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Thread: Trane zn520

  1. #1
    Join Date
    Aug 2006
    Location
    ohio
    Posts
    259

    Trane zn520

    A couple of weeks ago I went on a call for a unit vent overheating a room. heating valve 100% open and fan running. I connected to zn520 with rover and I found that setpoint was correct from thubwheel (cooling) but discharge air temp setpoint was for heating (150 or so can"t remember it has been awhile). So I downloaded controller and it seemed to operate fine until I disconnected then the same happened again. So I ordered a new zn520 and downloaded and everything was ok for maybe two weeks and I get a call on this again, I can only assume it is doing the same thing I was told it was overheating and the fan wont shut off, same as before. The bus of trane unit vents goes back to a metasis controller but I cant believe this is causing the problem because this is one of 100 uv's on site.

  2. #2
    Join Date
    Jan 2005
    Location
    NY
    Posts
    73
    fan runs all the time when occupied on a zn520

  3. #3
    Join Date
    Aug 2006
    Location
    ohio
    Posts
    259
    This is switchable from auto to low med high.

  4. #4
    Join Date
    Aug 2006
    Location
    ohio
    Posts
    259
    After approximately 5 minutes of run time with the controller in a cooling mode if the discharge air temp doesn't change then the datstpt becomes the same as the dat which will result in the room overheating. Is this some sort of safety, has anybody seen this before?

  5. #5
    Join Date
    May 2007
    Location
    Pacific Northwest
    Posts
    38
    Quote Originally Posted by michael26 View Post
    A couple of weeks ago I went on a call for a unit vent overheating a room. heating valve 100% open and fan running. I connected to zn520 with rover and I found that setpoint was correct from thubwheel (cooling) but discharge air temp setpoint was for heating (150 or so can"t remember it has been awhile).
    In this statement I assume you mean that you were seeing the correct setpoint from the thumbwheel in Rover and that the setpoint should have been generating a call for cooling yet it was heating with a DAT setpoint of around 150 degrees. I am curious what you were showing for the 'effective setpoints'. The ZN520 does not directly use the thumbwheel setpoint. It uses it in combination with the default setpoints to calculate 'effective setpoints'. If your local default setpoints are out of whack or if the Metasys is communicating wacky default setpoints, this can skew the thumbwheel setpoint to make your effective setpoints way different than the thumbwheel setpoint.

    If you haven't already, take a good read of the ZN520 IOM which is CNT-SVX04A-EN. It explains all of this fairly well.

    Good Luck,
    Knobber

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