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  1. #1
    Join Date
    Jun 2006
    Location
    Omaha, Nebraska
    Posts
    869

    Honeywell RapidZone Issue

    I've never really had to mess with a RapidZone system before. They usually just work. This one does some things I'm not liking, and I think it's primarily because the RTU is oversized.

    It's about a 3,000 Sq. Ft. office area served by a 12 ton 2 stage Voyager. The problem was the second stage almost never came on and the first stage short cycled all day long so there was not much humidity removed. I added a hot gas bypass of sorts to the 1st stage, a Rawal APR valve. It works great! Now the problem is the stages go 0..1..2..1..0. about every 5 minutes. The discharge temp never gets below 50 so I know it's not the low discharge epid dropping it out. It has 3 zones. Two of them are mostly satisfied most of the time. Very little if any terminal load. The other zone, East, stays about 1-1.5 above setpoint all the time. Its terminal load is usually around 25-35.

    The input signal to the CoolingStages epid moves rapidly from around 120 down to -25. Questions: What is this number? How is it calculated? If it's an epid, can I slow it down? I'm not sure why, but this number drops rapidly even when terminal load is not changing much. When it gets to zero, the stages are all off. I pretty much want stage one to stay on when there's any terminal load at all since the APR valve will throttle the load down.

    A Honeywell programmer told me that I need to use Lonspec to tweek the programming, but I can't figure out how to get my .rzb file to open in Lonspec. Can anyone shed some light on this? I've done a lot of programming in the past but this Honeywell stuff is confusing. Thanks!

  2. #2
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    1,024
    Open the existing Rapid Zone project , select network, dont worry if you are not connected, just close the message boxes. Select project, backup and it will create a ntb file. Copy the ntb file into a folder named as your project in your Lon Spec installation folder. Open Lon Spec and select restore project, select the ntb you just copied and you are done. The discharge low limit epid may be shutting off cooling in the cooling stages epid.

  3. #3
    Join Date
    Dec 2006
    Location
    Boston area
    Posts
    255
    After you set up your Rapidzone system the last tab is "Finish" in which you can save the job. After saving job a network tab opens up, if you open the network tab it brings up another screen and if you back up the job in that screen it is saved as an "ntb" file instead of a "rzb" file and that ntb file can be imported into Lonspec. If you open an existing job in Rapidzone the network tab should also be there.

  4. #4
    Join Date
    Jun 2006
    Location
    Omaha, Nebraska
    Posts
    869
    You guys rock! That worked. The first time I must have done something wrong because it told me I was missing a .hdr file.

    So the input to the cooling stages control loop is a math function, which is a result of a series of other math functions. I'll attempt to draw a diagram later and see if I can figure out which number to tweak. I didn't see terminal load in any of the math functions.

  5. #5
    Join Date
    Jun 2006
    Location
    Omaha, Nebraska
    Posts
    869
    That is some NASA level programming just to determine how many stages of cooling to run! Any idea what spCCPH is used for? I'm guessing cooling cycles per hour? It's set to 0.0011.

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