Emerson Exchange 365

In reply to Michael Krispin:

The benefit of using a DCC with a DC block would be that you could configure 8 Interlocks and 4 Permissives in the DCC but then have the Number of Used Conditions set to 0 for Interlocks and Permissives. This will essentially not execute any of those Interlock and Permissive condition expressions which is not possible with using CND/BFI blocks method.

The CND blocks have to execute every scan and this is why we have seen cases where loading dropped significantly in configurations because hundreds or thousands of pumps/motors/valves had unused conditions that is essentially removed by using a DCC block and number used set to 0 or the proper number of used conditions. Similar concept with Loop Tracking using the AT block instead of CND/BFI as well.

The difference is loading between CND/BFI and DCC is because the DCC is actually providing more flexibility/functionality than just CNDs/BFI. Since it is doing Interlocks, Permissives (both Prevent-Any True and Permit-Any Used that are False types) and Force SPs you would have to add some other config than just CNDs/BFI to get apples to apples comparison but again the benefit is the block allows essentially skipping blocks that you can't do with CND/BFI method.

I would only suggest/use the DC with DCC for existing configurations that are having issues with controller loading that would prevent expansion or having performance issues. This isn't a push the button type of change and is more like a migration because of how it would need to be done with saving any configured conditions, manually convert to new module type if class based (or delete and bulk edit create again if non-class) reconfigure the conditions required (or bulk edit back in depending on how the save of these conditions was done).