Installed a T3-LB into a Make-Up Air unit. When running it will restart itself every 5 minutes or so. When connected with ethernet only, it works fine. With BACnet and Ethernet and monitoring with T-3000, I noticed that only a few seconds go by before the program goes into Endless Loop
MAU project.prog (65.6 KB)
Make sure your program can exit every loop. You don’t need a goto at the end to restart the program, it’ll do that automatically. The system will execute the program till the last line after which it will exit and finally, at the end, it will update the outputs. If the program never exits then the outputs never get a chance to update. In fact the outputs will operate but the state is an ‘estimated’ state.
Check the execution time, it should be well below 100ms. If its longer check for overlapping gotos. In fact get rid of gotos altogether, you can search this forum for my many suggestions on how to get rid of gotos.
Here is the text of the current program I’m running.
There are no GOTO statements. And the scan time with out the BACnet cable in is 9ms.
10 IF OCC_IN = 1 THEN DMPENABL = 1 ELSE DMPENABL = 0
20 IF DMPPRV = 1 THEN FNENABLE = 1 ELSE FNENABLE = 0
30 IF DMPPRV = 0 THEN PLC_HLD = 0
40 IN_TEMP = INT ( INTAKE * 100 )
50 IF IN_TEMP < HT_ENTMP * 100 THEN HEATWT = 1 ELSE HEATWT = 0
60 IF HEATWT = 1 AND AIRPRV = 1 THEN HT_CONT = HEATWT + AIRPRV + DMPPRV
70 IF HEATWT = 0 THEN HTENABLE = 0 AND HT_OUTPT = 0
80 REM HT_CONT = HEATWT + AIRPRV + DMPPRV
90 WT_F_HT = TIME-ON ( HEATWT )
100 IF TIME-ON ( HEATWT ) > 00:30:00 AND HTALRM = 0 THEN START HTENABLE
110 IF HT_CONT < 3 THEN HTENABLE = 0 AND HT_OUTPT = 0
120 IF HTENABLE = 1 AND AIRPRV = 1 THEN HT_OUTPT = PID2
130 IF HTENABLE = 1 THEN HT_LVL = PID2
140 END
That looks pretty standard, good to see that. The only things whcih come to mind now are
- Update the firmware.
- Diable the program and see if that helps.
- Clear the program entirely and see if that helps.
If you’re still having trouble I will ask the team to step in and check through your prog file in more detail. Here’s a couple screen shots for reference.
