jcmorris2
30-03-2007, 03:58 PM
Hello All,
Here’s a problem for which I have run out of ideas. The system is a residential 1.5 tonn split heat pump by Trane, model # 2TWB0018. The system has been in operation for a year and a half with no issues. Suddenly inadequate cooling. Closer inspection reveals the “W” circuit energized. Disconnecting an isolating circuits brought me to the defrost control board.
Easy fix right? There is an identical unit available that is operating correctly so swap the boards. Ok, did that. The donor board did the same error. The “bad” board operated correctly in the donor machine. So, fine, not the board.
Sensors bad? The paperwork and diagnostic charts were still in the units and the thermistors ohmed within normal limits. Ok maybe the pins are dirty. The board has a procedure to check to see if the sensor signal is good. It checks out.
Power? AC at 60hz measures 29v. Maybe a little high, but the other unit has the same voltage on it’s board and that one operates.
So here’s the only real clue I have. The board energizes the “W” circuit when “O” is energized and the “W” circuit is de-energized when “O” is de-energized. Also the “W” circuit is not energized when the unit is forced into the defrost test cycle.
My only thought was that there might be a partial short in the “O” circuit causing a voltage drop when current is pulled as would occur when the switching valve is energized. Of course there is no technical data provided for the board tolerances and I can’t find a number for the guys at Trane that would know.
Any ideas? Any phone numbers to Trane folks?
Thanks
Here’s a problem for which I have run out of ideas. The system is a residential 1.5 tonn split heat pump by Trane, model # 2TWB0018. The system has been in operation for a year and a half with no issues. Suddenly inadequate cooling. Closer inspection reveals the “W” circuit energized. Disconnecting an isolating circuits brought me to the defrost control board.
Easy fix right? There is an identical unit available that is operating correctly so swap the boards. Ok, did that. The donor board did the same error. The “bad” board operated correctly in the donor machine. So, fine, not the board.
Sensors bad? The paperwork and diagnostic charts were still in the units and the thermistors ohmed within normal limits. Ok maybe the pins are dirty. The board has a procedure to check to see if the sensor signal is good. It checks out.
Power? AC at 60hz measures 29v. Maybe a little high, but the other unit has the same voltage on it’s board and that one operates.
So here’s the only real clue I have. The board energizes the “W” circuit when “O” is energized and the “W” circuit is de-energized when “O” is de-energized. Also the “W” circuit is not energized when the unit is forced into the defrost test cycle.
My only thought was that there might be a partial short in the “O” circuit causing a voltage drop when current is pulled as would occur when the switching valve is energized. Of course there is no technical data provided for the board tolerances and I can’t find a number for the guys at Trane that would know.
Any ideas? Any phone numbers to Trane folks?
Thanks