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Thread: N2 Bus problems

  1. #1
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    N2 Bus problems

    Hey guys,
    To start, this is a NCM change out to a FX70. This site consists of DX9100, UNT, VMA, MIG N2 devices. Since the FX70 has went on the N2 bus we have experienced several points going to fault state and back to normal. These points have been several different types, boolean mostly from the MIG's. Some numeric points from DX9100 example: chilled water dif pressure. Actions taken have been, checking all N2 bus voltages at end of lines and middle. They are all within correct range. Adding a acromag repeater in the center. On the N2 network changing default normal rate to 15 seconds putting response time out to default inner-message delay to default. The normal rate busy time is about 99%, that I was told is acceptable. I have talked to tech support several times and our in house N2 experts and could use some expert advice here. Not sure what route to take.

  2. #2
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    Quote Originally Posted by Norriski Tech View Post
    Hey guys,
    To start, this is a NCM change out to a FX70. This site consists of DX9100, UNT, VMA, MIG N2 devices. Since the FX70 has went on the N2 bus we have experienced several points going to fault state and back to normal. These points have been several different types, boolean mostly from the MIG's. Some numeric points from DX9100 example: chilled water dif pressure. Actions taken have been, checking all N2 bus voltages at end of lines and middle. They are all within correct range. Adding a acromag repeater in the center. On the N2 network changing default normal rate to 15 seconds putting response time out to default inner-message delay to default. The normal rate busy time is about 99%, that I was told is acceptable. I have talked to tech support several times and our in house N2 experts and could use some expert advice here. Not sure what route to take.
    Good day,

    Do you have the latest N2 jar files for the FX? Secondly, how many N2 devices do you have on the trunk (total as well as each side of the Acromag)? Thirdly, what type (vendor and part number if possible) of wire is used for the N2 trunk?

    Cheers,

    Sam

  3. #3
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    Thread Starter
    64 Total N2 Devices.I hope that we found the middle, this was done by install as builts , and some wire tracing. So 32 on A side, 32 on B side. This is a original branch job, the wire is all correct from other install I have seen. The N2 Jar is 3.5.34.9 Thanks for the reply.

  4. #4
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    Quote Originally Posted by Norriski Tech View Post
    64 Total N2 Devices.I hope that we found the middle, this was done by install as builts , and some wire tracing. So 32 on A side, 32 on B side. This is a original branch job, the wire is all correct from other install I have seen. The N2 Jar is 3.5.34.9 Thanks for the reply.
    Good day,

    Thanks for the response! I am unsure what the latest N2 jar file version is and so I will need to get back to you on this. I mention the N2 jar, as I had issues with a FX40 that had a bug in the N2 jar that caused some grief. Upgrading the jar sorted it out and hence my comment about this.

    As for your N2 network... Having more than 32 devices on a single trunk can cause issues because of loading which results in a reduction of noise immunity. This excessive loading does not cause issues all the time, but is something to watch out for. That being said since you have split the bus with a Acromag into two 32 segments, the loading should not be an issue. Ideally one would scope the bus to check for high noise, but I do not think this is the issue given your bus description.

    My feeling is that if the N2 networked worked fine with the NCM and only had these issues when you swapped to the FX70, then it is probably something amiss with the FX70... either a bug within the N2 jar, a hardware issue with the FX70's N2 interface (RS485 transceiver chio, etc), or perhaps a hardware issue (i.e. memory, etc) with the FX70. Do you have another FX70 that you can try to see if the problem remains or follows a particular FX70? If not, then you may need to call tech support unless you have some specific N2 bus analysis tools and experience with low-level N2 data.

    Cheers,

    Sam

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