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Thread: Metasys bus

  1. #1
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    Metasys bus

    Help! We have a system that has a space that was remodeled. The demo guys took 2 water source heat pumps out with unt controllers. The problem is that there is another space being remodeled on the other side of the building. The question is will it take the loop down if we put the controllers from there space onto the trunk in our space? Not sure we were given the correct ones. I know it's not much info but could it be a link issue? I have checked polarity and voltage on the bus in the mechanical room we are working in and from the controllers we reinstalled. It matches the readings we should be getting. We don't have good access to trace comm loop down to see where everything goes (Sheetrock ceilings):-(. Thanks for any help!

  2. #2
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    Adding two UNT's shouldn't be an issue even if you exceed 50 ASC's on the trunk. You will want to make sure you don't duplicate any device addresses.
    If you can't fix it with JB Weld, Duct Tape, and Ty Wire it has to be replaced.
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  3. #3
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    Actually there are a few things to determine first. Are the UNTs on the same front end controller. If they are on seperate controllers then they wont communicate or run any processes. Like Desert Guy said you don't want to duplicate any addresses. The other thing to consider is to make sure you keep the controllers daisy chained and not T-tapped.

  4. #4
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    Quote Originally Posted by desert guy View Post
    Adding two UNT's shouldn't be an issue even if you exceed 50 ASC's on the trunk. You will want to make sure you don't duplicate any device addresses.
    These are existing unt100's that were removed by demo guys. They would go back on the same comm link. We checked the addresses and they are what they are labeled. I'm wondering if something didn't happen to them when they were removed. It seems that the dc volts on the comm are reading correctly (2.3-2.7 vdc) from the controllers but when we attached to the chain the building manager said he had several devices go down. We reconnect without the devices everything comes right back. I plan on connecting directly to each one tomorrow to see if it one or the other that may bad.

  5. #5
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    Quote Originally Posted by simux View Post
    Actually there are a few things to determine first. Are the UNTs on the same front end controller. If they are on seperate controllers then they wont communicate or run any processes. Like Desert Guy said you don't want to duplicate any addresses. The other thing to consider is to make sure you keep the controllers daisy chained and not T-tapped.
    We are not sure about the front end controller. There are 2 comms coming through the room. That could be a possibility but we tried both loops. Made sure they were daisy chained and drain wires connected also. Thanks for the replies.

  6. #6
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    Make sure that you don't have the polarity reversed on the N2 bus connections. This could really cause problems. JCI has a good document on there site describing the N2 bus and associated communications. It is relatively old as it talks about their older generation Metasys systems but it is still very relevant. Use theit full text search engine to locate the document.
    Steve Jones
    Managing Partner
    The S4 Group, Inc.

  7. #7
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    Quote Originally Posted by steves4 View Post
    Make sure that you don't have the polarity reversed on the N2 bus connections. This could really cause problems. JCI has a good document on there site describing the N2 bus and associated communications. It is relatively old as it talks about their older generation Metasys systems but it is still very relevant. Use theit full text search engine to locate the document.
    Yes that document is pretty good for what we are dealing with. We've made sure of the polarity. We are going back out today to check some details of the devices.

  8. #8
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    As a confirmation I would bench test the individual devices using a RS485 converter to connect to the device with HVAC Pro. S Squared makes a very nice device that has built in circuitry to test the N2 bus and a downloadable utility to run the tests and record the results.
    Steve Jones
    Managing Partner
    The S4 Group, Inc.

  9. #9
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    Quote Originally Posted by steves4 View Post
    As a confirmation I would bench test the individual devices using a RS485 converter to connect to the device with HVAC Pro. S Squared makes a very nice device that has built in circuitry to test the N2 bus and a downloadable utility to run the tests and record the results.
    I have that device that's what we are going to try today. I've got hvac pro on windows 7 is there any issues that is known with 7?

  10. #10
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    Not that I know of. We use HVAC Pro with our Windows 7 systems and the S Squared device all the time. Make sure that you have downloaded the latest drivers from the S Squared site.
    Steve Jones
    Managing Partner
    The S4 Group, Inc.

  11. #11
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    Quote Originally Posted by steves4 View Post
    Not that I know of. We use HVAC Pro with our Windows 7 systems and the S Squared device all the time. Make sure that you have downloaded the latest drivers from the S Squared site.
    I didn't know about the updated drivers I'll have to get them. Thanks

  12. #12
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    HVACPro is not very Windows 7 friendly; It's not supported. That being said it runs on many Windows 7 machines (including JCI tech laptops) but I've also seen plenty of machines it will not run on. Ensure you're running it in Windows XP mode and cross your fingers! Also make sure you're running version 8.08b.

  13. #13
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    Quote Originally Posted by samwinter View Post
    I didn't know about the updated drivers I'll have to get them. Thanks
    If you download the USB485DiagN2 utility the latest drivers will come with it.
    Steve Jones
    Managing Partner
    The S4 Group, Inc.

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