Our Foxboro I/A series controller uses CP60 as its brain. We have 3 identical controllers ie. CP1001, CP1002 and MG1001.

CP1001 is heavily loaded (idle time = <2%). CP1002 slightly better (idle time = 15%) while MG1001 is quite free (idle time = > 70%).

Upon checking, CP1001 has many I/O modules (receive many inputs and send many outputs). Similarly for CP1002. But not for MG1001 - where it is used only for data input eg. data from other PLCs for display/historian).

1. Is this a common Foxboro design?

2. Can we re-route some of the I/O modules to MG1001 ?

P/S: Upon consultation w/ Invensys - they suggested their latest ZCP270 processor (which will eliminate idle time issue). We do not want to blindly upgrade to ZCP270 b4 understanding the real issue.

Hope someone can share your experience.

 

Seems your I/O is unequally distributed, and this should not be the case. Foxboro will very rapidly recommend CP270. However this will be a major reconstruction of the installation. First check what is causing the load, consider re-tuning the timing params. Worst case, you'll have to reorganize I/O to the CPUs. No choice.

EWG