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  1. #1
    Join Date
    Jun 2009
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    FX PCT Programming question

    I have a small office building that I need to replace an old Honeywell Rapid zone system and the customer wants it done in Johnson.
    It is just a VAV Air handler, 2 stages of DX and a hot water coil, Bypass damper for static control. It is set up as a voting system among the VAVs (They don't have reheat) to determine if the Air handler runs in heat or cool.
    My question is, is it possible to do this with just PCV VAV controllers and a PCA controller for the Air handler and build the logic in the PCA for the changeover mode, or would I need a JACE to network it all together?
    Any input is greatly appreciated

  2. #2
    Join Date
    Sep 2002
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    Sound like this might be a good application for the new Verasys system from Johnson, but talk your distributors technical team as see what they advise.

    Controls is a lifestyle not a job

  3. #3
    Join Date
    Dec 2007
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    Connecticut
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    I just did a job like this using a PCG for the AHU's and PCV's for the zones. There were 6 Ahu's with 10 VAV's each. All my voting was done peer to peer so no JACE was needed. The Verasys product is pretty good from what I here but I have never personally worked with it.

  4. #4
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    Jun 2009
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    Thread Starter
    Thanks! Looking at the Verasys bulletin now
    UA Local 420 Philadelphia, Pa

  5. #5
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    Jun 2009
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    Thread Starter
    Great thank you for the input. What did you need to do to reverse the action of the dampers when it switched between heat and cool?
    UA Local 420 Philadelphia, Pa

  6. #6
    Join Date
    Dec 2007
    Location
    Connecticut
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    I did a custom pressure dependent application for the zones. based on temp and Co2, I set the dampers to heat, cool, or vent. The AHU counts all the requests and makes a decision. I also put in a discharge air permissive that holds the dampers to min position if the air in the duct is not suitable for what the space is requesting.

  7. #7
    Join Date
    Jun 2009
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    Quote Originally Posted by RDF420 View Post
    ...is it possible to do this with just PCV VAV controllers and a PCA controller for the Air handler and build the logic in the PCA for the changeover mode...
    Yes,
    Johnson has canned routines that can be downloaded that are called Commercial Zoning Application.
    UA LU 562

  8. #8
    Join Date
    Feb 2009
    Location
    Northeast
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    I think Verasys is the route you should go. I have used the PCT zoning system. Works fine, but I had to customize both times I used it due to my equipment not the same as the programmer designed. (Retrofits) The PCT zoning is not set up to handle a modulating water coil. At first the VERASYS did not do modulating outputs either. The last seminar a couple of months ago indicated they support modulating outputs now.

    On both of my custom VVT jobs I was able to use Peer to Peer to standalone the application.

    On the first I followed the PCT application very closely. The big modification was modulating heating and cooling coils. I had to adjust the change over timing and voting priorities to get this system to switch back and forth properly. Also the plant does not make both hot and chilled water at the same time. So when heating we have to use ventilation for cooling, and in cooling we just recirculate Return air for heating. The system is easy at outdoor extremes, but near the plant H/C changeover it was difficult to get all the details worked out. DX cooling would have been much easier. It takes a long time for a six row cooling coil to warm up with 74 degree return air.

    The second custom job was hard because the system we were tearing out had the "brains" of the zones at the stat not the box. PCT and Verasys both put the brains at the box. So wiring in sheetrock walls and ceilings was not correct for the JCI applications. I used the PCG in the RTU and swapped JCI TEC3000 series for the stats. I had to redo all the peer to peer addressing. Only gotcha was the demand I read from the TEC did not increase when Stat was in opposite mode. So if the RTU was heating, stats locked in heating output only, cooling demand stayed at zero no matter how warm the zone got. I could have fixed this in the RTU using PCT so the RTU would calculate the demand, but it was easier at that point to put the demand calculation in the JACE.

    Both systems work well and the customers are happy.

  9. #9
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    Jun 2009
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    Quote Originally Posted by billcontrols View Post
    ... I have used the PCT zoning system. Works fine, but I had to customize both times I used it due to my equipment not the same as the programmer designed...

    Contrary to what JCI instructors say, PCT/CCT is all about the green triangles.
    UA LU 562

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  11. #10
    Join Date
    Jan 2008
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    Well said Dave CR! I'm going to use that one! I am not too much of a fan of the QA apps unless they are exact to what I need. Then they are just OK

    OP- if you are not very familiar with PCT programming i would look into Verasys. I have not used Verasys as i like to be able to get into the programs and have heard mixed things but it's worth looking at i hear.

    PCT certainly has its quirks and they can really consume some time.

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