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  1. #1
    Join Date
    Jan 2012
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    145

    Johnson Control FX16 goes haywire when connected to Front End or when overridden

    Has anyone come across this problem where the FX16, when it is running a program will work fine, but once it is connected to the front end, it may start behaving erratically? OR when the building operator overrides something to turn off (I created an override using a selector switch).

    Examples of the FX16 behaving erratically include:

    Temperatures reading -300 deg C, when resistance is within range.
    Staggered engaging and disengaging contacts (in the case of lead lag operations)
    Calibration/Offsets reading an arbitrary number, which consequently affect the actual temperature

  2. #2
    Join Date
    May 2011
    Location
    North Carolina
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    314
    are you hooking the front end to the supervisory link? does it have a display where you can disconnect the front end and manually override from the controller?

  3. #3
    Join Date
    Jan 2012
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    145
    Quote Originally Posted by sycontrol View Post
    are you hooking the front end to the supervisory link? does it have a display where you can disconnect the front end and manually override from the controller?
    Sorry for the severely delayed response, sycontrol. It is hooked through a BACnet network, and yes, I can disconnect it from the front end to the FX16 Supervisory Controller. I can also manually override on the LCD display on the FX16.


    DaveCR, I have not had issues in the past, but have occasionally seen this problem occur when I test systems using the override feature. What's more, when I am on the computer and logged through the FX60, when I override a pump (for example), it would automatically trigger some sort of chain reaction. Examples would include a 1000ohm temperature sensor reading -5 to become 327 deg C. Upon cold reboot of the FX16 will the controller become normal again, but another override attempt will kickstart this reaction again.

    mechdorn, This override was created using the Output "On/Off Output", the one with the Red Astrix on the object. Usually when I rename these inputs, I use slot 6 (off) and 7 (on), and 255 (auto). I have tried 0 and 1 in the past, but found these do not always work. Do you also use slot 6 and 7 for Off and On, respectively?

  4. #4
    Join Date
    Aug 2010
    Location
    NJ
    Posts
    99
    The only time I have had something similar happen is when the bus was not terminated properly with EOL resistors. I build overrides into every program and have never seen that happen specifically. I do have a system with an XM14 module on it that acts weird when the DIs change state. We narrowed it down to the 220 ohm EOL resistor. I have also had BACnet trunks act strange if the EOLs are not correct. How is your selector switch brought into the system? Using a hardwired DI?

  5. #5
    Join Date
    Jun 2009
    Location
    StL, MO
    Posts
    582
    N2, LON, BACnet? Front end? I've had no issues with N2 or BACnet FX16s connected to Johnson FX (JACE) front ends.
    UA LU 562

  6. #6
    Join Date
    Aug 2010
    Location
    NJ
    Posts
    99
    I have done lead lag a couple of different ways, using PLC and in one case using some logic blocks. Sometimes the timers act strange in the FX. Try this: First, you need a System Resources Block enabling a Clock and Date Set block. This will enable the RTC in the controller. Then, use an On-Off Time Scheduler Block to create your Switch Event. Make sure you set the Time Schedule details in the Application Point table to activate, say at 9 am every Monday. Set the duration as 1 minute. What's nice about this block is that you can connect Event overrides to the On Forcing and Off Forcing inputs. The on Forcing is used as a Manual Switch point. You turn it on, then off to force your switch. The Off Forcing is used to Hold the Switching function, maybe if a pump is out of service. Bring the Output of the Time Schedule Block to an Event Counter. Set its attributes to Full Scale 2 and AutoReset. Bring the Counter output to two Compare Blocks. Set one compare condition equal to zero, the other compare condition equal to one. Send those outputs to two separate AND blocks, together with a System Enable point and you will have your Lead Lag. One output will be Pump1 Lead. The other will be Pump2 Lead. The System Enable will allow your Operators to shut down the system when they need it off for service.

    I know that is a lot of information, but if you play around with that, you can get it to work. I prefer PLC, but you have to understand the ins and outs of the code.

  7. #7
    Join Date
    Jan 2008
    Location
    Near Philly
    Posts
    512
    Quote Originally Posted by Questionz View Post
    Has anyone come across this problem where the FX16, when it is running a program will work fine, but once it is connected to the front end, it may start behaving erratically? OR when the building operator overrides something to turn off (I created an override using a selector switch).

    Examples of the FX16 behaving erratically include:

    Temperatures reading -300 deg C, when resistance is within range.
    Staggered engaging and disengaging contacts (in the case of lead lag operations)
    Calibration/Offsets reading an arbitrary number, which consequently affect the actual temperature
    Exactly how did you create this override? The only override that I know of is SNVT hvac override.

  8. #8
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    I would make sure all your data types are right for what you are connecting to, seen weird things happen when one is volts and another is Temp and another is Percent, etc.....

  9. #9
    Join Date
    Aug 2010
    Location
    NJ
    Posts
    99
    I did not read your entire post at first; selective reading. Try setting up your Override point into the DO on the override input as a SNVT 10160. Then, clear all of the bits, but select only 0,4,5. Label 0 to Auto, 4 to Hand and 5 to Off. This gives you a good override using the typical Hand, Off, Auto type of point. You can bring it to the display, use it in CommPro, etc. This is really useful for me.

  10. #10
    Join Date
    Jan 2012
    Posts
    145
    Chris, I make sure my data types are correct, because it is confusing when I'm expecting one type of unit while another is being displayed.

    DST-Tech, Thanks for your suggestion! When I was trying to wait for your reply in the past, I was on site so I tried to use 0=OFF, 1=ON, and 255=AUTO. Unfortunately, I am unsure whether this will even work, so when I am on site next, I will try bit 0, 4, 5. Will the program know what bit 4 and 5 are? I ask this because I have never used these bits before, and when I choose bit0, I can confirm that the unit will be OFF, not in auto.

  11. #11
    Join Date
    Aug 2010
    Location
    NJ
    Posts
    99
    Try it, you'll like it. You should use the bits as specified, since these are what the controller recognizes. The bits have their default names, which also works, but putting in more familiar User Names makes it a little more user friendly. Also, set the points as Permanent Point types when selecting the SNVT, and default them to AUTO. If you don't, the DO's won't work until they are commanded to the AUTO position.

  12. #12
    Join Date
    Jan 2012
    Posts
    145
    I just want to make sure though, when I expose the "OVERIDE" from the DO block in FX Builder, my previous settings were to have 0=OFF, 1=ON, and 255=AUTO.

    If I follow your method, then 0=AUTO. When i was testing each bit on the front end (FX60), I was able to turn off the pump when I overrode the command to bit 0.

    Is it safe to assume that if I expose these bits the way you specified, the system will know bit 0 is not OFF, but it rather it should be AUTO? Through Lead Lag, the system was running in sequence at bit=255. When I overrode it to bit=0, the pump turned off. When I overrode it to bit=1, it turned on.

  13. #13
    Join Date
    Aug 2010
    Location
    NJ
    Posts
    99
    The pilot_status snvt 10160 has pre-defined states. Usually 255 is a null condition. State 0 is defined as pilot_auto, State 4 is defined as pilot_on and State 5 is defined as pilot_off. That is where you get the Auto, On and Off states from. To try this in lieu of what you are doing, you will probably have to go into the Application Points table and set the Override point to a different type initially to clear your previous selections, like 111 HVAC_Override. Once your information is cleared, go back and change the point type back to 10160. Then, open up the States table and clear everything, then only select the 0,4,5 as stated previously. You will have to download your FX controller with the new setup. I would also remove the override point from your profile (N2 or Bacnet) before making these changes, then once you are done, add it back. If you don;t change anything else, it will probably take the same point address as it previously had. Then I would also remove the point from your FX60 and add it back again. If you are N2, you can add it manually. Bacnet, as you probably know, just rediscover the points and add it back in.

    I have also had some AI point issues in the past when using Bacnet FX16's with the wrong AI blocks selected. Sometimes they work and sometimes they don't. So, I always use the starred points when building apps. There was also another occasion where the Family ID of the FX16 randomly changed to something else and I could not do anything with the controller, causing erractic readings on the AIs and BOs. I re-flashed it with the correct firmware and reset the controller ID, but ultimately the controller had to be replaced. They are good controllers, but sometimes they do things that do not make sense. Good Luck.

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