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Thread: HG bypass

  1. #14
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    Jul 2012
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    Correction if suction pressure is above 58 with solenoid disconnected then check your HGB regulator. Should only bypass when suction drops below pilot setting, usually around 58 on R22. With heavy or full load suction should be well above that and no bypass should take place.

  2. #15
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    Apr 2012
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    Quote Originally Posted by wadesquad View Post
    those are all great responses,

    first of all this is a retrofit newer condenser on an old evap and old controls

    the hg solinoid is energized at the same time as the LL solinoid so it is hot gas all the time but i uses the regulator as a load control.

    they make bread so on some days they use more ice water than other days (more or less mixers) so when all the mixers are on the load is high and the relulator is only alowing a small amout of HG to pass. on other days there are less mixers so more HG is needed.

    there is an estimated 200 feet from condenser to evap. the HG solinoid is @ the evap. my question is : if i control that solinoid with a pressure switch. on days that the HG is not really needed will there be 200 feet of condesed HG liquid that will slug and hammer the pipe as the solinoid opens and closes?

    im sure i am over thinking this but i want to be sure.

    thanx for all the replys
    That solenoid and HGBP pass should be on the Condensor side not at the evaporator.

    All you're going to get is hot gas up to the solenoid valve and then suction at the leaving side of the HGBP regulator.

  3. #16
    Join Date
    Aug 2006
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    Quote Originally Posted by wadesquad View Post
    ...there is an estimated 200 feet from condenser to evap. the HG solinoid is @ the evap. ...
    like i said, HGBV sizing and placement are very important...how is the insulation (not that it really matters now)?

    is the evap below or above the condenser? i don't remember reading that.
    It's tube brushing season...93% done (39.35 miles of tubing)...only 1,242 tubes to go!

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  4. #17
    Join Date
    Mar 2011
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    North Carolina Piedmont Area
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    407

    Remote Evaporator Air-Cooled Liquid Chiller

    Are you saying that you have an an air cooled condenser with a remote DX evaporator/ water cooler with a line set of 200 ft. If this is the case than there are many other thing to consider.

    But first the load criteria needs to be established so that a properly designed system can be designed. This is more involved, than just simply replacing a condensing unit with the same Horse power or tonnage. The biggest issue which you will have is that there will be a pressure drop in your liquid line per every 100 feet of total developed length which must be calculated so as to properly maintain your sub-cooling in the liquid line and up to the TXV or metering device. You will need to consider raising your sub-cooling to at least 15 degrees to overcome the pressure loss in the system. This will be a major concern and if not address will lead to issues with improperly feeding the metering device. Remember that a TXV needs Liquid to meter refrigerant correctly, and with a loss in sub-cooling you are sure to have flash gas in the line and at the TXV. This is a topic which needs to be addressed all by it self.

    The liquid line will need to be sized correctly but not over sized to the point where you will loose the velocity of refrigerant. Remember that oil must be returned to the compressor at an equal rate which will require a velocity of no less than 240 FPM and not more than 400 FPM. You will need to verify velocity for your application.

    As for the hot gas by-pass which is installed with a Tee connection at the discharge line close to the compressor. It is also important that this line be sized correctly so as to maintain velocity. As for the connection to the evaporator it is usually connected with a distributor with a side inlet after the TXV. This is the most practical as the higher temperature in the evaporator will cause the TXV to open and de-superheat. It will be important to install the Hot gas solenoid at the evaporator so as to prevent a lower pressure in the developed length of pipe which will have a saturation temperature of usually around 34 degrees or less when at low capacity. Insulation is recommended for this reason.

    There are also times where you can install at outlet of evaporator and is some times used for certain applications.

    Sizing of the suction line is also very important and will need to be considered again to maintain minimum and maximum velocity of refrigerant for proper oil return.

    Location of evaporator also needs to be considered depending if it is located above or below condenser. Trapping of oil needs to be considered for vertical lift and sometimes requires the installation of a double suction riser. Which leads to the question of circuits in the system.

    This is a topic where there is not enough room to talk about here. But just some elementary things to consider.


    I will try to upload a piping sizing chart soon for your use.

    ________________________________________
    Understand the symptoms and you will find a solution

  5. #18
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    Quote Originally Posted by alcomech View Post
    ... It will be important to install the Hot gas solenoid at the evaporator so as to prevent a lower pressure in the developed length of pipe which will have a saturation temperature of usually around 34 degrees or less when at low capacity....
    this is not a good idea...the HGBP valve and solenoid should be mounted at the condensing unit. this minimizes the charge at all load levels. at 200 feet, other piping precautions need to be considered as well.
    It's tube brushing season...93% done (39.35 miles of tubing)...only 1,242 tubes to go!

    Original member of the Raccoon Brotherhood.

    EVERYTHING IS AWESOME!!!

  6. #19
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    North Carolina Piedmont Area
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    You are absolutely right Jayguy

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