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  1. #14
    Join Date
    Oct 2011
    Location
    hayward ca
    Posts
    58
    Since it's happening to all of them, the main thing they have in common is the power source. I those are all good ideas. You could check the electrical room in the building, the breaker for the panel for the hvac? loose main line contact, difference of how much from there to your units?

  2. #15
    Join Date
    Jun 2005
    Location
    Henrico,VA
    Posts
    69
    Agreed.I am looking at voltage/power recording options now
    A.B.C.-always be careful!

  3. #16
    Join Date
    Nov 2011
    Location
    British Columbia
    Posts
    48
    Found same kinda pblm on McQuay RTU onetime. Eventually learned it only happned during or after rainy weather. Control section was under neg pressure from supply fan and cabinet panels let water draw in and trickle down inside sufficiently to short terminal block on back wall. Of course on a dry day, could not see reason for blown fuses. Made up sheetmetal stand-off for terminal block and later made better panel seals.

  4. #17
    Join Date
    Jun 2005
    Location
    Henrico,VA
    Posts
    69
    Thats good to know,thanks for sharing.
    btw Welcome to the forums
    A.B.C.-always be careful!

  5. #18
    Join Date
    Nov 2010
    Posts
    10
    i just had the same problem
    installed phase monitor- alarm on under/over voltage almost everyday.
    i thought that was causing the fuse to blow almost every two days but i finally spent time on tracing all the wires and found that one wire was rubbing to a point were the intermittent blowing fuse was happening. replaced wire and now the a/c been running fine.

  6. #19
    Join Date
    Oct 2003
    Location
    las vegas
    Posts
    1,505
    Quote Originally Posted by Brokanic View Post
    I had that problem before. Almost every week the fuse blow.
    Check temp on the fuses using infared thermometer, line side and load side if there is difference in temp change the fuse holder.
    i had one almost identical a week or so ago. changed fuse holders &
    problem solved. good indicator is the color on each end of fuse.

  7. #20
    Join Date
    Oct 2011
    Location
    hayward ca
    Posts
    58
    I f you think about it a blown fuse is usually always motor , or wire short.

  8. #21
    Join Date
    Oct 2003
    Location
    las vegas
    Posts
    1,505
    in some cases yes, but loose fuse holders can cause the fuse to get hot enough to melt the link.especially if the powder in the fuse
    has settled from being in the same position for years on the
    old fuses & you will notice the end of the fuse getting a
    purplish color instesd of normal color.

  9. #22
    Join Date
    Jun 2005
    Location
    Henrico,VA
    Posts
    69

    Update

    I paid a return visit to this rtu this week and checked the
    voltage,amps and for any bad wiring.The fuses were still good.
    I just checked it out because the customer thought he was having
    another problem.
    What I did find this time was an unusual amount of heat in the fuse block area.In excess of 170F in some spots using my
    infrared thermometer.
    I removed the fuses and squeezed the holders tighter and replaced the sta-con female spade connectors for some horseshoe connectors and tightened these down under the fuse block screws.
    Restarted the unit and the highest temperature was 90F.
    A.B.C.-always be careful!

  10. #23
    Join Date
    Apr 2007
    Location
    Saint Augustine, Florida, United States
    Posts
    1,168
    Nice. Loose connections are the devil. Glad you found something.

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