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  1. #1
    Join Date
    Dec 2004
    Location
    Raleigh
    Posts
    126

    EXV problems on Carrier 30GT Chiller

    I am the third tech put on this chiller 30GT 130. Problem is that Circuit B shuts off on High Superheat, then sometimes Low Superheat, and occasionally low oil. All sensors are good. Their are two new compressors on Circuit B, New EXV, new chiller barrell. It seems as if the EXV does the opposite that it should. The previous tech told me that the EXV wire colors changed on the new EXV (brown and white??). Going back on Tuesday to run through the Carrier EXV troubleshooting guide. Any further suggestions. I am the junior guy in our shop, would like to find the solution to his growing headache.

  2. #2
    Join Date
    Aug 2002
    Location
    Greenville SC
    Posts
    430
    Trace out your sensor wires and make sure the A's go to the A circuit, and the B's go to the B circuit.

  3. #3
    Join Date
    Dec 2004
    Location
    Raleigh
    Posts
    126
    Thanks chillirig. I helped do that once, but that was before the chiller barrell was replaced--could have been swapped..

    Note: I am able to see what the sensors are seeing with my DC volt meter and a chart. The unit will run for five minutes under high or low superheat conditions before shuting down. When it goes out on high superheat, the EXV actually closes completely and the compressor pulls into a vaccum.

    This is a chore, but I have the software to plug into the board, just waiting on the Model 65 converter.

  4. #4
    Join Date
    Mar 2004
    Location
    North Carolina
    Posts
    400
    First make sure the exv is the correct one , for some reason it's hard to get the right exv . There are two valves available a 700 step and a 1500 step valve don't quote me on exact # of steps . I have this info in my notes I'll look it up and post back .
    is this really happening or not

  5. #5
    Join Date
    Dec 2004
    Location
    Raleigh
    Posts
    126

    Thanks double bubble

    Thanks alot. I have read this in a previous post on this site. I am fairly certain that I need the 760 step EXV. The tech who changed the EXV told me that the wire colors in the new cable changed. He had to swap brown and white. I don't know what terminal that is but it is not common. Perhaps we do have the wrong exv. That could explain, I suppose why sometimes it locks out on High Superheat and then runs a while and then locks out on low superheat.

    Another note: It was suggested that I change the board settings temporarily to allow for no unloading. The unit has 4 compressors and eight stages of cooling. With this change I have only 4 stages. All compressors come on loaded and stay that way. This appeared to help-it didn't lock out last night, but it did several times today.

  6. #6
    Join Date
    Jul 2005
    Location
    south
    Posts
    588
    i would have the exv board program flashed(a carrier distributor can do this). if that does not work then you can get a pressure transducer kit that replaces evap. and compressor thermistors and monitors pressure to control exv.
    i have carrier part numbers if you need them.


    had a30GT-150 where exv board steps did not match exv motor steps causing exv to open futher than exv percentage said (display said 20% after 4 minutes runtime but exv was actually opened at 30%

  7. #7
    Join Date
    Dec 2004
    Location
    Raleigh
    Posts
    126

    Thanks Chill

    I contacted Carrier on Friday. They gave me a software program (DOS) that could give me all the thermistor readings in real time and the position of the EXV. I need to get a Telebyte Model 65 Converter in order to hook the unit's board to the my laptop. Is this what you are referring to??? And have you done this before. Apparently I hook up to the no. 3 and 6 pins of the J8 plug on the board.

  8. #8
    Join Date
    Dec 2004
    Location
    Raleigh
    Posts
    126

    A bit more information

    Spoke to the tech who changed out the exv. He told me that the motor of the new exv burned out because of the water in refrigerant circuit. The chiller barrell had a crack. It was changed. Is it possible that Carrier gave him the wrong motor??? This unit needs a 760 step motor. Do all these motors look the same?? How do you distinguish between them??

  9. #9
    Join Date
    Sep 2002
    Location
    Hampton Roads, Virginia
    Posts
    1,593

    Re: Thanks Chill

    Originally posted by hvac-alan
    I contacted Carrier on Friday. They gave me a software program (DOS) that could give me all the thermistor readings in real time and the position of the EXV. I need to get a Telebyte Model 65 Converter in order to hook the unit's board to the my laptop. Is this what you are referring to??? And have you done this before. Apparently I hook up to the no. 3 and 6 pins of the J8 plug on the board.
    "Flashing" the board means that they rewrite the code onto the EPROM or whatever memory they use to store the code. The DOS program they gave you just allows you to read the sensors and EXV position directly.
    Are you willing to share this DOS program with others on this site? If so my email is in the bottom left corner of my website.

    Kevin
    "Profit is not the legitimate purpose of business. The legitimate purpose of business is to provide a product or service that people need and do it so well that it's profitable."

    James Rouse

  10. #10
    Join Date
    Dec 2004
    Location
    Raleigh
    Posts
    126
    krogers,

    I sent you the attachment via email. I think that I sent it to the correct link. Let me know. According to Carrier it will let you look at all 8 thermistor temperatures without having to put a DC meter on the plug then converting it to a temp by a chart. It also lets you look at the position of the EXV. I will let you know how it works once I get the Model 65 converter. Has anyone done this before?????

  11. #11
    Join Date
    Dec 2004
    Location
    Raleigh
    Posts
    126

    Thanks KL rodgers

    If I understand your post, it would be possible to repair the board if it is giving the wrong commands to the exv?? The board is EPROM. Not sure what that is, but I read it in the controls literature.

  12. #12
    Join Date
    Feb 2005
    Posts
    23

    #0 gtn chiller

    I just had this prblem with this chiller, !st sometimes the sensors right at one temperature and not at other temperatures, i didnt believe until I proved it it myself,then due the sensor probelm cause the Exv valve to get hung up, so we replaced the Exv powerhead,cable and board,fianlly due to the compressors running improperly due to senosrs,valve,board we change cores. After all said and the chiller has been operating fine.

  13. #13
    Join Date
    Dec 2004
    Location
    Raleigh
    Posts
    126

    Thanks AC Eagle

    I am certain now that the sensors are working properly. Spent a good part of the day monitoring them. Saw what the board was seeing, ie a high superheat (the exv was closed completely). The valve should have opened, it didn't. The logic of the board indicates that it will allow the compressors to run with a SH of greater that 75 before shutting down on High superheat. Also saw the reverse happen several times where the board saw 0 superheat for 5minutes before shutting down on Low Superheat. The exv should have closed some to restrict the flow of refrigerant, it did not.

    According to the controls manual, the board looks at 2 sensors to control the superheat with the exv. The sensors are cooler saturation temperature (located in the cooler) and the return gas (located in the compressor). It measures the temperature of the returning suction gas after it has cooled the windings to the compressor.

    My thinking is that either the board or the exv are not working correctly or the cable. Would like to hold down cost for customer, they have already bought 2 compressors, exv, and chiller barrell. I am hoping that if it is the board it can be fixed (by flashing)instead of replacing.

    Thanks for your input. Did you notice a change in wire colors on the new cable for the exv??????

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