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  1. #27
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    Yeah, that looks like it was a pinch off bar used to isolate parts in small refer systems.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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  2. #28
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    Quote Originally Posted by timebuilder View Post
    Yeah, that looks like it was a pinch off bar used to isolate parts in small refer systems.
    Yep, you'll see a image of that in post #5 I think someone didn't like that subcooler.

  3. #29
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    Dam , another one where the o p is m I a !!!!

  4. #30
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    Quote Originally Posted by richper View Post
    Dam , another one where the o p is m I a !!!!
    I posted that picture this afternoon. How often do you want me to check in?


    Quote Originally Posted by richper View Post
    Also looks like the field replacement liquid line drier is way too small . You did say this was 20 tons ?
    Its 20 tons total, 2 circuits, not a 20 ton circuit. Thats a 30 CU drier. How much bigger does it need to be?


    Quote Originally Posted by VTP99 View Post
    Is that for the sub cooling circuit ?
    Yep,the plate heat exchanger is off the left side of the picture, mounted on the divider, over the drier. The main TXV is at the evaporator, and is far bigger, an 83VGA, or somewhere around that size.


  5. #31
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    I better explain.

    On screw and scroll, you have an interstage port, commonly known as an "economizer", in simple words, lets say half way through compression, there is a void that could be filled (for the purpose of understanding only), almost like a second compressor. At this stage of the compression cycle, the compression ratio is less, therefore more efficient. The econmiser can be used for a side load (at a SST higher that the original SST) It is quite normal to use this side load, for liquid sub cooling.
    Why sub cooling you are asking. The mass flow says the same but with increased sub cooling the amount of flash gas produced right after the expansion device decreases, (Vapour/liquid fraction) thus increasing the amount of liquid used for net refrigeration effect. External sub cooling is benefit on and above normal condensing.

  6. Likes parttimetech, CHAINIK liked this post
  7. #32
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    Quote Originally Posted by CHAINIK View Post
    I posted that picture this afternoon. How often do you want me to check in?



    Its 20 tons total, 2 circuits, not a 20 ton circuit. Thats a 30 CU drier. How much bigger does it need to be?



    Yep,the plate heat exchanger is off the left side of the picture, mounted on the divider, over the drier. The main TXV is at the evaporator, and is far bigger, an 83VGA, or somewhere around that size.
    Ok Take it easy . Please accept my apologies Sir . Would you explain the kink please ? Thanks !

  8. #33
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    Thread Starter
    Yes, everyone, the txv in question has been disabled with a pinchoff tool. I didn't do that, that's how I found it.


  9. #34
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    Quote Originally Posted by CHAINIK View Post
    This circuit has a replacement compressor, so I cant figure out if this was done by someone smarter than me, or dumber.
    It would be helpful if OP’s could verify that the compressor in this system is a two-stage and what temperature range the package unit is being used for.

    Here are a few select quotations from Copeland’s Technical Bulletin dated July 2005, Ref: D7.4.2/0205-0705/E, “Application and Operation of Two Stage Compressors” (not Carlyle, but should be similar):

    Caution: Never operate a two-stage compressor without the external intermediate pressure mixing line being in position otherwise there is no outlet for the high pressure gas discharged from the low-stage cylinders making an explosive situation.

    3. Liquid Sub-Cooler -- In order to increase the output and the efficiency of the system, a heat exchanger is used as liquid sub-cooler in two-stage compressors and installed between the expansion valve for the intermediate stage and the compressor intermediate pressure mixing line.

    4. Liquid Solenoid Valve -- In the liquid line to the intermediate stage, a solenoid valve must be installed directly before the expansion valve to prevent liquid flow during stand still periods. It is electrically connected in such a way that it is open when the motor runs and closed when the motor is off. A manual switch placed in the electric feed line the solenoid valve will facilitate service during pump down. A fine mesh filter also supplied must be installed in the liquid line to the expansion valve for the intermediate stage before the solenoid valve to protect both valves from impurities.

    7. Suction Line Accumulator -- In order to prevent damage to these compressors due to refrigerant and/or oil liquid slugging, especially in systems where there is the possibility of liquid or oil being returned to the compressor irregularly, the use of correspondingly dimensioned suction line accumulators is highly recommended. This is especially desirable in the case of two-stage compressors because the suction gas enters directly into the cylinder head. The motor housing, arranged ahead of the high pressure stage, is able to provide a certain separation function. This is only available in the interstage pressure area of two-stage compressors and as a result cannot be effective on the LP suction side. These accumulators must be designed in such a way that constant return of the gaseous refrigerant and oil is guaranteed.

    8. Suction Line Filter -- Suction line filters should be installed to prevent minute particles of scale, flux, sludge, dirt, copper filings, etc. from entering the compressor. The selection of the filter must be made very carefully as it creates pressure drop and thus output losses.

    9. Liquid Sight Glasses -- A liquid line sight glass is supplied and must be installed directly before the intermediate stage expansion valve (de-superheating expansion valve). This enables the liquid supply to be checked.

    My takeaway from this is that two stage compressors are very susceptible to damage from liquid flood back and system debris, and they may be damaged if they are used with the interstage port sealed off.

  10. #35
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    Thread Starter
    Here is the unit in question. My mistake, these were Danfoss. The first time I saw these, the compressors were virtually identical, but were Carlyle.



    The left is a single, and the right two are tandems, one of which is a burnout, which is what leads us to here.


    The compressor model number (for the single) is ECH087T4LC2 which doesn't show in any Danfoss literature. I suspect it's a Carrier-specific part number, due to the customer PN above the model number. So if anybody can find technical info on the Danfoss or Carrier sites, that'd be awesome.


    Quote Originally Posted by parttimetech View Post
    It would be helpful if OP’s could verify that the compressor in this system is a two-stage and what temperature range the package unit is being used for.

    It's just a regular AC unit. Comfort cooling. This is a grocery store, the other site is a clothing store.
    I want to make sure I'm on the same page as you here. You don't mean two-stage as if it had an unloader, right? You mean two-stage in the sense that one of the "inputs" is an intermediate stage of compression? That's what I took away from that, that's why I was digging for technical information on this compressor. Is that possible with a scroll compressor? I'm sure that information is available somewhere.


  11. #36
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    Quote Originally Posted by barbar View Post
    I better explain.

    On screw and scroll, you have an interstage port, commonly known as an "economizer", in simple words, lets say half way through compression, there is a void that could be filled (for the purpose of understanding only), almost like a second compressor. At this stage of the compression cycle, the compression ratio is less, therefore more efficient. The econmiser can be used for a side load (at a SST higher that the original SST) It is quite normal to use this side load, for liquid sub cooling.
    Why sub cooling you are asking. The mass flow says the same but with increased sub cooling the amount of flash gas produced right after the expansion device decreases, (Vapour/liquid fraction) thus increasing the amount of liquid used for net refrigeration effect. External sub cooling is benefit on and above normal condensing.
    Light bulb in head just went on. Thanks for powering it up.


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  13. #37
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    Quote Originally Posted by CHAINIK View Post
    You mean two-stage in the sense that one of the "inputs" is an intermediate stage of compression?
    That is close to what I meant. Since your last post it looks to me that BARBAR nailed it and I was slightly on the wrong track.

    It appears to me that you have the Danfoss version a single stage scroll compressor with an interstage vapor injection port similar to the Emerson setup described in this technical bulletin here:

    http://www.emersonclimate.com/europe...for%20HP_0.pdf

    The benefit of this arrangement is increased compressor capacity and efficiency due to the interstage cooling (I believe the reason for this is the heat of compression is tempered by the interstage cooling, lowering head pressure and temperature at a given capacity).

    Sorry to say that I have not yet had any first hand experience with this particular setup.

  14. #38
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    @OP:

    Incidentally, which one of the tandems is the burnout, the lead or lag compressor?

    I am also curious if you identified the underlying cause of the burnout and if you plan to replace just the burnout and replace only the oil on the working tandem compressor or if you will be replacing both tandems?
    Last edited by parttimetech; 02-17-2017 at 01:03 PM.

  15. #39
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    Quote Originally Posted by parttimetech View Post
    @OP:

    Incidentally, which one of the tandems is the burnout, the lead or lag compressor?

    I am also curious if you identified the underlying cause of the burnout and if you plan to replace just the burnout and replace only the oil on the working tandem compressor or if you will be replacing both tandems?
    I've always been told never to replace a single scroll compressor in a tandem set. Not because it's wrong, necessarily, it's just that every time I source a compressor using the UNIT info rather than the COMPRESSOR info, if it's tandem, the distributor sells it as a tandem set, common piping and everything. I don't claim to know the true reason, but it's the only way they will warranty them. My guess is to remove the human element of replacing just one, and/or repiping incorrectly.

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