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  1. #1
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    Question TRANE RTHD Chiller "MP: Reset Has Occurred" Alarm on CH530 Controller

    Hi guys,

    A lil' bit of introduction: I am a fresh-grad project engineer in a small-ish HVAC company and recently, a client of the company called us to troubleshoot a Trane chiller as it is not providing sufficiently cold chilled water.

    During the troubleshooting, the service crew noticed that the alarm history is full of the alarm "MP: Reset Has Occurred". The log suggests that there were approximately 53 incidents of this alarm over the past year of log history in the chiller processor. Is this normal or is there a cause for concern?

    The service crew suggested to perform a software update to see if it will get rid of this issue. When I pressed for more detail from him, he suggested that updates for the software will enable the controller to capture the real trip cause and display it in the diagnosis history instead of just passing it off as another "MP: Reset Has Occurred Alarm". Is this really the case? Does this mean that past versions of the software did not enable the controller to capture the trip cause or error?

    It all sounds a bit fishy as the service crew then mentioned that there may be a possibility that even with the software update, the situation may not be resolved and if that is the case, the entire controller unit will have to be changed to another unit of the same model or to a newer model.

    Anybody here with similar experiences which can perhaps enlighten the situation? Any feedback welcomed.

    Thanks in advance.

    Skye

  2. #2
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    That will show up any time the power is lost, ie power failure, or someone cycling the power.

  3. #3
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    Quote Originally Posted by cperk View Post
    That will show up any time the power is lost, ie power failure, or someone cycling the power.
    What he said. Anytime power is cycled that is what you get

  4. #4
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    Also, if I recall correctly, this diagnostic can be the result of the High Pressure Switch lightly "bumping" open the NO contact to shut down the machine, but not closing the NC contact to indicate a high pressure trip. The "unexplained" shutdown is then interpreted as a loss of power. This sometimes happens when tower water is too warm and condenser pressure rises slowly.

  5. #5
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    Quote Originally Posted by cperk View Post
    That will show up any time the power is lost, ie power failure, or someone cycling the power.
    Both possibilities seemed highly unlikely. If there were to be a power failure, the chargeman would have informed the service team about it while the troubleshooting was performed. In the log, this message popped up several times, sometimes up to 4 or 5 times a day. Cycling the power also should not be a possibility as the chargemen have daily logs of when they switched on or shut off the chiller.

    Service crew informed me that it may be controller's internal logic failure and to update the software, any insights on this?

  6. #6
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    Quote Originally Posted by Nuclrchiller View Post
    Also, if I recall correctly, this diagnostic can be the result of the High Pressure Switch lightly "bumping" open the NO contact to shut down the machine, but not closing the NC contact to indicate a high pressure trip. The "unexplained" shutdown is then interpreted as a loss of power. This sometimes happens when tower water is too warm and condenser pressure rises slowly.
    Thank you for the direction pointed, will look into it hopefully can find some sources to support this. A quick note, the service crew also noted that the both entering and leaving tower water is actually lower than design spec, but the temperature differential is about the same, and condenser pressure differential is also significantly lower than design spec (by half the value).

    Do you think the controller software update can solve this? Service crew also recommended to change the flow switch, probably have to look into it.

  7. #7
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    Update the software. What will it hurt? The software is free on Trane's website. If the diagnostics stop then yay it's fixed. If it doesn't you know to dig a little deeper.

  8. #8
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    cperk,

    My company doesn't specialize in chiller servicing so we have to depend on the local Trane service crews. Which translate into cost for the company to bear, thus would like to investigate a little bit further before committing to any actions.

  9. #9
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    "What does the manufacturer's tech, who is standing in front of the unit say?"

    "That can't be right, let's ask some random people on the internet"
    The key to happiness is lower expectations.

  10. #10
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    I don't understand why, if you already had them out there, they didn't just update the software. The time it takes to do this is minimal.
    The key to happiness is lower expectations.

  11. #11
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    I would be curious as to when the trips occurred. The alarm history will put a time and date stamp on each one. Perhaps those trips occurred on warmer days than the day your service crew was there. As a cooling tower becomes dirty and loses efficiency, it may not be noticed until it's reduced capacity is exceeded, such as on a warmer day.

  12. #12
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    Tech Rob, I must have missed where it was stated the manufacturer's tech was there. I presumed by "service crew", the OP was referring to the service crew of his company. I could be wrong. Wouldn't be the first time...
    I have experienced that frustration, too. So I can understand yours.

  13. #13
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    Quote Originally Posted by Tech Rob View Post
    "What does the manufacturer's tech, who is standing in front of the unit say?"

    "That can't be right, let's ask some random people on the internet"
    FYI, I have already posted what the manufacturer's tech (yes, the manufacturer's tech are the service crews) proposed but I sorta wanted to dig in a little bit more. With the minimal experiences that I have, I have thus decided to "ask some random people on the internet". Apparently that thinking of wanting to dig in a little bit more other than blindingly trusting the manufacturer's tech is inappropriate?

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