Help spread the word / share us on your favorite social media networks

Facebook Twitter StumbleUpon Reddit LinkedIn

Results 1 to 4 of 4

Thread: Help

  1. #1
    Join Date
    Jun 2015
    Posts
    2

    Default Help

    I changed the contactor on my ac unit at home because the old one burned up. I checked the input and output voltage and both were 240 volts. The coil voltage is 24 volts. I noticed the following morning the house wasn't cooling like it should, so I went outside and noticed the fan would kick on, run for 1 minute and then the compressor would kick on. They both ran together for about 5 minutes and then would shut off. This cycled occurred about every 5 minutes.
    The new contactor is a single pole, 24 volt, which the original was. The difference between the old and new is the lra rating. The old one was 180, 150, and 120 where as the new is 150, 125, and 100. Could the lra difference be causing the short cycling or something else like low refrigerant?

  2. #2
    Join Date
    Feb 2012
    Location
    Lala land, OH
    Posts
    238

    Default

    The outside blower and compressor should start at the same time in most traditional condenser units. Was it always like this? This doesn't sound right.

    A failing starter cap, thermal cutout, low/high pressure switch can cause this... If the compressor is overheating, the fan kicking on may cool it to the point it will run again. If the compressor is working harder then it should be, it will be drawing more current, which can burn up a contactor when it has to switch under load. I'm guessing that you have other issues and the contactor going was a heads up of things to come.

    I would get a service tech out before you run it anymore, show them the old contactor. The first thing they will probably do is take some current readings. If it's something that's repairable, hopefully it hasn't caused more damage yet.

    lra is your locked rotor current rating, how much current the motor will draw if it's not turning (a motor is not turning for a period of time when it is started). A lower number means it will handle less. Your contactor should have 3 voltage ratings (probably 120, 208, 240) and the voltage you are running at corresponds to 1 of the the 3 lra ratings. Look at the locked rotor current rating on your nameplate. If the new contactor is less for the voltage, then you will want to consider changing it out, but if your compressor is toast then there's no need....

    If its more then 10-15 years old then it may be about time....

  3. #3
    Join Date
    Jun 2015
    Posts
    2

    Default

    Thanks for the reply. The unit is about 8 years old. The compressor was changed about 2-3 years ago. I also bought a dual run capacitor but have not put it on due to the burned contactor, thinking the problem was the contactor. The system ran fine up until last week when the fan wouldn't cut on. The short cycling and the compressor not cutting on with the fan didn't start until after I changed the contactor.

    The guy that replaced the compressor and who has worked on it the last few summers said it might be low on freon...I was wondering how that would be possible. The freon level was checked about 3 weeks ago by him and it was good. The ac is blowing cool, it's just short cycling.

    As far as the contactor, I'm not sure what the voltage is. On the box, it says 600 volts max. The lra for the compressor on the nameplate is 78 and 208-230 volts.

    Should I try changing the capacitor out? It's not bulging at the top, which I've read in some cases means it might be bad....not sure how to check it.

  4. #4
    Join Date
    Feb 2012
    Location
    Lala land, OH
    Posts
    238

    Default

    Sound's like you've had alot of problems with it and there's been alot of stuff changed out. If parts other then what is specified in the manual or by the manufacturer are used (like the contactor) then you are going away from the nameplate specs and anything can happen.

    I would get a different set of eyes looking at the system and see what they think. You may be throwing money at a helpless cause.

    The voltage rating on the contactor is what it is rated to handle, not what goes through it. It will handle different amounts of current at different voltages due to ohm's law.

    As for the cap, it sounds like you are guessing at this point. If you have a exact replacement cap (as specified in the manual) you can try it but it's a gamble. If it's not a EXACT replacement, dont install it, you may create other problems.n

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •