone looked already to the schematics were everywhere an overload relay is installed?
    There are no O.R in the chillers because -that's what the manufacturer tries to let believe me - the Kriwan protection is more than enough.
    Bitzer should check this if this was also a special agreement between them and the manufacturer.

    Practical experience of others with this type of Kriwan's is important.

    As you could see on the rather large movie, the oil level varies widely when running.

    USIceman, according tho the evaporator, I have to check this once again because what I said can't be true: we have 3 compressors, so we can't have 2 circuits.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  10. #10
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by Peter_1 View Post

    Fact was that the contacts of the original relays were welded together. This is of course extremely important.
    The manufacturer says that the relays were properly selected by Schneider/Télémécanique. They were not selected according the specs of Bitzer - much smaller - but this was done again after a 'special' agreement between Bitzer and the OEM client.
    Bitzer advises to select at - if I remember well- 120% of full load. We had something of 60% of full load.
    When you have 1 phase winding burnt, it is almost certain thing that contactor is welded. You just proved that.
    If contactor is welded then power supply cannot be disconnected from motor no matter what Kriwan protection do. Even, if you have thermal and over current relays they cannot disengage contacts of welded contactor.

    Regarding contactors from Telemehanique, by my experience, they are not good as Siemens and I always change them with Siemens when I am in need to change them. My favorite was Končar (now bought by Siemens). They were bigger in size as others and built like Russian tanks.
    But, Siemens was endangered, and he bought them, to stop production.
    Last edited by nike123; 18-11-2008 at 08:57 AM. Reason: Some addition

  11. #11
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Now, question is why was contacts welded?
    Could you give us original model number of contactor ?

    These are current data for that compressor:
    Max operating current 216.0 A
    Winding ratio 50/50
    Starting current (Rotor locked) 612.0 A D / 943.0 A DD

    My selection of contactor from this data (and for direct starting) would be (for AC-4 duty=6 times starting current): Siemens 3TF68

    Telemecanique/Schnieder equivalent would be LC-1F630
    Last edited by nike123; 18-11-2008 at 11:39 AM.

  12. #12
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Is it part winding, star-delta or as direct online starting?

  13. #13
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    If the manufacturer only provided contactors and depended on the Kriwan modules to protect the motor I don't think I can say on the forum what I think about this. I would not do that.

    Contactors offer no motor protection without the overload relays. I think the Kriwans were sensing the problem correctly and shutting off the compressors. However, without the LED's or some other visual reference it would be very difficult to find the fault that caused the trip.

    And, if one set of contacts welded together that is not a motor problem and probably not due to power quality. Just the contactor itself.

    If I remember correctly IEC rated contacts have lower allowable current ratings than the NEMA (the US equivalent) ratings. I ran into this many years ago when IEC rated parts started to come into the US.

    However, if Bitzer says the contactor should be rated for XX amps or %, then that is the minimum that should be used. Typically, if the maximum current required was close to the maximum contact rating, I would use a larger contactor for a good selection. But from a chiller manufacturers viewpoint, cheapest is the best to remain competitive or to make more money.
    Last edited by US Iceman; 18-11-2008 at 09:17 PM. Reason: spelling fix
    If all else fails, ask for help.


  14. #14
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    Peter,

    I found this on another forum. It may help to explain why Bitzer does not want the power factor to be greater than 92-93%.

    I'd like to know what the major consequences are of over-correcting power factor, i.e leading power factor.
    Answers (both by same person)
    If you over correct using static correction (capacitors applied directly to the motor circuit and controled by the motor starter) you are going to have major problems. The reactance of the capacitors and the reactance of the motor combine to create a resonant circuit. If you under correct, the resonant frequency is higher than line frequency. If you over correct, the frequency is less than line frequency.
    If you switch OFF the motor (i.e. open the contactor) and the capacitors remain connected to the motor terminals, the motor will generate voltage as it slows down. The frequency is dependent on the motor speed. It will pass through resonance and create very high voltages. These high voltages will cause damage to the motor, switchgear and capacitors. Additionally, if the insulation breaks down with the high voltages, there can be severe torque transients generated also which can damage the equipment.

    If you over correct with bulk correction, there is generally no problem provided that the supply is well loaded. The only negative is that the current is minimum at a correction of 1. As you increase the correction into a leading power factor, the current begins to rise again and you are not getting any benefit.

    If the supply is lightly loaded and you over correct, you can get supply resonances which can generate high voltages and cause damage to equipment.

    Power factor correction is only really beneficial under high load conditions, so it can be eliminated under light load conditions.
    With induction motors, the magnetising current is essentially constant and independant of load. For this reason, it is usually OK to use a fixed capacitor for a motor. (static correction)

    In your installation, I suspect that you are using some form of variable speed control and there will be rectifiers rather than induction motors connected to the supply. If this i9s the case, then there will be a poor power factor due to harmonics rather than inductive currents.

    Power factor correction capacitors will improve displacement power factor only and will not improve distortion power factor.

    Excessive capacitance across a supply can cause supply resonance issues when the load is light. Resonance will cause voltage surges triggered by transients.
    If the load on the supply transformers is light, there will be low dampening of any supply resonance (power factor capacitors with supply inductance)

    The problem with over correction of the supply is very different from over correction with static correction.
    A poor leading power factor will draw the same current as lagging power factor so there is no advantage in over correcting.
    Now I know why leading power factor is bad for motors.
    If all else fails, ask for help.


  15. #15
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Check this service tip.

    Also, it should be checked that voltage unbalance is not higher than 1% (number found on this compressor field guide) from the mean value! I don't know what is Kriwan value to act for voltage balance protection (if any)!
    Last edited by nike123; 18-11-2008 at 05:54 PM. Reason: Some addition

  16. #16
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    I did some research on voltage unbalance some time ago and found some interesting results.

    A small increase in voltage unbalance leads to a much greater percentage of motor heating. And motor insulation does NOT like high temperatures. I seem to remember a value of 3-4% unbalance was getting to be considered too high. But that is an old value from many years ago when I attended a class.

    Today, that value may be much lower. A lower unbalance would be better of course but it can depend on how the loads on the power supply are shared and how the transformers are tuned.

    Therefore, the Kriwans may have been sensing the winding temperatures correctly (if these are similar to the black boxes Copeland used to use) and shutting the compressor off.
    Last edited by US Iceman; 18-11-2008 at 04:45 PM. Reason: edit
    If all else fails, ask for help.


  17. #17
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by US Iceman View Post
    I did some research on voltage unbalance some time ago and found some interesting results.

    A small increase in voltage unbalance leads to a much greater percentage of motor heating. And motor insulation does NOT like high temperatures. I seem to remember a value of 3-4% unbalance was getting to be considered too high. But that is an old value from many years ago when I attended a class.

    Today, that value may be much lower. A lower unbalance would be better of course but it can depend on how the loads on the power supply are shared and how the transformers are tuned.

    Therefore, the Kriwans may have been sensing the winding temperatures correctly (if these are similar to the black boxes Copeland used to use) and shutting the compressor off.
    Here is article about that!

    And another one!
    Last edited by nike123; 18-11-2008 at 05:44 PM.

  18. #18
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    That is a different article than the one I saw, but shows similar information. Thanks, I'm sure others will find this very interesting also.
    If all else fails, ask for help.


  19. #19
    Join Date
    Mar 2006
    Location
    Merate (LC) - Italy
    Age
    52
    Posts
    2,554
    Rep Power
    24

    Re: Bitzer CSH8561-125Y oil sight glass

    It all ignores the fact the oil is leaving the compressor. What refrigerant is that?

  20. #20
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by NoNickName View Post
    It all ignores the fact the oil is leaving the compressor. What refrigerant is that?
    So far, nothing proves or point to, that lack of oil is cause of trouble.
    Last edited by nike123; 18-11-2008 at 07:16 PM.

  21. #21
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    I happen to agree with NoNickName, the oil loss is a separate issue from the motor problems based on what I have read so far.
    If all else fails, ask for help.


  22. #22
    Join Date
    Oct 2006
    Location
    Bucks, U.K.
    Age
    70
    Posts
    604
    Rep Power
    18

    Re: Bitzer CSH8561-125Y oil sight glass

    Nike, Interesting articles on 3 phase imbalance - Thanks.

  23. #23
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by nike123 View Post
    Is it part winding, star-delta or as direct online starting?
    Just back behind my PC Part winding start Nike123
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  24. #24
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by nike123 View Post
    Check this service tip.

    Also, it should be checked that voltage unbalance is not higher than 1% (number found on this compressor field guide) from the mean value! I don't know what is Kriwan value to act for voltage balance protection (if any)!
    This is something they mentioned already but how does we have to read or understand this 1%? Over what time? 0.1 second or 1 minute?
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  25. #25
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by Peter_1 View Post
    This is something they mentioned already but how does we have to read or understand this 1%? Over what time? 0.1 second or 1 minute?
    If that time is short, than there is not danger of overheating. It takes some time for heat to develop.
    I think that is meant for longer periods, or for all the time.

  26. #26
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by nike123 View Post
    Now, question is why was contacts welded?
    Could you give us original model number of contactor ?

    These are current data for that compressor:
    Max operating current 216.0 A
    Winding ratio 50/50
    Starting current (Rotor locked) 612.0 A D / 943.0 A DD

    My selection of contactor from this data (and for direct starting) would be (for AC-4 duty=6 times starting current): Siemens 3TF68

    Telemecanique/Schneeder equivalent would be LC-1F630

    Original relays were LC1D115 from Télémécanique
    Now we have 6 pieces of LC1D150
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  27. #27
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by US Iceman View Post
    I happen to agree with NoNickName, the oil loss is a separate issue from the motor problems based on what I have read so far.
    Agree also USICeman and NoNickname.
    I think it's better to say that the oil isn't lost but is somewhere else in the system. Am I right?
    But is the oil-descending-level anyhow a problem?

    NoNickName, I will confirm the correct type of refrigerant to you.

    NoNickName, I think that the oil dancing up and down is something that's not unusual for this type of machine when it's going in partial load. But I can be wrong.
    Reason why I ask some uncertainties to the pro's here.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  28. #28
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    Anyhow, thanks so far for your much appreciated help.
    I will post tomorrow the answers to some questions.
    USIceman and Nike123, you both posted helpful information.
    I think this is a problem where we all can learn from.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  29. #29
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by Peter_1 View Post
    Original relays were LC1D115 from Télémécanique
    Now we have 6 pieces of LC1D150
    That contactor have 55 kW at AC-3 power rating. If we consider maximum power input for that compressor of 98,6 kW and 60% of that is 59,16 kw for part winding contactor by rcomendations of Bitzer.
    But, knowing quality of Telemehanique that is prety much above capacity of that contactor.
    In this case my choice would be Siemens 3TF54 (61kW
    at AC-4 rating) or his equivalent Telemecanique LC1F265

    Or best to use definite purpose contactor Schneider/SquareD DPA123
    Last edited by nike123; 19-11-2008 at 12:26 AM.

  30. #30
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,326
    Rep Power
    25

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by Peter
    I think it's better to say that the oil isn't lost but is somewhere else in the system. Am I right?
    I'm not very familiar with the Bitzer screw packages Peter. However, if this is true...

    Quote Originally Posted by Peter
    In the compressor was only 9 l oil instead of the 16 recommended by the chiller manufacturer (or 22 l as stated in the Bitzer manual)
    ...then my question is, where is the oil? The oil volume is either low because:

    • It was not charged properly into the system
    • The oil leaked out
    • Or, the oil is in the system (receiver, condenser, or evaporator)

    The first two are service items, the last could be a system design problem. The second part of this issue is: why did the oil carryover into the system?
    If all else fails, ask for help.


  31. #31
    Join Date
    Mar 2006
    Location
    Merate (LC) - Italy
    Age
    52
    Posts
    2,554
    Rep Power
    24

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by Peter_1 View Post

    NoNickName, I think that the oil dancing up and down is something that's not unusual for this type of machine when it's going in partial load. But I can be wrong.
    Reason why I ask some uncertainties to the pro's here.
    Not at all unusual, but the type of solution very much depends on the type of refrigerant.
    And of course, the oil return from the suction line riser depends on the refrigerant speed: the lower the capacity step, the lower the refrigerant speed, the worse the oil return.

  32. #32
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    62
    Posts
    5,645
    Rep Power
    34

    Re: Bitzer CSH8561-125Y oil sight glass

    The refrigerant is R407c NoNickname.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  33. #33
    Join Date
    Mar 2006
    Location
    Merate (LC) - Italy
    Age
    52
    Posts
    2,554
    Rep Power
    24

    Re: Bitzer CSH8561-125Y oil sight glass

    the problem with blends containing R134a, like R407c and R404a, is that they have a lower mass flow thanks to R32 or R125, but a high miscibility thanks to R134a.
    Miscibility tends to reduce when the subcooling is little, in fact R134a is the highest of the three components in terms of condensing temperature, and condensation is normally controlled in pressure, not in temperature.
    Basicly what happens is a composition shift of the component who has got the highest miscibility.
    I would check the subcooling and relate it to the oil carry over, to see whether at high subcooling oil returns and viceversa oil disappears at low subcooling.
    If you have the possibility of checking the composition with a spectrometer, also please do it.

  34. #34
    Join Date
    Dec 2008
    Location
    Moncton,N.B. Canada
    Age
    48
    Posts
    44
    Rep Power
    0

    Re: Bitzer CSH8561-125Y oil sight glass

    Was just reading all the posts from everybody i was just wondering , were i am from most of the compressors are started by softstarters (reduced voltage starts)i only see contactors on older installs. If the compressor is 216 amp rla it would be appr. 200 hp. I would usually install a softstarter not contactors,part winding start ect.just curious.

  35. #35
    Join Date
    Sep 2006
    Location
    Indonesia
    Posts
    5
    Rep Power
    0

    Re: Bitzer CSH8561-125Y oil sight glass

    Hi Samlee and every one!

    I have problem with one screw compressor bitzer, when we tried to start the current very high goes to 500A for 3 or 4 second and the main breaker stop.

    We have soft starter for start up as well.

    and finally found less oil in the compressor but i was surprise that the compressor was not detect by any oil indicator, i mean that unit only have PTC for oil temperature but it was not open at all so always close.

    after that I measured again the resistance and merger, so far everything ok


    my question,1) after we top up the oil, will the compressor start again (any body had experience before?)
    2) is that oil level switch is a compulsory? because i checked with bitzer website that it is an option.

    thanks for your comment.
    Achiel

  36. #36
    Join Date
    Dec 2008
    Location
    Portugal
    Age
    48
    Posts
    1,044
    Rep Power
    19

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by Peter_1 View Post
    I posted on http://www.megaupload.com/?d=AR1DNT54 a movie o 7 minutes (+/- 35 MB) of an oil sight glass of a running CSH8561 Bitzer screw

    You will see the machine at startup in partial load then running full load and going back again in partial load before shutting down.
    You will also hear the reverse running when shutting down.

    In +/- 2 to 2.5 months, 2 compressors burned (one winding) Chiller was then +/- 2.5 years old.
    Their was no mechanical wear (pictures taken at Bitzer Germany after opening 1 compressor)
    See pictures.
    They're mounted in a monobloc chiller of +/- 1MW. (3 screws)

    In the compressor was only 9 l oil instead of the 16 recommended by the chiller manufacturer (or 22 l as stated in the Bitzer manual)

    After you've seen the movie, can someone tell me where the oil is going? It's a compact screw.



    Does someone have an idea how much oil there is in the sump while running in partial load?
    Or how much will is needed before shutting down in alarm.

    You also see the oil coming back when running full load.
    The circuit is very short, suction of perhaps 2 meter (6 feet)
    Tube and shell evaporator with 2 equal circuits.
    No economizer.

    Can we assume that the motors burned when running in partial load or when shutting down or starting up because there's only 9 l in the sump?

    They were originally protected with a INT69, the 2 new compressors came with A SE-B2 and SE-E1 and recently changed by Bitzer with the brand new a SE-C1.
    Does someone had in the recent past specific problems with one of these Kriwan types?

    I would like to hear your opinion about the fact that the machines are only protected with the Kriwan's (so no overload relay)

    Hi Peter,

    Maybe is to late to express my opinion, nevertheless here it goes (then please give me your feed back about the actual situation).

    I have downloaded the movie but I just can see the firsts 46 seconds the the movie stops and a error messages about the codecs appears.
    In the move at 0 seconds I saw the oil disappear then it came again and then starts disappear (47 seconds)

    The first thought I had was very possibilities such as:

    Partial load » less velocity to carry on again the oil to the suction line. The oil disappear process is just to fast...so I don't think this is the cause or the only cause.

    Very low condensing pressures when enters in part load which could result on a non oil separation due to the high velocities and the lower coalescent effect. BUT the fact is that we have less mass load (part load) to be transported through the oil separator so I don't believe this is the cause. And also the oil disappear process is just to fast...so also I don't think this is the cause.


    It seems the oil is foaming (see between 41 and 46 seconds). Maybe this is due the presence of liquid refrigerant emulsionized in the oil and due to a super rapid decrease of the high pressure the oils carried by the vapor refrigerant and pass through the oil separator to the discharge line and to the evaporator.
    If my thoughts are correct I suggest you try the folowing:

    - Try to stablize the discharge pressure as fast as you can. Does the discharge pressures have big variations?

    - Apply a PMC+CVC to inject automatically hot gas in the feeding of the evaporator (after the expansion valve) soon as the suction pressure starts to down (adjust the CVC as you want). This will also ensures that the compressors will operate near the 100% and so you be sure that the oil is all back to the compressors...and avoid that the compressors stops for low capacity demand.

    Regards
    To make progress is never good enough, I want to do better and better and better

  37. #37
    Join Date
    Nov 2008
    Location
    australia
    Posts
    136
    Rep Power
    16

    Re: Bitzer CSH8561-125Y oil sight glass

    hello all
    have seen the same problem on a set of bitzer screws, we were lucky that no compressors were burnt . the bitzers we work on have trax oil devices on them maybe its a device you want to install also were the compressors going out on overtemp/ overload? we found that once we got the super heat to about 9k ( dont quote me dont have bitzer book in front of me they want 12k from memory). do you have oil coolers on them? if so what temp are the fans cycling. what we found is that our oil sight glass was always low then we got the s/h right and the oil was a lot better. do you have a filter in the oil seporator line? is that blocked? whats your oil pressure when running low and full load.

  38. #38
    Join Date
    Sep 2006
    Location
    Indonesia
    Posts
    5
    Rep Power
    0

    Re: Bitzer CSH8561-125Y oil sight glass

    Quote Originally Posted by NoNickName View Post
    Not at all unusual, but the type of solution very much depends on the type of refrigerant.
    And of course, the oil return from the suction line riser depends on the refrigerant speed: the lower the capacity step, the lower the refrigerant speed, the worse the oil return.
    Hi NoNickName and Peter!
    I also have the same problem with oil dancing, and I found that if the compressor run with 25%load than the oil will be less and less, and since it comes to 50% and 75% the oil is return back. but the worst is when the compressor run with very low pressure (pump down time) the oil really disappear from the compressor.

    I also have some question,
    1. There is one oil level switch as optional from Bitzer, if it's installed, will it solve the problem of damage of the bearing?
    2. Understand this compressor has internal oil separator, why is it not working as well?
    3. Peter, can you tell me what is your oil type and viscosity, I'm trying to compare with my chiller that we used POE68.

    Hopefully it's not too late for discussing.

    Besrgrds.

  39. #39
    Join Date
    Mar 2006
    Location
    Merate (LC) - Italy
    Age
    52
    Posts
    2,554
    Rep Power
    24

    Re: Bitzer CSH8561-125Y oil sight glass

    The oil switch does not solve the problem, only signals and stop the compressor when oil is low.
    Oil return is a problem of the system, not of the compressor. If the system traps the oil, it's a just a matter of time before the compressor runs dry, no matter what is the efficiency of the oil separator. Basically, your question n.2 is incorrect: it's not the separator not working well, but the piping is trapping the oil at low refrigerant flow rate. You need a double riser on the suction.

    Generally speaking, the oil viscosity of screw compressors is higher than recips, between 150 and 220cSt.

  40. #40
    Join Date
    Jun 2007
    Location
    South Africa
    Age
    66
    Posts
    120
    Rep Power
    17

    Re: Bitzer CSH8561-125Y oil sight glass

    I am late in this discussion. Running a system with 4 Bitzer 140hp screws. Had the same problems with motor burn outs. Contactors are properly sized. Happened always to the 2 closest compressors to the substation.

    Eventually found blown capacitors on the power factor correction. After fixing that, no problems.

    Oil in the sightglass will come and go, depending on capacity steps and we only had oil problems on start up, 3 years ago. Suction accumulator could not bring oil back. Install a pulsing solenoid valve operated return line into the suction line to bring oil back from the accumulator.

  41. #41
    ahmadwahidi's Avatar
    ahmadwahidi Guest

    Re: Bitzer CSH8561-125Y oil sight glass

    hi all
    i have bitzer screw type CSH 7551-70 used ***** R22
    can i used 4GS oil ?

Similar Threads

  1. Odd view in a sight glass
    By dkemper in forum Trouble Shooting
    Replies: 16
    Last Post: 16-06-2010, 12:10 PM
  2. Leaking sight Glass!?!!
    By The MG Pony in forum Fundamentals
    Replies: 10
    Last Post: 19-04-2007, 06:09 AM
  3. liquid line sight glass mystery
    By austech in forum Technical Discussions
    Replies: 19
    Last Post: 18-07-2006, 08:16 PM
  4. Sight glass , Flashing ?
    By kfjoe in forum Fundamentals
    Replies: 15
    Last Post: 14-02-2004, 05:41 AM
  5. Sight Glass Located
    By Abe in forum Trouble Shooting
    Replies: 3
    Last Post: 22-01-2002, 02:22 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •