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  1. #1

    Metasys AHU Issues

    I'll try to keep this short.
    We have a building with 17 AHU's, 100+ vav's ect using Metasys NAE's and FEC controllers. The building is 2 years old and most things run ok. I have 2 AHU's in particular with a strange issue. Each AHU has its own schedule and exception schedule. These AHU's have nearly every possible point displayed on the front end, complete overkill, but whatever. They have optimal start, and they are scheduled to be occupied @ 6am, Unoccupied @ 5pm.

    The issue I am having is around 4 am I see (with a trend) the unit go Occupied, 4:05am Unoccupied, 4:10 Occupied, 4:18 Unoccupied ECT. Every morning I see these units doing this, banging on and off until it reaches its "actual" start time of 6am and then it just runs smooth until Unoccupied.
    It will also do similar things at 5pm when it goes unoccupied. I thought it might be something with the optimal start since the other units are starting early also, but I compared the settings of units that are working and I didn't catch anything different. The schedule looks fine, optimal start is set up the same as other units ect. I do notice that these units are hunting really bad all day, OA swings 100%, MA drops to 36 degrees, OA damper goes to 0%, heat valve goes open ect. This may be part of the problem but I'm just not sure. I figured I would start with "why am I getting a Occ, UnOcc multiple times between 4am and 6am." I'm stumped on this one. I've had Training on Metasys MSEA and CCT. I don't work with it every day but I can navigate around pretty well if anyone has any ideas.

    Thanks

  2. #2
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    Mar 2010
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    Quote Originally Posted by justtoofast1968 View Post
    I'll try to keep this short.
    We have a building with 17 AHU's, 100+ vav's ect using Metasys NAE's and FEC controllers. The building is 2 years old and most things run ok. I have 2 AHU's in particular with a strange issue. Each AHU has its own schedule and exception schedule. These AHU's have nearly every possible point displayed on the front end, complete overkill, but whatever. They have optimal start, and they are scheduled to be occupied @ 6am, Unoccupied @ 5pm.

    The issue I am having is around 4 am I see (with a trend) the unit go Occupied, 4:05am Unoccupied, 4:10 Occupied, 4:18 Unoccupied ECT. Every morning I see these units doing this, banging on and off until it reaches its "actual" start time of 6am and then it just runs smooth until Unoccupied.
    It will also do similar things at 5pm when it goes unoccupied. I thought it might be something with the optimal start since the other units are starting early also, but I compared the settings of units that are working and I didn't catch anything different. The schedule looks fine, optimal start is set up the same as other units ect. I do notice that these units are hunting really bad all day, OA swings 100%, MA drops to 36 degrees, OA damper goes to 0%, heat valve goes open ect. This may be part of the problem but I'm just not sure. I figured I would start with "why am I getting a Occ, UnOcc multiple times between 4am and 6am." I'm stumped on this one. I've had Training on Metasys MSEA and CCT. I don't work with it every day but I can navigate around pretty well if anyone has any ideas.

    Thanks
    This is just a flying grasp at a falling straw.... Since you have two AHU's acting up, one- are they on the same com trunk and two- have you tried re-addressing them?

    Does anything else on the system start at 4AM that may share some programming similarities?

    More often than not these problems are more of what is NOT causing it.

    Good luck. Keep us posted.

    GT
    If a day goes by and you have learned nothing, I hope you got a lot of sleep.

  3. #3
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    Nov 2006
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    Without being there to test, it is impossible to say.

    I would consider what factors the two units have in common, and confirm the temps you are seeing on the screen with an independent temp device. If those temps being displayed are not accurate, then you may have an electronics-based issue instead of a software issue. I would also consider, if temps are correct, whether there is a program command to maintain a setting while in unoccupied mode that would bring the units up.
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  4. #4
    Join Date
    Jan 2013
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    7
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    Last edited by jpsmith1cm; 02-23-2013 at 08:15 PM. Reason: non AOP member

  5. #5
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