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  1. #1
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    Question refrigerated drinking fountain


    Hello,
    I have been trying to fine tune a refrigerated 8 gph drinking fountain to meet the ARI standard and increase efficiency. The compressor specs are
    R134a
    Capacity
    W 7% 843
    kcal/h 7% 725
    Btu/h 7% 2883
    The Evap coil is a coil on coil tankless type and has proven it can meet the capacity requirements for ARI with 4.25 oz charge. The standard calls for 8gph at these conditions Ambient 90 water inlet 80 water outlet 50. The HS pressure is the issue 240-280 psi. I thought it could have non condensables or moisture so I revacuated for 4 hrs down to 125 microns, it held. Ran it again, no change in the pressure. Thought maybe there was restriction at the expansion point (drier cap tube type) so I changed both, reevacuated successfully, recharged, ran it and still no change in the pressure. It was suggested to cut the cap tube length 6" and try again. Went through all steps again and re ran still no change. Cut six more 6" off at the request of my boss. Still no change in pressure but the flow dropped down to 6 gph. The system temps and subcooling and superheat all seem good, but he keeps saying the pressure is to high. I can not get why it is to high out of him. Can it be the compressor is low quality and just doesn't perform like a danfoss (our standard compressor)?I am suspicious that the vacuum pump is not working as it should. Can there still be moisture in the system even after a 4 hr evac to 125 microns? Could it be the wrong oil type for the pump? Is it ok to liquid charge at the compressor service port? I am no expert and my boss is not either but thinks he knows everything which makes it pretty hard to tune this unit. Any advice would be appreciated.





  2. #2
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    Re: refrigerated drinking fountain

    You have not given enough detail.
    But yes your discharge pressure does seem high.
    Reduce your refrigeration charge, as a starting point

  3. #3
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    Question Re: refrigerated drinking fountain

    What further details are needed? I would be happy to post them.

  4. #4
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    Re: refrigerated drinking fountain

    Please also try to use standard text formatting, I find your post hard to read.

    Mind you, it could be my age.
    Brian - Torquay, Devon, UK
    I have to stop saying "how stupid can you be?" to my co-workers.
    They're starting to take it as a challenge...

    BASIC MAINTENANCE. If it doesn't move and it should then use WD40. If it moves but it shouldn't then use Duct Tape.

  5. #5
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    Re: refrigerated drinking fountain

    Quote Originally Posted by regigoz View Post
    What further details are needed? I would be happy to post them.
    Discharge pressure, discharge temp
    Liquid pressure, liquid temp
    Pressure at evap inlet, temp at evap inlet
    Pressure at evap outlet, temp at evap outlet
    Pressure at comp inlet, temp at comp inlet
    How does the water flow?
    How is the condenser cooled (with a fan or static)
    In metric would be nice!!!

  6. #6
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    Re: refrigerated drinking fountain

    Here is the additional information. The locations listed below are thermocoupled and the thermocouples are connected to a data logger. The pressure readings are guage readings and their locations are: LS on comp suction line 6" before compressor, HS in btwn comp out and cond in approx 6" from the compressor. The water supply is connected to the top of the evap coil out through the bottom to a push button valve, then out to the bubbler(outlet) The refrigeration goes from the fan cooled condenser, through the drier, then cap tube to the bottom of the evap coil and out to the the top of the evap coil to the compressor. The evap coil is a coil on coil type in a helix, there is no tank to store water.
    The copper tubing is 1/2" od(12.7mm) for the water and 5/16"(7.5mm) for the refrigeration(only on the coil) The rest of the refrigeration tubing is 1/4"(6.35mm).
    BUBBLER OUTLETAMBIENTINLET SUPPLYCOMP INCOMP OUTEVAP INEVAP OUTCOND INCOND OUTDRIERCAP TUBECOMP CASE
    FFFFFFFFFFFF
    50/ 1091/ 32.779/ 26.157/ 13.8178/81.147/8.351/10.5154/67.7138/58.8139/59.4136/57.7141/60.5

    12 inches removed from cap tubeCap Tube: .042 id 4 ft long including drier
    Flow: 6.73 gphCHARGE: 4.25 OZFan Motor: 5W
    HIGH SIDE PRESS 250 PSI/17.5 kilogramcm2COMPRESSOR: TatungFan blade: 30" pitch
    LOW SIDE PRESSURE:35 psi/2.4kgcm2 5.22 A
    WATER LINE PRESSURE: 35 PSI122 V
    These test results were after cutting 12" (304mm) off the cap tube to reduce the head pressure, but the only thing that was reduced was the water flow(was at 8.47 gph(32.06lph) with a 280psi(19.68kgcm2) head pressure). This compressor we are testing is in three different units and the high head pressure is showing on all three. I'm at a loss on how to get the pressure down without losing anything else. Tried using less charge 4 oz, 4.25 oz, but then I lose the 50F-55F evap out, the 70-90F comp in, and the 130F condenser out. The water flow output changes as well.

  7. #7
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    Re: refrigerated drinking fountain

    without actually feeling the unit (which is very important), the data given indicates that the condenser is to small or not enough airflow or airflow is re-cycling

  8. #8
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    Re: refrigerated drinking fountain

    Reason
    little subcooling (showing condenser is not flooded)
    Little superheat showing that the evap is flooded with liquid.
    High suction pressure.
    Do you have a cowl around the condenser fan (air flow problem)

  9. #9
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    Re: refrigerated drinking fountain

    I suspected the air flow to be insufficient. I am going to try a better fan.

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