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  1. #1
    Join Date
    Apr 2004
    Location
    Michigan
    Posts
    295

    VMA Controller configuration

    I've got some series fan powered VAV boxes at a job that used to be controlled by an old C.S.I. system, and have had new johnson controls installed by another company.

    They have VMA controllers, and TMZ room sensors.

    This is my first time hooking up a laptop to these, or any for that matter, and have some time to kill on this job, so I thought I'd use it as a learning experience, and the customer has been having some problems with these zones.

    Everything in the config file looks normal, but there are a couple things about the inputs on these particular controllers that make me wonder what the installer was trying to accomplish.

    There is a fan proving current relay installed on BI-1, which I understand is dedicated to the temporary occupancy button on the room sensor.
    There is a jumper installed on BI-2, which I understand is meant for an occupancy sensor.
    Nothing is attached to BI-3.

    In the Q&A list, Sensor for occupancy mode, and it's action = Occupied mode when occupancy sensed.
    In the config. parameters, the occupancy mode = occupied, and the occupancy timer is set for 60 minutes.

    I only got a quick look at the facitities front end, as it is in a locked room, and the operators are not very friendly, so I don't remember exactly which points are mapped to the front end.

    Can anyone explain the logic in this setup?

  2. #2
    Quote Originally Posted by lenb View Post
    I've got some series fan powered VAV boxes at a job that used to be controlled by an old C.S.I. system, and have had new johnson controls installed by another company.

    They have VMA controllers, and TMZ room sensors.

    This is my first time hooking up a laptop to these, or any for that matter, and have some time to kill on this job, so I thought I'd use it as a learning experience, and the customer has been having some problems with these zones.

    Everything in the config file looks normal, but there are a couple things about the inputs on these particular controllers that make me wonder what the installer was trying to accomplish.

    There is a fan proving current relay installed on BI-1, which I understand is dedicated to the temporary occupancy button on the room sensor.
    There is a jumper installed on BI-2, which I understand is meant for an occupancy sensor.
    Nothing is attached to BI-3.

    In the Q&A list, Sensor for occupancy mode, and it's action = Occupied mode when occupancy sensed.
    In the config. parameters, the occupancy mode = occupied, and the occupancy timer is set for 60 minutes.

    I only got a quick look at the facitities front end, as it is in a locked room, and the operators are not very friendly, so I don't remember exactly which points are mapped to the front end.

    Can anyone explain the logic in this setup?
    When button{BI-1} is pushed or motion sensor {BI-2} will occ for an hour after pushed or triggered. But with the jumper on sensor will always cause the box to stay occupied.
    Regardless of schedule , or the timer.

  3. #3
    Join Date
    Apr 2004
    Location
    Michigan
    Posts
    295
    So the only thing that would change it to unoccupied would be an override from the supervisor, and then nothing would change it back to occupied until the override was released?

    And the current relay attached to BI-1, is there any purpose for that? To indicate proven fan operation at the front end, in case a motor failed,
    even though that input is meant for the wall sensor button?

    Could it possibly cause any problems, perhaps on start up after a power failure, or something? Starts up in occupied, but once the fan starts, closing the current relay, could that be interpreted as a button push at the wall sensor, changing the mode to unoccupied, if there were no jumper on the occupied sensor input?

  4. #4
    Man, i missed the part where the current sensor was on BI-1, have no clue what thay were thinking. Time to startover on the wiring.

  5. #5
    Join Date
    Sep 2007
    Location
    Michigan
    Posts
    290
    What kind of problems is the owner having? The better question may be, what would you like the box to do with the occupancy sensor? You have "Occupancy when occupancy sensed" selected; only an Operator Override on the Occ BD point will allow you to control the mode.

    Typically you Schedule the box to standby during "occupied hours" used with the temp bias, and then to unoccupied when the building is "unoccupied" with a larger unocc bias. Even if the box is scheduled to unoccupied the box will still use the occupancy sensor and switch to that mode if contact closes. With a series box if your shutting down the air handler or heating system during unoccupied the box should be commanded to the shutdown mode.

    Controls setup this way usually have complaints about recovery time, people don't understand the room isn't going to jump from 68 to 72 in 5 minutes after they walk in.
    It helps that you understand the box changes in the different modes, we've had issues with some customers understanding that set point doesn't change during modes, the box contains all the logic. It helps to map actual cooling/actual heating.
    Example:
    UnOcc CLG BIAS 11.5 (giving 85)
    Stanby CLG BIAS 5.5 (giving 79)
    CLG BIAS 1.5 (giving 75)
    Common SP 73.5 (TMZ your probably using HTG/CLG SPs?)
    HTG BIAS -1.5 (giving 72)
    Stanby HTG BIAS -5.5 (giving 68)
    UnOcc HTG BIAS -11.5 (giving 62)



    I don't understand the jumper on BI-2, that could have someone that didn't have access to HVAC-Pro to change the config and that was their solution to OCC-S problems. Your fan status should be on BI-3 if using occ-s.
    "Yeah I can figure out whats wrong with it, but you were here first and there isn't room for two, plus it's cold up here, I'll be in the van"

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