If you try to apply power from the Trex unit when the device is externally-powered, the Loop Diagnostics application prevents the Trex unit from supplying power. This protects the Trex unit from damage.
Warning: Connecting power to the positioner may cause changes to the tuning set that cause the valve/actuator assembly to stroke. To avoid personal injury and property damage caused by moving parts, keep hands, tools, and other objects away from the valve/actuator assembly.
Warning: When power is provided to a positioner that is in service, the valve may move causing process fluid or pressure to be released. To avoid personal injury and property damage caused by the release of process fluid or pressure, isolate the valve from the process and equalize pressure on both sides of the valve or bleed off the process fluid.
- Connect the lead set to the HART + pwr terminals on the Trex unit and to the positioner.
- On the Loop Diagnostics screen, tap Trex Unit Power.
Select one of the following options.
Option Description Power Positioner with 4 mA(0%) Power a positioner with 4 mA. Power Positioner with 20 mA (100%) Power a positioner with 20 mA. Power Positioner with other mA value Power a positioner with a specified mA value.
- Tap OK.
To change the current being supplied by the Trex unit, do one of
- Tap a quick current button.
- Tap the up or down arrow keys to slowly increase or decrease the current. The default increment is 0.1 mA.
- Tap the pencil icon to set a mA value.
- Wait for the valve to move.
- Repeat steps 5 and 6 until the valve moves through all the required positions.
To stop powering the device, do one of the following:
- Tap Trex Unit Power to set the option to OFF. You are prompted to select a power option to set the position of the valve.
- Tap Exit. You are prompted to select a power option to set the position of the valve.
- Remove the lead set from the Trex unit. You are not prompted to select a power option to set the position of the valve.