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  1. #1
    Join Date
    Sep 2011

    Need help with Trane Summit comm trunk issues with unit vents and UPCM's

    I am trying to repair a 10 year old Trane Summit BCU panel with 3 communication trunks. Two of the three trunks work fine but the third trunk we can old see about 1/2 of the devices. There doesn't appear to be any rime or reason as to which devices we can communicate with because we will see 5 unit vents, then not be able to see 2 unit vents, then we can see the next 2 unit vents. The system has Summit version 17.00.0053 SP1 software and the effected trunk has 33 unit ventilators (VUVC7511BODE) and 4 UPCM's on it.

    Any suggestions on what to try? We have already tried resetting the BCU, turning off all the devices on the trunk and turning them back on, bringing one devise at a a time online. This all started happening during a week where there were tons and tons of thunderstorms.


  2. #2
    Problems like this can be nothing short of maddening. You didn't say if it was Comm3, Comm4 or Comm5. Either way it may become necessary to trace the entire trunk foot by foot looking for a crossed or tee connection or defective UCM. Trane recommends you keep the device polarity consistent on Comm3 or Comm4. I even maintain polarity on Comm5 (LON) even though they say it doesn't matter. If there are there any surge protectors or repeaters on the affected comm card, disconnect them and see if there's a change. Check your EOL resistor values (LON). Most of these things I'm sure you've already tried.
    If you can pinpoint the date and time the communications problems began, try grilling the building owner or manager as to who was working in the building around that time. Demolition contractors have made me a lot of money over the years. Have there been any recent tenet fit outs, major or minor remodeling, telecom or computer network installation performed recently. If so, I'd find out where and start my search there. Most of all, be patient, methodical and record everything you do. Good Luck.

  3. #3
    PS... Check for Summit v17 upgrades. I think they're up to Service Pack 10 or better.

  4. #4
    Join Date
    Aug 2010
    Middle GA
    The UPCM is a Comm4 device. If you have rover, you can try and search the link with it and see what you can see. I don't think you can see the UPCM with Rover, but you should be able to see the UV controllers. The only way I have been successful in troubleshooting comm issues is to "divide and conquer" Go about halfway down your link and pull the comm off it. If your comm remains stable with the connected devices, reconnect and go further down the link and disconnect and observe again. You should be able to isolate it further that way.
    I've spent a week troubleshooting comm 4 VAV boxes communications problems, and that was the only way to find it. I isolated it down to a comm. jack in a zone sensor that had failed and was causing the link to go down.

    Also, have you looked at the LEDs on the comm boards? One thing I have seen is the Tx LED is lit all the time, or is on enough to tie up communication on the link.

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