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  1. #1
    Join Date
    Mar 2005
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    Cleveland, Ohio
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    11

    York YCAS amperage question

    York chiller

    M/N YCAS0440EC46YGABT
    S/N RCNM007835

    All modules are using the 2ACE motor protector module. This is a wye/delta start system. All tests were done with all compressors loaded to step 75.

    I have had problems with the compressors overloading and kicking out the disconnect/breaker for the individual circuit. None of the amperage readings on the microprocessor match amprobe readings. I have verified the amprobe readings with a number of other amprobes to take that out of the equation. The micro reads between 22 and 50 amps lower than the actual amp draw. This is happening on 2 machines, all 8 circuits. The micro is programmed for the exact RLA per compressor. I was forced to reprogram the unload point to 85% in order to keep the RLA in line.

    Does anyone know if there is a way to calibrate the amp draw on the microprocessor. All the inputs are into the IO board #1. I have checked the inputs voltages to the IO board and have about 11.8 volts to it. I was not real hot on how they supplied voltage to the board, running 120V to a 240V transformer primary, therefore getting 12 volts out a 24 volt secondary so I tried a 120V/10V supply but nothing changed.

    Any help would be appreciated.

  2. #2
    Join Date
    Aug 2000
    Location
    Austell, Ga.
    Posts
    1,296
    I trust that you are aware on a wye-delta motor reading the motor lead current requires some math to obtain the correct amp reading. I trust that you are reading the "Line Side" current to get the "Full" compressor current of ph1-2-3...
    Lastly..the use of a 230/24v transformer fed with 115v to obtain the 12v is used to protect everything from an errant EMS overcurent frying any of the York boards. The term used is "Impedance-Protected", as the undersaturated transformer can now not put out enough current to fry anything worthwhile.
    Ain't "None" of us as smart as "All" of us..

  3. #3
    Join Date
    Mar 2005
    Location
    Cleveland, Ohio
    Posts
    11
    Thank you Richard for your reply.

    I am reading the amperage directly off the disconnect feeding the starters. I am not taking the reading off the contactors. I am then deducting the amperage for the condenser fan motors.

    Even after 34 years in the field, I have much to learn and I am happy your pointed out the reason for the 240/24 transformer. I attended a YCAV school in Dallas last year, but apparently didn't retain that fact if it was presented.

  4. #4
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,490
    i have run into the exact same problem, but without the tripping. a YCAS that i started taking care of recently has an amp draw significantly higher than displayed. so far so good, but i am always waiting for the phone call that it is tripping. programming is accurate. almost everything else is displaying perfectly. i even measured the DC voltage going to the board and performed the math which came within 4 amps of the measured voltage but the display was 16 amps LOWER.

    here is the thread that i had and the responses...http://hvac-talk.com/vbb/showthread.php?t=670141

    i still don't have a good answer.
    "If you pull one more stunt like you just pulled with Tommy, you won't have to get on a plane because I will personally kick your ass from here to Korea!" - Best of the Best

  5. #5
    Join Date
    Aug 2006
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    Mixing oil and fire with a big spoon.
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    Quote Originally Posted by RichardL View Post
    I trust that you are aware on a wye-delta motor reading the motor lead current requires some math to obtain the correct amp reading...
    what??
    "If you pull one more stunt like you just pulled with Tommy, you won't have to get on a plane because I will personally kick your ass from here to Korea!" - Best of the Best

  6. #6
    Join Date
    Aug 2000
    Location
    Austell, Ga.
    Posts
    1,296
    Quote Originally Posted by jayguy View Post
    what??
    On a Wye/Delta connected motor that is running in the Delta condition, reading either the terminals 1,2 or 3 (or 4,5,6)will "Not" give you 50% of the motor current but would be 58% of of the total Ph1,2 or3 motor current.
    To me that requires some computating..wit' da' calculator built into me cell phone.

    Is computating a word anyway???
    Ain't "None" of us as smart as "All" of us..

  7. #7
    Join Date
    Aug 2000
    Location
    Austell, Ga.
    Posts
    1,296
    The actual formula for obtaining the actual "Line" current on a Wye/Delta motor running in Delta is 1/1.732, of any of the six motor leads.Which closely resembles 58%, but not precisely, but close enuff fer' cotton country.
    Ain't "None" of us as smart as "All" of us..

  8. #8
    Join Date
    Dec 2008
    Location
    Dixiana, AL
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    2,611
    Or you can just read T1/T6, T2/T4, & T3/T5, depending.......


    I think computate is a good word - it means "to compute". Sort of like agitate means "to agit". The art of conjuring up new words can also be a real good indication of one's rednekkidness....

  9. #9
    Join Date
    Aug 2006
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    Mixing oil and fire with a big spoon.
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    Quote Originally Posted by RichardL View Post
    On a Wye/Delta connected motor that is running in the Delta condition, reading either the terminals 1,2 or 3 (or 4,5,6)will "Not" give you 50% of the motor current but would be 58% of of the total Ph1,2 or3 motor current...
    oh, ok. i see what you mean.

    i find reading both lines or the incoming power to be easier and no math required!
    "If you pull one more stunt like you just pulled with Tommy, you won't have to get on a plane because I will personally kick your ass from here to Korea!" - Best of the Best

  10. #10
    Join Date
    Feb 2009
    Location
    good old Europe
    Posts
    160
    Across the YCAS range are two different compressor motor current measurement strategies fitted. One with both wires per phase run through the ct module and one with just one wire per phase. This is with regards to the limited sensing range of the module (max 225A). The calibration of the measured amps (0 to 5 VDC signal), is achieved by the programed full load amps and the motor protector input signal setting. Both values have to be set right to achieve a maximum deviation of about 10A. You can use the motor protector input value to fine tune the reading in the display and allign it with my clamp meter. The correct settings are within the IOM! So as always: RTFM
    "Quality exists, when the price is long forgotten."

    Henry Royce

  11. #11
    Join Date
    Aug 2006
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    Quote Originally Posted by Entropie View Post
    ... RTFM...
    i tried reading that as 'rolling on the floor...something or other'....then i got it!

    it has to do with the IOM doesn't it?
    "If you pull one more stunt like you just pulled with Tommy, you won't have to get on a plane because I will personally kick your ass from here to Korea!" - Best of the Best

  12. #12
    Join Date
    Feb 2009
    Location
    good old Europe
    Posts
    160
    You are right! RTFM is totally underestimated today. There are basically two possibilites to translate RTFM. The g-rated and the x-rated version. The g-rated version means: read the fine manual.
    "Quality exists, when the price is long forgotten."

    Henry Royce

  13. #13
    Join Date
    Mar 2005
    Location
    Cleveland, Ohio
    Posts
    11
    Thanks to all for your input with my problem.

    This morning I ran each compressor to step 75, then obtained an accurate amp draw with a meter. I then adjusted the voltage in the motor protector settings until the readings were within 2 amps of the clamp readings. I rechecked the system later with all four compressors running at partial load and found the readings still to be accurate.

    Kudos to all

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