Tridium BACnet & Modbus setpoint priorities NEED HELP!
Hello! Here is my general question followed by a detailed description of what is in place...
How can we allow both a Distech Smart Vue sensor (bacnet) as well as an AMX system (separate vendor, using Modbus) to both control (and update) the same setpoint?
Have a JACE 6 on jobsite connected to Distech BACnet controllers. The general automation system is AMX, driven by Modbus. We are using Smart Vue wall sensors, which allow the customer to change the setpoint at the sensor. So far all easy, basic stuff.
We are sending the cooling and heating setpoints to the Modbus system and the customer needs to be able to change the setpoints from the AMX panel/tablet/etc. We have the Modbus points set up under a slave network and are able to have them change the setpoints from the AMX panel...IF we have the priority level of that link (the modbus point linked to the Analog Value object) higher than the priority of the Smart Vue sensor (native setting of priority 14).
So, Modbus setpoint set at priority 1-13 (sensor at 14), the AMX panel controls the setpoint but the sensor will not allow a change. Modbus setpoint at 16 with sensor at 14, sensor controls setpoint just fine and AMX panel cannot change it.
With both the sensor control and AMX/Modbus at the same priority, it will only allow the sensor to change the setpoint (I guess since the AMX is coming from outside the native bacnet system).
Not sure if this what you need, maybe not the most elegant way of achieving what you want either.
Try using the 'Latest Number' block from the AxCommunity Logic folder.
Only one "point" can control a set point. That is what you are finding. the point with the higher priority level is the one writing the set point.
What you need to do is set your main system to write the setpoint then use your wall stat to trim it. The final value Sp + or - trim is then written to the unitary devices as a working set point.
If possible its the working sp that you need to display on the wall stat.
Keith, thanks for the response. I'm trying this right now and waiting for the AMX guys to test the setpoint from their end.
prtadko, thanks for the suggestion. I'm trying Keith's first, but will look into the trim idea as well.
So the bacnet setpoint can be changed by the Vue locally AND you want AMX to do it off a modbus point?
If you bring in the setpoint as a numeric writable and apply a separate tuning policy that has max write time of 0. Then link the modbus setpoint to priority to 14 on this numeric. The Jace should only send the setpoint once when its changed via modbus or from within the Jace. If the occupant comes along and changes it, it should then stick without being overwritten by the Jace. Then you can also link this point on the gfx and it will have the current setpoint and the ability to adjust it there also.
The issue there is the house system and the local bacstat will show different set points at the same time. Only someone with access to the Jace will be able to see which one is the current control point. The occupant could have the room set low bit someone has remotely set it high. They would not know and would likely complain that the system is not working.
Originally Posted by orion242
It all sounds pretty messy to me. I still stand by having the setpoint set remotely and the local stat used to trim.
Its a mess either way. Even if they trim at the stat, the AMX system will not have indication of the actual setpoint unless you bust out another modbus point and have them link their GFX to that.
We were able to accomplish this using Keith's suggestion using the 'Latest Number' block. I've attached a screenshot of the added AX logic as well as a note to the links used. This has been physically verified from both the AMX touch panels as well as the Smart Vue sensor. When either one is adjusted, the updated setpoint shows up on the other device.
HUGE THANKS TO EVERYONE WHO COMMENTED WITH SUGGESTIONS/IDEAS!!! I cannot speak to the other options as we were able to achieve what we wanted with the first option. Have a great weekend all!
I am working with an AMX system and am having trouble passing info to the AMX system. I was wondering if you would be willing to share a screen shot of how your modbus network/device are setup and maybe how a few modus points are configured.
Thank you so much in advance!!!!
Tags for this Thread