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  1. #1

    Alerton Envision Bactalk 2.5 and incremental actuators

    Hello,

    I am working on a building that has incremental or time based actuators on all of the terminal boxes and reheat actuators. Currently I see the time is set anywhere from 45 to 75 seconds. My main concern is I do not see anywhere in the system that an autocalibrate function is in place. Other control systems that I have installed and programmed with incremental actuators have a means of auto-zero or autocalibrate. It resides in the controller or is scheduled in groups. If the actuators are not being driven closed to get back in sync, every 24hrs poor control of airflow and reheat will be the results.

    Any help would be appreciated.
    Thanks
    Sean

  2. #2
    Join Date
    Dec 2008
    Location
    Seattle WA
    Posts
    100
    Alerton controllers don't need to do a scheduled autozero, ever. Here's why:
    There is a motor timing value you spoke of, 'n' seconds. The Alerton controller drives the actuator open and shut as necessary, keeping track of how many seconds it has commanded the actuator, so it knows what % of open the actuator is. If the actuator ever reaches 0% or 100%, it will continue to drive the actuator in the same direction for 'n' seconds, effectively (and passively) calibrating itself.
    It's rare for an Alerton controller to lose it's position in the first place, and because of the overdrive at 0% and 100%, every night when the box shuts off and goes to zero, this drives it shut for an extra 'n' seconds... effectively calibrating it.

    Cheers!

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