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  1. #1
    Join Date
    Sep 2012
    Location
    USA!!
    Posts
    52

    cvhf non-cond. check

    I learned that the right way to check for non cond. on a cvh machine is to put a gauge on the machine and compare the gauge pressure to the saturated condenser refrigerant temperature converted to pressure. If it matches up I should be ok.
    I had a machine that had a purge min. count that was up 57 min from 2 months ago. I put my gauge on and I was actually in a deeper vacuum than what the pt chart said I should be. This is with the machine off of course. The only thin I can think of is that maybe the sat. refrigerant temperature sensor might be a little off? When the machine turned off, my sat. ref. temp. went from 84 when running to 45 then up to 60. I had my gauge on the sampling line on the top of the condenser going into the purge. does this sound right? my gauge reading was 12" standing pressure. does this sound right? If I had non-cond in the system, would my readings be more positive pressure than the pt chart said I should be or can it be in a deeper vac? I'm thinking it should be in a higher pressure I would assume.

  2. #2
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,145
    With the chiller off, use the saturated evaporator refrigerant temperature sensor for comparison to the chiller pressure. What you saw was , after shutting down, the entire chiller equalizes to one pressure. There is no liquid line solenoid valve or check valves to isolate any of the components. So the liquid refrigerant in the condenser drains, and flashes off, to the colder evaporator. That was the initial large drop in condenser temperature that you saw. Meanwhile the evaporator is no longer doing any work, so it slowly warms up. That is the reason for the slow climb that came later. The easy way to check for noncondensibles on that chiller, while it's off, is to look at evaporator pressure first. The panel reads the temperature and converts it to what the saturation pressure is. In other words, it does the conversion for you. Now, this is what the chiller pressure should be, for that temperature. Now compare that to the oil tank pressure. Why oil tank and not condenser? The condenser pressure transducer is an option that your machine may or may not have. The oil tank pressure transducer is standard on all of them. With noncondensibles present, a temperature converted to pressure will be incorrect. I make it a habit to always compare evap pressure and oil tank pressure whenever I walk up to one of these. It's quick and easy, and reveals important info.

  3. #3
    Join Date
    Sep 2012
    Location
    USA!!
    Posts
    52
    THANKS NUCLRCHILLER!!

    This time I KNOW its your help!!! LOL!!

    Is there a way to check it with the chiller running? I was thinking approach, but it seems like non cond. would mimic fouled tubes in every way except delta t which would make it harder to prove than say with the chiller off using pt chart.

  4. #4
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,145
    When the chiller is running is the time to use saturated condenser refrigerant temperature, converted to pressure using a p/t chart, and compare that to actual condenser pressure, using a gauge to measure it. If your chiller has a pressure transducer for condenser pressure, then using that is probably sufficient for day to day use. But if there is any doubt, or you just want to be sure, then use a dependable gauge.

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