Results 1 to 12 of 12
  1. #1
    Join Date
    Jun 2013
    Location
    Maryland
    Posts
    11
    Post Likes

    Trane "Purple Wire" and Bacnet trunk.

    Hi,
    I've just gotten roped into troubleshooting intermittent comm problems that apparently have persisted for a year.
    I'm trying to trace the comm trunk and locate any EOL resistors. That's slow going. The topology is supposedly daisy-chained. There are (9) KMC Bacnet VAV controllers, (2) Jeneysy Viconic stats, (2) Trane UC-400's and (1) Trane BCI-I. These MS/TP devices are brought into a KMC FullBac Router and fed to the Lynxspring JENE over Bacnet/IP.
    I'm trying to wrap my head around this.
    One thing I am questioning now is wire.... This Bacnet trunk is all ran in Trane Purple Wire. I've never used anything other than ConnectAir W221P-2003ORRB1 for Bacnet and no strange problems.
    Does this purple wire work for Bacnet?
    I know there's lots more to verify.
    Thanks!
    Eric

  2. #2
    Join Date
    Aug 2006
    Location
    Beachwood, NJ
    Posts
    197
    Post Likes
    Havn’t seen That purple wire in a long time but I do remember trane was famous for that purple wire color when running Lon trunks. Not sure what the wire spec were.
    Just when I thought I knew it all, I realize that I am still learning something new everyday!

  3. #3
    Join Date
    Jan 2004
    Location
    Oregon
    Posts
    2,017
    Post Likes
    Purple wire is 18-2 and is not compatible with Lon, I would re pull the comm link with proper Lon rated wire, I think 24-2.
    Federal Reserve, stealing your kids futures since 1913

    UA290

  4. #4
    Join Date
    Jun 2013
    Location
    Maryland
    Posts
    11
    Post Likes
    Thread Starter
    Yes, this is the purple 18/2 stranded/shielded wire Trane makes for comm5 and such. This system is all bacnet ms/tp, not lon.

  5. #5
    Join Date
    Jun 2004
    Posts
    833
    Post Likes
    The purple Trane 18-2 shielded wire is what is used for the BACnet links. You should be fine if it is this. Check for BACnet terminating resistor at the EOL

  6. #6
    Join Date
    May 2012
    Posts
    58
    Post Likes
    Go to Chipkins site and download their "BACnet for Field Technicians". Beyond lots of straightforward stuff there is a chapter on MSTP troubleshooting.
    Things to remember:
    1. Lots of people don't bother with EOLs because "It was working when I left".
    2. People change wire types on a bus. Don't!
    3. Shields have to be continuous and grounded only once.

  7. #7
    Join Date
    Aug 2006
    Location
    Beachwood, NJ
    Posts
    197
    Post Likes
    Quote Originally Posted by acjourneyman View Post
    Purple wire is 18-2 and is not compatible with Lon, I would re pull the comm link with proper Lon rated wire, I think 24-2.
    Trane did use the purple wire with lon, they used a 82ohm resistor at each end. I have seen it on startups, not saying it was first choice but it was used.

    Here is the Trane Comm5 info:

    BASSVN01AEN_603.pdf



    Bacnet we use 22/3wire twisted shielded cable for the Big Blue controllers. But I have seen some others use 18/2 and 18/3 wire out in the field when reusing an old communications trunk. Again not my first choice but its out there.

    Craftyringwiseveteran is right about EOL terminators. Heres the PDF he mentioned on chipkins bacnet for field technicians.

    Bacnet For Field Technicians.pdf

    Hope this helps.
    Just when I thought I knew it all, I realize that I am still learning something new everyday!

  8. #8
    Join Date
    Feb 2016
    Location
    Swansea, MA
    Posts
    2
    Post Likes
    I have run into this issue few times with bad lon cards as well. Only way I was able to dial it in was disconnecting one card at a time and monitoring/recomissioning.

    Sent from my SM-J700T1 using Tapatalk

  9. #9
    Join Date
    Jun 2013
    Location
    Maryland
    Posts
    11
    Post Likes
    Thread Starter
    Thanks for the info and links, guys.

  10. #10
    Join Date
    Jun 2013
    Location
    Maryland
    Posts
    11
    Post Likes
    Thread Starter
    Thanks again. I noticed that there is one run to a Trane UC400 that is using the Orange 22/3 added after the original job. Different wire than rest of job. I'll change that so the whole trunk is the 18/2 Trane purple wire. Someone had added a 120 ohm resister to that controller. But it's not an EOL device, it's the last device before the KMC fullbac router. But when I removed the resistor, the entire comm link went down, not just the 5 devices we have apparently typically lose sporadically. One of the End of Lines is the KMC fullbac router, with its jumpers set to be EOL. Maybe I should re-jumper that and put an 82 ohm resister at the router? And maybe find the KMC vav controller that might be at the other end, re-jumper that and put an 82 ohm resistor in?

  11. #11
    Join Date
    Feb 2009
    Location
    Northeast
    Posts
    481
    Post Likes
    I would use the KMC jumpers on the 2 ends to terminate the trunk. Remove all other resistors. Then take the Viconics devices off the trunk.

    If the trunk is still down then you should start taking voltage measurements on the trunk, + to - to GND to SHD in all combinations. Record data. Maybe unhook everything then start adding close to the router. Record voltages of trunk as you add devices 1 at a time. Plus while segment is disconnected at both ends check OHMS between all conductors including to ground.

    Your network is small enough that starting from nothing and methodically adding is probably the best way to find the fault. On bigger networks I usually split it in the middle and try communications and voltage readings on each side until I narrow down the fault.

  12. #12
    Join Date
    Jun 2013
    Location
    Maryland
    Posts
    11
    Post Likes
    Thread Starter
    Great. Thanks billcontrols.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.