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  1. #1
    Join Date
    Jan 2006
    Location
    n.e.illinois
    Posts
    81

    19DH oil presure

    Im having a problem with two vintage 1980 19DH chillers, on a cold start after about 3 minutes run time I loose oil presure, the sump foams up the oil pump cavitates & makes all kinds of racket,this lasts about 30 to 45 seconds,then things slowly come back to normal. oil temp at start up 140,oil cooler maintains 140, someone along the line installed time delays that wont allow the machine to load up for 20 minutes trying to get past the oil presure problem, but the're redundent to the vane close switch that drives them closed on loss of oil presure. i was considering installing a timer that would run the oil pump for 60 seconds or so every few hours during shut down to hopfully keep the oil warm enough to keep the refrigerant out,but am reluctant for fear of eventually emptying the oil sump.any help or sugestions will be apprieciated,al o

  2. #2
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Quote Originally Posted by al o View Post
    ...hopfully keep the oil warm enough to keep the refrigerant out....
    Refrgerant in the oil is bad but it sounds like you like the chiller barrel may be full of liquid (accumulating in the off cycle) and giving you a severe initial floodback. This can happen if the TXVs do not shut down tight at off-cycle pressures (above 100# for R-22)

    Also make sure the running superheat is high enough to keep the oil hot during normal operation. (Flooding is bad.)

    I don't know what these particular chillers are. Does each system have a "pump down" or "pump out" cycle as it shuts down? (Temperature closes a liquid line solioid and the compressor continues to run until it cycles of on low pressure.)
    Lynn
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  3. #3
    Join Date
    Mar 2004
    Location
    North Carolina
    Posts
    400
    No pumpout no pumpdown no TXV's 19DH is a centrifugal .
    is this really happening or not

  4. #4
    Join Date
    Feb 2003
    Location
    Wichita Ks
    Posts
    1,463
    is the oil cooler using chill water? or any other water that may be cool to cold? if so is the solenoid valve stuck open? is the oil level correct? also check the accuracy of the oil sump thermometer. as far as running the oil pump every once in a while should not hurt anything. if i start up one that has been off a while i will sometimes run the oil pump to warm up the rest of the oil manually. also if you do run the pump by it self it will probally power the oil cooler solenoid valve and start cooling the oil if water flow is available. be aware of it or you will make it worse.

  5. #5
    Join Date
    Mar 2004
    Location
    eastern north carolina
    Posts
    80

    19dh oil pressure

    cut a thin steel plate the same size as the plate on the compressor end of
    the vent line, put a gasket on both sides, cut a 5/8 hole in the center of the plate, works every time.

  6. #6
    Join Date
    Dec 2004
    Location
    Chicago area
    Posts
    1,439
    Quote Originally Posted by al o View Post
    Im having a problem with two vintage 1980 19DH chillers, on a cold start after about 3 minutes run time I loose oil presure, the sump foams up the oil pump cavitates & makes all kinds of racket,this lasts about 30 to 45 seconds,then things slowly come back to normal. oil temp at start up 140,oil cooler maintains 140, someone along the line installed time delays that wont allow the machine to load up for 20 minutes trying to get past the oil presure problem, but the're redundent to the vane close switch that drives them closed on loss of oil presure. i was considering installing a timer that would run the oil pump for 60 seconds or so every few hours during shut down to hopfully keep the oil warm enough to keep the refrigerant out,but am reluctant for fear of eventually emptying the oil sump.any help or sugestions will be apprieciated,al o
    Why are you starting the machine with cold oil in the sump? Maybe you heaters are bad? Your'e oil eductor off the evap may be to far closed, a 1/4 turn on the angle stop (if available) should be sufficient. if the oil goes away on start, then most likely place is in the evaporator, and traped at the bottom of the impellar valute, those lines must be clear for oil to return.

  7. #7
    Join Date
    Jan 2005
    Posts
    604
    Cold start, with warm chilled water and cold condenser water, creates a situation where the chiller will behave like it's short of refrigerant. This causes low evap. pressure that will cause oil to foam on loading up. Check the demistor and make sure it's good.
    I'm not going to give you any more info than that. Except floats are a metering device and require a certain pressure drop to work properly.
    Make sure charge is good, then try to avoid cold condenser water.

  8. #8
    Join Date
    Mar 2004
    Location
    Windsor ON Canada
    Posts
    403
    As you are aware the oil heater only maintains temperature in the compressor cavity. The remaining oil sitting in the oil pump-filter cavity has its temperature drop to ambient when shut down. When the oil pump starts you get the mixing of cooler oil with warmer oil and some flashing of refrigerant which is what you are seeing with the foaming. Running the oil pump periodically during the off cycle may help. Before I tried this however, I would replace the entire oil charge in the chiller. Some oils are more prone to foaming than others....during my tenure at Carrier I used a product from shell callled Tellus 68 in all my 19D series chillers. This oil while not eliminating the oil foaming did reduce it to the point where nuisance oil pressure tripouts on startup were eliminated. The foam eliminator in the compressor which is accessible thru the inspection cover should also be inspected to ensure its integrity. Later version 19D series chillers with the 3200MP control had a built in algorithm to allow the vanes to open very slowly to eliminate this problem. Good luck and let us know what you find.

  9. #9
    Join Date
    Jan 2006
    Location
    n.e.illinois
    Posts
    81
    turbo vac I think you hit the nail on the head ! also the machine is not started with cold oil oil cooler is chilled water from this machine only no external or other source, I think its carriers oil in it or possibly Mobil dte 68 thanks for your help alo

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