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  1. #1
    Join Date
    Jun 2010
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    Many Places in the World
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    9

    Hmm York 50 Ton Package Unit

    I have 6 - 50 Ton York Package A/C units on a restaurant building in the dining area. The LP (low Pressure) cut out is at 55 psi and the HP (High Pressure) cut out is at 350. There's a control board that shuts the compressors off if the pressures are low or high. The units consists of four compressors, there are two compressors on each stage (1st and 2nd stage). The ambient temperature outside is 130F. The problem I having with the York Package units started last week when the temps exceed 110F last week. The evap, condenser and filters are clean. The evap and cond fan motor runs fine. Every package unit was going out on HP (High Pressure) all four compressors. The low side was 85 psi and high side was 400. Which is understandable. I lowered the pressures on the units to 60/310. The units ran fine for a couple hours until the next morning. When the weather cooled to about 90F, The control board kicked off the compressors on LP (Low Pressure). The LP cut off switch is at 55 psi. I charged the units just a little to 65/325. The units ran fine till about mid-day when temps soared to 130F. On some units, the compressor kicked off on LP on one stage and HP on the other stage. I disconnected the comp from the contactor and adjusted the pressures for each compressor. After all four compressors were running the correct pressures, I reconnect all compressors and started the package unit. (Yes, this took forever because this was happening to all 6 package units.) After precisely adjusting the pressures on each compressor, The same thing happens again, the unit runs fine for a day or two and then shuts down again on either high or low pressures. Not all the compressors are shutting down, at times when I check the unit, there's one comp out on HP, so 3 are running. The building is constantly blazing hot. Today the building was 104F during lunch and 108F shortly after the lunch period ended. I checked the units again, one units had 3 compressors running but my return temp was 104F and supply temp was 102F. On another unit, the return temp was 89F with a supply temp of 102F (2 comp running, 1 out on HP and 1 bad comp and no the supply/return numbers are not switched). Another unit supply temp was 103F return with a 99F supply temp (all 4 comp running). Another unit, 100F supply and 101F return with 3 compressors. I cannot find a medium pressure for these units to continuously run in the heat without it constantly shutting down. One day the comp will be out on LP and the next day it's out on HP, this happens even if I leave the unit off and restart it even it's cooler without adding any refrigerant. I am beginning to think that the units are unable to the 130F heat. With hat being said the hottest time of the year isn't even here yet. The units are new, Installed about 5 months ago and ran with no problems until last week when the outdoor temps soared. I am aware that I could jump out the pressure switches but that would void any warranty. Some advice would help other that dredging a river through the compressor to keep them cool. heh. Thanks

  2. #2
    Join Date
    Jul 2004
    Location
    Maryland
    Posts
    333
    If the units are still under warranty ,I wouldnt be making any adjustments to the refrigeration or controls. I would have the installing company back out. Sounds like you may have a YPAL unit. Post model number if you can. Verify you OA dampers are closed or at minimum . Also verify the unit isnt heating as well as trying to cool.

  3. #3
    Join Date
    Feb 2010
    Location
    MEXICO
    Posts
    466
    with respect to the low pressure you could say that this hurt your low pressure switch cut is factory adjusted 22psig, high-wing pressure over the temperature outside is very alta.una asks you what type of refrigerant R-22 or R410 -A?

  4. #4
    Join Date
    Oct 2001
    Posts
    6,945
    where are you and these temps..are the units on top of each other on the roof..i would remove freon from each circuit till you see slight bubbles in the sightglasses then let them sit and see how thosae heads are.your saying you adjusted the pressures is that what you call pulling freon out..if you have 2 compressors per freon circuit stages as you call it there should only be one HP/LP for stage not per compressor...why is it so hot in the space that hi return temp isn't helping cooling the compressors..this stuff 3 phase condenser fans blowing up supply fan supplying god air compressors running the right directions....did you call the factory on the highest ambients allowed for these condensers
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  5. #5
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,055
    Sounds like a call to your installing contractor and YORK is in order, if these are only 5 months old.

    With a high pressure setting at 350psi and your ambient temp at 130 degrees it just wont work.

    Where are you at in the world?

  6. #6
    Join Date
    Dec 2005
    Posts
    1,908
    He's done screwed up the charge on all 6 units. They are 50 tons each.
    If they ain't operate in the 130 degrees enviroment, then they ain't.
    What threw me off is the systems cutout on low pressure ????

    Take all freon out and weight them back in. If too hot day then use water sprinkler until engineer envolve to let you know they are design for this enviroment.

  7. #7
    Join Date
    Jan 2010
    Posts
    24
    1. Either weigh in the charge, or set to manufacturer recomended subcool (see IOM).
    2. Verify operation of OA dampers (minimum position, etc.).
    3. Verify that there are no smoke dampers, volume dampers, etc. that may be installed in the duct that could be in the closed position.
    4. Verify all CFM's are on, at full speed, and turning the correct direction.
    5. Once all of this is done, put sprinklers on the condensors to get you out of the pinch and keep you online.
    6. Contact YORK/JCI for proper factory authorized service. They will take care of most "equipment" issues under warranty. You'll be on your own for anything outside the unit. You or the installing contractor/engineer will be on your own if the units were not ordered properly.
    7. Recomend that the customer builds his next resturaunt someplace other than the planet Mercury! Just Kidding!

  8. #8
    Join Date
    Jan 2010
    Posts
    24
    Just one more thought, those pressure and temp cutouts sound about right for a 22 or 407c unit. You never stated what flavor of refrigerant your dealing with. Make sure your not running 410a with the wrong cutouts programmed.

    Also, if you've been pulling out refrigerant, and it is 407c or 410a, you better be pulling liquid. Otherwise there's no telling what you've pulled out, put back in etc. Due to the properties and chemical makeup of 407c and 410a!

  9. #9
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,055
    Quote Originally Posted by just_opinion View Post
    ,
    What threw me off is the systems cutout on low pressure ????

    .
    Same here.

  10. #10
    Join Date
    Feb 2010
    Location
    MEXICO
    Posts
    466
    All rooftop units such safety switches (lp, hp) are encapsulated no adjustment for the court, and s are two unpar circuitoon not compressor circuit, the switches for condenser fan cycling

  11. #11
    Join Date
    Jan 2010
    Posts
    24
    All rooftop units such safety switches (lp, hp) are encapsulated no adjustment for the court, and s are two unpar circuitoon not compressor circuit, the switches for condenser fan cycling

    If this is a YPAL unit, and it sounds like it is, it should have a transducer on the discharge line which monitors DP. That transducer has control over condensor fans and discharge pressure unloading. There is some programming that can be done to those controls on that unit. It depends on the MOD. I'm still not certain of the type of machine though???

  12. #12
    Join Date
    Jun 2010
    Location
    Many Places in the World
    Posts
    9

    Hmm RESPONE TO QUESTIONS!!

    Well, these package units are not located on the rooftop, these units are located on the ground. The 130F ambient temperature is high because of the location: Iraq. These 6 - 50 Ton units are on the dining facility. The York Package units are still under warranty by the installing company but the installing company is in Turkey. (York coming here is completely outta the question). They claim they will be arriving "next week" but I can't have the dining facility at 104F for a week. The units are R-22. The make-up air is completely closed off and there are no dampers installed in the system. (I cannot open the fresh air because of the outdoor temps). On this unit, there is a HP/LP cutoff for each compressor. That why when I adjusted the pressure in the unit, I must do it one compressor at a time or the control board will shut down the stage that goes out on HP/LP. The control board has a flash indicator that tells you which compressor has been cutoff and why. Example: 6 red flashes, HP2 - High pressure Compressor #2. The unit has two control boards one for each stage. One control board controls two compressors. The data plate says the max designed ambient temp is 125F. The units are manufactured in Saudi Arabia. The units were running fine till the temps soared and I never had to open the system (pressures), they were at manufacture. With a 85/400, obviously I am way overcharged. Here's the model number for one of the units. York 50T Package : DMS600C00B411DGJMRWZ11. I am need these units to hold at least till the installing contractor gets here.

  13. #13
    Join Date
    Jun 2010
    Location
    Many Places in the World
    Posts
    9

    Response to: Justopinion

    Sometimes we get equipment that was factory charged in Georgia, or any other place in the US. When that equipment arrives here in Iraq with the temps we have, they are automatically overcharged. Some equipment we get factory charged from the states on start-up runs 80+ LP and 375+ HP. That's just a fact that I have to deal with using equipment from the states. Although these units came from Saudi Arabia, these units are designed to deal with these temps. But if that was a true statement, I guess I wouldn't be having this problem.

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