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  1. #14
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    Jan 2013
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    The problem for the compressor with backspin is that it can wash metallic and copper debris from the oil separator back into the rotors and lock up the compressor, you can fit a standard Danfoss check valve between the oil separator outlet and condenser inlet to stop back spin


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  2. #15
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    Feb 2008
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    Thread Starter
    Quote Originally Posted by raptyr View Post
    The problem for the compressor with backspin is that it can wash metallic and copper debris from the oil separator back into the rotors and lock up the compressor, you can fit a standard Danfoss check valve between the oil separator outlet and condenser inlet to stop back spin


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    what will be the york's recommendation on this? if the chiller is new, the new compressor's warranty will be voided if they found any additional on discharge pipe. i was told by a hvac senior guy that york purposefully omitted the check valve due to compressor's operation by VSD. he cannot say the logic behind that.

  3. #16
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    Jan 2013
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    They did not fit based on cost and effect on efficiency but thats about 0.5% and its no good having an efficient broken compressor due to debris from the oil separator


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  4. #17
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    Nov 2011
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    Quote Originally Posted by moideen View Post
    what will be the york's recommendation on this? if the chiller is new, the new compressor's warranty will be voided if they found any additional on discharge pipe. i was told by a hvac senior guy that york purposefully omitted the check valve due to compressor's operation by VSD. he cannot say the logic behind that.
    the logic is that the compressor is on speed drive, and ramps down to minimum HZ before shutdown, therefor, backspin is minimal compared to a unit that shuts the compressor off while running full speed (higher pressure differential).

    If the factory engineers say that it isn't problem, don't make it one.

  5. #18
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    Jan 2013
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    United Kingdom
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    The initial minimum speed was 50hz and although thereafter the compressor does ramp down to 0hz in an electronically soft stop way, but this is not really a mechanical or refrigerant related soft stop , it is a slow ramp down in electronic terms where milliseconds can be a long time , so they have introduced soft stop software that does ramp the compressor down in a controlled manner to minimise the back-spin under normal stopping conditions . I dont really know where the thread is going though


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  6. #19
    Join Date
    Feb 2008
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    Dubai
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    Thread Starter
    the check valve was avoided so as to improve energy efficiency. then, how much or percentage could be saved?

  7. #20
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    Jan 2013
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    United Kingdom
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    cost and efficiency are improved without the check valve but reliability isn't , effect on efficiency in not much in my opinion , 1% but that can be a lot if you are a marketing or sales person rather than e tech stood in front of a chiller wailing and then breaking down. You can easily get the 1% back keeping your condenser coils clean and operating the chiller in an efficient manner and with regular maintenance and leak tests.

  8. #21
    Join Date
    Sep 2007
    Location
    Ohio
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    The backspin like everyone else has said is minimal when unloaded. The problem could arise if personnel shut the machine off by the rocker switch at given speeds over time.

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