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  1. #1
    Join Date
    Jun 2006
    Posts
    192

    Carrier rtu, breaker tripping every 2-3 days

    hi everyone,
    got question on carrier 48TFD009-511BA S/N:1802G50521
    y1 & y2 jump at the terminal block at the unit,unit will come on for 1-2 seconds and shut and for about 2-3 second then will come on again and run ok .check electrical connection,amp draw of both comp., and both cond. fan,breaker size,pressure ok.now this unit run like this for 5 yrs,should i put a time delay on the y2 terminal or should i replace the stat with a 2 stage cooling,will this fix the problem? should i replace the breaker(maybe the breaker is getting weak)cond. fan check ok,cond fan mfd ok.coil & filter ok.
    thanks in advance
    fishunter

  2. #2
    Join Date
    Feb 2007
    Location
    Dallas, Tx.
    Posts
    572
    a two stage unit needs a two stage stat. when the stages are coming on together, do they both shut down then restart, or only one of them? use your meter and see where you are dropping out. if both compressors are dropping out and restarting together, my guess would be that there is a problem with the stat.
    mike

  3. #3
    Join Date
    Jun 2006
    Posts
    192
    everything shut off then start again.

  4. #4
    Join Date
    Feb 2007
    Location
    Dallas, Tx.
    Posts
    572
    everything including the blower?
    mike

  5. #5
    Join Date
    Nov 2005
    Location
    Shreveport, Louisiana
    Posts
    2,329
    My guess the condensor coils are dirty and it is causing the condensor motors to heat up and overamp causing thebreaker to trip. and your compressors are overamping also because of the dirty coils. Take the NUBRITE to the condensor coils before you replace the breaker....

    The high side pressure is no high at start up but increses as the unit runs...

  6. #6
    Join Date
    Jun 2006
    Posts
    192
    yes including the blower,total amps on start up is 25.6,has a x3 45amp fuse at the disconnect none of them ever blown,OT 78, IT 75, pressure 64/226.
    cond. mtr both pulling 1.0 rated at 1.4.i watch this unit for about 45 minutes yesterday and today for 30 minutes and check my amp reading 5 minutes before i headed home and still reading ok.now on the same roof theres another unit that is doing the same thing but is a single stage(smaller unit)but not tripping the breaker,now on the west side theres exact same unit 2 stage cooling but run just fine with y1 &y2 jump at the unit.as i mention earlier i was here today so i installed a 2 stage cooling stat and did not make any difference at all.cond. coil was cleaned 2 months ago.

  7. #7
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,060
    Did you check the contactors?

    I had one doing the same thing as what your talking about and that was the problem. It was pitted and discolored very badly. it would start fine then the contact would heat up after a while to the point where the connection started to get lost and trip the breaker. That damn thing tripped about 3 times in the hour I was there, after the contactor it never did it again.

  8. #8
    Join Date
    May 2006
    Location
    Mooresville, North Carolina
    Posts
    224
    Quote Originally Posted by y7turbo View Post
    Did you check the contactors?

    I had one doing the same thing as what your talking about and that was the problem. It was pitted and discolored very badly. it would start fine then the contact would heat up after a while to the point where the connection started to get lost and trip the breaker. That damn thing tripped about 3 times in the hour I was there, after the contactor it never did it again.
    Therefore your other units will eventually do the same thing because with Y1 & Y2 wired together your cycling both compressor contactors more frequently than design.
    Refer all arguments to the wife, she's better at it.
    www.fairtax.org

  9. #9
    Join Date
    Jun 2006
    Posts
    192
    Quote Originally Posted by lirunaway View Post
    Therefore your other units will eventually do the same thing because with Y1 & Y2 wired together your cycling both compressor contactors more frequently than design.
    well contactor seems to be fine,theres three of them one for the blower and two for the comp. will they go bad at the same time?

  10. #10
    Join Date
    Nov 2004
    Location
    Southern Minnesota
    Posts
    28
    Try checking the transformer primary AND secondary. What is th VA rating on the transformer. It could be getting weak. It has enough voltage to pull in one contactor but can't hold two.

  11. #11
    Join Date
    Oct 2007
    Location
    Southern Indiana
    Posts
    94
    Have you looked for a bare wire? I had this problem on a Trane RTU, four techs had looked at it and couldn't figure out why it was tripping the breaker intermitently. I found a bare spot on the line voltage wire coming into the unit. The insulation was rubbed off and touching the metal, it would vibrate while the unit was running then everyonce in a while it would touch the metal. So the techs would reset it and it would run for a while then touch and trip the breaker.

  12. #12
    Join Date
    Jan 2003
    Location
    Kansas City
    Posts
    1,482
    May be a low voltage issue. Digital thermostat flaking out, voltage drop of the secondary due to a thermostat, long t-stat wire run, improperly tapped transformer. What is the voltage of the secondary and what does it drop to when you energize the unit?

  13. #13
    Join Date
    Sep 2007
    Location
    Michigan
    Posts
    290
    Sounds like the customer should call someone that knows how to troubleshoot commercial equipment. You have to think in and orderly way of what could be causing the problem and work back.
    "Yeah I can figure out whats wrong with it, but you were here first and there isn't room for two, plus it's cold up here, I'll be in the van"

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