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  1. #1
    Join Date
    Aug 2011
    Location
    USA
    Posts
    32

    Trane Heat Pump with communicating thermostat

    I'm not sure if I'm in the right forum area. I worked on a heat pump air conditioning unit the other day and the communicating control board was flashing a code saying it was on high pressure lock out. After checking all the basics nothing showed obvious as to what was the problem. I disconnected the power supply to the control board to see if it would reset and it did. I decided that it was the control board itself and replaced it. The person did not have the problem again before I changed it but just to be sure I replaced it anyway as it is under warranty. What do you think the problem is???

  2. #2
    Join Date
    May 2004
    Location
    Frederick, MD
    Posts
    955

    I would look

    at all the things that could cause a high pressure situation and go from there. Did you put gauges on the unit? How clean is the outdoor coil? Etc, Etc, Etc.

  3. #3
    Join Date
    Aug 2011
    Location
    USA
    Posts
    32
    The coils looked clean and the unit is no more than a couple years old. I noticed for a brief moment the compressor kicked on before the fan which suggested there was a problem with the fan but it checked out fine. The other tech was checking the inside unit and he didn't find any problems there. I did not put the gauges on it because I pulled the power to the control board and it reset with no problems. I'm pretty sure it's not overcharged. The person has not called back with any problems. I'm pretty stumped on this one what do you think some of the most common causes would be. It's a Trane a/c heat pump with the communicating board.

  4. #4
    Join Date
    May 2004
    Location
    Frederick, MD
    Posts
    955

    Did you

    operate the unit in both stages? What is the model # of the outdoor unit?

  5. #5
    Join Date
    Apr 2003
    Location
    Columbus Ohio
    Posts
    96
    it probably got switched over into heat mode on accident

  6. #6
    Join Date
    Oct 2008
    Location
    Nashville ,TN
    Posts
    285
    ive had something close to your problem could be a weak run capacitor, have you checked the play in the outdoor fan shaft , sometimes when bearings go bad it runs fine while youre their and when you leave locks up.It shouldnt move alot from left to right .

  7. #7
    Join Date
    May 2009
    Posts
    271
    Quote Originally Posted by GSC View Post
    The coils looked clean and the unit is no more than a couple years old. I noticed for a brief moment the compressor kicked on before the fan which suggested there was a problem with the fan but it checked out fine. The other tech was checking the inside unit and he didn't find any problems there. I did not put the gauges on it because I pulled the power to the control board and it reset with no problems. I'm pretty sure it's not overcharged. The person has not called back with any problems. I'm pretty stumped on this one what do you think some of the most common causes would be. It's a Trane a/c heat pump with the communicating board.
    Always put your gauges on a system. You cannot begin to troubleshoot without superheat, subcool, temp diff across a coil, amp draws, static pressure and capacitor readings.

  8. #8
    Join Date
    Aug 2011
    Location
    USA
    Posts
    32
    I cant remember the model#. If I get a call to go back there I will have to check the run capacitor. The unit is pretty new so I dont think its the fan but I didn't check it. It was one of those situations were the problem was fixed quickly and then I moved on to the next call. I'll have to remember to ask the other service tech that was with me on some of these questions. My description is kind of vague. I was thinking it might have been the sensor malfunctioning but I'm not to firmiliar with these kind of units with communicating conrtol boards. Do any of you guy's know were I can get some literature on these type of systems?

  9. #9
    Join Date
    May 2009
    Posts
    271
    Trans has a service manual on them. High superheat can cause a reciprocating compressor to go into thermal cutoff occasionally.

  10. #10
    Join Date
    Aug 2011
    Location
    USA
    Posts
    32
    I guess if Trane tests the control board I'll know for sure if that wasn't the problem. I'm a FNG in this field and I was with another service tech training me. I definitely agree on putting guages on at all times that will be kept on the top shelf when I get out on my own!!!!!!!

  11. #11
    Join Date
    May 2009
    Posts
    271
    Sorry, your problem was high pressure lockout, not thermal cutout. Blocked txv overcharge,etc,etc fan motor .....at least you ruled out the board. Get all your measurements.

  12. #12
    Join Date
    Aug 2011
    Location
    USA
    Posts
    32
    If it had high superheat than that means it is low on refrigerant? There wasn't any signs of that but then again the systems was off long enough to avoid those signs. I think the other service tech asked if there was water around the furnace and she said no.

  13. #13
    Join Date
    Aug 2011
    Location
    USA
    Posts
    32
    The only reason I said low on refrigerant is because the outside coil was clean.

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