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  1. #1
    Join Date
    Nov 2012
    Location
    Knoxville TN
    Posts
    22

    Defrost saga continues

    Does this sound right:

    My heat pump split system was constantly going into defrost. Same problem for three years in a row. So this year tech comes out says pressure is good and replaces defrost board. Did not fix problem. He calls American Standard and the field service guy says replace pressure transducer. This was replaced last year and it ran all winter. My tech tells the AS field guy this and the AS field guy says I have dirty power and that the ground on the transducer relies on a earth ground. So my tech says he needs to install an 8' ground rod by the unit and run a wire between the rod and unit to protect the pressure transducer. This seems rather odd since I already have a rod at the meter box on other side of house.

    I asked if the control board could be bad that it plugs into and got a no.

    Any thoughts is this plausible or is smoke being blown around.

    Thanks.

  2. #2
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    3,422
    the defrost circuit is fairly simple. and the board has a test built in. it could be wired wrong, it could be defective, it could need parts changed to get it working properly... a true service tech needs to investigate what's wrong and fix it.
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  3. #3
    Join Date
    Nov 2012
    Location
    Knoxville TN
    Posts
    22
    Well I called another company and they are scratching their head. The defrost board tests okay when commanded to go into defrost. He looked at the EEV board and ran a test and it controlled the EEV valve as it was supposed to. He said it could be a bad board or timer. I am tired of this plug and pray. I have spent more on this unit in repairs in three years than I did in 20 years on the old one. Something has to give but I don't know who to contact.

  4. #4
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    Sometimes a temp sensor is in wrong spot.

  5. #5
    Join Date
    Nov 2012
    Location
    Knoxville TN
    Posts
    22
    He checked two sensors one that hangs out the unit and one that was in a tube connected to one of the lines and they read right to the chart based on temp.

  6. #6
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,189
    Quote Originally Posted by bspreng View Post
    Well I called another company and they are scratching their head. The defrost board tests okay when commanded to go into defrost. He looked at the EEV board and ran a test and it controlled the EEV valve as it was supposed to. He said it could be a bad board or timer. I am tired of this plug and pray. I have spent more on this unit in repairs in three years than I did in 20 years on the old one. Something has to give but I don't know who to contact.
    how old is this unit?
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  7. #7
    Join Date
    Nov 2012
    Location
    Knoxville TN
    Posts
    22
    Quote Originally Posted by hvacvegas View Post
    how old is this unit?
    3 years.

  8. #8
    Join Date
    Apr 2010
    Location
    NC Sandhills
    Posts
    412
    I dont think the out door temp sensor would be at fault as it doesnt tell the defrost board to go into defrost mode, only that it "can". The coil sensor is what tells the board to go into defrost mode. If you had "dirty power" I think you would also be having other issues. When they tested the EEV did they check it with a ohm or multimeter, or did they just do a force close and force open and be done with it? Did they also chech the two temp sensors on inside coil that control EEV also? If they replaced the Defrost board and sensors out side and the new ones check ok, I would be looking closer at the EEV. Ask the next tech out there to check the EEV stepper motor and gas/liquid temp sensors for calibration. When it gets stuck in defrost, does it stay in one continuious defost cycle or defrost for several minutes then stop and reset back into defrost? When it first goes into defrost does it do it only at colder temps or anytime you turn heat on even when its above 50 degrees outside?

  9. #9
    Join Date
    Nov 2012
    Location
    Knoxville TN
    Posts
    22
    It will start going into defrost once the outside temp is below ~35°. It goes into defrost about every other cycle. The unit will run for about 10-12 minutes.
    He jumped some terminals on the board and watched pressures. When he did one the unit ran then shut down. He said it triggered a low pressure something. I did not see a meter to check the EEV he was only around the board. The unit will not go into defrost above 40°. I should mention it did this last year and the company put on a transducer and it ran all winter fine. Does this help?

  10. #10
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,189
    Quote Originally Posted by bspreng View Post
    3 years.
    No warranty?
    If it's happened since day one, I wouldn't pay.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  11. #11
    Join Date
    Apr 2010
    Location
    NC Sandhills
    Posts
    412
    Quote Originally Posted by bspreng View Post
    It will start going into defrost once the outside temp is below ~35°. It goes into defrost about every other cycle. The unit will run for about 10-12 minutes.
    He jumped some terminals on the board and watched pressures. When he did one the unit ran then shut down. He said it triggered a low pressure something. I did not see a meter to check the EEV he was only around the board. The unit will not go into defrost above 40°. I should mention it did this last year and the company put on a transducer and it ran all winter fine. Does this help?
    It isnt doing it as bad as I assumed. When he jumped the EEV to force close it caused the unit to shut down on low pressure as it should. So, when it gets to about the mid 30's, the heat cycle run time is about 10-12 minutes. After every other 10-12 min run time the unit will go into defrost mode. After defrost is over how long does the unit not run before it begins another ~10 min heat cycle? How long does it typicaly stay in defrost mode and does the system keep up with the heat demand of the thermostat? Its going into dft at the correct temps but a ~10 minute run time is short for a outdoor temp of 35 degrees. I agree with hvacvegas on warranty issue, do you have documentation of the times they have been out since the first year for same problem. Do you know the model # of heat pump and or size?

  12. #12
    Join Date
    Nov 2012
    Location
    Knoxville TN
    Posts
    22
    At 35 it might run longer, I have an spreadsheet with times that I showed both techs but they were not interested. The unit does keep the temp steady in the house, it rearely goes into 2nd stage. The air handler only ramps up when it goes into defrost. When it enters defrost with no ice on coil I would say it runs in defrost mode for a minute, not a long time, sometimes the call for heat is not needed in the middle of a defrost cycle so the next cycle starts with a defrost. The unit is under warranty for parts now but I have to keep paying labor and trip call which is the frustrating part.

    After defrost is over the unit might run for 3-5 minutes, I guess since the eheat came on and a higher blower speed it typically satisfy the tstat faster.

    I do have documentation but I am not sure what good that will do.

    I called American Standard and they were uterally useless, basically told to call another service company.

    Model #4A6H6036E1000AA.

  13. #13
    Join Date
    Nov 2012
    Location
    Knoxville TN
    Posts
    22
    It got cold enough last night and the unit is still entering defrost. The replaced transducer evidently was not the problem.

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