Page 1 of 2 12 LastLast
Results 1 to 13 of 18
  1. #1
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    427

    Carrier 4 ton package unit

    Having a control circuit issue Carrier 48TME006-A-501. 208/230 3p. Blower runs fine but when terminal Y is energized the contactor chatters like mad with the compressor jumping all over trying to start. Easy right, I install a new contactor. BUT, same results.

    I start searching for a loose or corroded 24v control circuit connection. not finding anything. I check both the LP & HP cut out switches for continuity. Both good but for the good measure I temporary remove both switches from the circuit and test. Still, heavy chattering of contactor. I check actual voltage at the contactor coil, 23.8v. Little low, I notice the control transformer is wired for 240. My service is 208 3p.

    With the fluke hooked up to the contactor coil and I energize Y, I see my meter voltage reading dropping out. Can I have a bad control transformer? It is able to send 24v to G for the blower but craps out when asked to send 24v to Y & G?

    I think so, will pick up a new 40va control trans in the morning. Is there anything I could be missing? Thanks

  2. #2
    Join Date
    May 2013
    Location
    near knoxville tenessee
    Posts
    168
    is the 24 volt constant at the contactor or does it bounce? Take thermostat leads off the board and just jump out the contactor from r to y and see if it continues. If it still bounces with the thermostat out make sure the contactor is a 24 volt coil. If it is trace back wires to the board and make sure no other stuff is in there like hp or lp switch. Last replace the board.

  3. #3
    Join Date
    Jan 2010
    Posts
    6,206
    That is a five ton unit.
    Did you check the FPT ( freeze protection thermostat ) ?

  4. #4
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    211
    Econo? bypass with the factory bypass plug if still around,Also check all control wiring around compressor for chafing and above the indoor blower if wires run on top of it.Original factory trans should have a 208 tap.Like john said run it without the stat maybe a short in the stat wiring.

  5. #5
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    427
    Quote Originally Posted by buford View Post
    Econo? bypass with the factory bypass plug if still around,Also check all control wiring around compressor for chafing and above the indoor blower if wires run on top of it.Original factory trans should have a 208 tap.Like john said run it without the stat maybe a short in the stat wiring.
    I did look at the Econ yesterday. This unit doesn't have a plugged connection as you suggest, I have seen the plugs in which you refer on other units. This one is somewhat different, it's actually in nice looking condition, not covered in dirt! Dampers opens and close with the adjustment and is set at "C". Yesterday conditions called for a full close.

    I think the issue is in a faulty thermostat. I did jump R & Y, my chattering continued, but with the red & yellow stat wires disconnected, the unit/compressor ran well. The factory control transformer must have an internal breaker, it popped & smoked. I don't need to get it finished till Monday. Will pickup a new Pro 6000 Thanks

  6. #6
    Join Date
    Sep 2007
    Location
    NH
    Posts
    1,146
    Quote Originally Posted by Capz View Post
    I did look at the Econ yesterday. This unit doesn't have a plugged connection as you suggest, I have seen the plugs in which you refer on other units. This one is somewhat different, it's actually in nice looking condition, not covered in dirt! Dampers opens and close with the adjustment and is set at "C". Yesterday conditions called for a full close.

    I think the issue is in a faulty thermostat. I did jump R & Y, my chattering continued, but with the red & yellow stat wires disconnected, the unit/compressor ran well. The factory control transformer must have an internal breaker, it popped & smoked. I don't need to get it finished till Monday. Will pickup a new Pro 6000 Thanks
    Check your freeze stat some of those carrier units break the common leg to the coil.

  7. #7
    Join Date
    Jun 2004
    Location
    St Paul, minnesota
    Posts
    1,163
    voltage drop from long thermostat wires or less than 20 Gage wire

  8. #8
    Join Date
    Jun 2013
    Location
    N. Canada
    Posts
    394
    Quote Originally Posted by Dchappa21 View Post
    Check your freeze stat some of those carrier units break the common leg to the coil.
    But then why does it run with lifted stat wires & jumpered?

  9. #9
    Join Date
    Jun 2013
    Location
    N. Canada
    Posts
    394
    Quote Originally Posted by superfittertech View Post
    voltage drop from long thermostat wires or less than 20 Gage wire
    But then, why does it NOT run jumpered R to Y ?

  10. #10
    Join Date
    Jun 2013
    Location
    N. Canada
    Posts
    394
    Quote Originally Posted by Capz View Post
    I think the issue is in a faulty thermostat. I did jump R & Y, my chattering continued, but with the red & yellow stat wires disconnected, the unit/compressor ran well. The factory control transformer must have an internal breaker, it popped & smoked. I don't need to get it finished till Monday. Will pickup a new Pro 6000 Thanks
    I don't work on these units, don't know them, but as you lay out the facts (quite well) it's screaming that you have a grnd (not short) on your YELLOW wire on the STAT side of your jumpering point. Take note that your problem goes away when you lift your stat wires. It won't be the R wire as G works ok. To humour an old man, lift R & Y wires and see if you have continuity (grnd) between Y wire and chassis.

  11. #11
    Join Date
    Jun 2013
    Location
    NORTHERN
    Posts
    989
    as well said: ~ like the 208 TX tap on a 208 service

  12. #12
    Join Date
    Jul 2010
    Location
    napping on the couch
    Posts
    1,560
    So you are saying it runs with the t stat wires removed from the unit and jumpered R to Y to G? Or no?


    Try this. I had this happen to me once. A compressor on a unit was on its way out and over amping, but not enough to cause the breaker/fuse to trip. When it started it over amped it caused a voltage drop to the unit. 208 3 phase dropped into the high 100's(don't remember exactly how low it went) this caused the transformer voltage to drop also because it was being supplied less than 208 which caused the contactor to drop out because it was seeing in the high teens for a voltage.

    It happened so quick, my meter wasn't picking it up. As soon as the compressor started the voltage dropped and caused the contactor to drop out and chatter.

    To test this, put your meter on the transformer and push the contactor in and see if the 24v remains constant. Also, check the compressor amps and meg the windings if you have a megger.

    Unit had a failing compressor. Changed it out and of course the chattering went away. We also got an electrician fix a problem with the line voltage wiring to the unit adding to voltage sag.
    In 1959, Cuba wanted "CHANGE" too.

  13. #13
    Join Date
    Jun 2013
    Location
    NORTHERN
    Posts
    989
    Quote Originally Posted by Brian8383 View Post
    ...208 3 phase dropped into the high 100's,,,adding to voltage sag.
    In Clev , monitored by Ut'y the voltage as lo194 ! for days
    a little 20 T w:w "chiller" contactor - all the same, and ended up with another tx24vac from references by nice Trane distributors

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event