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  1. #14
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,906
    Quote Originally Posted by timebuilder View Post
    New transformer?

    Correct tap?

    Measured load on secondary?
    Hello.......?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  2. #15
    Join Date
    Feb 2010
    Location
    NE Alabama
    Posts
    301
    Stick your amp probe on 24v side to see the draw at restart then you can watch the load grow towards overload. You can also put the probe on different component coils and see the individual draw. If the power side is in series you use temp wire direct from trans to each component coil to isolate the draw from each. Having chased this ghost before I even found it hiding in a normally closed high limit that built more resistance the longer it was energized.

  3. #16
    Join Date
    Apr 2012
    Location
    So. Fl.
    Posts
    57
    Hi guys, it's bklyntek, same thing has happened turned out it was the cf motor on the 2nd stage ck. On a air cool chiller. Moderate temps. Kept me from diagnosing it faster. At the time, I had removed the 3.2amp from an old decommissioned carrier rtu & used it to isolate the coil problem. Now, It's part of my tool bag, don't have to stock up on the small glass fuses in my truck. It's worth having with you. Hope this helps out.

  4. #17
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,906
    Quote Originally Posted by Bklyntek View Post
    Hi guys, it's bklyntek, same thing has happened turned out it was the cf motor on the 2nd stage ck. On a air cool chiller. Moderate temps. Kept me from diagnosing it faster. At the time, I had removed the 3.2amp from an old decommissioned carrier rtu & used it to isolate the coil problem. Now, It's part of my tool bag, don't have to stock up on the small glass fuses in my truck. It's worth having with you. Hope this helps out.

    You mean it was in the control circuit for the CF motor, right?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  5. #18
    Join Date
    Mar 2007
    Location
    Sterling Heights, MI
    Posts
    142
    If this is a rooftop with an economizer, there is always the possibility of a short in the circuits going through econo wiring/modules.
    Better Service Through Knowledge...
    RSES, The HVACR Training Authority. www.rses.org

  6. #19
    Join Date
    Apr 2012
    Location
    So. Fl.
    Posts
    57
    Let me explain,in fl. we can have power swings up/dn in excess of 10-15%,(summer). So as a precaution I would add TDR relay's(var.10min.) and adjust times to protect all my loads. Also,served to stage eqpt.in (1-2m.)increments. Because of the added TDR's, 45'-60' mornings that year,left it lurking in the background. There is a method behind the madness, I hope that explains it. Take care guys, bklyntek.

  7. #20
    Join Date
    Apr 2012
    Location
    So. Fl.
    Posts
    57
    Sorry "time builder",I can be alittle long winded in my answers sometimes, but yes it was in the control circuit for 2nd stage condenser fan bank. just read where I wrote "cf motor", my mistake. Thanks for calling my attention to that, proper terminology is a must.
    I will be more careful in the future.

  8. #21
    Join Date
    Aug 2010
    Posts
    3,360
    If you have something like Fluke 189, this is where it gets useful.

    Another option is to hookup a needle volt meter to monitor the voltage between R and C at the thermostat that's controlling this and monitor it with security camera, so that it can see both the thermostat and the needle.

    The fuse blowing current level will cause a significant voltage drop. See if there is a relationship between what the thermostat is calling for and the voltage.

  9. #22
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    Quote Originally Posted by wika_boy View Post
    The 460v to 24v 4amp transformer overload keeps tripping about every 4 hours. Unit is a dx system. Any ideas why. Thanks
    Every Four hours eh ? That should be helpful in tracing down your faulty component to some degree.

    You could isolate components one at a time while monitoring current on R. Transformers tripping usually wind up being something simple.

    One of my customers at a local server farm who likes to trouble shoot and "repair" electrical problems ran one leg of 460 through the thermostat wire on a Trane 2 stage 20 ton split and then called me.

    Of course it smoked various low voltage components and compromised the insulation on the plenum rated thermostat wire.

    Didnt start having issues with the t-stat wire until a month later.

    Just yanked it out and pulled new wire. Not a big deal.

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