1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

Central AC outside compressor buzzing after the coil cleaning? Help!

Post in 'DIY and General non-hearth advice' started by Don2222, Aug 13, 2012.

  1. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Hello

    My neighbor's central AC 30 amp circuit breaker kept tripping. We checked it and the compressor was working, the line was cold as if there was enough freon but the air blowing out the top did not seem very strong. The FLA - Full Load Voltage is 17 Amps and we measured each of the 240 legs at 15 amps.

    So today I went back and the 30 amp breaker in the panel was tripped again. So I got the coil cleaner out and cleaned the coil and put in a brand new Simens 30 Amp breaker. Yes it is a Siemens 200 amp 40 circuit panel. The coils do look cleaner on the inside but it did not seem like the hose spay water was super dirty. See pics(Pic 2 is coils before cleaning and pic 5 is coils after cleaning) Were they real dirty?

    After doing all this the 30 amp breaker tripped almost right away when it was started up. Sounded like the compressor may have come on for a min.

    So I shut the 60 amp breaker off outside and reset the 30 amp breaker back on inside. Then I went outside and turned the 60 amp breaker back on and just heard a buzz. The fan was not moving and the compressor did not turn on!

    Please help? I can check and take more pics if needed.

    Attached Files:

    Helpful Sponsor Ads!





  2. heat seeker

    heat seeker Minister of Fire

    Joined:
    Feb 25, 2011
    Messages:
    1,907
    Loc:
    Northern CT
    Sounds like one of the motors is locked/shorted/dead. Can you disconnect one or the other and try again? I'd try disconnecting the compressor first, and see if the fan operates. I tend to think cleaning the coils, while a good idea, will not help in this case. The fan doesn't draw much current; the compressor draws the most. The compressor may be bad, have a bad starting capacitor (if it has one), or is trying to start against head pressure (not too likely).
    It might be easiest to remove the top of the condenser and disconnect the fan?
    You might have to call in the pro's on this one.
    BTW - one of the lines from the compressor should be hot - the one going to the fins. The return line from the evaporator should be cool/cold.
    If the compressor runs for a while, then shuts down - is the air handler fan working in the house? If not, that might overload the compressor.


    Disclaimer: I am no AC guru, just have a little experience with motors.
  3. lukem

    lukem Minister of Fire

    Joined:
    Jan 12, 2010
    Messages:
    3,687
    Loc:
    Indiana
    +1 on the start capacitor, if equipped.
  4. blujacket

    blujacket Minister of Fire

    Joined:
    Oct 2, 2008
    Messages:
    616
    Loc:
    West Carrollton,Ohio
    Usually the capacitor's top will be bulged when bad.
  5. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Thanks for the tips.
    The air handler fan in the house is running fine.
    This does have a capacitor that had a label stating it was replaced in 2007.
    The compressor lines are not warm or cold because it was not working all weekend. Saturday morning when we tested it, everything was working fine. So it could be the capacitor.
    How do I test this Capacitor? The cap looks ok but you never know?

    See pics
    See old round capacitor in upper left of pic 1
    Pic 3 - Outside water proof 240 vac circuit breaker and water proof 240 vac outlet.
    Pic 4 - Inside 30 Amp breaker that started tripping and started causing this whole problem!

    Attached Files:

  6. blujacket

    blujacket Minister of Fire

    Joined:
    Oct 2, 2008
    Messages:
    616
    Loc:
    West Carrollton,Ohio
  7. blujacket

    blujacket Minister of Fire

    Joined:
    Oct 2, 2008
    Messages:
    616
    Loc:
    West Carrollton,Ohio
    Push the contactor in and see if the fans kicks on.
  8. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Hello

    Well, I asked an old timer how to check the starting capacitor in the outside condensing unit.

    This Lenox Condenser Unit has a:
    CMCI25/5DVR
    25/5 MFD +/- 5% CBB -65
    370/440VAC 50/60Hz
    MPP3306370/440J
    Protected 10,000AFC
    E236128
    US C22.2 NO. 190

    Since this is a double cap or 2 caps in one.
    The Fan uses the 5 MFD Cap
    The 240 VAC Compressor uses the 25 MFD Cap
    There is one Common Terminal
    The terminals are marked
    Fan C HERM

    So take the leads and use a high ohm scale like 1K
    Put the black on C and the red on the other 2 one at a time.
    The battery in the ohm meter to power the ohm scale for continuity is enough to charge the cap. This makes the needle go full scale and then the needle will swing back when it discharges. You can also revers the leads to create another charge.
    He says if you see the charge/discharge or Bounce as he called it, the capacitor is working correctly.

    I tried it and it does seem the cap is working! What next? The contactor?

    Attached Files:

  9. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    How do you push the contactor in without getting Zapped with 240vac?
  10. blujacket

    blujacket Minister of Fire

    Joined:
    Oct 2, 2008
    Messages:
    616
    Loc:
    West Carrollton,Ohio
    Use a pencil or a stick
  11. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Is that the 1 small metal tab in the middle on top of the contactor? If so it seems to be already in? WTF?
    See yellow arrows in pic below. Click to enlarge

    Attached Files:

  12. blujacket

    blujacket Minister of Fire

    Joined:
    Oct 2, 2008
    Messages:
    616
    Loc:
    West Carrollton,Ohio
    That means it's energized and should be sending 220v to fan and compressor. You have either a bad fan motor or compressor.
  13. heat seeker

    heat seeker Minister of Fire

    Joined:
    Feb 25, 2011
    Messages:
    1,907
    Loc:
    Northern CT
    I'd also make sure the motors are really getting 220 volts.
  14. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Hello

    Yes, I went up stairs and even though the T-Stat was set for 80 Deg F, I turned the switch to off. Then the contactor in the previous post. (See pic with yellow arrows) turned off!

    Then I replaced the Capacitor. PITA. The old one was round and the new one is oblong! See pic

    So now when I push in the contactor there is no fan or compressor going! Strange both are not moving?

    I disconnected the heavy compressor wires from the contactor and when I pushed it on, there was no buzzing.

    Still the Fan did not go on either!

    Both the fan and the compressor were working before the weekend and the 30 amp breaker tripping! ! ! PITA
    What is the next step?

    Attached Files:

  15. blujacket

    blujacket Minister of Fire

    Joined:
    Oct 2, 2008
    Messages:
    616
    Loc:
    West Carrollton,Ohio
    The wall t-stat sends 24v to contactor coil on a call for cooling. That pulls the contacts down to send the 220v to fan and compressor. Next step is to ohm compressor and fan. To trip those breakers, I have to believe the compressor is the culprit.
  16. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Right on!
    Very unlikely that both the Fan and the Compressor would be bad. So when I opened the top again I found the broken purple wire that goes to the common terminal on the capacitor. Bingo!

    Reconnected the wire and it all works! The Fan on top now seems alot stronger since the coils have been cleaned. That really makes a difference even though I did not see much come off!

    Also cleaned the cold air return with shop vac. See pic 2 below

    See yellow arrows pointing to broken purple wire in pic 1 below!

    Thanks all for your help!

    Attached Files:

  17. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Hello

    Well 3 things I learned on Central AC servicing!

    1. If the AC outside condenser that contains the fan and compressor motor has dirty coils, Then the air coming out the top of the condenser is greatly reduced.
    2. If the filter that filters return air is dirty, the volume of air coming out of the cooling register in the house is also reduced.
    3. If the evaporator coils inside the house are dirty, Then
    The air coming out of the cooling register in the house will not be as cold as it should be!

    If any or all of the 3 items above are dirty, then the air conditioner will take much longer to cool the house and can trip the breakers and stop cooling the house!
  18. heat seeker

    heat seeker Minister of Fire

    Joined:
    Feb 25, 2011
    Messages:
    1,907
    Loc:
    Northern CT
    Congrats! Glad you got it going.

    I would, however, not agree with your statement #1. The outside unit has no bearing on the amount of air moving in the house, but would affect the temperature. The air handler fan (inside the house) moves the air in the house. I totally agree with your other statements. Yeah, picky, I know.

    Now you've got me thinking (and that's dangerous!) that I oughta go out and check my condenser coils for dirt.

    Anyway, good work! And you saved your neighbor probably a couple hundred bucks. Hope he springs for some beer, or better yet, pellets for your stove.
  19. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,290
    Loc:
    SE PA
    Nice work Don.....w00t.
  20. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Thanks
    I just have to go back tomorrow and clean the Evaporator A coil out. Still a little way slow in cooling the house but it does not trip the breaker anymore!
  21. heat seeker

    heat seeker Minister of Fire

    Joined:
    Feb 25, 2011
    Messages:
    1,907
    Loc:
    Northern CT
    While you're at the evaporator, don't forget the check the condensate drain/pump.
  22. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Thanks, you are right if that gets partially clogged that can be a real issue too.

    These video helps

  23. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    What is your point pgmr?
  24. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,562
    Loc:
    Salem NH
    Hey Heat Seeker

    Is this how you do it with DIYVac? >> http://circlepad.com/vac/
  25. heat seeker

    heat seeker Minister of Fire

    Joined:
    Feb 25, 2011
    Messages:
    1,907
    Loc:
    Northern CT
    Wow, that's a great idea! I thought my line was plugged a while back, so I just took an air tank and air gun and gave a quick shot of air up the pipe. It wasn't plugged, just had dried the house out enough so water wasn't dripping out as usual.

    My unit should never overflow. Code here requires a drip pan under the evaporator with a moisture sensor that shuts the compressor off if it senses moisture in the drip pan. My previous house had a bad installation of the condensate line, so the unit overflowed into the drip pan, and the unit shut down. The bill was over $200 about 8 years ago. I didn't pay, as the unit was still under warranty, and it was a bad install. The drip pan prevented a load of ceiling damage, for sure!

    Most of the time, there is a steady, small, stream of condensate coming out, since summer is usually humid here.

    I am going to make an adapter for my vac like the one in the video. It makes more sense to suck the crud out instead of blowing it back in!

Share This Page