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  1. #1
    Join Date
    Feb 2011
    Location
    Fogelsville, Pa.
    Posts
    120

    At wits end with this Trane RTU Model YCS072

    Ok I called Trane support after being on hold for 40 minutes and they could not help me out, and today I broke down and called Trane service and he couldnt figure it out after an hour and a half!
    About a month ago I found this YSC072 1h/1C RTU not heating with a one flash code on the ignition board meaning communication failure. On the main board (rtrm) no lights were on. But there was 24v at R and on the main connector and coming back from the stat at W.(using conv stat not sensor) The board had 24volts and I proceeded to change the board. I also changed the ignition board also. Well it lasted a couple days to a week and I had the same senario, one blink on the ign board and no lights(no led or communication leds) on the RTRM board. I tried another RTRM board and that lasted a couple days. Same senario.
    The weird thing is, after I took the failed board out and put it in a week later it worked again???????
    Today when the Trane tech was out he saw the the one blink on the ign board and no lights on the RTRM, he took the R wire off the RTRM and he cycled power and it started back up. Usually when I cycled power I would get nothing. Thats as far as he got. No recomendations or solutions to the problem. Im hoping one of you guys have seen this before or maybe point me in the right direction. Ive checked most the low voltage wiring and found no shorts. I also unplugged the plug(off the RTRM J4) for the economizer board to illimunate that whole side of it and that didnt work. This is a stand alone system with one Honeywell Pro8000.

  2. #2
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,593
    What EXACTLY is your low voltage running? I have not heard of this before on a Trane unit, but I have heard of it before on a Carel. I high running low side voltage will shut the board off to protect itself.

  3. #3
    Join Date
    Feb 2011
    Location
    Fogelsville, Pa.
    Posts
    120
    Quote Originally Posted by jayguy View Post
    What EXACTLY is your low voltage running? I have not heard of this before on a Trane unit, but I have heard of it before on a Carel. I high running low side voltage will shut the board off to protect itself.
    That was a possible concern. Incoming to the transformer was 485v but the name plate is good for 505v the low volt side is 29v. Wasn't sure if 29 was high enough to effect anything.

  4. #4
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,593
    Carel told me they automatically shut down at 30 VAC. Like I said, I don't know if Trane has adopted this feature or not.

  5. #5
    Join Date
    Dec 2014
    Location
    waterford pa
    Posts
    131
    have found that 1 spark and straight to lockout is a dead give away on a over amping gas valve some boards are know for this to prevent board failure , to often the board gets swapped first, and it works for a few days till the new wears off

  6. #6
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,808
    I know you said you believe the low volt wiring is good, but in this situation, I would eliminate is by using a focus pro hanging in the return duct on a couple of feet of new stat wire. Set the fan control on the stat to "ON." If the problem continues after a few days, that will eliminate any possibility of having an issue with the wiring to the vision pro, because it was taken out of the equation.

    Jayguy mentioned that high voltage might be the cause. There is also a possibility of high current, and this test will eliminate that wire as a potential issue. No pun intended.

    Then, if the drop stat makes the problem go away, remove it and the new wire, and change the vision pro to another unit to make sure nothing on that stat board could be drawing too much current.

    This way, you are making a check of both the wire and the thermostat, and either finding the cause, or eliminating them as suspects.
    Last edited by timebuilder; 01-19-2015 at 08:41 AM.
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  7. #7
    Pull the orange spark wire off and check for cracks. Also make sure it's ran separate with no other wires zip tied to it.

  8. #8
    Join Date
    Jan 2014
    Location
    Richland Hills, Texas, United States
    Posts
    474
    You didn't say how old it is. Has it been in service long? Anything new on it? Anything else been changed in the area of the system or stat? These are good questions to ask when dealing with an oddball problem. Sounds like you've eliminated the boards so I would try timebuilders suggestion to eliminate control wiring issue. Maybe there's another appliance recently installed and the control wire is picking up weird EMF? Control wire in conduit?


    James 4:10

  9. #9
    Join Date
    Dec 2014
    Location
    Austin TX
    Posts
    7
    Try getting and OHM rating for all control voltage components and take a reading to see if it matches up. If component/s are out of range try jumping it out if possible, and see if the amps drop and let it ride for a couple weeks. What I'm thinking is the amp draw on your control side do to a component is out of the OHM range and is pulling an amp draw close to the tripping point but not yet tripping the fuse. I'm shooting from the hip here but maybe the prolonged high amps is over working the micro capacitors in the board and the board will basically locking itself out. Let me know what te out come is. These are my favorite calls lol!!!!

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