Trane CVHE - Page 2
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Thread: Trane CVHE

  1. #14
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    Centrif Surge

    Everyone has had a go and noone is answering the question, so I will add my bit.
    What your seeing is the unit is being operated below it's minimum part load point for a given condenser temperature, typically the impellors are sized for the design condenser water temperature, at ARI conditions this is 85 F. ent. and 95 F. lvg. the minimum part load for this unit at these conditions could be as high as 20 - 30% depending on the condenser selection.
    If condenser relief is available i.e. for every 10% off loading the condenser water drops 1 deg. the unit will operate down to a lower level.
    The cause of this surge is due to the vanes being closed off and there is insufficient gass flow to overcome the condenser pressure which tries to go back thru the impellor into the evaporator which is at a lower pressure.
    I f you call your local Trane office and give them the unit model number they can give you the minimum part load at design conditions and also the igpl values which is for every 10% of off loading the condenser water drops 1 deg.
    IGPL is (Intigrated Part Load Value)
    If you cannot obtain condenser relief you need to put more load on the machine, which is not always possible in which case you should suggest a small chiller be installed for when the sysytem is below the minimum load.
    Hope this answers your question?

  2. #15
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    Obviously you did not read my last post fully I did say that by leading the first stage vanes the compressor can pull more gas creating more push to overcome the condenser pressure, therefore eliminating the low end surge .Also you can only do condenser water relief if you maintain the cooling load or the chiller will loose oil..?? you cant have cold tower water and no load the chiller will fall flat on its ass????

  3. #16
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    Quote Originally Posted by edward j View Post
    Everyone has had a go and noone is answering the question, so I will add my bit.
    What your seeing is the unit is being operated below it's minimum part load point for a given condenser temperature, typically the impellors are sized for the design condenser water temperature, at ARI conditions this is 85 F. ent. and 95 F. lvg. the minimum part load for this unit at these conditions could be as high as 20 - 30% depending on the condenser selection.
    If condenser relief is available i.e. for every 10% off loading the condenser water drops 1 deg. the unit will operate down to a lower level.
    The cause of this surge is due to the vanes being closed off and there is insufficient gass flow to overcome the condenser pressure which tries to go back thru the impellor into the evaporator which is at a lower pressure.
    I f you call your local Trane office and give them the unit model number they can give you the minimum part load at design conditions and also the igpl values which is for every 10% of off loading the condenser water drops 1 deg.
    IGPL is (Intigrated Part Load Value)
    If you cannot obtain condenser relief you need to put more load on the machine, which is not always possible in which case you should suggest a small chiller be installed for when the sysytem is below the minimum load.
    Hope this answers your question?
    Thanks for the reply. I found that the IGPL @ 82 F entering condenser water was 20 % load. I set the controls for min. 20% load to prevent the surge. I also have the controls contractor to drop tower set point from 82 to 75 to help at start up. The chillers have refrigerant pumps for motor cooling. You really hit it on the head with the vague question.

  4. #17
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    Centri surge

    Quote Originally Posted by graham View Post
    Obviously you did not read my last post fully I did say that by leading the first stage vanes the compressor can pull more gas creating more push to overcome the condenser pressure, therefore eliminating the low end surge .Also you can only do condenser water relief if you maintain the cooling load or the chiller will loose oil..?? you cant have cold tower water and no load the chiller will fall flat on its ass????
    Yes, I read all the posts and I answered because nobody answered the question, you miss the my point and if you go to Trane they will confirm my what I have mentioned.
    Leading the 2nd stage vane will only help get the compressor balanced during start up, (and this only applies to the older CVHB units) on the CVHE there is a problem during start up of reverse gas-flow? (which I will tell you about later, because it's a differant subject)
    If you calculate what I said you will under stand what I have pointed out and that is a given for all centrif manufacturers they state that their units can operate down to within 17 deg of the lvg c/w temp on the ent cond. water.
    So if you check the selection for any given unit you can find out what is the minimum part load point.
    NO argument but your solulution, it does not work because if you know about and how a centrif really works and how it is applied then you would not tell me to read your last post.
    If you lead the 1st stage you have a problem with the compressor motor over load and the design motor torque because not all motors can accept 100% torque, And further where will the gas from the first stage go? (during startup) I did not join this string to be objectionable my points are based sound engineering and design engineering for these units.
    You seem to be a lord on this site how ever I hope not too many people listen to you because there is no credability in you coments.
    My point was I explained what caused the problem and what was occuring inside the machine, and what was needed to resolve this situation.
    Your attitude is not really condusive to the industry as a know it all with no back up

  5. #18
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    Quote Originally Posted by edward j View Post
    Yes, I read all the posts and I answered because nobody answered the question, you miss the my point and if you go to Trane they will confirm my what I have mentioned.
    Leading the 2nd stage vane will only help get the compressor balanced during start up, (and this only applies to the older CVHB units) on the CVHE there is a problem during start up of reverse gas-flow? (which I will tell you about later, because it's a differant subject)
    If you calculate what I said you will under stand what I have pointed out and that is a given for all centrif manufacturers they state that their units can operate down to within 17 deg of the lvg c/w temp on the ent cond. water.
    So if you check the selection for any given unit you can find out what is the minimum part load point.
    NO argument but your solulution, it does not work because if you know about and how a centrif really works and how it is applied then you would not tell me to read your last post.
    If you lead the 1st stage you have a problem with the compressor motor over load and the design motor torque because not all motors can accept 100% torque, And further where will the gas from the first stage go? (during startup) I did not join this string to be objectionable my points are based sound engineering and design engineering for these units.
    You seem to be a lord on this site how ever I hope not too many people listen to you because there is no credability in you coments.
    My point was I explained what caused the problem and what was occuring inside the machine, and what was needed to resolve this situation.
    Your attitude is not really condusive to the industry as a know it all with no back up
    Could you explain futher about the 17 F. Is that ent. cond water -ent chilled water?

  6. #19
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    Your so called sound engineering may be well intentioned but I speak as a service tech with 28 yrs of trade experience and ten of those working for Trane . He asked how and what was low end surge and I tried to explain it a very simple way. I am by no means a "know it all' if I was I wouldnt be on here because I would already know everything ??? so get down of your engineering high horse and maybe when you have a few more posts and have read some of the other help that I have given on here that I know was of help then I may start to take what you say as correct.
    Ps I did not at any point tell him to lead the second stage vanes , it was the first stage and I only mentioned that to prove that the surge would go away due to the greater mass flow of gas through the impeller which would then overcome the condenser pressure.

  7. #20
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    Centrifs

    Quote Originally Posted by ej45 View Post
    Could you explain futher about the 17 F. Is that ent. cond water -ent chilled water?
    The 17 deg F. is pretty much the given point for the lvg c.w to the ent cond wtr before the unit will start to lose oil, the reason being is that the oil will migrate to the evaporator because there is not enougth pressure/temperature differential in side the machine/oil tank, and since the oil and refrigerant are mixed the oil is carried into the evap.
    Regards

  8. #21
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    Centrifs

    Quote Originally Posted by graham View Post
    Your so called sound engineering may be well intentioned but I speak as a service tech with 28 yrs of trade experience and ten of those working for Trane . He asked how and what was low end surge and I tried to explain it a very simple way. I am by no means a "know it all' if I was I wouldnt be on here because I would already know everything ??? so get down of your engineering high horse and maybe when you have a few more posts and have read some of the other help that I have given on here that I know was of help then I may start to take what you say as correct.
    Ps I did not at any point tell him to lead the second stage vanes , it was the first stage and I only mentioned that to prove that the surge would go away due to the greater mass flow of gas through the impeller which would then overcome the condenser pressure.
    I am not a service tech, (although I did start as one) I have been in the refrigeration industry for over 35 years, I have experience on all types of systems and a full knowledge of of every aspect of our industry. Weather it be absorption chillers or recips or ammonia or R 123, I have worked with OEMS and enjoy every minute of it
    I just love this industry the machines are great and the people you meet in it just add to the overal job satisfaction.
    Apologise and no offense ment, however your points are not valid, in the subject being discussed.
    Regards

  9. #22
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    The posts on here that I have contirbuted to are based on a "been there done that ,tried this tried that practical hands on experience" they are not based on sound engineering slide rule and abacus calculations. I have even had guys thank me for my no frills to the point heres what to do approach to fixing problems .I have been there and seen the problems talked about and do know what causes them, and know how to correct them from a service techs prospective,if I didnt I would probably not have lasted in the trade.????? Regards Graham

  10. #23
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    Quote Originally Posted by graham View Post
    Your so called sound engineering may be well intentioned but I speak as a service tech with 28 yrs of trade experience and ten of those working for Trane . He asked how and what was low end surge and I tried to explain it a very simple way. I am by no means a "know it all' if I was I wouldnt be on here because I would already know everything ??? so get down of your engineering high horse and maybe when you have a few more posts and have read some of the other help that I have given on here that I know was of help then I may start to take what you say as correct.
    .
    Ps I did not at any point tell him to lead the second stage vanes , it was the first stage and I only mentioned that to prove that the surge would go away due to the greater mass flow of gas through the impeller which would then overcome the condenser pressure

    My point was that I explained the effects of leading both the 1st and 3rd stage vane (2nd if it's a CVHB).
    Now question your logic what happens to the gas on start up if you lead the 1st stage vane? Right, now question the increase on the motor torque?
    Now, go to a unit and try to do what you are suggesting. IT'S not possible, there is NO adjustment unless you cut the rods?
    I think you you do not really know much about these units?

  11. #24
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    Mar 2004
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    Your trying to tell me there is no adjustment on a vane actuator rod on a centravac?????????????????????????? Put down your slide rule and abacus and go and look at a chiller !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  12. #25
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    graham, I don't reply to much on this site because of people like this. your answers are always on the money. You never mislead anyone. I've always set my trane chillers up the same way. Keep up the good answers. Could this be the new Chiller32?By the way 33 years in the trade.Don't get in a pi$$ing contest, it will take the fun out of it.

  13. #26
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    Quote Originally Posted by graham View Post
    The posts on here that I have contirbuted to are based on a "been there done that ,tried this tried that practical hands on experience" they are not based on sound engineering slide rule and abacus calculations. I have even had guys thank me for my no frills to the point heres what to do approach to fixing problems .I have been there and seen the problems talked about and do know what causes them, and know how to correct them from a service techs prospective,if I didnt I would probably not have lasted in the trade.????? Regards Graham

    Graham,
    I picked up this thread because as I mentioned no one had given an answer to the question that ej45 asked, nobody was able to explain the cause or what was happening inside the m/c, or how to prevent the problem.
    I answered him with sound engineering advice and he has responded that how I answered has given him an understanding of what is causing the problem and he is now in a situation where by he can solve it by adjusting the system to prevent it in the future.
    I'm not expecting any glory from my experience, i'm just offering my knowledge for someone who asked a simple question and got allot of vague answers.
    I appreciate your input however you did not offer a full explanation to ej45's question and you did not elaborate for him/her to understand where you were coming from?
    In fact if I were in a situation were-by I had to ask a question on this site I may think pretty hard in view of the criticle comments passed back, which is a shame because we all can help one an other which I think is the intention of this site.
    Regards

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