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  1. #1
    Join Date
    Jul 2017
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    RTU replacement affects control system

    Hello,
    I am new to this community and have no knowledge of HVAC, but have been put in charge of overseeing the cost analysis and eventual replacement of our HVAC RTU. Here is my current dilemma: We have 17 year old 50 Ton Trane Intellapak RTU with an outdated Trane Tracer control system. I am wondering if I replaced our RTU with a different manufacturer such as Carrier and we added the Carrier control system would this control system work with our existing VAV's or would there have to be a board replacement on each VAV? Thank you in advance for any help and assistance.

  2. #2
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    27,871
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    I think you need a greater level of in-person advice then you can get from any website.

    There is more to your situation than you may realize. A 50 ton Trane intellipak sits on a roof curb which matches the placement of the ductwork that it serves. Carrier likely does not manufacture a unit which will sit on that same curb and meet the same footprint requirements of your duct work. Now....you're talking about either using a curb adapter (which raises the height of the unit making it more difficult to service and introduces resistance to airflow) and as to whether or not your VAV system would work with a different brand...I would say the most likely answer is no, since you're using Tracer, most likely your VAV boxes are designed to work with the Trane control system.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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  3. #3
    Join Date
    Jul 2017
    Posts
    3
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    Thread Starter
    Yes a curb adapter would be required if we switched away from Trane, which raises the unit about 14 inches requiring us to install additional screening. I was worried that the VAV system would be an issue. We had a contractor that said the Carrier BACNet might be able to work but I was a little unsure. Thank you for your help.

  4. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    13,326
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    I think Might Work sends some red flags flying!

  5. #5
    Join Date
    Jul 2017
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    3
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    Thread Starter
    That part made me nervous as well which is why I came here!

  6. #6
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,781
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    I would verify what controllers are in each VAV box and then go from there. If they run on a proprietary bus it's a good idea to know what bus that is, and if any replacement control system can use it. Some of the Tridium stuff can talk to various proprietary busses, but you need to know what that bus is.
    Building Physics Rule #1: Hot flows to cold.


    Building Physics Rule #2:
    Higher air pressure moves toward lower air pressure


    Building Physics Rule #3:
    Higher moisture concentration moves toward lower moisture concentration.

  7. #7
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    4,028
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    Do you have a control contractor that you use, to help out on this?
    UA Local 32

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